Content:

ERE – Energy, Resources and the Environment

ERE1.1 – Energy, Resources and the Environment - Open session

EGU21-15574 | vPICO presentations | ERE1.1 | Highlight

Impacts of COVID-19 induced energy demand changes on emissions and mitigation challenges 

Adriano Vinca, Jarmo S. Kikstra, Francesco Lovat, Benigna Boza-Kiss, Bas van Ruijven, Charlie Wilson, Joeri Rogelj, Behnam Zakeri, Oliver Fricko, and Keywan Riahi

The COVID-19 pandemic is causing radical temporary breaks with past energy use and GHG emissions trends. However, how a post-pandemic recovery will impact longer-term transformations to a low-carbon society is unclear. Here, we present different global COVID-19 shock-and-recovery scenarios that systematically explore economic uncertainty and the demand-side effect on emissions. We consider changes in the residential, industry and transport energy sub-sectors under diverging cases that might lead to a more carbon intensive and individualistic way of consumption, or to a policy-advised new future that supports the emission reduction opportunities seen during the pandemic. The resulting impact on cumulative CO2 emissions over the coming decade can range from 28 to 53 GtCO2 reduction depending on the depth and duration of the economic downturn and the extent and persistence of demand-side changes. Recovering from the pandemic with low energy demand practices - embedded in new patterns of travel, work, consumption, and production – reduces climate mitigation challenges in the long run. We show that a low energy demand recovery reduces carbon prices for a 1.5°C consistent pathway by 19%, saves energy supply investments until 2030 by 2.1 trillion USD, and lessens pressure on the upscaling of renewable energy technologies.  

How to cite: Vinca, A., Kikstra, J. S., Lovat, F., Boza-Kiss, B., van Ruijven, B., Wilson, C., Rogelj, J., Zakeri, B., Fricko, O., and Riahi, K.: Impacts of COVID-19 induced energy demand changes on emissions and mitigation challenges , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15574, https://doi.org/10.5194/egusphere-egu21-15574, 2021.

EGU21-13802 | vPICO presentations | ERE1.1 | Highlight

Visualizing the Energy Production, Imports and Exports for Countries

Luisa Vargas Suarez and Jason Donev

There are extensive conceptual difficulties in understanding a country’s energy story. Every country in the world uses some combination of energy production, imports, and exports energy to meet their society’s needs. Thermal inefficiencies converting primary energy into electricity further confuse the issues. A visualization using large, publicly available data can help illustrate these different energy perspectives. This data visualization helps clarify the following perspectives: Production, Imports, Exports, Total Primary Energy Supply (TPES), Total Final Consumption (TFC), and the conversion losses from turning TPES into TFC. TPES refers to the total amount of energy a country obtains directly from natural resources such as fossil fuels or wind. TFC refers to the addition of the all energy directly consumed by a user for an energy service such as electricity for lighting in a house. This paper discusses the interactive simulation that was built to allow users to explore the composition of a country’s energy production, imports and exports through the conversion into energy people consume. The simulation allows users to explore the energy stories for different countries, and how these change over the decades.

How to cite: Vargas Suarez, L. and Donev, J.: Visualizing the Energy Production, Imports and Exports for Countries, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13802, https://doi.org/10.5194/egusphere-egu21-13802, 2021.

EGU21-900 | vPICO presentations | ERE1.1 | Highlight

Environmental impacts of smart local energy systems

Samuel Robinson and Alona Armstrong

Energy systems around the world are rapidly transitioning towards decentralised and digitalised systems as countries aim to decarbonise their economies. However, broader environmental effects of the upscaling of these smart local energy systems (SLES) beyond reducing carbon emissions remain unclear. Land-use change associated with increased deployment of renewables, new infrastructures required for energy distribution and storage, and resource extraction for emerging energy technologies may have significant environmental impacts, including consequences for ecosystems within and beyond energy system project localities. This has major implications for biodiversity, natural capital stocks and provision of ecosystem services, the importance of which are increasingly recognised in development policy at local to international scales. This study assessed current understanding of the broader environmental impacts and potential co-benefits of SLES through a global Rapid Evidence Assessment of peer-reviewed academic literature, with a critical evaluation and synthesis of existing knowledge of effects of SLES on biodiversity, natural capital and ecosystem services. There was a striking overall lack of evidence of the environmental impacts of SLES. The vast majority of studies identified considered only energy technology CO2 emissions through simulation modelling; almost no studies made explicit reference to effects on ecosystems. This highlights an urgent need to improve whole system understanding of environmental impacts of SLES, crucial to avoid unintended ecosystem degradation as a result of climate change mitigation. This will also help to identify potential techno-ecological synergies and opportunities for improvement of degraded ecosystems alongside reaching decarbonisation goals.

How to cite: Robinson, S. and Armstrong, A.: Environmental impacts of smart local energy systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-900, https://doi.org/10.5194/egusphere-egu21-900, 2021.

EGU21-7040 | vPICO presentations | ERE1.1

Potential synergy between solar energy and biodiversity 

Sacha de Rijk, Ruurd Noordhuis, Bas van den Boogaard, and Ineke Roell

Like other countries The Netherlands are facing several societal challenges. As space is very scarce in the Netherlands it is vital to find chances for synergy in solutions to the challenges. It is investigated whether an upgrade of natural values in a large Dutch freshwater lake could go together with installing solar panels on water and thus generate sustainable energy. Our first exploration shows that this kind of synergy has potential for both biodiversity and renewable energy. The presentation will show the design, requirements, uncertainties, chances and risks.

The area of interest is Lake IJssel, a freshwater lake covering an area of 1,100 km2 with an average depth of 5.5 m. Lake IJssel was constructed by the completion of a dam in 1932, transforming the former brackish water of the Zuiderzee into a lake. The water levels are precisely controlled, and the lake provides several ecosystem services. The present ecosystem is imbalanced with low productivity and low biodiversity.

To strengthen the delta nature in the Dutch waters a national Program for nature restoration has been launched. Goal for Lake IJssel is creating more natural transitions: from wet to dry and from fresh to salt. This is done by creating the missing habitats necessary for a healthy ecosystem like shallows with submerged vegetation and wetlands with a natural fluctuation of water levels. At the same time, the region surrounding Lake IJssel is trying to find opportunities for generation of renewable energy. Solar panels on the open water of the lake is one of the options. We have developed a design consisting of a cluster of artificial island modules.

The entire design consists of seven modules of which four modules provide space for solar panels. Each solar module consists of a constructed ring dike with an open connection to the lake providing a water surface where wave action is greatly reduced so thatsolar panels can be installed safely. In this exploration, we opted for a panel coverage percentage of 50% of the surface. If we decrease the water depth by one or two meters under the solar panels with local sediment, the light can penetrate to the lake floor. This creates a favorable environment for aquatic plants. Under the panels, a relatively open, structure-rich vegetation of mainly pondweeds is expected, which is interesting for growing young fish in the summer due to a combination of food supply and shelter. In winter, when the vegetation has disappeared, these waters are expected to be attractive for the wintering of (larger) fish. In addition, the mounting structures of the panels also contribute, providing a substrate for mussels and other invertebrates.

The idea has not yet been tested in practice. The possibility of multiple use of space for ecology and energy is so far based on the judgement of the best available experts and experiences. A pilot study and monitoring are required to gain more insights in the ecological impacts of solar panels in this ecosystem.

How to cite: de Rijk, S., Noordhuis, R., van den Boogaard, B., and Roell, I.: Potential synergy between solar energy and biodiversity , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7040, https://doi.org/10.5194/egusphere-egu21-7040, 2021.

EGU21-2800 | vPICO presentations | ERE1.1

Post-processing numerical weather prediction ensembles for probabilistic solar irradiance forecasting

Sebastian Lerch, Benedikt Schulz, Mehrez El Ayari, and Sándor Baran

In order to enable the transition towards renewable energy sources, probabilistic energy forecasting is of critical importance for incorporating volatile power sources such as solar energy into the electrical grid. Solar energy forecasting methods often aim to provide probabilistic predictions of solar irradiance. In particular, many hybrid approaches combine physical information from numerical weather prediction models with statistical methods. Even though the physical models can provide useful information at intra-day and day-ahead forecast horizons, ensemble weather forecasts from multiple model runs are often not calibrated and show systematic biases. We propose a post-processing model for ensemble weather predictions of solar irradiance at temporal resolutions between 30 minutes and 6 hours. The proposed models provide probabilistic forecasts in the form of a censored logistic probability distribution for lead times up to 5 days and are evaluated in two case studies covering distinct physical models, geographical regions, temporal resolutions, and types of solar irradiance. We find that post-processing consistently and significantly improves the forecast performance of the ensemble predictions for lead times up to at least 48 hours and is well able to correct the systematic lack of calibration.

How to cite: Lerch, S., Schulz, B., El Ayari, M., and Baran, S.: Post-processing numerical weather prediction ensembles for probabilistic solar irradiance forecasting, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2800, https://doi.org/10.5194/egusphere-egu21-2800, 2021.

Solar and storage based microgrids offer a unique opportunity for both climate change mitigation by reducing CO2 emissions and for climate change adaptation by increasing infrastructure resiliency. In this work, we design a time-of-use (ToU) optimization algorithm to determine whether it would be economically viable to install microgrids within two school campuses in the Bay Area, California that have unique load profiles. Our algorithm, which combines machine learning for accurate site-level net load forecasts, examines three years of electricity consumption data to compute the school’s savings from peak demand charges, energy charges, and demand response revenue generated by providing ancillary services to the grid. Given the school’s unique load profile combined with SGIP and MACRS incentives available in the state of California, we determine that a 15-year battery installed at these two campuses with a cost of $600/kWh provides a net positive internal rate of return (IRR) of 11.9% and 18.3% respectively year-over-year. In addition, the battery provides backup power in case of a power outage and improves grid resilience by providing peak shaving when the power grid is stressed. We hope that our computational analysis can motivate other schools to examine the huge economic and climate benefits that a microgrid poses at their campus. 

How to cite: Narayan, Y.: Solar and Energy Storage Based Microgrids:  Data-Driven Optimization and Economic Analysis to Examine Energy Savings from a Microgrid within a School Campus, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6785, https://doi.org/10.5194/egusphere-egu21-6785, 2021.

EGU21-8091 | vPICO presentations | ERE1.1

Identification of the socio-technical factors within geothermal exploration based on Plays with examples from Central America 

Javiera Chocobar, Bernhardt Johst, Rolf Bracke, and Erik H. Saenger

     The development of geothermal exploration has benefited from the inclusion of exploration protocols based on geological Plays classically used in hydrocarbon exploration projects. Despite being a research topic in which many efforts have been devoted, it presents weaknesses when evaluating the role of the communities (the social dimension) during the exploration process. To address the lack of studies, a qualitative research has been carried out in Central America (Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Panamá) to determine the necessary factors to be considered in the social dimension within the geothermal exploration based in Plays.

     We have identified the social factors within each social dimension (demand, infrastructure, land access) and from this, a catalogue of the necessary activities required in the social dimension during the geothermal exploration process based on plays is proposed. The results of our survey will greatly contribute to the implementation of the Play-based exploration in geothermal projects because it reduces the risks associated in the initial phase of the exploration process and offers a step-by-step methodology that, when adapted to the needs of each country, can improve the efficiency of the current geothermal exploration protocols.

How to cite: Chocobar, J., Johst, B., Bracke, R., and Saenger, E. H.: Identification of the socio-technical factors within geothermal exploration based on Plays with examples from Central America , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8091, https://doi.org/10.5194/egusphere-egu21-8091, 2021.

EGU21-4301 | vPICO presentations | ERE1.1

Benefit of poroelasticity for geothermal research

Bianca Kretz, Willi Freeden, and Volker Michel

For geothermal purposes (heat and electricity generation) it is necessary to have an aquifer from which the contained hot water can be lifted by drilling. The exchange of the hot water against some cooled off water has an effect on the surrounding material and displacement of the material has an influence on the pore pressure and the water. Poroelasticity can model these influencing effects by partial differential equations.

We want to apply poroelasticity in geothermal research by so-called multiscale modelling. Scaling functions and wavelets are constructed with the help of the fundamental solutions. A related method has been previously used for the Laplace, the Helmholtz and the d'Alembert equation (cf. [2],[4],[5]) as well as for the Cauchy-Navier equation, where the latter requires a tensor-valued ansatz (cf. [3]). We pursue this concept to develop such an approach for poroelasticity, where a fundamental solution tensor is known (cf. [1]).

The aim of this multiscale modelling is to convolve the constructed scaling functions with the data of the displacement $u$ and the pressure $p$. With this, we have the opportunity to visualize structures in the data that cannot be seen in the whole data. Especially, the difference of the convolution of two consecutive scaling functions is expected to reveal detail structures.

For the theoretical part, we can show that the scaling functions fulfill the property of an approximate identity. Furthermore, with numerical results we want to show the decomposition.

References

[1] M. Augustin: A method of fundamental solutions in poroelasticity to model the stress field in geothermal reservoirs, PhD Thesis, University of Kaiserslautern, 2015, Birkhäuser, New York, 2015.

[2] C. Blick, Multiscale potential methods in geothermal research: decorrelation reflected post-processing and locally based inversion, PhD Thesis, Geomathematics Group, Department of Mathematics, University of Kaiserslautern, 2015.

[3] C. Blick, S. Eberle, Multiscale density decorrelation by Cauchy-Navier wavelets, Int. J. Geomath. 10, 2019, article 24.

[4] C. Blick, W. Freeden, H. Nutz: Feature extraction of geological signatures by multiscale gravimetry. Int. J. Geomath. 8: 57-83, 2017.

[5] W. Freeden, C. Blick: Signal decorrelation by means of multiscale methods, World of Mining, 65(5):304--317, 2013.

How to cite: Kretz, B., Freeden, W., and Michel, V.: Benefit of poroelasticity for geothermal research, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4301, https://doi.org/10.5194/egusphere-egu21-4301, 2021.

EGU21-10951 | vPICO presentations | ERE1.1

Evaluating river driftwood potential for energy storage applications 

Abdullah F Qatarneh, Capucine Dupont, Virginia Ruiz-Villanueva, Julie Michel, Loic Simonin, Hervé Piégay, and Mário J. Franca

Around the world rivers transport large volumes of driftwood into lakes, seas and oceans. Recruited commonly during flooding events and transported by rivers, driftwood poses a hazard for the point of view of the safety of infrastructures and river dwellers. For that reason, it is many times extracted locally and stored; driftwood removal prevents sinking and protects the dam infrastructure. Collected driftwood is a neglected river resource that is generally combusted or landfilled. Génissiat dam on the Rhone River in France presents a case study where annually approximately 1300 tons of driftwood is intersected.

 

Among the different processes that are capable of converting driftwood, HydroThermal Carbonization (HTC) is of high interest due its ability to process biomass with high moisture content, such as driftwood. HTC of biomass leads to the production of a solid product referred to as hydrochar, which is a high added-value material that can be used in different applications, such as fuel cooking, soil amendment, water treatment and energy storage. The goal of the study was to characterize the driftwood collected upstream of the Génissiat dam and to investigate its potential for hydrochar production as precursor of anode in sodium-ion batteries. Sodium-ion batteries have received more interest lately as an alternative for the resource intensive and expensive lithium-ion batteries.  The study follows a novel approach in study driftwood by categorizing based on their genera. HTC of the different identified genera was conducted in a 2L batch reactor following a temperature of 200 °C for a residence time of 11.5 h. Results show that the impact of driftwood genera is not significant for processing of driftwood through HTC. Produced hydrochar had a high carbon content (from 55.4 to 57.0 %) and lower ash content (from 0.2 to 1.4 \% of dry biomass). Electrochemical results show that driftwood-based hydrochar is a promising precursor of hard carbon anodes in sodium-ion batteries due to its excellent electrochemical performance.

 

Key words: Driftwood, Hydrothermal carbonization, Hydrochar, Rhone river, Sodium-ion batteries

How to cite: Qatarneh, A. F., Dupont, C., Ruiz-Villanueva, V., Michel, J., Simonin, L., Piégay, H., and Franca, M. J.: Evaluating river driftwood potential for energy storage applications , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10951, https://doi.org/10.5194/egusphere-egu21-10951, 2021.

EGU21-16061 | vPICO presentations | ERE1.1

Maximising climate protection through minimising gas leakage – the Danish biogas measurement programme

Anders Fredenslund and Charlotte Scheutz

The Danish voluntary methane monitoring programme for agricultural biogas producing facilities was launched by the Danish Biogas Association in autumn, 2016. The Danish Biogas Association had set a san overall goal of reducing the total methane loss from Danish biogas and upgrading plants on a national level to less than 1% of production by 2020.

The Danish Government has allocated approximately 1.3 million € to monitor and reduce methane emissions from the biogas sector in the period 2019-2020, based on previous experiences. The funds are used to administer this new programme, method testing, validation of measurement service providers and to provide partial funding for the participation of biogas plants. Also, the project includes recommendations to the Danish Energy Agency regarding use of measurements in regulation based on the results of the programme. The programme includes agricultural biogas plants (both farm-scale and centralized plants), industrial biogas plants and biogas plants treating sludge from wastewater treatment. The biogas plants provide partial funding. Three levels of own-funding are used depending on the magnitude of gas production. Large biogas plants pay a larger fraction of expenses than smaller plants. This was chosen to ensure participation of smaller facilities.

At each biogas plant, two or more of the following actions are performed:

1. Initial agreement on services and expectations

2. Development of self-monitoring programme

3. Leakage search and mitigation recommendations

4. Quantification of methane loss using remote sensing

5. Draft project of emission reduction initiatives

Actions 1 and 4 are mandatory for the participating biogas plants. The leakage search (Action 3) is performed using Optical Gas Imaging (OGI). Here, a measurement technician uses OGI to identify leakages both outdoors on tanks, pipes etc., and indoors. The report lists and illustrates leakages (through video documentation) and provides advise on mitigation actions were applicable. Even though OGI is not used quantitatively, the leaks are categorized as low, medium and high emission rates based on the operator’s assessment from the OGI videos.

Quantification of the biogas plants total methane emission (Action 4) is done using a tracer gas dispersion method. This remote sensing method includes the controlled, continuous release of a tracer gas (C2H2 in this case) combined with downwind, cross-plume measurements of methane and tracer gas. This method is described in Scheutz and Fredenslund (2019). It has been used to quantify emissions from biogas plants in the previous voluntary programme as well as to measure fugitive emissions from other area sources such as landfills, composting facilities and wastewater treatment plants.

About 60 plants have signed up and measurement and consultation activities are currently ongoing. The plants include about 35 manure-based biogas plants, 2 industrial biogas plants and 22 wastewater treatment plants. All activities are to be completed by the end of February, 2021.

This presentation will include a short introduction to the programme, observed emission rates and emission factors, typical sources of methane emission, mitigation options, recommendations regarding regulation and economic factors such as expenses for the monitoring activities.

Reference

Scheutz, C., Fredenslund, A.M. 2019. Total methane emission rates and losses from 23 biogas plants. Waste Management, 97, 38-46.

How to cite: Fredenslund, A. and Scheutz, C.: Maximising climate protection through minimising gas leakage – the Danish biogas measurement programme, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16061, https://doi.org/10.5194/egusphere-egu21-16061, 2021.

EGU21-12927 | vPICO presentations | ERE1.1

Sustainable management of water environment in anthropopressure area for municipal purposes, water quality improvement and utilization of renewable energy sources

Artur Wilczynski, Barbara Namyslowska-Wilczynska, and Pawel Maslankiewicz

The Authors deal with the problems of management of post-industrial areas affected by high unemployment leading to prevailing frustration, increasing migration of the population and other socially and economically adverse phenomena. This is accompanied by the considerable degradation of the natural environment and the deterioration in the quality of life of the local population. The aim of the studies is showing the possibilities to create a model to manage the resources in order to achieve sustainable development, particularly to manage water and energy in the post-industrial areas. The studies have been carried out for a region heavily industrialized in the recent past with present closed down mines. In particular, the work relates to examine the possibility of: improving the quality of the surface and underground waters, using the water as a source of low-temperature heat, storing energy and producing energy in local renewable sources, ensuring proper water retention, developing post-industrial tourism through managing the post-industrial facilities and making them available. Innovation of work is to create an integrated model of resources and the environment management, in particular water resources and non-conventional energy.

The proposals constitute a contribution to the implementation of the principles of sustainable development by focusing on three of its dimensions - economic, environmental and social. At the same time it would be a way for the sustainable management of the water environment in the areas of anthropopressure, in industrial and post-industrial areas, for the purpose of collecting water, improving water quality and the use of local energy sources. The possibility of energy storage, which is extremely important in the area of an intensive development of unconventional sources of energy (wind farms, solar sources, hydroelectric, etc.), the characteristics of which are irregular, referred to simply as chimeric sources, also exists.

How to cite: Wilczynski, A., Namyslowska-Wilczynska, B., and Maslankiewicz, P.: Sustainable management of water environment in anthropopressure area for municipal purposes, water quality improvement and utilization of renewable energy sources, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12927, https://doi.org/10.5194/egusphere-egu21-12927, 2021.

EGU21-9905 | vPICO presentations | ERE1.1

Quantifying the mechanical response of the Izaña area (Tenerife) to sustained groundwater withdrawal 

Anthony Lamur, Silvio De Angelis, Rayco Marrero, Yan Lavallée, and Pablo J. Gonzalez

Surface water resources on volcanic islands with moderate rainfall and relatively high permeability are usually scarce or non-existent. As such, life and local economies of these islands mostly relies on groundwater exploitation. It is therefore important to characterise the sustainability of volcanic aquifer systems. In short, an aquifer is deemed in equilibrium when the recharge rate equals or exceeds the exploitation rate. The Izaña area in Tenerife Island (Canary Islands, Spain) has been exploited since the 1900s via a series of ~30 horizontal drilling or water galleries coming from both flanks of the NE-Ridge. Since exploitation began, the water table has dropped continuously, in some area even more than 200 m. Since the 2000s, aquifer dynamics (compaction) have been observed using InSAR indicating a subsidence rate of up to 2 cm per year.

Here, we investigate a suite of rock samples collected. The samples were collected at several water galleries aiming to be representative of the aquifer materials from the Izaña area. We first characterise the basic physical properties of each samples (porosity, permeability, solid density) before quantifying the elastic parameters (Young’s modulus, Poisson ratio) and uniaxial strength of the lithologies collected. We also measure Vp under dry and wet conditions (i.e. different saturation levels) to assess whether water saturation can alter the velocity of P-waves passing through those rocks.

Preliminary results show that connected porosities range from 0.16 to 45%, conferring a wide range of mechanical response to increasing effective pressure, with strength ranging from 18 – 315 MPa and Young’s moduli ranging from 3 – 57 GPa. In a similar fashion, results for Vp measurements also exhibit a range of values (~1.5 – 4.5 km/s). These data show that materials present in the aquifer are extremely varied, suggesting that both fluid flow and observed deformation are likely to be controlled by the weakest, most porous lithologies.

These results will further be integrated with the lithostratigraphic record of the aquifer in order to model the mechanical response of the aquifer to changes in effective pressures, and specifically pore pressure reduction with water extraction. Additionally, chemical and textural analysis will provide insights on the evolution of the porous network at different alteration levels, here serving as a proxy for time at saturation in the aquifer. Finally, we aim to compare the experimental results from laboratory measurements to those of hydro-geophysical measurements that will be collected in the field starting in mid-2021.

How to cite: Lamur, A., De Angelis, S., Marrero, R., Lavallée, Y., and Gonzalez, P. J.: Quantifying the mechanical response of the Izaña area (Tenerife) to sustained groundwater withdrawal , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9905, https://doi.org/10.5194/egusphere-egu21-9905, 2021.

EGU21-9514 | vPICO presentations | ERE1.1

Assessment of groundwater contamination by chlorpyrifos using the PWC model in Valencia Region (Spain)

Ricardo Pérez Indoval, Javier Rodrigo-Ilarri, and Eduardo Cassiraga

Chlorpyrifos is commoly used as an pesticide to control weeds and prevent nondesirable grow of algae, fungi and bacteria in many agricultural applications. Despite its highly negative effects on human health, environmental modeling of this kind of pesticide in the groundwater is not commonly done in real situations. Predicting the fate of pesticides released into the natural environment is necessary to anticipate and minimize adverse effects both at close and long distances from the contamination source. A number of models have been developed to predict the behavior, mobility, and persistence of pesticides. These models should account for key hydrological and agricultural processes, such as crop growth, pesticide application patterns, transformation processes and field management practices.

This work shows results obtained by the Pesticide Water Calculator (PWC) model to simulate the behavior of chlorpyrifos. PWC model is used as a standard pesticide simulation model in USA and in this work it has been used to  simulate the fate and transport of chlorpyrifos in the unsaturated zone of the aquifer. The model uses a whole set of parameters to solve a modified version of the mass transport equation considering the combined effect of advection, dispersion and reactive transport processes. PWC is used to estimate the daily concentrations of chlorpyrifos in the Buñol-Cheste aquifer in Valencia Region(Spain).

A whole set of simulation scenarios have been designed to perform a parameter sensitivity analysis. Results of the PWC model obtained in this study represents a crucial first step towards the development of a pesticide risk assessment in Valencia Region. Results show that numerical simulation is a valid tool for the analysis and prediction of the fate  and transport of pesticides in the groundwater.

How to cite: Pérez Indoval, R., Rodrigo-Ilarri, J., and Cassiraga, E.: Assessment of groundwater contamination by chlorpyrifos using the PWC model in Valencia Region (Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9514, https://doi.org/10.5194/egusphere-egu21-9514, 2021.

EGU21-2343 | vPICO presentations | ERE1.1

Integrated geological-geophysical and UAS proximal sensing approach to the study of ground water movement between two open-pit pools in an abandoned mine area.

Stefano Cara, Silvana Fais, Paola Ligas, Carlo Matzuzzi, and Federica Podda

The aim of this work is to combine geological/geophysical techniques with proximal sensing based on Unmanned Aerial System (UAS) for advanced 3D modeling, in a possible post-mining landscape recovery of abandoned mine sites. In this framework a test area in central Sardinia (Italy) was studied. In this area, several talc-chlorite-feldspar bodies have long been mined in open pit operation greatly modifying the original landscape. At present the rearrangement of the mining site and particularly the open pit works that have been occupied by newly formed pools filled with waters from aquifers can be considered an overall project of landscape recovery. The project team have focused on developing a UAS proximal sensing technique for the acquisition of high-definition digital images and by means of photogrammetric algorithms (CMPMVS) in order to generate a dense 3D point cloud and successively high-resolution digital models (DSM and DTM). The proximal sensing survey was performed at different flight heights to obtain a Ground Sample Distance (GSD) according to the scale of investigation. The availability of a detailed topographic dataset is fundamental to characterize a complex morphology and is a basic support for integration with the data resulting from the geological-geophysical survey conducted in the abandoned mine area. Based on this a geophysical investigation by the electromagnetic very low frequency (VLF) method was carefully planned and carried out to localize potential structural discontinuities that can guide groundwater circulation between the newly formed pools encased in the crystalline basement rocks. The VLF method has a high-resolution power in detecting lateral variations in the electrical properties (i.e., conductivity) of the rock formations related to the presence of underground geological structures. To facilitate the interpretation of the VLF-EM anomalies the Karous–Hjelt linear filter was applied on the EM data. Thanks to the application of this filtering procedure, it was possible to obtain the current density pseudosections along the profiles crossing the basement rocks. The pseudosections provide a representation of the various current concentrations in depth and hence the spatial arrangement of subsurface geological features such as faults, fracture zones and geological contacts. The VLF data were also quantitatively interpreted with a 2D code for the VLF data inversion. Both in the pseudosections and in the 2D resistivity models two main conductive zones are present. These conductive zones could be the signature of a preferential path of the water circulation between the newly formed pools encased in the basement rocks. The application of the integrated geological-geophysical and UAV photogrammetric survey approach proved successful in characterizing the basement rocks of the investigated area and allowed to localize structural discontinuities that can guide the groundwater circulation. The results of this study can represent the indispensable knowledge base to contribute to constraining the hydrogeology numerical model needed for the mine site rehabilitation and reasonable planning of the possible post-mining landscape recovery. The methodological sequence used in this study can be reproduced in other similar abandoned mining sites thus giving an important contribution to an efficient and cost-effective performance of the restoration project.

How to cite: Cara, S., Fais, S., Ligas, P., Matzuzzi, C., and Podda, F.: Integrated geological-geophysical and UAS proximal sensing approach to the study of ground water movement between two open-pit pools in an abandoned mine area., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2343, https://doi.org/10.5194/egusphere-egu21-2343, 2021.

This geostatistical study investigates the variation in the basic geological parameters of the lithologically varied deposit in mining block R-1 in the west (W) part of the Rudna Mine (the region Lubin – Sieroszowice, SW part of Poland).

Data obtained from the sampling (sample size N = 708) of excavations in block R-1 were the input for the spatial analyses. The data are the results of chemical analyses of the Cu content in the (recoverable) deposit series, carried out on channel samples and drilled core samples, taken systematically at every 15-20 m in the headings.

The deposit profile comprises various rock formations, such as: mineralized Weissliegend sandstones, intensively mineralized upper Permian dolomitic-loamy and loamy copper-bearing schists and carbonate rocks: loamy dolomite, striped dolomite and limy dolomite, of various thickness. No schists formed in some parts of block R-1, which are referred to as the schistless area. The deposit series here is considerably less mineralized (comparing with other mining blocks) even though the mineralization thickness of the sandstone and carbonate rocks reaches as much as 20 m.

The variation in the Cu content and thickness of the recoverable deposit and the estimated averages Z* of the above parameters were modelled using the variogram function and the ordinary (block) kriging technique. The efficiency of the estimations was characterized.

As part of the further spatial analyses the Zs values of the analysed deposit parameters were simulated using the conditional turning bands simulation. Confidence intervals for the values of averages based on the estimated averages Z* and averages  based on the simulated values (realizations) Zs, showing the uncertainty of the estimations and simulations, were calculated.

The results of the analyses clearly indicate the shifting of the mineralized zone (the mineralizing solutions), sometimes into the sandstones while spreading throughout the floor of calcareous-dolomitic formations and sometimes into the carbonate rocks, partly entering the roof layers of sandstones. It can be concluded that the process of deposit formation and copper mineralization variation had a multiphase character and the lateral and vertical relocation of the valuable metal ores could play a significant role.

The combination of various geostatistical techniques - estimation and simulation - will allow for more effective management of natural resources of mineral resources, including copper ore deposits.

How to cite: Namysłowska-Wilczyńska, B.: Estimation of copper ore deposit parameters – case study of Rudna Mine mining block R-1 (SW part of Poland) using geostatistics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12397, https://doi.org/10.5194/egusphere-egu21-12397, 2021.

Surface ozone pollution has been proven to impose significant damages on crops. However, the quantification of the damages was extensively derived from chamber experiments, which is not representative of actual results in farm fields due to the limitations of spatial scale, time window, etc. In this work, we attempt to empirically fill this gap using county-level data in the United States from 1980 to 2015. We explore ozone impacts on corn, soybeans, spring wheat, winter wheat, barley, cotton, peanuts, rice, sorghum, and sunflower. We also incorporate a variety of climate variables to investigate potential ozone-climate interactions. More importantly, we shed light on future yield consequences of ozone and climate change individually and jointly under a moderate warming scenario. Our findings suggest significant negative impacts of ozone exposure for eight of the ten crops we examined, excepting barley and winter wheat, which contradicts experimental results. The average annual damages were estimated at $6.03 billion (in 2015 U.S. dollar) from 1980 to 2015. We also find rising temperatures tend to worsen ozone damages while water supply would mitigate that. Finally, elevated ozone driven by future climate change would cause much smaller damages than the direct effects of climate change itself.

How to cite: Da, Y., Xu, Y., and McCarl, B.: Effects of ozone and climate on historical (1980-2015) crop yields in the United States: Implication for mid-21st century projection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-399, https://doi.org/10.5194/egusphere-egu21-399, 2021.

This work aims to identify means of analysing the gravimetric composition of solid waste retained in the fences of some operational units of the Insular sewage system in the municipality of Florianópolis, State of Santa Catarina, Brazil. Two sewage pumping stations (Beira-Mar Norte and Hospital Universitário-Trindade) units were chosen and the railing at the entrance to the sewage treatment station of the system (Insular). The following classes of solid waste were adopted: plastics, metals, styrofoam, civil construction material, dead animals, sanitary napkins, diapers, rags and cloths, organic matter, other or tailings. It is being identified the solid waste observed in greater quantities and in percentages in the sanitary sewage system, which may cause damage to the operational units. The intending action is to be able to propose to local government and the system operator, different ways to educate the population and try to prevent or reduce the appearance of these residues in the sewage systems.

How to cite: Bortolotto, N. L. and Poleto, C.: Gravimetric Analysis of Solid Waste from Sanitary Sewage Operating Units of the Insular System, Florianópolis, State of Santa Catarina, Brazil., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6668, https://doi.org/10.5194/egusphere-egu21-6668, 2021.

EGU21-1847 | vPICO presentations | ERE1.1

Optical detection of alpha emitting radionuclides in the environment

Faton Krasniqi

Radiological emergencies involving accidental or deliberate dispersion of alpha emitting radionuclides in the environment can cause significant damage to humans and societies in general. A detection system to measure large-scale contamination of these radionuclides is currently not available. In case of a contamination, the only option is to evacuate the population from the affected areas and then run diagnostics by hand due to the short range of alpha particles in air, exposing thus the emergency teams to considerable risk. Even then, the results of emergency field applications are notoriously ambiguous, time consuming and tedious due to the centimetre range of the alpha particles in air. A novel detection approach which is capable of remote detection of alpha-emitting radionuclides in the environment will be reported. This approach will assist the on-site incident management and will enable detection of contamination threats without contact—from safe distances—avoiding thus contamination of operators and equipment.

How to cite: Krasniqi, F.: Optical detection of alpha emitting radionuclides in the environment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1847, https://doi.org/10.5194/egusphere-egu21-1847, 2021.

EGU21-8003 | vPICO presentations | ERE1.1

Comfort-energy nexus in naturally ventilated affordable mass housing with alternative constructions in the developing world

Roshmi Sen, Shankha Pratim Bhattacharya, and Subrata Chattopadhyay

There is a strong positive correlation between thermal comfort quality experienced inside a building and its energy efficiency. This is more obvious in case of mechanically ventilated spaces where the energy gains are directly related to the thermal load, as compared to free running or naturally ventilated spaces. Current state of arts assess the energy efficiency of building envelops in terms of the cumulative thermal load in the operating phase of the building that are catered by mechanical ventilations. Our study aims at addressing this gap of research in assessing the thermal comfort quality of naturally ventilated residential living spaces. Our study is designed in a warm-humid climate setting and in the context of affordable mass housing in the developing world where mechanical ventilation is unaffordable or affordable only for a definite period of the day and during peak summer seasons; such buildings are said to be operating in temporal mixed mode.

Affordable mass housing constitutes 95% housing demand in the residential sector in India. Various alternative materials and composite roofing and walling envelops have been envisioned in the past decade for such constructions, however, their effectiveness in terms of comfort quality has not been assessed for naturally ventilated envelops. Our study introduces a model to assess the thermal performance of naturally ventilated bedrooms constructed with alternate building envelop configurations. We attempt to review  and compare alternative walling technologies and the currently emerging mass housing construction systems in India with the base case housing envelop constructions commonly in practice in India that use ordinary burnt clay brick walls and reinforced concrete roofs. We compare the thermal comfort purveyed in the indoor bedroom spaces using the adaptive thermal comfort model in EN15251 as thermal neutrality temperature. We assess and compare alternative envelop performance using two measuring thermal comfort indices suited for naturally ventilated scenarios - the discomfort hours index and the cooling indoor degree hours index. Discomfort hours measures the number of hours of discomfort experienced during the summer solstice and spring equinox months whereas the cooling indoor degree hours measures the cumulative average temperature elevation from the comfort temperature in the hours marked as discomfort hours. In our study, light gauge steel framed structure with foam concrete filling records the minimum number of discomfort hours, however purveys maximum cooling indoor degree hours.

The above two comfort indices have not been compared in the past to assess the thermal comfort quality in naturally ventilated or temporal mixed mode buildings. Our study frames a thermal comfort assessment model for naturally ventilated envelops and thereby offers a paradigm shift from life cycle cooling load minimization models which are appropriate for mechanically conditioned spaces. Our observations are also important for mass housing envelop selection and in the context of the current policy frameworks in the developing world, aimed at minimizing the projected demand for residential space cooling and future energy footprints in the housing sector.

How to cite: Sen, R., Bhattacharya, S. P., and Chattopadhyay, S.: Comfort-energy nexus in naturally ventilated affordable mass housing with alternative constructions in the developing world, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8003, https://doi.org/10.5194/egusphere-egu21-8003, 2021.

EGU21-14275 | vPICO presentations | ERE1.1

Building’s Energy Consumption Pattern and Design-Built Parameters - Influence of Climate on Design Guidelines

Abdulrahman Almufarrej and Tohid Erfani

Increasing buildings energy efficiency is a challenging task. The two main contributing factors that control the overall buildings energy performance are the Heating Ventilation & Air Conditioning (HVAC) system and the building envelope design. Our research investigates how three main building envelop design factors (orientation, compactness and window to wall ratio) impact the overall building’s energy consumption. We focus on typical rectangular shaped buildings and vary the geometry between a square to a rectangular floor plan to provide a basis of energy performance in early stage building design guidance. We test the analysis on building’s energy performance specific to the Middle East’s Kuwait climate condition and environment, and discuss the least energy consumption patterns. This is of importance as most of the electricity consumption in Kuwait are due to HVAC use in residential buildings. The major energy consumption factors are broken down to show how the patterns are unique compared to the previously researched efforts and how a regional set of guidance is of need. The results of this study’s implication on energy and resource use in the Gulf Cooperation Council (GCC) region is discussed, given the high proportion of GHG emission compared to the population within the region.

How to cite: Almufarrej, A. and Erfani, T.: Building’s Energy Consumption Pattern and Design-Built Parameters - Influence of Climate on Design Guidelines, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14275, https://doi.org/10.5194/egusphere-egu21-14275, 2021.

EGU21-15362 | vPICO presentations | ERE1.1

Evaluating the Effect of Green Infrastructure in Mitigating the Urban Heat Island Effect Using Remote Sensing

Sofia Fidani, Ioannis Daliakopoulos, Thrassyvoulos Manios, Manolis Grillakis, Vasiliki Charalampopoulou, and Panagiotis Nektarios

Urban green infrastructure in the form of green roofs and vertical gardens is gradually becoming a mainstream development option to mitigate the negative impacts of dense urbanization, and primarily those associated with the urban heat island effect and the consequent vulnerability due to climate change (Nektarios and Ntoulas, 2017). Nevertheless, the quantification of the effect of green infrastructure in comparison to conventional infrastructure as well as tree parks and gardens, can be a challenge in a rapidly changing urban environment, especially due to historical gaps in environmental parameter monitoring. Here we propose the use of land surface temperature (LST) [oC] produced using freely available LandSat imagery at 30 m resolution, to evaluate the effect of green infrastructure on urban surface temperature. The method relies on the comparison of historical LST timeseries of an area of interest which has undergone urban greening interventions with adjacent city blocks that have retained their conventional urban character. The method is applied to evaluate the impact of the recently constructed Eco Campus Orange (ECO) garden, which has resulted from the renovation of 4 city blocks in Paris, France. Within an area over 3 ha, ECO employs environmentally friendly materials and 100,000 plants to feature 2,300 m2 of green wall and “the largest green roof of Europe”. For the area of interest, over 250 LandSat 5, 7, and 8 multispectral images dating from 2010 to 2020, were analyzed after Ermida et al. (2020). Results show that, since its construction, LST at ECO quickly dropped by over 2 oC, reaching the LST levels of adjacent urban parks. The method is ideal for ambient temperature timeseries reconstruction where long-term monitoring is sparce and can be applied to evaluate drastic landscape changes such as urban greening or vegetation thinning.

References

Ermida, S.L., Soares, P., Mantas, V., Göttsche, F.M., Trigo, I.F., 2020. Google earth engine open-source code for land surface temperature estimation from the landsat series. Remote Sens. https://doi.org/10.3390/RS12091471

Nektarios, P.A., Ntoulas, N., 2017. Designing green roofs for arid and semi-arid climates. The route towards the adaptive approach, in: Acta Horticulturae. International Society for Horticultural Science, pp. 197–202. https://doi.org/10.17660/ActaHortic.2017.1189.39

Acknowledgements

The research was co-financed by the European Union and Greek national funds through the Operational Program RIS3Crete (COMPOLIVE: ΚΡΗΡ3-0028773)

The research of MG was co-financed by the European Union and Greek national funds through the Operational Program "Human Resource Development, Education and Lifelong Learning", under the Act "STRENGTHENING post-doctoral fellows / researchers - B cycle" (MIS 5033021) implemented by the State Scholarship Foundation.

How to cite: Fidani, S., Daliakopoulos, I., Manios, T., Grillakis, M., Charalampopoulou, V., and Nektarios, P.: Evaluating the Effect of Green Infrastructure in Mitigating the Urban Heat Island Effect Using Remote Sensing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15362, https://doi.org/10.5194/egusphere-egu21-15362, 2021.

ERE1.2 – GeoERA: Developing integrated geoscience services to address European resource supply and management challenges

EGU21-6407 | vPICO presentations | ERE1.2

Susceptibility assessment of gas hydrate dissociation occurrence along European continental margins and adjacent areas. GARAH project (GeoERA)

Ricardo León, Christopher Rochelle, André Burnol, Carmen Julia Giménez- Moreno, Tove Nielsen, John Hopper, Isabel Reguera, Margaret Stewart, Miguel Llorente, Pilar Mata, and Silvia Cervel

The Pan-European gas-hydrate relate GIS database of GARAH project has allowed assessing the susceptibility of seafloor areas affected by hydrate dissociation. This study has been applied as a first step for the hydrate related risk assessment along the European continental margins. Several factors and variables have been taken into account. They have been defined by their relationship with the presence of hydrates below seafloor and weighted depending on the confidence of finding hydrates in this site. The maximum weight (or confidence) has been given to the recovered samples of gas hydrates or hydrate-dissociation evidences such as degassing or liquation structures observed in gravity cores. Seismic indicators of the presence of gas hydrate or hydrocarbon seabed fluid flow such as BSR, blanking acoustic, amplitude anomalies or the presence of geological structures of seabed fluid flow in the neighbouring of the GHSZ have been weighted with a lower value. The theoretical gas hydrate stability zone (GHSZ) for a standard composition for biogenic gas has been taken into account as another control factor and constrain feature. Seafloor areas out of the theoretical GSHZ have been excluded as potential likelihood to be affected by hydrate dissociation processes. The base of GHSZ has been classified as a critical area for these dissociation processes.

The proposed methodology analyses the geological hazard by means of the susceptibility assessment, defined by the likelihood of occurrence of hydrate dissociation, collapses, crater-like depressions or submarine landslides over seafloor. The baseline scenario is that gas hydrate occurrence is only possible in seafloor areas where pressure (bathymetry) and seafloor temperature conditions are inside the theoretical GHSZ. Inside GHSZ, the occurrence of gas hydrate is directly related to the presence of its evidences (direct samples of hydrates) or indicators (eg. pore water and velocity anomalies, BSR, gas chimneys, among others), as well as the occurrence of hydrocarbon fluid flow structures inside GHSZ. Finally, the likelihood of the seafloor to be affect gas hydrate dissociation processes will be major at the base of the GHSZ and in the neighbouring of the gas hydrate evidences and indicators. In order to proof this initial hypothesis, a susceptibility assessment has been carried out throughout map algebra in a GIS environment from a density map of evidences and indicators and the Pan-European map of the GHSZ over seafloor. Specifically, it has been conceived as a segmentation in three levels by quantiles resulting of the addition of the density map of evidences and indicators and the weighted map of the GHSZ over seafloor.

 

Acknowledgment

GARAH project. GeoERA - GeoE.171.002

How to cite: León, R., Rochelle, C., Burnol, A., Giménez- Moreno, C. J., Nielsen, T., Hopper, J., Reguera, I., Stewart, M., Llorente, M., Mata, P., and Cervel, S.: Susceptibility assessment of gas hydrate dissociation occurrence along European continental margins and adjacent areas. GARAH project (GeoERA), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6407, https://doi.org/10.5194/egusphere-egu21-6407, 2021.

EGU21-7262 | vPICO presentations | ERE1.2

3D basin and petroleum system modelling in the North Sea Central Graben - a Dutch, German, Danish cross-border study

Rüdiger Lutz, Susanne Nelskamp, Anders Mathiesen, Niels Hemmingsen Schovsbo, Stefan Ladage, and Peter Britze

A Geological Analysis and Resource Assessment of selected Hydrocarbon Systems (GARAH) is carried out as part of the overarching GeoERA project. Here, we report results on the first public 3D basin and petroleum system model developed in a cross-border area of the Dutch, Danish and German North Sea Central Graben. This pilot study reconstructs the thermal history, maturity and petroleum generation of potential Lower, Middle and Upper Jurassic source rocks and assesses potential unconventional resources in a first phase. The 3D pilot study incorporates new aggregated and combined layers of the three countries. Results of the study feed back into the 3DGEO-EU project of GeoERA.

Eight key horizons covering the whole German Central Graben and parts of the Dutch and Danish North Sea Central Graben were selected for building the stratigraphic and geological framework of the 3D basin and petroleum system model. The model includes depth and thickness maps of important stratigraphic units as well as the main salt structures. Petrophysical parameters, generalized facies information and organic geochemical data from well reports are assigned to the different key geological layers. Further, the model is calibrated with temperature and maturity data from selected offshore wells as well as from publications. The time span from the Late Permian to the Present is represented by the model, including the most important erosional phases related to large-scale tectonic events during the Late Jurassic to Late Cretaceous. Additionally, salt movement through time expressed as diapirs and pillows is considered within the 3D basin and petroleum system model. Simulations depict that unconventional petroleum resources (oil and natural gas) are present in varying amounts in the source rocks across all three countries.

This is a part of an ongoing EU Horizon 2020 GeoERA project (The GARAH, H2020 grant #731166 lead by GEUS).

How to cite: Lutz, R., Nelskamp, S., Mathiesen, A., Schovsbo, N. H., Ladage, S., and Britze, P.: 3D basin and petroleum system modelling in the North Sea Central Graben - a Dutch, German, Danish cross-border study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7262, https://doi.org/10.5194/egusphere-egu21-7262, 2021.

EGU21-16232 | vPICO presentations | ERE1.2

A European Fault Database as a stepping stone towards improved subsurface evaluation of hazards and resources

Serge Van Gessel, Rob van Ede, Hans Doornenbal, Johan ten Veen, and Esther Hintersberger and the HIKE Team

Faults are prominent features in the subsurface that define the geological development and distribution of geological formations and resources therein. Faults can define resources themselves (e.g. minerals, thermal conduits), but more often they can pose a hazard to subsurface drilling, injection and extraction activities . Well-known examples are Basel – Switzerland (geothermal stimulation), Oklahoma – US (waste water injection) and Groningen – The Netherlands (conventional hydrocarbon extraction).

Despite that faults are a typical product of geological mapping, there was, until now, no consistent insight in these structures in a pan-European context. There are some examples focusing on the publication of seismogenic faults (e.g. GEM Global Active Faults Database, SHARE  European Database of Seismogenic Faults, USGS Quaternary faults database), yet deeply buried faults are under-represented here. With the European fault database, the GeoERA-HIKE project addresses the following objectives: i) develop a consistent and uniform repository for fault data and characteristics across Europe, ii) Implement an associated tectonic vocabulary which provides a framework for future interpretation, modelling and application of fault data, and iii) assess the applicability of fault data in case studies.

The current fault database is envisioned to be a major stepping stone for a sustained and uniform development and dissemination of tectonic data and knowledge which will be applicable to a broad spectrum of subsurface research challenges. The database contains data from Geological Survey Organizations and partners in the Netherlands, Germany, Austria, Belgium, Iceland, Denmark, Poland, Lithuania, Italy, France, Ukraine, Portugal, Slovenia, Albania and various countries in the Pannonian Basin Area.

The GeoERA-HIKE project has received funding from the European Union’s Horizon 2020 research and innovation programme under agreement No. 731166

How to cite: Van Gessel, S., van Ede, R., Doornenbal, H., ten Veen, J., and Hintersberger, E. and the HIKE Team: A European Fault Database as a stepping stone towards improved subsurface evaluation of hazards and resources, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16232, https://doi.org/10.5194/egusphere-egu21-16232, 2021.

EGU21-1218 | vPICO presentations | ERE1.2

GeoConnect³d: transforming geological data into a knowledge system in support of the clean energy transition

Renata Barros, Kris Piessens, and the GeoConnect³d team

The transition towards a clean and low carbon energy system in Europe will increasingly rely on the use of the subsurface. Despite the vastness of subsurface space, only a fraction of it is suitable for the exploitation of geo-resources. The distribution and fitting combination of required conditions is determined by geological processes. We are, therefore, constrained in where we can develop resources and capacities. Moreover, increased subsurface use in a restricted area will inevitably lead to high chances of interferences and conflicts of interest. This means that sound geological information is essential to optimise the subsurface contribution to a safe and efficient energy transition.

Within this scope, the main goal of the GeoConnect³d project is to convert existing geological data into an information system that can be used for various geo-applications, decision-making, and subsurface spatial planning. This is being accomplished through the innovative structural framework model, which reorganises, contextualises, and adds value to geological data. The model is primarily focused on geological limits, or broadly planar structures that separate a given geological unit from its neighbouring units. It also includes geomanifestations, highlighting any distinct local expression of ongoing or past geological processes. These manifestations, or anomalies, often point to specific geologic conditions and, therefore, can be important sources of information to improve geological understanding of an area.

Geological data in this model are composed of spatial data at different scales, with a one-to-one link between geometries and their specific attributes (including uncertainties), and of semantic data, with data organised conceptually and categorised and/or linked using SKOS hierarchical and generic schemes. Concepts and geometries are linked by a one-to-many relationship. The combination of these elements then results in a multi-scale, harmonised and robust model.

The structural framework-geomanifestations methodology has now been applied to different areas in Europe. The focus on geological limits brings various advantages, such as displaying geological information in an explicit, and therefore more understandable, way, and simplifying harmonisation efforts in large-scale geological structures crossing national borders. The link between spatial and semantic data is the essential step adding conceptual definitions and interpretations to geometries. Additionally, geomanifestation data successfully validates or points to inconsistencies in specific areas of the model, which can then be further investigated.

The model demonstrates it is possible to gather existing geological data into a comprehensive knowledge system. We consider this as the way forward towards pan-European integration and harmonisation of geological information. Moreover, we identify the great potential of the structural framework model as a toolbox to communicate geosciences beyond our specialised community. This is an important step to support subsurface spatial planning towards a clean energy transition by making geological information available to all stakeholders involved.

This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731166.

How to cite: Barros, R., Piessens, K., and team, T. G.: GeoConnect³d: transforming geological data into a knowledge system in support of the clean energy transition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1218, https://doi.org/10.5194/egusphere-egu21-1218, 2021.

EGU21-11944 | vPICO presentations | ERE1.2 | Highlight

Introducing digital information products of the four GeoERA groundwater projects for assessment and sustainable use of water resources and the subsurface in a changing climate

Klaus Hinsby, Laurence Gourcy, Hans Peter Broers, Anker Lajer Højberg, Marco Bianchi, and Peter van der Keur

Sustainable evolution of groundwater quantity and quality is essential for sustainable development and protection of society and nature, globally, as acknowledged in the UN sustainable development goals and the European Green Deal. Too much? – too little? – and/or too polluted? are important questions to pose and answer in a changing climate with increasing pressures on water resources, severe loss of biodiversity, and a projected increase in extreme events resulting in an increasing risk of floods, droughts, landslides and land subsidence.   

Easy access to digital and FAIR (Findable, Accessible, Interoperable and reusable) data on groundwater quantity and quality is imperative for informed decision making and efficient climate change mitigation and adaptation to which sustainable groundwater management will contribute. Here we briefly present selected highlights and digital data products from the four GeoERA groundwater projects developed for and made available on the digital subsurface information platform of the European geological survey organizations. The ambition is to develop the digital information platform, EGDI (the European Geological Data Infrastructure) as the leading information platform for sustainable and integrated management of subsurface resources in Europe and one of the leading platforms, globally.

How to cite: Hinsby, K., Gourcy, L., Broers, H. P., Højberg, A. L., Bianchi, M., and van der Keur, P.: Introducing digital information products of the four GeoERA groundwater projects for assessment and sustainable use of water resources and the subsurface in a changing climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11944, https://doi.org/10.5194/egusphere-egu21-11944, 2021.

EGU21-14289 | vPICO presentations | ERE1.2

Towards a European denitrification concept for improved groundwater quality management and chemical status assessment

Laurence Gourcy, Klaus Hinsby, Laerke Thorling, Stephanie Pinson, Matthew Ascott, Hans-Peter Broers, Eline Malcuit, and Christos Christophi

Denitrification potential is an important parameter to know for adequate and efficient management and assessment of groundwater vulnerability and chemical status. Denitrification removes nitrate in groundwater, but the denitrification capacity is highly variable in space and time, and it may be used up with time. When linking pressure and impact the effect of partial or complete denitrification and denitrification capacity should be taken into account. In some areas, denitrification is seen as an advantage, allowing higher N release below soil without leading to a decrease of the groundwater quality and eventually concentrations in groundwater higher than the WFD and DWD threshold values, which EU member states have to establish to protect drinking water and groundwater dependent terrestrial and associated aquatic ecosystems.    

Within the GEOERA HOVER project, the aim was to assess the spatial extent and importance of denitrification. The studied cases permitted at a first step to highlight the heterogeneities of the approaches due to the variability of information obtained i.e. the likelihood of denitrification, depth and thickness of redox transition zone, complete denitrification status. The parameters used to define the denitrification vary also from one country to another based on a large set of redox sensitive ions (Eh, O2, NO3, NO2, Fe, Mn, SO4, CH4, δ18O-NO3 et δ15N-NO3, H2S or N2). Some of these parameters can be accessed by standard methods in most laboratories, used for groundwater quality monitoring, while others require specialized analysis and interpretations.

Considering groundwater and hydrogeological data available in most of the EU countries, a simple method is proposed in order to classify the monitoring points into three classes: oxic, anoxic and mixed. After being tested in different well-known areas the method will be applied in various lithologies and hydrogeological contexts The proposed method will enable the development of European maps supporting groundwater quality management across Europe.

How to cite: Gourcy, L., Hinsby, K., Thorling, L., Pinson, S., Ascott, M., Broers, H.-P., Malcuit, E., and Christophi, C.: Towards a European denitrification concept for improved groundwater quality management and chemical status assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14289, https://doi.org/10.5194/egusphere-egu21-14289, 2021.

Work package 7 of the GeoERA HOVER project deals with groundwater vulnerability assessment to pollution of the shallow upper aquifer. We present vulnerability assessments across Europe applying the DRASTIC method in 11 pilot areas and the COP method for karst systems in 5 pilot areas. The presented assessments are carried out at multiple scales (between 1:1K and 1:250K), pilot areas sizes (catchment to national scale; 15 to 338 000 km²) and hydro-climatic contexts (ranging from extremely high and steady recharge to very low and seasonal recharge). The core item of this presentation is a detailed investigation and statistical assessment on respective data availability, data density and methodologies applied to retrieve input parameters for the assessment (e.g., groundwater recharge) and how this affects the final vulnerability assessments. We also focus on the definition (numerical ranges) of the individual vulnerability classes, which are valid across all pilots.

In an attempt to generate information summarizing affected aquifer volumes, a method based on a lumped index and 2D conceptual cross-sections is proposed. It was originally designed for sea-water intrusion assessments, and has been adapted and applied in some pilot areas to estimate aquifer volumes of each individual vulnerability class.

How to cite: Broda, S. and the HOVER WP7 Team: Multi-scale input data assessment for harmonized index-based aquifer vulnerability evaluations across Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14449, https://doi.org/10.5194/egusphere-egu21-14449, 2021.

EGU21-16210 | vPICO presentations | ERE1.2

Comparing methods to estimate chloride natural background levels to assess sea water intrusion

David Pulido-Velazquez, Leticia Baena-Ruiz, Denitza Voutchkova, Birgitte Hansen, Klaus Hinsby, Georgina Arnó, Victor Camps, Judite Fernandes, Inga Retike, Janis Bikse, Gualbet Oude Essink, Timo Kroon, Joost Delsman, Antonio-Juan Collados-Lara, Ignacio Morel, Juan Antonio Luque, and Juan Grima

In order to assess the anthropogenic impacts on groundwater quality we generally need to identify the natural conditions or Natural background levels (NBLs) within groundwater systems, which are used as references to assess the evolution of the contamination status. This information, in addition to the threshold values (TVs), which are derived from NBLs and based on specific criteria values for legitimate water uses and the environment (terrestrial and aquatic ecosystems), is required to appropriately assess of the chemical status of groundwater in accordance with the European Water Framework Directive and to analyse and propose potential measures where they are required.

In literature, different methodologies are available to assess NBLs and reference TVs for different geochemical substances based on the available measurements of groundwater salinity (e.g. based on probability plots). In this work we analyze and compare three previously proposed methods for derivation of chloride NBLs, which is a conservation solute and is closely related to salt water intrusion in inland and coastal aquifers. We discuss and compare their applicability in pilots located in different settings (southern /northern European / Mediteranean/ North Sea /Baltic Sea) covering different typologies (detrital, karstic, fissured aquifers) and management issues (overexploitation, land use and land cover changes, etc). We perform sensitivity analysis to different constraints applied to remove samples affected by human activity (Nitrate and the brackish saline constraints) in the assessment of NBLs. Finally, based on this analysis, we propose a general approach for derivation of NBLs that could be applied to any of the tested pilots as well as other similar settings in Europe.

 

This research has been partially supported by the SIGLO-AN project (RTI2018-101397-B-I00) from the Spanish Ministry of Science, Innovation and Universities (Programa Estatal de I+D+I orientada a los Retos de la Sociedad).

This work has been partially supported by the GeoE.171.008-TACTIC and GeoE.171.008-HOVER projects from GeoERA organization funded by European Union’s Horizon 2020 research and innovation program.

How to cite: Pulido-Velazquez, D., Baena-Ruiz, L., Voutchkova, D., Hansen, B., Hinsby, K., Arnó, G., Camps, V., Fernandes, J., Retike, I., Bikse, J., Oude Essink, G., Kroon, T., Delsman, J., Collados-Lara, A.-J., Morel, I., Luque, J. A., and Grima, J.: Comparing methods to estimate chloride natural background levels to assess sea water intrusion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16210, https://doi.org/10.5194/egusphere-egu21-16210, 2021.

EGU21-15519 | vPICO presentations | ERE1.2

REY contents in Fe-Mn crusts in Macaronesia: evidence of variation with depth and mineralogy

Egidio Marino, Francisco Javier González, Teresa Medialdea, Luis Somoza, Pedro Ferreira, Thomas Kuhn, Vitor Magalhaes, and Ana Lobato

Bulk mineralogy and geochemistry data of Fe-Mn crusts from seamounts of the Macaronesia region (Canary Islands and Madeira and Azores archipelagos) compiled for the MINDeSEA Database, have been analyzed using statistical tools and related with their location and sampling depth.
Results show that the predominant mineralogy is represented by hydrogenetic Fe-vernadite and goethite, with minor abundance of other Mn-oxides such as buserite, asbolane and todorokite in crusts influenced by early diagenesis. Bulk geochemistry is dominated by Fe and Mn (ranging from 7 to 29 wt. %) with low aluminum-silicate elements (10 wt. % in average) and with significant average contents of several strategic and critical metals like Co, Ni, V, Mo, Te and especially REYs (4700, 2300, 1000, 400, 50 and 2500 µg/g respectively).
Variation of REYs and energy critical element (Co, Mn and Te) contents as a function of water depth and mineralogy are clearly evident in this study. Geochemical and statistical studies (Pearson correlation and factorial analysis with Varimax) reveal that Fe-Mn crusts recovered at water depths just below the oxygen minimum zone (that in this area is located between 300 and 1000 m) at Tropic, Tore, Unicorn and Bimbache seamounts, show an enrichment of all REYs and especially LREEs (Ce is the most enriched element with up to 2900 µg/g). On the other hand, the crusts recollected from the deepest seamounts: Drago, Gaire and MTR (up to 4900 m water depth) show a slightly depletion in all the REYs, especially La and Ce (300 and 1800 µg/g in average respectively). A similar behavior can also be observed for the other energy critical elements where enrichment or depletion is clearly linked to water depth. Additionally, there is a correlation of REY abundance with the mineralogy.  High-resolution studies show that REY are concentrated up to an order of magnitude lower in the diagenetic Mn oxide minerals than in the hydrogenetic phases, possibly due to their high growth rates that don’t allow the concentration of these elements. This work is part of the investigation related to the metallogenetic models for marine minerals developed in the Geo-ERA MINDeSEA1 European project.

[1] This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731166

How to cite: Marino, E., González, F. J., Medialdea, T., Somoza, L., Ferreira, P., Kuhn, T., Magalhaes, V., and Lobato, A.: REY contents in Fe-Mn crusts in Macaronesia: evidence of variation with depth and mineralogy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15519, https://doi.org/10.5194/egusphere-egu21-15519, 2021.

EGU21-15563 | vPICO presentations | ERE1.2

Predicting potential areas for the formation of Co-rich ferromanganese crusts in the Canary Islands Seamount Province using multi-criteria GIS analysis

Ana Lobato, Egidio Marino, Javier González, Teresa Medialdea, and Luis Somoza

Marine ferromanganese crusts are metal-rich chemical sediments showing an increasing economic interest as potential mineral resources for strategic and critical metals. Formation of Fe-Mn crusts is linked to a series of different factors that favor or limit their genesis on the seabed. The objective of this work is the search of areas for potential formation of these deposits, using data obtained in the Canary Islands Seamount Province. The study has been carried out based on multi-criteria analysis, using a Geographic Information System (ArcGis 10.5, Spatial Analysis and Statistical tools). For this purpose, it has been created a cartographic model, which considers data related to depth, seabed substrate nature and age, slope and exposure to marine bottom currents. This model has been applied to non-sampled areas, contrasting them with data derived from the analysis of samples taken in different oceanographic surveys, in order to establish the correct conclusions. This work has been carried out using bathymetric and geological data shared by the Geological Survey of Spain (IGME) with the MINDeSEA [1] and EMODnet-Geology [2] European projects.

[1] This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731166.

[2] EMODNET-Geology project (EASME/EMFF/2018/1.3.1.8-Lot 1/SI2.811048).

How to cite: Lobato, A., Marino, E., González, J., Medialdea, T., and Somoza, L.: Predicting potential areas for the formation of Co-rich ferromanganese crusts in the Canary Islands Seamount Province using multi-criteria GIS analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15563, https://doi.org/10.5194/egusphere-egu21-15563, 2021.

The ROBOMINERS (Resilient Bio-inspired Modular Robotic Miner) project aims at developing new methods and technologies (prototype automation and robotics technology) to locate and exploit underground mineral deposits and is funded under the European Union’s Research and Innovation programme Horizon 2020. The project targets mineral deposits that are generally considered “non-economical” either because they are not accessible anymore for conventional mining techniques, or they have been previously explored but exploitation was considered uneconomic due to the small size of the deposits or the difficulty to access them (abandoned, small, ultra-depth deposits).

 

The European Federation of Geologists (EFG) is part of the Robominers consortium and its role includes the collection of publicly available data at a national level on mineral deposits which are potential targets on the developed mining technology. The Association of Greek Geologists (AGG) is participating as an EFG Linked Third Party in the project aiming, among others, at the creation of a European database of potentially suitable ore deposits for the utilization of the Robominers technology.

 

The creation of an ore deposits’ European database is a crucial procedure for the best possible design of exploration and exploitation applying the Robominers innovative approach. The AGG has contributed in the building of a database at a national level (for Greece), of the major and most important mineral deposits, according to the project requirements. A number of ore deposits in which Robominers advanced technology may provide a unique solution to mineral extraction, include porphyry and epithermal deposits and especially vein-like types, but volcanogenic massive sulphide (VMS-type) and lense-like or layered orthomagmatic deposits can also be of high importance. From the above mentioned ore deposits the most abundant in Greece are epithermal deposits, deposits in hydrothermal veins, porphyry copper, as well as chromites in ophiolite complexes. Regarding the spatial distribution vein-type or metasomatic deposits are located mostly in Northern Greece (Western Macedonia and Thrace regions) while significant variable-mineralization deposits are related with the Attico-Cycladic belt volcanism (mainly Lavrion, Evia, and islands in the Aegean Sea). Finally, PGE bearing chromite deposits and bauxite deposits, located mainly in Central Greece, may also be significant for the project.

 

The establishment of a joined European Robominers database is of great significance for the progress of the project since it will provide essential information on key outputs such as the deposit type and commodities, the host rock, and the spatial distribution of the project’s targeted ore deposits and will provide valuable knowledge regarding the future planning of the exploration and exploitation from the developed Robominers innovative technology approach.

Dr Eleni Koutsopoulou

Coordinator of the project

On Behalf of the:

Association of Greek Geologists

Didotou 26,10680, Athens, Greece

VAT ID: EL-999600130

 

 

How to cite: Koutsopoulou, E., Servou, A., and Aggelopoulos, G.: The ROBOMINERS project: a promising tool for the re-evaluation of “non-economical” deposits. Aiming at the development of a joined European database of potentially suitable ore deposits for the utilization of the Robominers technology., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13158, https://doi.org/10.5194/egusphere-egu21-13158, 2021.

EGU21-14730 | vPICO presentations | ERE1.2

Value assessment of ornamental stone resources

Tom Heldal and Kari Aslaksen Aasly

Throughout Europe, there are large industrial and cultural landscapes originating from the exploitation of ornamental stone through history. Such landscapes may contain a range of potential values; economic, such as future resources and reserves, and non-economic, such as cultural and industrial heritage, areas for recreation and tourism, and geological heritage. Based on case studies in two areas, we will explore different paths and methods for assessing values of ornamental stone resources.

The Iddefjord granite, SE Norway, has been exploited since the middle ages, but the main phase came with the industrial revolution. During the last half of the 19th Century, the granite industry here grew to a considerable size, culminating around the turn of the century when more than 5000 people worked in the quarries, producing paving and building stone. At present time, only one active natural stone quarry remains, but the quality of the granite should encourage further future developments. The study summarizes the geology and evolution of quarrying and quarry technology and provides a characterization of the quarry landscape: its resources that can provide economic values for the future and the anthropogenic morphology of the landscape created by exploitation through history. From the characterization, we propose a scheme for value assessment of the Iddefjord natural stone resource. In particular, we focus the non-economic values. For instance, the importance of the Iddefjord granite as a historic marker in world architecture may provide significant arguments for future designation of exploitation areas.

The Larvik monzonite (larvikite) in SE Norway is composed of varieties of monzonite with a distinct play of colour (chatoyancy), making the stone highly attractive in the global markets. Although use of larvikite goes back to the medieval period, industrial production started in the Late 19th Century and is still large scaled and increasing. This case study investigates the future resources, applying 3D modelling and UNFC. In addition, secondary value chains from the primary ornamental stone production are evaluated.

These case studies are parts of the Eurolithos and Mintel4EU Projects within the GeoEra umbrella, aimed at harmonizing and visualizing information about natural stone resources in Europe.

How to cite: Heldal, T. and Aasly, K. A.: Value assessment of ornamental stone resources, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14730, https://doi.org/10.5194/egusphere-egu21-14730, 2021.

EGU21-15566 | vPICO presentations | ERE1.2

Testing UNFC as a harmonized supporting tool for resource management in Europe

Kari Aasly, Pasi Eil, Frands Schjøth, and Lisbeth Flindt-Jørgensen

With the global increase in raw material demand comes the need for harmonized supporting tools for sustainable resource management in Europe. Europe needs to assess their resource potential, but the European countries do not have a common tool to aggregate information for continent-wide resource inventories. The United Nations Framework Classification for Resources (UNFC) is a system that may be used for this purpose.

One of the specific tasks in the MINTELL4EU project under the GeoERA programme is to test if the European geological surveys will be able to use UNFC as a tool to evaluate a country’s known and potential resources across variable levels of knowledge. The project will also show, if the application of UNFC can provide better harmonization of mineral resource data nationally and across Europe.

The work on UNFC in MINTELL4EU is based on case studies to gain experience. Based on the knowledge and lessons learned from the case studies, guidelines and recommendations for further work will be given. Preliminary results show that there is a need for a more harmonized system and that stricter guidelines are required. On top of this, there are different levels of experience in UNFC among the European geological surveys, and the approach and methods on UNFC varies between the countries.

How to cite: Aasly, K., Eil, P., Schjøth, F., and Flindt-Jørgensen, L.: Testing UNFC as a harmonized supporting tool for resource management in Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15566, https://doi.org/10.5194/egusphere-egu21-15566, 2021.

EGU21-14690 | vPICO presentations | ERE1.2 | Highlight

Collecting, harmonizing and sharing data on European Raw Materials

Lisbeth Flindt Jørgensen, Špela Kumelj, and Teresa Brown

Geological raw materials cover a wide range of materials from sand and gravel over granites and marbles to precious or critical metals and minerals. Man has extracted these materials from the (sub)surface since prehistorical eras, and these indispensable substances have to a very large extent contributed to the evolution of humankind.

In the latest decades, raw materials of economically and strategically importance for society but with high-risks associated with their supply, referred to as Critical Raw Materials (CRMs). To a large extent they form the basis for modern society as they are essential in key industry sectors. In the latest years, access to CRMs is a strategic security question for Europe’s road towards the green transition.

In September 2020, The European Commission launched a new list of CRMs as well as a strategy to enhance Europe’s resilience as most of these substances are sourced from other continents, and as the global competitions is increasing (EC, 2020). Among others, one of the suggested actions in this strategy is to ‘strengthen the sustainable and responsible domestic sourcing ……. in the European Union’. Although Europe has a long tradition of mining and extractive activities, it is acknowledged that there are several challenges to reach a situation with European sourcing of a certain amount of CRMs. Challenges include lack of interest in investment, strict permitting procedures or low levels of public acceptance. Nevertheless, it is recognized that the European geological conditions carry significant potential for CRMs, but more harmonised knowledge across borders is needed. This is where the Geological Survey Organisations of Europe play an important role as they are key partners in collecting and storing information on raw materials at national levels, and in making these available for endusers as policy and decision makers.  

All European countries have a national geological survey organization, some in addition a number of regional surveys. Most host data on raw materials, however, data are typically organized in different ways from one country to another based on different geological traditions and legal commitments. In the GeoERA MINTELL4EU project we build on previous projects as Minerals4EU, ProSUM, SCRREEN, ORAMA, and cooperate with ongoing projects as RESEERVE to collect raw material data in central database and to visualize these data in harmonized way at the European Geological Data Infrastructure (EGDI). Data includes, among other things, the location of individual mineral occurrences, mines, etc. stored in a central database called MIN4EU, and aggregated statistical data at national level on production, trade and reserves etc, compiled in what we know as the electronic Minerals Yearbook. The methods used for collecting (harvesting) and storing data will be discussed, and examples of harmonized visualizations will be shared.

MINTELL4EU is a part of the GeoERA programme supported by European Union's Horizon 2020, grant agreement no. 731166. 

How to cite: Flindt Jørgensen, L., Kumelj, Š., and Brown, T.: Collecting, harmonizing and sharing data on European Raw Materials, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14690, https://doi.org/10.5194/egusphere-egu21-14690, 2021.

EGU21-15047 | vPICO presentations | ERE1.2 | Highlight

GeoERA´s Contribution Towards Resilience in Europe’s Raw Materials Supply Chains

Antje Wittenberg, Daniel P. S. de Oliveira, F. Javier González Sanz, Lisbeth Flindt Jørgensen, and Tom Held

The well-being of society and the interdependencies of national economies depend heavily on reliably functioning supply chains as the COVID-19 pandemic proved this long-known statement in everyone's daily life. None of the supply chains can do without the mostly mineral raw materials. The United Nations sees raw materials as the key component for achieving all 17 Sustainable Development Goals (SDGs). The European Green Deal (COM(2019) 640 final) of the European Union as well as the Paris Agreement cannot be achieved without raw materials. The IPR Global Resources Outlook 2019 [1] foresees an increasing demand for raw materials worldwide regardless of all efforts to further close the raw material cycles. At the same time, the demand for responsible procurement under ethically, socially and ecologically sound conditions is becoming more and more stringent.

The four GeoERA Raw Materials projects EuroLITHOS, FRAME, MINDeSEA and Mintell4EU share expertise, information and focus on European on-shore and off-shore resources as a first step to take our share of responsibility to ensure responsible sourcing from domestic sources [2]. It is among the tasks of the GeoERA raw material projects to know and evaluate in a comparable way the raw materials of the geology under our feet and to visualize these results in accessible databases, maps and publications.

Results will be presented and discussed on the example of selected raw materials that are particularly important for the energy transition to make Europe climate-neutral by 2050.

 

 

How to cite: Wittenberg, A., de Oliveira, D. P. S., González Sanz, F. J., Flindt Jørgensen, L., and Held, T.: GeoERA´s Contribution Towards Resilience in Europe’s Raw Materials Supply Chains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15047, https://doi.org/10.5194/egusphere-egu21-15047, 2021.

EGU21-14652 | vPICO presentations | ERE1.2

GeoERA Information Platform (GIP), geoscientific information from all over Europe in one place.

Jørgen Tulstrup, Andrej Vihtelič, Ángel Prieto Martín, Martin Schiegl, Dana Čápová, and Martin Hansen

ERE1.3 – Carbon emissions/removals estimates under Land use, land-use change and forestry (LULUCF) sector: field measurements, remote sensing and modelling

EGU21-277 | vPICO presentations | ERE1.3

 Implementation of mycorrhizal mechanism into a soil carbon model improves the prediction of long-term processes of plant litter decomposition

Weilin Huang, Peter van Bodegom, Toni Viskari, Jari Liski, and Nadejda Soudzilovskaia

Mycorrhizae, a plant-fungal symbiosis, is an important contributor to below ground-microbial interactions, and hypothesized to play a paramount role in soil carbon (C) sequestration. Ectomycorrhizae (EM) and arbuscular mycorrhizae (AM) are the two dominant forms of mycorrhizae featured by nearly all Earth plant species. However, the difference in the nature of their contributions to the processes of plant litter decomposition is still understood poorly. Current soil carbon models treat mycorrhizal impacts on the processes of soil carbon transformation as a black box. This retards scientific progress in mechanistic understanding of soil C dynamics.

We examined four alternative conceptualizations of the mycorrhizal impact on plant litter C transformations, by integrating AM and EM fungal impacts on litter C pools of different recalcitrance into the soil carbon model Yasso15. The best performing concept featured differential impacts of EM and AM on a combined pool of labile C, being quantitatively distinct from impacts of AM and EM on a pool of recalcitrant C.

Analysis of time dynamics of mycorrhizal impacts on soil C transformations demonstrated that these impacts are larger at the long-term (>2.5yrs) litter decomposition processes, compared to the short-term processes. We detected that arbuscular mycorrhizae controls shorter term decomposition of labile carbon compounds, while ectomycorrhizae dominate the long term decomposition processes of highly recalcitrant carbon elements. Overall, adding our mycorrhizal module into the Yasso model greatly improved the accuracy of the temporal dynamics of carbon sequestration.

A sensitivity analysis of litter decomposition to climate and mycorrhizal factors indicated that ignoring the mycorrhizal impact on the decomposition leads to an overestimation of climate impacts. This suggests that being co-linear with climate impacts, mycorrhizal impacts could be partly hidden within climate factors in soil carbon models, reducing the capability of such models to mechanistically predict impacts of climate vs vegetation change on soil carbon dynamics.

Our results provide a benchmark to mechanistic modelling of microbial impacts on soil C dynamics. This work opens new pathways to examining the impacts of land-use change and climate change on plant-microbial interactions and their role in soil C dynamics, allowing the integration of microbial processes into global vegetation models used for policy decisions on terrestrial carbon monitoring.

How to cite: Huang, W., van Bodegom, P., Viskari, T., Liski, J., and Soudzilovskaia, N.:  Implementation of mycorrhizal mechanism into a soil carbon model improves the prediction of long-term processes of plant litter decomposition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-277, https://doi.org/10.5194/egusphere-egu21-277, 2021.

EGU21-1833 | vPICO presentations | ERE1.3

Enhancement of soil organic carbon storage and aggregation following cropland afforestation

Chih-Hsin Cheng, Pei-Chen Lee, and Xiao-Yi Fang

The cropland afforestation policy was initiated in 2002 in Taiwan and had been approaching the 20-year term. From the scientific perspective, it is a critical issue to understand the public welfare role and ecosystem services provided by the cropland afforestation. In this study, we investigated the changes of soil organic carbon (SOC) on plantations after 14 years conversion from the sugarcane fields. Soil samples were collected at 0-10 and 10-20 cm depth. Soil organic C concentration, bulk density, soil aggregation, and the stable isotopic 13C of the SOC and aggregates were determined. The results indicated the SOC stocks on the afforested plots were between 1000 and 1500 g m-2 significantly higher than those under the sugarcane plots (p < 0.05). The analyses of stable 13C indicated that the net increases in SOC stocks on the afforested plots were mainly attributed to the inputs of the forest-derived SOC that outweighed the loss of sugarcane-derived SOC. The afforestation also enhanced the aggregation with higher stability and SOC concentration. The comparatively depleted 13C values in the stable macroaggregates further suggested the ecological function from this new SOC source. Combining with the stand development and aboveground biomass accumulation, we expected the cropland afforestation would provide ecosystem services and functions.

How to cite: Cheng, C.-H., Lee, P.-C., and Fang, X.-Y.: Enhancement of soil organic carbon storage and aggregation following cropland afforestation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1833, https://doi.org/10.5194/egusphere-egu21-1833, 2021.

EGU21-8483 | vPICO presentations | ERE1.3

Greenhouse gas exchange of young rewetted swamp in northern Netherlands

Bart Kruijt, Hanne Berghuis, Jan Biermann, Wilma Jans, Wietse Franssen, Ed Nijhof, Ad Peltenburg, Rien Lettink, Cor Jacobs, Ronald Hutjes, and Jeroen Veraart

There are many initiatives to re-wet drained nature or former agricultural land. These young wetlands provide a natural habitat for a range of endangered species, while serving as a natural climate buffer by retaining water, regulating air temperature, and sequestering CO2 from the atmosphere. However, wetlands may also emit CH4, which has a global warming potential (GWP) of about 30. Thus, all carbon fluxes need to be quantified in order to assess if, from a climate perspective, CO2 uptake outweighs CH4 emission.

To assess the net effect of young wetlands on Greenhouse Gas exchange, we study the CO2 and CH4 fluxes of two recently rewetted areas near Groningen, the Netherlands. The fluxes are measured directly using the Eddy Covariance (EC) technique on a moveable station, alternating between the two sites. Meteorological observations are performed at these stations as well, along with other supportive measurements such as soil/water temperature. The alternating time gaps are filled by interpolation based on observed ecosystem responses. Footprint analysis provides insight into the role of various vegetation types inside these swamps. The resulting carbon budgets provide insight into GHG exchange over typically small temporal and spatial scales.

The study also examines the feasibility of these moveable stations, as they may reduce the relatively high research costs of EC measurements. The data from moveable stations is reliable if the data is regular, as the time gaps are filled by interpolation. At this stage, the timeseries is too short to draw any conclusions upon the reliability of the data. However, the moveable stations appear to be feasible from a practical point of view, as the station can be relocated relatively easy within the time span of a day.

The first results suggest both substantial CO2 uptake and CH4 emissions but a full year of data was not collected yet. Observed exchange compares well to similar studies previously performed.  

Ultimately, annual budgets of the carbon exchange response will be correlated to weather conditions but also to hydrological measures such as water levels. This should allow extrapolation of the data, which may serve as a basis for policy makers to manage the carbon balance when re-wetting nature to achieve net mitigation of greenhouse warming potential.

How to cite: Kruijt, B., Berghuis, H., Biermann, J., Jans, W., Franssen, W., Nijhof, E., Peltenburg, A., Lettink, R., Jacobs, C., Hutjes, R., and Veraart, J.: Greenhouse gas exchange of young rewetted swamp in northern Netherlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8483, https://doi.org/10.5194/egusphere-egu21-8483, 2021.

EGU21-10977 | vPICO presentations | ERE1.3

Soil carbon balance in Hungarian crop rotation systems

Giulia De Luca, János Balogh, Krisztina Pintér, Szilvia Fóti, Meryem Bouteldja, Insaf Malek, and Zoltán Nagy

Although characteristics of the carbon balance and the organic carbon stock changes of arable lands have been the primary research focus of numerous studies, uncertainity is still a major factor in this area of research. Our aim is to determine the dynamics of carbon cycling in croplands in regards to a crop rotation consisting of different crop types and to clarify the factors driving the carbon fluxes between its main components.

A field-scale eddy covariance (EC) station was established in 2017 at a cropland site in Central Hungary in order to obtain the cropland’s annual net ecosystem exchange of CO2 (NEE). Net ecosystem carbon budget (NECB) was calculated considering vertical and lateral C fluxes as well. Soil management is a conventional management with yearly deep ploughing and mineral fertilizer application.

During the three years of our experiment the crop rotation included winter wheat, winter rapeseed, sorghum and winter wheat. The largest net CO2 uptake was observed during the sorghum season (from sowing to harvest, -309 g C m-2 yr-1). However, extreme autumnal drought resulted in the incomplete germination of rapeseed in 2018, which led to carbon loss (108 g C m-2 yr-1) during this vegetation period. Results show a significant difference between the two winter wheat seasons – sown in 2017 and 2019 – which can be explained by the differing precipitation of the two periods. Despite the strong CO2 uptake of winter wheat and sorghum, NECB ranged between negligible C gain (-18.26 g C m-2 year-1, sorghum) to C losses of up to 108 g C m-2 year-1 (rapeseed). During three years the C loss was 420 g C m-2 as C export through harvest and fallow periods counterbalanced the crops’ CO2 uptake.

As a conclusion we can state this cropland could not sequester enough carbon to maintain the soil organic carbon pool and in order to reduce the risk of the depletion of soil carbon stock further efforts are needed in the field of soil management practices.

How to cite: De Luca, G., Balogh, J., Pintér, K., Fóti, S., Bouteldja, M., Malek, I., and Nagy, Z.: Soil carbon balance in Hungarian crop rotation systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10977, https://doi.org/10.5194/egusphere-egu21-10977, 2021.

EGU21-15734 | vPICO presentations | ERE1.3

Soil respiration under different agricultural land use types in Croatia

Darija Bilandžija, Marija Galić, and Željka Zgorelec

In order to mitigate climate change and reduce the anthropogenic greenhouse gas (GHG) emissions, the Kyoto protocol has been adopted in 1997 and the Paris Agreement entered into force in 2016. The Paris Agreement have ratified 190 out of 197 Parties of the United Nations Framework Convention on Climate Change (UNFCCC) and Croatia is one of them as well. Each Party has obliged regularly to submit the national inventory report (NIR) providing the information on the national anthropogenic GHG emissions by sources and removals by sinks to the UNFCCC. Reporting under the NIR is divided into six categories / sectors, and one of them is land use, land use change and forestry (LULUCF) sector, where an issue of uncertainty estimates on carbon emissions and removals occurs. As soil respiration represents the second-largest terrestrial carbon flux, the national studies on soil respiration can reduce the uncertainty and improve the estimation of country-level carbon fluxes. Due to the omission of national data, the members of the University of Zagreb Faculty of Agriculture, Department of General Agronomy have started to study soil respiration rates in 2012, and since then many different studies on soil respiration under different agricultural land uses (i.e. annual crops, energy crop and vineyard), management practices (i.e. tillage and fertilization) and climate conditions (i.e. continental and mediterranean) in Croatia have been conducted. The obtained site specific results on field measurements of soil carbon dioxide concentrations by in situ closed static chamber method will be presented in this paper.

How to cite: Bilandžija, D., Galić, M., and Zgorelec, Ž.: Soil respiration under different agricultural land use types in Croatia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15734, https://doi.org/10.5194/egusphere-egu21-15734, 2021.

Since an increasing number of global gross primary productivity (GPP) products have become available and been applied in climate change research, there is an urgent need to compare their performance in capturing spatial and temporal variability, especially in the regions where the number of training data is limited or model parameters are of relatively larger uncertainty. Here, we investigated the spatial patterns of interannual trends and variations, and seasonal-cycle amplitudes of GPP in the arctic and boreal zones, and explored the differences across various GPP products during the overlapping period (2000−2010). We compared three main types of state-of-the-art GPP products, including simulations derived from terrestrial biosphere models of the Multi-scale Synthesis and Terrestrial Model Intercomparison Project using drivers under different scenarios, 3 datasets up-scaled from FLUXNET eddy covariance measurements based on machine-learning algorithms, and 2 semi-empirical or empirical remotely sensed products based on different satellite data. We also examined the differences of GPP variability across the main ecosystem types, mainly including tundra and taiga, and assessed the contributions of different ecosystems to the temporal variations of total GPP in this zone. The results showed all the products could capture the interannual and seasonal variability of GPP, but the spatial patterns varied largely, which was in-deep discussed. This study will benefit the usage of the GPP products in the carbon cycle research for the arctic and boreal ecosystems.

How to cite: Huang, Y., Yu, Z., Hu, L., and Yao, W.: Assessment of spatiotemporal patterns of gross primary productivity in the arctic and boreal ecosystems using multi-source products, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10824, https://doi.org/10.5194/egusphere-egu21-10824, 2021.

EGU21-3641 | vPICO presentations | ERE1.3

Modelling carbon fluxes from New Zealand’s pastoral agriculture

Elizabeth Keller, Scott Graham, John Hunt, Aaron Wall, Louis Schipper, Andrew McMillan, Dora Hidy, Zoltán Barcza, Beata Bukosa, and Sara Mikaloff-Fletcher

Grasslands cover half of New Zealand’s land area, with much of it consisting of pastoral agriculture systems of varying intensity. Carbon fluxes from grazed pasture are thus a crucial part of the national carbon budget. We have used Biome-BGCMuSo v6 to model national CO2 fluxes from grasslands, calibrated with eddy covariance measurements at grazed farms at various sites around the country. We discuss the challenges of scaling up site measurements to the national level and modelling the diversity of New Zealand's pastoral sector. Model outputs will subsequently be used as a prior estimate of CO2 fluxes in an atmospheric inversion to obtain a total carbon budget for New Zealand as part of the CarbonWatch-NZ project.

How to cite: Keller, E., Graham, S., Hunt, J., Wall, A., Schipper, L., McMillan, A., Hidy, D., Barcza, Z., Bukosa, B., and Mikaloff-Fletcher, S.: Modelling carbon fluxes from New Zealand’s pastoral agriculture, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3641, https://doi.org/10.5194/egusphere-egu21-3641, 2021.

EGU21-10889 | vPICO presentations | ERE1.3

Can we reach a sensible balance between generality of model parameters and accuracy of simulations?

Katarina Merganicova, Laura Dobor, Roland Hollos, Ján Merganič, Zoltán Barcza, Daniel Kurjak, Jiri Novák, Zuzana Sitková, Peter Fleischer, Hrvoje Marjanovic, Dóra Hidy, Katarína Střelcová, and Tomáš Hlásny

Process-based ecosystem models are versatile tools providing profound insights into ecosystem processes and interactions between vegetation and environment. The ongoing development of the Biome-BGCMuSo model has delivered multiple improvements in model structure and parameters, and subsequently in simulated ecosystem dynamics. Since the number of parameters has increased during the model development, model parametrisation for biomes or tree species of interest is required to enable reliable model usage in the future.

Here we explore the issue of site-specific versus multi-site calibration of model parameters for the European beech (Fagus sylvatica L.) along an extended environmental gradient across Central Europe, covering Croatia, Hungary, Slovakia, Poland and the Czech Republic. First, thorough literature search for the plausible ranges of individual model parameters was conducted. This was followed by the sensitivity analysis to identify the most influential model parameters. Finally, model calibration was performed based on the generalised likelihood uncertainty estimation method and the data from long-term research plots located in the five countries. The calibration was conducted at levels of individual sites and the region as a whole to evaluate different aspects of site-specific and multi-site calibration approaches and to develop a generalised parameter set for the European beech in Central Europe.

How to cite: Merganicova, K., Dobor, L., Hollos, R., Merganič, J., Barcza, Z., Kurjak, D., Novák, J., Sitková, Z., Fleischer, P., Marjanovic, H., Hidy, D., Střelcová, K., and Hlásny, T.: Can we reach a sensible balance between generality of model parameters and accuracy of simulations?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10889, https://doi.org/10.5194/egusphere-egu21-10889, 2021.

EGU21-9837 | vPICO presentations | ERE1.3

Spatio-temporal comparison of different approaches to derive land use and land cover change emissions by models

Wolfgang Obermeier and the LASC task-force

The quantification of the net carbon flux from land use and land cover changes (fLULCC) is essential to understand the global carbon cycle, and consequently, to support climate change mitigation. However, large-scale fLULCC is not directly measurable, and can only be inferred by models, such as semi-empirical bookkeeping models, and process-based dynamic global vegetation models (DGVMs). By definition, fLULCC estimates between these two model types are not directly comparable. For example, transient DGVM-based fLULCC of the annual global carbon budget includes the so-called Loss of Additional Sink Capacity (LASC). The latter accounts for environmental impacts on the land carbon storage capacities of managed land compared to potential vegetation which is not included in bookkeeping models. Additionally, estimates of transient DGVM-based fLULCC differ from bookkeeping model estimates, since they depend on arbitrarily chosen simulation time periods and the timing of land use and land cover changes within the historic period (which includes different accumulation periods for legacy effects). However, DGVMs enable a fLULCC approximation independent of the timing of land use and land cover changes and their legacy effects by simulations run under constant pre-industrial or present-day environmental forcings.

In this study, we analyze these different DGVM-derived fLULCC definitions, under transiently changing environmental conditions and fixed pre-industrial and fixed present-day conditions, within 18 regions for twelve DGVMs and quantify their differences as well as climate- and CO2-induced components. The multi model mean under transient conditions reveals a global fLULCC of 2.0±0.6 PgC yr-1 for 2009-2018, with ~40% stemming from the LASC (0.8±0.3 PgC yr-1). Within the industrial period (1850 onward), cumulative fLULCC reached 189±56 PgC with 40±15 PgC from the LASC.

Regional hotspots of high LASC values exist in the USA, China, Brazil, Equatorial Africa and Southeast Asia, which we mainly relate to deforestation for cropland. Distinct negative LASC estimates were observed in Europe (early reforestation) and from 2000 onward in the Ukraine (recultivation of post-Soviet abandoned agricultural land). Negative LASC estimates indicate that fLULCC estimates in these regions are lower in transient DGVM simulations compared to bookkeeping-approaches. By unraveling the spatio-temporal variability of the different DGVM-derived fLULCC estimates, our study calls for a harmonized attribution of model-derived fLULCC. We propose an approach that bridges bookkeeping and DGVM approaches for fLULCC estimation by adopting a mean DGVM-ensemble LASC for a defined reference period.

How to cite: Obermeier, W. and the LASC task-force: Spatio-temporal comparison of different approaches to derive land use and land cover change emissions by models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9837, https://doi.org/10.5194/egusphere-egu21-9837, 2021.

EGU21-3065 | vPICO presentations | ERE1.3

Assessment of land use and land cover datasets for Brazil and impact on C emissions

Thais M. Rosan, Kees Klein Goldewijk, Raphael Ganzenmüller, Michael O'Sullivan, Julia Pongratz, Lina M. Mercado, Luiz E. O. C. Aragao, Viola Heinrich, Celso Von Randow, Andrew Wiltshire, Francesco N. Tubiello, Ana Bastos, Pierre Friedlingstein, and Stephen Sitch

Brazil is responsible for about one third of the global land use and land cover change (LULCC) carbon dioxide emissions. However, there is a disagreement among different methodologies on the magnitude and trends in emissions and their geographic distribution. One of the main uncertainties is associated with different LULCC datatasets used as input in the different approaches. In this work we perform an evaluation of LULCC datasets for Brazil, including the global dataset (HYDE 3.2) used in the annual Global Carbon Budget (GCB), and national Brazilian dataset (MapBiomas) over the period 2000-2018. We also analyze the latest global HYDE 3.3 dataset based on new FAO inventory estimates and multi-annual ESA CCI satellite-based land cover maps. Results show that the new HYDE 3.3 can represent well the observed spatial variation in cropland and pastures areas over the last decades compared to national data (MapBiomas) and shows an improvement compared to HYDE 3.2 used in GCB. However, the magnitude of LULCC assessed with HYDE 3.3 is lower than national estimates from MapBiomas. Finally, we used HYDE 3.3 as input to two different approaches included in GCB, a global bookkeeping model (BLUE) and a process-based Dynamic Global Vegetation Model (JULES-ES) to determine the impact of the new version of HYDE dataset on Brazil’s land-use emissions trends over the period 2000-2017. Both JULES-ES and BLUE now simulate a negative land-use emissions trend for the last two decades. This negative trend is in agreement with Brazilian INPE-EM, global H&N bookkeeping models, FAO and as reported in National GHG inventories (NGHGI), although magnitudes differ among approaches. Overall, the inclusion of the multi-annual ESA CCI Land Cover dataset to allocate spatially the FAO statistical data has improved spatial representation of agricultural area change in Brazil in the last two decades, contributing to improve global model capability to simulate Brazil’s LULCC emissions in agreement with national trends estimates and spatial distribution.

How to cite: Rosan, T. M., Goldewijk, K. K., Ganzenmüller, R., O'Sullivan, M., Pongratz, J., Mercado, L. M., Aragao, L. E. O. C., Heinrich, V., Von Randow, C., Wiltshire, A., Tubiello, F. N., Bastos, A., Friedlingstein, P., and Sitch, S.: Assessment of land use and land cover datasets for Brazil and impact on C emissions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3065, https://doi.org/10.5194/egusphere-egu21-3065, 2021.

EGU21-15126 | vPICO presentations | ERE1.3

A Bayesian data assimilation approach to estimating land-use change

Peter E. Levy

The aim of this work was to make improved estimates of land-use change in the UK, using multiple sources of data. We applied a method for estimating land-use change using a Bayesian data assimilation approach. This allows us to constrain estimates of gross land-use change with national-scale census data, whilst retaining the detailed information available from several other sources. We produced a time series of maps describing our best estimate of land-use change given the available data, as well as the full posterior distribution of this space-time data cube. This quantifies the joint probability distribution of the parameters, and properly propagates the uncertainty from input data to final output. The output data has been summarised in the form of land-use vectors. The results show that we can provide improved estimates of past land-use change using this method. The main advantage of the approach is that it provides a coherent, generalised framework for combining multiple disparate sources of data, and adding further sources of data in future is straightforward.

How to cite: Levy, P. E.: A Bayesian data assimilation approach to estimating land-use change, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15126, https://doi.org/10.5194/egusphere-egu21-15126, 2021.

EGU21-16400 | vPICO presentations | ERE1.3

Monitoring changes in carbon pools matched to land use and land-use change based on field sampling measurements

Hans Petersson, Johannes Breidenbach, David Ellison, Mattias Lundblad, and Alex Appiah Mensah

Changes in carbon pools, land use and land-use change can be monitored based on field inventoried sampling units without using maps or remote sensing products. One way is to use a sampling framework. The framework can be based on a map, but the map does not necessarily need to be used for improving the estimates. The map can consist of a Member state’s total land and freshwater area. The sampling units can be distributed using a systematic grid with randomized location in the framework. A permanent design (the same sample units are re-inventoried in a periodic cycle) has been proven efficient when estimating change. Stratification into assumed homogenous strata is another way to further improve the accuracy of estimates. The distribution of sampling units can be spatially explicit (geo-referenced) in the sense that their locations are identified using GPS. This, combined with the permanent design, makes it possible to estimate both gross and net land use transfers in order to provide a land use matrix. The area-based sampling combined with the Horvitz and Thompson-estimator, makes a sampling unit representative of a certain area and all sample units together comprise the total land and freshwater area. This design makes it possible to match changes in carbon pools to land use and land-use change and to trace them back in time. 

We present a monitoring design based on the Swedish NFI and adapted to reporting under the UNFCCC/KP frameworks or the EU-regulation. Pros and cons are discussed and we compare with alternative designs (combining ground truth with remote sensing). Finally, we assess the accuracy of estimates of selected variables (sample and model errors).

How to cite: Petersson, H., Breidenbach, J., Ellison, D., Lundblad, M., and Appiah Mensah, A.: Monitoring changes in carbon pools matched to land use and land-use change based on field sampling measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16400, https://doi.org/10.5194/egusphere-egu21-16400, 2021.

EGU21-11217 | vPICO presentations | ERE1.3

New estimate of growing stock volume and carbon sequestration of Russian forests based on national forest inventory and remote sensing data

Dmitry Schepaschenko, Elena Moltchanova, Stanislav Fedorov, Victor Karminov, Petr Ontikov, Maurizio Santoro, Linda See, Vladimir Kositsyn, Anatoly Shvidenko, Anna Romanovskaya, Vladimir Korotkov, Sergey Bartalev, Steffen Fritz, Maria Shchepashchenko, and Florian Kraxner

Since the collapse of the Soviet Union and transition to a new forest inventory system, Russia has reported (FAO, 2014) almost no changes in growing stock (+1.8%) and biomass (+0.6%). Yet remote sensing products indicate increased vegetation productivity (Guay et al., 2014), tree cover (Song et al., 2018) and above-ground biomass (Liu et al., 2015). Here, we challenge the official national statistics with a combination of recent National Forest Inventory and remote sensing data products to provide an alternative estimate of the growing stock of Russian forests and assess the relative changes in the post-Soviet era. Our estimate for the year 2014 is 118.29±1.3 109 m3, which is 48% higher than the official value reported for the same year in the State Forest Register. The difference is explained by increased biomass density in forested areas (+39%) and larger forest area estimates (+9%). Using the last Soviet Union report (1988) as a reference, Russian forests have accumulated 1163×106 m3 yr-1 of growing stock between 1988–2014, which compensates for forest growing stock losses in tropical countries (FAO FRA, 2015). Our estimate of the growing stock of managed forests is 94.2 109 m3, which corresponds to sequestration of 354 Tg C yr-1 in live biomass over 1988–2014, or 47% higher than reported in the National Greenhouse Gases Inventory (National Inventory Report, 2020).

Acknowledgement: The research plots data collection was performed within the framework of the state assignment of the Center for Forest Ecology and Productivity of the Russian Academy of Sciences (no. АААА-А18-118052590019-7), and the ground data pre-processing were financially supported by the Russian Science Foundation (project no. 19-77-30015).

How to cite: Schepaschenko, D., Moltchanova, E., Fedorov, S., Karminov, V., Ontikov, P., Santoro, M., See, L., Kositsyn, V., Shvidenko, A., Romanovskaya, A., Korotkov, V., Bartalev, S., Fritz, S., Shchepashchenko, M., and Kraxner, F.: New estimate of growing stock volume and carbon sequestration of Russian forests based on national forest inventory and remote sensing data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11217, https://doi.org/10.5194/egusphere-egu21-11217, 2021.

EGU21-13243 | vPICO presentations | ERE1.3

No “Abrupt increase in harvested forest area over Europe after 2015” – How the misuse of a satellite-based map led to completely wrong conclusions

Johannes Breidenbach, David Ellison, Hans Petersson, Kari Korhonen, Helena Henttonen, Jörgen Wallerman, Jonas Fridman, Terje Gobakken, Rasmus Astrup, and Erik Næsset

In a recent Nature article, the satellite-based Global Forest Change (GFC) map was used to estimate the yearly harvest area in each of the EU26-states over the period 2004 to 2018 (Ceccherini et al. 2020). Finland and Sweden were identified as the countries with the largest harvest increases and the biggest effect on the EU’s climate policy strategy. Here, we employ more than 45,000 field observations from the Finnish and Swedish national forest inventories as reference observations to analyze the accuracy of GFC data. We find that harvested area increases only marginally, if at all, after 2015. What did increase abruptly after 2015, however, was GFC’s sensitivity to detect harvested areas and thinnings.

The results of the Nature article are therefore a consequence of an inconsistent time series in GFC due to a change in the mapping algorithm or the sensor system and are thus both incorrect and misleading. The article is thus a good example for how wrong results based on satellite data can be, if no adequate estimators utilizing reference data are used.

 

References

Ceccherini, G. et al. Abrupt increase in harvested forest area over Europe after 2015. Nature 583, 72-77 (2020).

How to cite: Breidenbach, J., Ellison, D., Petersson, H., Korhonen, K., Henttonen, H., Wallerman, J., Fridman, J., Gobakken, T., Astrup, R., and Næsset, E.: No “Abrupt increase in harvested forest area over Europe after 2015” – How the misuse of a satellite-based map led to completely wrong conclusions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13243, https://doi.org/10.5194/egusphere-egu21-13243, 2021.

EGU21-16261 | vPICO presentations | ERE1.3

Reversing the European Trend Toward a Declining Land Carbon Sink?

David Ellison, Johannes Breidenbach, Hans Petersson, Kari T. Korhonen, Helena Henttonen, Jörgen Wallerman, Jonas Fridman, Alex Appiah Mensah, Terje Gobakken, and Erik Naesset

The announced goal of reversing the European trend toward a declining land carbon sink has garnered much ink. Words can, however, be misleading. Annual additions/contributions (sinks) to the land carbon sink (stocks) from growing forest and increasing forest cover have slowed marginally in recent years. However, the existing European land forest sink (stocks) has (have) expanded continuously across most or all of the 20th century and on into the 21st. More importantly perhaps, EU Member states with significant long-term investments in the forestry sector have historically witnessed strong forest expansion and notmerely with the initiation of international attention to climate change mitigation through the UNFCCC negotiating and climate commitment framework. In this context, frequent assaults on forestry from multiple directions are cause for some bewilderment. We first highlight weaknesses in claims of increased forest use intensity and illustrate that forestry in the Nordic countries has a remarkably small and stable footprint over the 20th and 21st centuries. Addressing the second problem, however, understanding why such attacks occur in the first place, is more complex. Methodologically speaking, challenges to forestry should presumably be balanced by an understanding of the many human welfare benefits forests and the practice of forestry currently provide, as well as the costs of relinquishing those practices. Perhaps due to strong preferences among NGO’s and in parts of the academic community for natural, untouched, biodiverse forests, the benefits of forestry and forest resource use are consistently under-appreciated. Striking a balance between the desire for natural and biodiverse-rich forest environments on the one hand, and the climate change mitigation (and adaptation) benefits of forestry, forest resource use and substitution on the other is presumably a political and socio-economic necessity. The real question may be to what extent bias in favor of the “natural” may ultimately disrupt real, measurable progress toward effective climate change mitigation? Continuous, positive mitigation-related contributions to the growing European land cover sink (stocks), as well as to the global carbon budget (through annual net removals and substitution), have been and should remain the norm. These goals ultimately require an aggressive EU LULUCF strategy capable of fully mobilizing forest and forest resource use in favor of the goal of climate change mitigation (and adaptation).

How to cite: Ellison, D., Breidenbach, J., Petersson, H., Korhonen, K. T., Henttonen, H., Wallerman, J., Fridman, J., Mensah, A. A., Gobakken, T., and Naesset, E.: Reversing the European Trend Toward a Declining Land Carbon Sink?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16261, https://doi.org/10.5194/egusphere-egu21-16261, 2021.

EGU21-16472 | vPICO presentations | ERE1.3

On the Role of Forestry in Climate Change Mitigation

Alex Appiah Mensah, Hans Petersson, Göran Berndes, Gustaf Egnell, David Ellison, Mattias Lundblad, Tomas Lundmark, Anders Lundström, Johan Stendahl, and Per-Erik Wikberg

Long-standing debates over the benefits of forest conservation vs. those of substitution and forest resource use continue to occupy attention in Europe and beyond. Moreover, many argue the carbon sequestration benefits of standing forest are greater than those from forest resource use and replanting. To study this question, we generate long-term scenario analyses based on different forest management strategies in Sweden, in particular comparing increasing forest use and increasing land set-asides over 100, 200 and 500 year cycles. We find that the cost of increasing land set-asides is reflected in a significant loss of the carbon benefits created by forest use (substitution and carbon sequestration). We explain this outcome through the loss of additional growth that occurs as forest in land set-asides matures and eventually reaches a steady state. For the Swedish forest, these costs are significant and may amount to the loss (lost opportunity) of annually providing and additional -14 MtCO2e in net annual removals. The EU-based LULUCF carbon accounting framework, however, does not recognize this benefit and thus may effectively encourage land set-asides at the expense of real, measurable forest and forest resource-based climate change mitigation.

How to cite: Appiah Mensah, A., Petersson, H., Berndes, G., Egnell, G., Ellison, D., Lundblad, M., Lundmark, T., Lundström, A., Stendahl, J., and Wikberg, P.-E.: On the Role of Forestry in Climate Change Mitigation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16472, https://doi.org/10.5194/egusphere-egu21-16472, 2021.

EGU21-13486 | vPICO presentations | ERE1.3

The effect of harvesting on national forest carbon sinks up to 2050 simulated by the CBM-CFS3 model: a case study from Slovenia

Bostjan Mali, Jernej Jevsenak, and Matija Klopcic

With the advent of global warming, forests are becoming an increasingly important carbon sink that can mitigate the negative effects of climate change. An understanding of the carbon dynamics of forests is, therefore, crucial to implement appropriate forest management strategies and to meet the expectations of the Paris Agreement with respect to international reporting schemes. One of the most frequently used models for simulating the dynamics of carbon stocks in forests is the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). We applied this model in our study to evaluate the effects of harvesting on the carbon sink dynamics in Slovenian forests. Five harvesting scenarios were defined: (1) business as usual (BAU), (2) harvesting in line with current forest management plans (PLAN), (3) more frequent natural hazards (HAZ), (4) high harvest (HH) and (5) low harvest (LH). The simulated forest carbon dynamics revealed important differences between the harvesting scenarios. Relative to the base year of 2014, by 2050 the carbon stock in above-ground biomass is projected to increase by 28.4% (LH), 19% (BAU), 10% (PLAN), 6.5% (HAZ) and 1.2% (HH). Slovenian forests can be expected to be a carbon sink until harvesting exceeds approximately 9 million m3 annually, which is close to the calculated total annual volume increase. Our results are also important in terms of Forest Reference Levels (FRL), which will take place in European Union (EU) member states in the period 2021-2025. For Slovenia, the FRL was set to –3270.2 Gg CO2 eq/year, meaning that the total timber harvested should not exceed 6 million m3 annually.

How to cite: Mali, B., Jevsenak, J., and Klopcic, M.: The effect of harvesting on national forest carbon sinks up to 2050 simulated by the CBM-CFS3 model: a case study from Slovenia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13486, https://doi.org/10.5194/egusphere-egu21-13486, 2021.

ERE1.4 – Impacts and co-benefits of the energy transition on terrestrial ecosystems – implications and prospects for Natural Capital and Ecosystem Services

EGU21-13670 | vPICO presentations | ERE1.4

Opportunities for renewable energy in regenerative development

Sarah Klain and Lauren Tango

Various philanthropic, development and agricultural organizations have begun to prioritize regenerative development, which aims to reverse ecological degradation while generating benefits, including ecosystem services, for people and biodiversity. These efforts aim to transcend sustainable development, which aims to minimize harm to the environment and human health. Here, we review the literature on ways in which renewable energy infrastructure could play important roles in regenerative development initiatives, e.g., offshore wind projects designed with artificial reef structures, photovoltaic (PV) projects accompanied with pollinator plantings, and agrivoltaics that combine crops with PV. We also identify anticipated challenges to such development, e.g., potentially larger land area requirements and higher costs than typical renewable energy development. Lastly, we provide recommendations on policies and practices that could strengthen the role of renewable energy in regenerative development.

How to cite: Klain, S. and Tango, L.: Opportunities for renewable energy in regenerative development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13670, https://doi.org/10.5194/egusphere-egu21-13670, 2021.

EGU21-6129 | vPICO presentations | ERE1.4

A life cycle perspective on the land use and ecosystem services of energy transitions

Sarah Jordaan

EGU21-13887 | vPICO presentations | ERE1.4

Integrating wind energy forecasting and species population models to consider trade offs in a lower carbon future. 

Jay Diffendorfer, Anthony Lopez, Wayne Thogmartin, Trieu Mai, Bethany Straw, Brad Udell, and Asthon Wiens

Renewable energy has crossed key technological hurdles related to costs and energy system stability yet impacts to wildlife may present a long-term challenge to the development and operation of renewables.  We describe a number of approaches to address interdisciplinary questions related to enhancing renewable energy development while minimizing unintended consequences to wildlife and habitat.  These approaches range from relatively simple geospatial models and Monte Carlo simulations to more sophisticated integration of spatially explicit techno-economic/physics wind energy forecasting models with bat population models. We present results from demographic models estimating impacts from future wind energy development, how including geographic constraints related to conserving natural capitol and ecosystem services may impact wind energy development and costs, and early work on temporally dynamic integration of energy and population models. We then summarize a few broader ideas on integrated modelling related to ecosystem services and energy systems. 

How to cite: Diffendorfer, J., Lopez, A., Thogmartin, W., Mai, T., Straw, B., Udell, B., and Wiens, A.: Integrating wind energy forecasting and species population models to consider trade offs in a lower carbon future. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13887, https://doi.org/10.5194/egusphere-egu21-13887, 2021.

EGU21-768 | vPICO presentations | ERE1.4

Wind turbine operation influences near surface air temperature and humidity

Gang Wang, Guoqing Li, and Alona Armstrong

Surface meteorology regulates ecosystem processes, with implications for the supply of important ecosystem services. Wind farms have been shown to alter the local climate, but there have been limited field measurements of the variability of impact in different directions relative to the find farm. In addition, the influence of land coverage variability on atmosphere temperature and humidity has not been eliminated, which will lead to the impact of wind turbines on atmosphere temperature and humidity may be over topped or underestimated. Here, we show the impact of Huitengliang wind power base, China, on air temperature and humidity using data from five automatic meteorological monitoring stations. After eliminating the influences of land surface coverage as much as possible, by comparing the variability of temperature and humidity inside the wind farm, and in the upwind, downwind and side wind directions, daily and seasonal variations in temperature and humidity were obtained. We found that wind turbines increase the temperature and decrease the humidity of the surface atmosphere, the influences are more obvious than the existing results. Particularly, these effects are most obvious in the upwind and downwind directions. The annual average temperature rise was 0.97 °C in the upwind direction and 1.25 °C in the downwind direction. On average throughout the year, humidity decreased by 3.71 % in the upwind direction and 5.66 % in the downwind direction. The magnitudes of these effects are sufficient to alter ecosystem processes, including greenhouse gas emissions, with implications for the carbon intensity of electricity generation. 

How to cite: Wang, G., Li, G., and Armstrong, A.: Wind turbine operation influences near surface air temperature and humidity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-768, https://doi.org/10.5194/egusphere-egu21-768, 2021.

EGU21-6737 | vPICO presentations | ERE1.4

Improved biodiversity from food to energy: Meta-analysis of land-use change to dedicated bioenergy crops

Caspar Donnison, Robert Holland, Zoe Harris, Felix Eigenbrod, and Gail Taylor

Whilst dedicated bioenergy crops with non-food uses are currently sparsely deployed across the world, most future energy pathways necessitate a sizeable scale-up of 100-500 million ha of land converted to these crops to provide both energy substitutes for fossil fuels and negative emissions through bioenergy with carbon capture and storage (BECCS). In the face of expected bioenergy expansion, understanding the environmental and societal impact of this land-use change is important in determining where and how bioenergy crops should be deployed, and the trade-offs and co-benefits to the environment and society. Here we review the existing literature on two difficult to measure impacts which could prove critical to the future wide-scale acceptability of global bioenergy cropping in the temperate environment: biodiversity and amenity value. We focus on agricultural landscapes, since this is where large-scale bioenergy planting may be required. A meta-analysis of 42 studies on the biodiversity impacts of land-use change from either arable and grassland to bioenergy crops found strong benefits for bird abundance (+ 109 % ± 24 %), bird species richness (+ 100 % ± 31 %), arthropod abundance (+ 299 % ± 76 %), microbial biomass (+ 77 % ± 24 %), and plant species richness (+ 25 % ± 22 %) and a non-significant upward trend in earthworm abundance. Land-use change from arable land led to particularly strong benefits, providing an insight into how future land-use change to bioenergy crops could support biodiversity. Evidence concerning the impact of bioenergy crops on landscape amenity value highlighted the importance of landscape context, planting strategies, and landowner motivations in determining amenity values, with few generalizable conclusions. In this first meta-analysis to quanitfy the impacts of land-use change to bioenergy on on biodiversity and amenity,  we have demonsrated  improved farm-scale biodiversity on agricultural land but also demonstrated the lack of knowledge concerning public response to bioenergy crops which could prove crucial to the political feasibility of bioenergy policies such as BECCS.

How to cite: Donnison, C., Holland, R., Harris, Z., Eigenbrod, F., and Taylor, G.: Improved biodiversity from food to energy: Meta-analysis of land-use change to dedicated bioenergy crops, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6737, https://doi.org/10.5194/egusphere-egu21-6737, 2021.

EGU21-585 | vPICO presentations | ERE1.4

Impacts of miscanthus growth on soil carbon and water deficit

Anita Shepherd and Astley Hastings

Miscanthus x giganteus thrives on poor soils, requiring little or no farm operations except annual harvest, efficiently recycles nutrients into the rhizome at senescence to be reused the following season and has a high water efficiency compared to other arable crops.  As such it is a popular choice for bioenergy crop growers, it can thrive on waste land, or poor agricultural soils that cannot give sufficient economic returns for food crops in many areas of the world.

We present work to better understand the global potential for M x giganteus yields and impacts as a bioenergy crop grown in the 21st century under IPCC climate RCP 8.5 and using the MiscanFor bioenergy model, showing how bioenergy crops compare across different countries for dry matter yield, water use, and soil carbon. We also show the uncertainty of projections inherent in choosing input data and the sensitivity of the model.

How to cite: Shepherd, A. and Hastings, A.: Impacts of miscanthus growth on soil carbon and water deficit, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-585, https://doi.org/10.5194/egusphere-egu21-585, 2021.

EGU21-13541 | vPICO presentations | ERE1.4 | Highlight

Co-locating Food and Energy Production to Create Sustainable Agricultural Systems

Greg A Barron-Gafford, Mitchell Pavao-Zuckerman, Kai Lepley, and Andrea Gerlak

We have significant vulnerabilities across our food, water, and energy systems – any of which could undermine societal resilience in light of growing populations and climatic change. Rising average temperatures, extremes in precipitation, and more severe storms present increasing agricultural production risks – particularly across dryland regions. Land managers across the southwestern United States are already feeling the pressures of a changing climate. Between 11–21% of the total irrigated acreage experienced yield declines over the past 40 years due to irrigation interruptions — despite increased water usage. Food producers are experiencing increased uncertainties around production security from severe weather, interest rates to invest in climate adaptations, income support payments or incentives, and climate-related risks to pollinator abundance that affect crop yields and labor conditions and availability. Combined with trends towards increases in retirements from farming, these risks are leading to more land moving out of food production — often shifting to energy production. A growing demand for photovoltaic (PV) solar energy from ground-mounted systems, projected to require ~8,000 km2 by 2030, is resulting in an increase of land-use conflicts for these two primary needs — food and energy. Is it possible to improve both food and renewable energy production security sustainably? An ‘either-or’ discourse between food and PV solar energy production unnecessarily compounds issues related to allocating space, water, and capital for development of sustainable strategies.

We believe that a hybrid agricultural-PV solar ‘agrivoltaics’ can increase resilience in food and renewable energy production, water and soil conservation, and rural prosperity and economic development—critical sustainability metrics. However, successful adoption of this technology requires research from a socio-environmental systems perspective to optimize bio-technical trade-offs at the field scale, while also rigorously assessing the sociopolitical barriers and how to overcome them at both individual and societal levels. Our research design is centered on stakeholder engagement approaches with impactful, associated outreach activities to communicate and enhance the reach of potential benefits of agrivoltaics. An emerging trend in sustainability research has been to recognize that resource challenges need to be addressed as integrated and interconnected sets of issues, where outcomes result from interacting social (S), ecological (E), and technological (T) subsystems (SETS). Often, sustainability transitions are seen more as a governance challenge than an infrastructure or technological challenge. That is, while technological solutions such as agrivoltaics can be developed, the adoption and spread of innovations takes place through a myriad of social, political, and economic processes. This is further complicated across food and energy systems, where multiple stakeholders present different backgrounds, cultures, demographics, and decision making processes. We describe an evaluation of agrivoltaic systems from a holistic SETS perspective in order to develop implementation pathways for widespread adoption of agrivoltaics across the US.

How to cite: Barron-Gafford, G. A., Pavao-Zuckerman, M., Lepley, K., and Gerlak, A.: Co-locating Food and Energy Production to Create Sustainable Agricultural Systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13541, https://doi.org/10.5194/egusphere-egu21-13541, 2021.

EGU21-2927 | vPICO presentations | ERE1.4

Is it possible to embed the ecosystem impacts of solar parks into industry practice?

Lucy Treasure, Dr Alona Armstrong, Dr Stuart Sharp, Dr Simon Smart, and Dr Guy Parker

The energy sector is the largest contributor to global greenhouse gas emissions. Therefore it is imperative that we take steps to de-carbonise energy supplies if we are to meet the 2°C goal of the Paris Agreement.  Of the existing renewable energy technologies, Photovoltaic (PV) capacity has seen exponential growth in the past decade, with 508.1 GW of PV currently installed globally and predictions that it will become the dominant renewable energy source by 2050. A large proportion of this capacity is deployed as ground-mounted solar parks. Despite the rapid growth of solar parks, little research has been conducted into the ecosystem impacts. Here we use a systematic literature review of the available evidence to show that the main ecosystem impacts of solar parks can be grouped into five themes: microclimate, land-use change, soil and vegetation, wildlife impacts and pollution. Impacts can be positive or negative, and vary according to site location, former land use and management practices throughout the construction, operational and decommissioning phases of the solar park life cycle. The most widely reported impacts associated with the construction phase were habitat loss and fragmentation, with subsequent effects on fauna, flora, and soil. Commonly reported operational impacts included changes to local microclimate, pollution, mortality of wildlife and disturbance due to site maintenance. Decommissioning impacts depended largely on the site management objectives; sites continued to be managed to deliver ecosystem service co-benefits or returned to their original state prior to construction. The review also revealed significant knowledge gaps. Understanding the ecosystem impacts of solar parks is pivotal, both for informing site management that maximises ecosystem co-benefits and avoids detrimental impacts, and for quantifying the potential ecosystem costs and gains as required by policy, for example the upcoming mandatory biodiversity net gain requirement for UK planning applications.

How to cite: Treasure, L., Armstrong, D. A., Sharp, D. S., Smart, D. S., and Parker, D. G.: Is it possible to embed the ecosystem impacts of solar parks into industry practice?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2927, https://doi.org/10.5194/egusphere-egu21-2927, 2021.

EGU21-8046 | vPICO presentations | ERE1.4

Reduced ecosystem services of desert plants from ground-mounted solar energy development

Steven M. Grodsky and Rebecca R. Hernandez

Deserts are prioritized as recipient environments for solar energy development; however, the impacts of this development on desert plant communities are unknown. Desert plants represent long-standing ecological, economic and cultural resources for humans, especially indigenous peoples, but their role in supplying ecosystem services (ESs) remains understudied. We measured the effect of solar energy development decisions on desert plants at one of the world’s largest concentrating solar power plants (Ivanpah, California; capacity of 392 MW). We documented the negative effects of solar energy development on the desert scrub plant community. Perennial plant cover and structure are lower in bladed treatments than mowed treatments, which are, in turn, lower than the perennial plant cover and structure recorded in undeveloped controls. We determined that cacti species and Mojave yucca (Yucca schidigera) are particularly vulnerable to solar development (that is, blading, mowing), whereas Schismus spp.—invasive annual grasses—are facilitated by blading. The desert scrub community confers 188 instances of ESs, including cultural services to 18 Native American ethnic groups. Cultural, provisioning and regulating ESs of desert plants are lower in bladed and mowed treatments than in undeveloped controls. Our study demonstrates the potential for solar energy development in deserts to reduce biodiversity and socioecological resources, as well as the role that ESs play in informing energy transitions that are sustainable and just.

How to cite: Grodsky, S. M. and Hernandez, R. R.: Reduced ecosystem services of desert plants from ground-mounted solar energy development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8046, https://doi.org/10.5194/egusphere-egu21-8046, 2021.

EGU21-8257 | vPICO presentations | ERE1.4 | Highlight

Economic benefits of establishing honeybee hives on solar parks in agricultural landscapes

Alona Armstrong, Lauren Brown, Gemma Davies, Duncan Whyatt, and Simon Potts

To mitigate climate change, land take for renewable energy is accelerating at a time of increasing land use pressure and environmental degradation. Given land use change is the dominant driver of nature decline, over and above that of climate change, inclusion of local ecosystem consequences of land take for renewable energy decisions is critical. However, consideration of ecosystem impacts is hindered by lack of understanding and robust quantification methodologies. Here, we quantify the economic benefits of installing honeybee hives in solar parks by estimating the potential contribution to crop yields. We estimated that if honeybee hives were installed in all existing solar parks within England, pollination service benefits for pollinator dependent field crops, top fruits and soft fruit would have been £5.9 million in 2017, grounded in honeybee pollination crop values of £4.81-£75.04 ha-1 for field crops and £635-£10,644 ha-1 for fruit. If crop distributions were optimised to maximise solar park honeybee pollination, economic benefits could reach up to £80 million per year. However, this indicative of the maximum possible return and is unlikely to be viable given the other factors that influence crop distribution. Quantification of ecosystem co-benefits and costs of land take for renewable energy could inform location and management decisions, with the potential to improve ecosystem health in addition to energy system decarbonisation.

How to cite: Armstrong, A., Brown, L., Davies, G., Whyatt, D., and Potts, S.: Economic benefits of establishing honeybee hives on solar parks in agricultural landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8257, https://doi.org/10.5194/egusphere-egu21-8257, 2021.

EGU21-7838 | vPICO presentations | ERE1.4

Evaluating the Ecosystem Service Benefits of Native Vegetation Management at Solar Energy Facilities

Leroy Walston and Heidi Hartmann

Concomitant with the increase in solar photovoltaic (PV) energy development over the past decade has been the increasing emphasis on land sharing strategies that maximize the land use efficiency of solar energy developments.  Many of these strategies focus on improving the compatibility of solar energy development with other co-located land uses (e.g., agriculture) and by improving several ecosystem services that could have natural, societal, and industrial benefits. One such land opportunity is the restoration and management of native grassland vegetation beneath ground-mounted PV solar energy facilities, which has the potential to restore native habitat to conserve biodiversity and restore previously altered ecosystem services (e.g., natural pollination services). This presentation will discuss various assessment and modeling approaches to evaluate the scale and magnitude of the ecosystem services provided by different vegetation management strategies at solar PV energy development sites. This work demonstrates how multifunctional land uses in energy systems represents a win-win solution for energy and the environment by optimizing energy-food-ecology synergies. This work was conducted by Argonne National Laboratory for the U.S. Department of Energy Solar Energy Technologies Office under Contract No. DE-AC02-06CH11357.

How to cite: Walston, L. and Hartmann, H.: Evaluating the Ecosystem Service Benefits of Native Vegetation Management at Solar Energy Facilities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7838, https://doi.org/10.5194/egusphere-egu21-7838, 2021.

EGU21-7677 | vPICO presentations | ERE1.4

Development of a Solar Park Carbon Calculator (SPCC) to assist deployment decisions

Ryan Holland, Alona Armstrong, and Fabio Carvalho

Following the Paris agreement, many nations have committed to targets of net zero emissions, resulting in a significant increase in low-carbon energy generation. Recent improvements in the cost and efficiency of photovoltaic (PV) technology have made their deployment cheaper than new coal and gas fired power stations in a number of regions, with the uptake of PV projected to surpass fossil fuels by 2035. Large-scale, ground-mounted systems are likely to constitute a considerable portion of this expansion, with the International Energy Agency suggesting that 69% of new capacity additions in 2021 will be utility scale deployments (although some of this may be building-mounted). Despite the expansion of ground-mounted solar parks and the knowledge that land use change is a greater threat to nature than climate change, there is very little understanding of the environmental implications. In particular, the effect on ecosystem carbon cycling, and thus the decarbonisation attraction of the technology, is unknown. Whilst the carbon impacts of the technological components have been relatively well resolved, the true carbon costs cannot be determined without quantifying the impacts on land carbon. Here, we present a solar park carbon calculator (SPCC) that quantifies the full suite of solar park carbon impacts.

The SPCC provides information on the technological and environmental carbon flows, drawing on established quantifications of carbon costs for system components, operation, and land management. Key components include the emissions factors for production of panels and mounts, machinery related emissions and the associated carbon flows of ground disturbances, before and after park construction. The SPCC is applied to a case-study solar park, providing insight into the dominant carbon flows and payback time in light of grid electricity carbon intensities. Ultimately, the SPCC can help inform solar park developer decisions in order to minimise carbon costs and maximise carbon sequestration.

How to cite: Holland, R., Armstrong, A., and Carvalho, F.: Development of a Solar Park Carbon Calculator (SPCC) to assist deployment decisions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7677, https://doi.org/10.5194/egusphere-egu21-7677, 2021.

EGU21-122 | vPICO presentations | ERE1.4

Decarbonising UK transport: Implications for electricity generation, land use and policy

Kathryn G. Logan, John D. Nelson, James D. Chapman, Jenny Milne, and Astley Hastings

Transitioning away from internal combustion engine private vehicles in favour of public transport, including electric and hydrogen alternatives, is recognised as an essential part of the solution to reduce the scale of climate change and meet net zero in the UK by 2050. This decarbonisation transition to low carbon transport will likely result in an increase in energy demand which will have impacts on both ecosystem services (ES) and natural capital (NC). Robust projections of societal energy demands post low carbon transition are therefore required to ensure adequate power generation is installed. In this study, we project the energy demand for electric and hydrogen cars, buses and trains between 2020 and 2050 based on the number of vehicles and distance travelled using the Transport Energy Air Pollution UK (TEAM-UK) model outputs. In this work, the spatial requirements of additional renewable energy (onshore/offshore wind and solar), nuclear and fossil fuels, on ES and NC was predicted by considering the expected electricity generation mix expected by 2050, the number of generation installations and energy density of each energy source. The outcomes of this analysis can assist policymakers in better understanding what energy types and transport networks need to be prioritised to efficiently meet net zero. Legislation requires increased low carbon electricity generation, though the impact on ES and NC are not currently quantified.

Energy demand was lower for electric transport (136,599 GWh) than hydrogen transport (425,532 GWh) for all vehicle types in 2050, however a combination of both power types will be needed to accommodate the full range of socioeconomic requirements. In addition, to power electrical transport, 1,515 km2 of land will be required for solar, 1,672 km2 for wind and 5 km2 for expansion of the average nuclear power station by 2050. This will be approximately doubled for hydrogen provision due to the additional energy and conversions required to generate hydrogen.

In reality the finer scale mix between hydrogen and electric transport types in the future will depend on geographical location and resource availability. Rural areas may favour hydrogen power due to range restrictions, with electric transport more readily suited to urban areas with greater installed infrastructure. To reduce the requirements for additional electricity and maximise carbon output decreases, minimising the impact on NC and ES, policymakers need to focus on encouraging a modal shift towards low carbon public transport from private vehicles and to ensure a more sustainable route to decarbonising transport.

How to cite: Logan, K. G., Nelson, J. D., Chapman, J. D., Milne, J., and Hastings, A.: Decarbonising UK transport: Implications for electricity generation, land use and policy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-122, https://doi.org/10.5194/egusphere-egu21-122, 2021.

EGU21-5654 | vPICO presentations | ERE1.4

Investigation of Fluidized Backfill Materials for Optimized Bedding of Buried Power Cables

Maximilian Eckhardt, Hung Pham, Markus Schedel, and Ingo Sass

The transition towards renewable energy systems leads to increased loads on the electrical power grid. As a result, many transmission lines have to be extended or newly built. According to a government resolution, in Germany the preferred implementation of new high-voltage, direct current (HVDC) electric power transmission systems should be buried power cables.

When operating buried power cables, the mechanical and thermal properties of the cable bedding need to meet certain requirements. On the one hand, accurate positioning and protection of the cable and protection pipe from mechanical stress demand mechanical stability. On the other hand, electric losses during transmission result in thermal energy that needs to be dissipated. Since the ampacity of the cable depends on the maximum permissible temperature of the conductor, the potential load of the power line is directly connected to the thermal properties of the bedding.

To ensure both of these technical requirements, the pre-existing soil mostly is disposed and replaced by sand or artificial fluidized backfill materials with well-known material properties, resulting in potentially high logistical effort, environmental impact and costs. One way to address these effects could be the reuse of the excavated soils as a basic material for the on-site production of a fluidized backfill material, allowing for the adjustment of soil properties (within limits) by adding cement and other additives. By enhancing the thermal properties of the cable bedding, the ampacity of the cable route can be increased, potentially reducing land use due to smaller dimensions of the cable trench. Reusing excavated soils further reduces potential land use, since less material needs to be disposed in landfill sites. 

Within the scope of our research, the technical and economical possibilities and limits of reusing excavated soils for the production of fluidized backfill materials are explored. In addition, the stability of fluidized backfill materials under cyclic load scenarios is investigated to assess possible alterations of such materials during cable operation, which may affect the long-term efficiency of the transmission system.

How to cite: Eckhardt, M., Pham, H., Schedel, M., and Sass, I.: Investigation of Fluidized Backfill Materials for Optimized Bedding of Buried Power Cables, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5654, https://doi.org/10.5194/egusphere-egu21-5654, 2021.

EGU21-16317 | vPICO presentations | ERE1.4

Predicting future energy and biodiversity trade-offs globally

Sebastian Dunnett, Robert A Holland, Gail Taylor, and Felix Eigenbrod

Protected areas and renewable energy generation are key tools to combat biodiversity loss and climate change respectively. Over the coming decades, very large-scale expansion of renewable energy infrastructure will be needed to meet climate change targets, while simultaneously large-scale expansion of the protected area network to meet conservation objectives is planned. However, renewable energy infrastructure has negative effects on wildlife, and co-occurrence may mean emissions targets are met at the expense of conservation objectives. However, data limitations mean that the degree of likely future conflict of these two key land management objectives has not been fully assessed. Here, we address this gap by examining current and projected future overlaps of wind and solar photovoltaic installations and important conservation areas globally using new spatially explicit wind and solar photovoltaic data, and new methods for predicting future renewable expansion. We show similar levels of co-occurrence of important conservation areas and wind and solar installations as previous studies but also show that once area is accounted for previous concerns about overlaps in Northern Hemisphere may be largely unfounded, though are high in some high-biodiversity countries (e.g. Brazil). Future projections of overlap between the two land uses are generally lower than previously predicted using new data, with regional correlation coefficients peaking at -0.3418 and 0.2053, suggesting a low risk of future conflict. Our results show that the current and future overlap of the two land uses may not be as severe as previously suggested. This is important, as global efforts to decarbonise energy systems are central to mitigating against climate change and against the strong negative impacts of projected climate change on biodiversity.

How to cite: Dunnett, S., A Holland, R., Taylor, G., and Eigenbrod, F.: Predicting future energy and biodiversity trade-offs globally, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16317, https://doi.org/10.5194/egusphere-egu21-16317, 2021.

ERE1.5 – Land use dynamics, land degradation and insights for land sustainability in agriculture and forest landscapes

EGU21-14471 | vPICO presentations | ERE1.5 | Highlight

Spatiotemporal patterns of global land use change: Understanding processes and drivers

Karina Winkler, Richard Fuchs, Mark Rounsevell, and Martin Herold

Land use change is a major contributor to greenhouse gas emissions and biodiversity loss and, hence, a key topic for current sustainability debates and climate change mitigation. To understand its impacts, accurate data of global land use change and an assessment of its extent, dynamics, causes and interrelations are crucial. However, although numerous observational data is publicly available (e.g. from remote sensing), the processes and drivers of land use change are not yet fully understood. In particular, current global-scale land change assessments still lack either temporal consistency, spatial explicitness or thematic detail.
Here, we analyse the patterns of global land use change and its underlying drivers based on our novel high-resolution (~1x1 km) dataset of global land use/cover (LULC) change from 1960-2019, HILDA+ (Historic Land Dynamics Assessment+). The data harmonises multiple Earth Observation products and FAO land use statistics. It covers all transitions between six major LULC categories (urban areas, cropland, pasture/rangeland, forest, unmanaged grass-/shrubland and no/sparse vegetation).
On this basis, we show (1) a classification of global LULC transitions into major processes of land use change, (2) a quantification of their spatiotemporal patterns and (3) an identification of their major socioeconomic and environmental drivers across the globe. By using temporal cross-correlation, we study the influence of selected drivers on processes such as agricultural land abandonment, deforestation, forest degradation or urbanisation.
With this, we are able to map the patterns and drivers of global land use change at unprecedented resolution and compare them for different world regions. Giving new data-driven and quantitative insights into a largely untouched field, we identify tele-coupled globalisation patterns and climate change as important influencing factors for land use dynamics. Learning from the recent past, understanding how socio-economic and environmental factors affect the way humans use the land surface is essential for estimating future impacts of land use change and implementing measures of climate mitigation and sustainable land use policies.

How to cite: Winkler, K., Fuchs, R., Rounsevell, M., and Herold, M.: Spatiotemporal patterns of global land use change: Understanding processes and drivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14471, https://doi.org/10.5194/egusphere-egu21-14471, 2021.

EGU21-16050 | vPICO presentations | ERE1.5

Global Deforestation Revisited: The Role of Political and Institutional Factors

Ianna Raissa Moreira Dantas and Mareike Söder

In times of international agreements and efforts to mitigate climate change and meet sustainable development, ecosystem management and forest conservation deserve special attention to promote human and environmental sustenance. Tropical forests have been declining worldwide, and biodiversity is under constant threat. Understanding the future potential of environmental services requires analysis of the relationship of socioeconomic drivers and anthropogenic land use change (LUC). Population and economic growth, agricultural production, and human capital have a dual relationship of cause and consequence with LUC. Likewise, changing patterns of land use, through agriculture and silviculture activities, is directly associated to market and technical progress, but also to political, institutional, and socioeconomic development. Studying such relationships enhances the analyses on the ability of institutional factors to promote environmental conservation, economic growth, and social welfare. Studies on LUC are historically based on physical variables; however, institutional and political drivers have shown to be core to forest degradation. The present paper aims at investigating the role of physical and institutional factor on global deforestation. This paper draws from recent global remote sensing data on land use from ESA Climate Change Initiative (ESA/CCI) from 1992 and 2015. To assess drivers of deforestation, we employ a logit model regression accounting for a global spatially explicit dataset on land use, regressed with physical, economic, and socioeconomic variables. We make use of the suitability indicators calculated by IIASA for different agricultural crops within the Global Agro-Ecological Zones modelling. As institutional factors we consider areas under protection based on spatial datasets provided by UNEP and wetland international, and include the country level corruption index of Transparency International. Our preliminary analysis shows that institutional instability is significantly related to LUC. In areas where land should be under protection due to non-market ecosystem services, political instability is likely to stimulate land use. Likewise, insecurity in land tenure might lead to a short-term maximization of profits, through full deforestation and exploitation of the soil fertility, instead of a long-term sustainable use.

How to cite: Moreira Dantas, I. R. and Söder, M.: Global Deforestation Revisited: The Role of Political and Institutional Factors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16050, https://doi.org/10.5194/egusphere-egu21-16050, 2021.

EGU21-10921 | vPICO presentations | ERE1.5

Detection and Mapping of Forest Disturbance in Eurasian Continent

Yusha Zhang, Yanchen Bo, Mei Sun, and Tongtong Sun

The global distribution and disturbance information of forest have strong impact on the change of Earth’s ecosystems. In the 1990s, the Eurasian continent forest cover an area of 182 million ha, accounting about 33.2% of the Eurasian continent land area. However, we lack a complete mapping of high-resolution forest disturbances in Eurasia. Remote sensing can regularly obtain forest cover data across expansive range. Therefore, a complete set of Landsat time-series-based forest disturbance detection method is constructed in this paper to map a 30-meter forest disturbance detection distribution map of Eurasian continent.

In the construction of Landsat time series(LTS) data, the Landsat TM, ETM +, and OLI images of forest growth season were selected and synthesized into inter-annual time series over 35 years from 1986 to 2020. And the appropriate indices, NBR and NDVI, were selected as the input data for time series analysis. In time series analysis, the adaptive threshold of model learning is effectively applied in the process of extracting potential disturbance points, and the rich temporal information of LTS is fully mined to optimize and filter the disturbances.

The LTS images and forest disturbance based on adaptive threshold model are used to map three decades of forest disturbances, including the characteristics of the disturbance, spatiotemporal distribution and disturbance frequency across Eurasian continent. The derived disturbance year maps revealed that the disturbed forest area is 237 million ha and 12.8% of Eurasia’s forest area. In order to validate the accuracy of the map, 10066 interpreted Landsat pixels, including 3932 disturbed samples and 6134 undisturbed samples, are selected as reference data. The overall accuracy of the disturbance map is 86.6%, with a commission error of 13.4% and an omission error of 9.4%. The results indicated that the LTS and adaptive threshold model can effectively support the mapping of forest disturbance in Eurasian continent.

How to cite: Zhang, Y., Bo, Y., Sun, M., and Sun, T.: Detection and Mapping of Forest Disturbance in Eurasian Continent, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10921, https://doi.org/10.5194/egusphere-egu21-10921, 2021.

EGU21-10020 | vPICO presentations | ERE1.5

Understanding the relationship between environmental policies and deforestation activities in the Paraguayan Chaco

Monserrat Garcia Calabrese, Shirley Salinas Romero, Chynthya Cassacia Ibarrola, Luis Morinigo, Magali Alvarenga, and Emmanuel Da Ponte

Over the past 40 years, Paraguay has lost the majority of its natural forest cover, thus becoming one of the countries with the highest deforestation rates in the world. Uninterrupted deforestation practices in the Paraguayan Chaco between 1987 and 2012 resulted in the loss of 27% of its original cover, accounting for almost 44,000 km2 of forested areas depleted. The rapid expansion of the agricultural frontier, cattle ranching, and illegal logging has converted the last forest remnants into isolated patches, thus endangering their continuity and biodiversity within them. In response to these events, the Paraguayan government has implemented numerous environmental programs and regulations to amend the damage that had happened in the past. Although governmental agencies claim a reduction in deforestation activities in the region, proper scientific environmental data that analyze the long-term effect of such regulations/programs remain scarce. Within this context, the present research analyzes the impact of local governments on changes occurred in Paraguayan Chaco forest between the years 1986 and 2020. Remote sensing data acquired from Landsat 4, 5, 7 and 8 images were used to derive the extent of the forest cover and deforestation rates over 34 years. Dynamics of the forest cover was correlated with each of the 10 government terms within the timeframe of the study. By analyzing the forest cover data during and after each term (around five years per government term), we sought to understand the influence of local policies on deforestation activities in the eco-region, aiming to identify social, political, and institutional drivers of change. A comprehensive assessment of creation and effectivities of protected areas, land concession to indigenous communities, and development/implementation of local policies and environmental laws are part of this study. Preliminary results show a significative difference on forest cover loss among governments terms ranging between 1% (2,385 km2) and 9% (14,422 km2). The lack of clear regulations, sound law enforcement, financial support, and inappropriate governance were initially identified as key drivers of change. The use of multi-temporal information was demonstrated to be a key component for designing, supporting, and monitoring conservation strategies and policies. It is crucial to consider not only the outlook of laws and policies aiming to halt deforestation activities but their actual influence on the behavior of natural resources over time.

How to cite: Garcia Calabrese, M., Salinas Romero, S., Cassacia Ibarrola, C., Morinigo, L., Alvarenga, M., and Da Ponte, E.: Understanding the relationship between environmental policies and deforestation activities in the Paraguayan Chaco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10020, https://doi.org/10.5194/egusphere-egu21-10020, 2021.

EGU21-12671 | vPICO presentations | ERE1.5

Evaluation of the land use evolution near solid waste landfills using a new weighted environmental index based on GIS techniques

Javier Rodrigo-Ilarri, Claudia P. Romero-Hernández, and María-Elena Rodrigo-Clavero

Land use in the nearby of a Municipal Solid Waste (MSW) landfill can be strongly affected by the waste management tasks (transport, landfilling and closure). Effects extend from the phases prior to the construction of the landfill until years after the completion of the landfilling process in areas located beyond the perimeter of the plot occupied by the landfill. In this work a new methodology for the analysis of land use change over time is presented. The methodology is based on the use of a new environmental index named WEI (Weighted Environmental Index). WEI is based on the use of GIS techniques accounting for different information sources (digital cartography, aerial photographs and satellite images). WEI assigns environmental values to land use based on the degree of anthropogenic intervention and its occupation surface. A georeferenced multitemporal statistical analysis is performed considering the values of WEI previously assigned to every land use. The methodology has been applied to analyze the land use change near the main MSW landfills of Valencia Region (Spain) where landfilling is currently the only waste disposal technique available. Data have been obtained from the Spanish Land Occupation Information System (SIOSE) public database and integrate GIS information about land use/land cover on an extensive, high-detailed scale. Results demonstrate the application of the WEI to real case studies and the importance of integrating statistical analysis of WEI evolution over time to arrive at a better understanding of the socio-economic and environmental processes that induce land-use change.

How to cite: Rodrigo-Ilarri, J., Romero-Hernández, C. P., and Rodrigo-Clavero, M.-E.: Evaluation of the land use evolution near solid waste landfills using a new weighted environmental index based on GIS techniques, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12671, https://doi.org/10.5194/egusphere-egu21-12671, 2021.

EGU21-7232 | vPICO presentations | ERE1.5 | Highlight

Modelling biomass and biodiversity in temperate grasslands with Sentinel-1, Sentinel-2 and Unmanned Aerial Vehicles.

Javier Muro, Lisa Schwarz, Florian Männer, Anja Linstädter, and Olena Dubovyk

Land use practices in grasslands are major determinants of their biodiversity and ecosystem functions. Relationships between biodiversity, ecosystem functions and land use practices can vary across climatic and management gradients and across scales. New generations of remote sensing sensors can model grasslands’ biomass and biodiversity parameters with relative RMSE that range between 10% and 40%. However, most of these experiments have been carried out in rather small and homogenous areas. In the project SeBAS (Sensing Biodiversity Across Scales) we are using machine learning algorithms (random forest and neural networks) to model biomass and biodiversity indicators along spatial and management gradients and across scales. Field data (above ground biomass and species inventories) was obtained during summer 2020 from the Biodiversity Exploratories: a set of 150 grassland plots across spatial and management gradients in Germany. Remote sensing information at farm level was obtained from microwave Sentinel-1 and multispectral Sentinel-2 satellites, and at plot level from a multispectral camera mounted on a UAV.

First results show the limitations of satellite images to map vegetation parameters in heterogeneous landscapes, and how the incorporation of UAV information can be used to improve model estimations of biomass production and biodiversity indicators.

How to cite: Muro, J., Schwarz, L., Männer, F., Linstädter, A., and Dubovyk, O.: Modelling biomass and biodiversity in temperate grasslands with Sentinel-1, Sentinel-2 and Unmanned Aerial Vehicles., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7232, https://doi.org/10.5194/egusphere-egu21-7232, 2021.

EGU21-1590 | vPICO presentations | ERE1.5

Mapping trends in woody cover throughout Namibian savannah with MODIS seasonal phenological metrics and field inventory data

Vladimir Wingate

EGU21-2612 | vPICO presentations | ERE1.5

Degradation or recovery of argan woodlands in South Morocco? Tree count from satellite imagery between 1967–2019 may underestimate pressures on dryland forests status

Irene Marzolff, Mario Kirchhoff, Robin Stephan, Manuel Seeger, Ali Aït Hssaïne, and Johannes B. Ries

In semi-arid to arid South-west Morocco, the once ubiquitous endemic argan tree (Argania spinosa) forms the basis of a traditional silvo-pastoral agroforestry system with complex usage rights involving pasturing and tree-browsing by goats, sheep and camels, smallholder agriculture and oil production. Widespread clearing of the open-canopy argan forests has been undertaken in the 12th–17th century for sugarcane production, and again in the 20th century for fuelwood extraction and conversion to commercial agriculture. The remaining argan woodlands have continued to decline due to firewood extraction, charcoal-making, overgrazing and overbrowsing. Soil and vegetation are increasingly being degraded; natural rejuvenation is hindered, and soil-erosion rates rise due to reduced infiltration and increased runoff. Numerous studies indicate that tree density and canopy cover have been generally decreasing for the last 200 years. However, there is little quantitative and spatially explicit information about these forest-cover dynamics.

In our study, the tree-cover change between 1967 and 2019 was analysed for 30 test sites of 1 ha each in argan woodlands of different degradation stages in the provinces of Taroudant, Agadir Ida-Outanane and Chtouka-Aït Baha. We used historical black-and-white satellite photography from the American reconnaissance programme CORONA, recent high-resolution multispectral imagery from the commercial WorldView satellites and ultrahigh resolution small-format aerial photography taken with an unmanned aerial system (UAS) to map the presence, absence and comparative crown-size class of 2610 trees in 1967 and 2019. We supplemented the remotely-sensed data with field observations on tree structure and architecture.

Results show that plant densities reach up to 300 argan trees and shrubs per hectare, and the mean tree density has increased from 58 trees/ha in 1967 to 86 trees/ha in 2019. While 7% of the 1967 trees have vanished today, more than one third of today’s trees could not be observed in 1967. This positive change has a high uncertainty, however, as most of the increase concerns small trees (< 3 m diameter) which might have been missed on the lower-resolution CORONA images.

When combined with our field data on tree architecture, tree count – albeit a parameter easily attained by remote sensing – is revealed as too simple an indicator for argan-forest dynamics, and the first impression of a positive development needs to be revised: The new small trees as well as trees with decreased crown sizes clearly show much stronger degradation characteristics than others, indicating increased pressures on the argan ecosystem during recent decades. Structural traits of the smaller trees also suggest that the apparent increase of tree count is not a result of natural rejuvenation, but mostly of stump re-sprouting, often into multi-stemmed trees, after felling of a tree. The density of the argan forest in the 1960s, prior to the general availability of cooking gas in the region and before the stronger enforcement of the argan logging ban following the declaration of the UNESCO biosphere reserve, may have marked a historic low in our study area, making the baseline of our change analysis far removed from the potential natural state of the argan ecosystem.

How to cite: Marzolff, I., Kirchhoff, M., Stephan, R., Seeger, M., Aït Hssaïne, A., and Ries, J. B.: Degradation or recovery of argan woodlands in South Morocco? Tree count from satellite imagery between 1967–2019 may underestimate pressures on dryland forests status, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2612, https://doi.org/10.5194/egusphere-egu21-2612, 2021.

EGU21-1258 | vPICO presentations | ERE1.5

Modelling dynamics of land use and ecosystem services changes in the Luanhe River Basin in China

Jiren Xu, Brian Barrett, and Fabrice Renaud

Quantifying land use dynamics is central to evaluate changes in terrestrial and aquatic ecosystems. It also allows for understanding how ecosystem services (ES) and ecosystem disservices (EDS) are affected by human interventions in the landscape. Finally, it can lead to the development of improved future land use management strategies for the achievement of the Sustainable Development Goals (SDGs). The Luanhe River Basin (LRB) is the most afforested river basin in North China and provides multiple ecosystem services which are related to several SDGs (e.g. SDG 6: Clean Water and Sanitation, 7: Affordable and Clean Energy, and 13: Climate Action). In this study, four scenarios: Trend, Expansion, Sustainability, and Conservation were developed based on different socioeconomic development and environmental protection targets as well as local plans and policies. Local stakeholders were consulted to develop these scenarios and to explore land use dynamics of the LRB and major challenges that the river basin may face by 2030. Land use change was modelled with CLUMondo and ES and EDS were characterised using capacity matrices. The ecosystem services potential index (ESPI) and ecosystem disservices potential index (EDSPI) was calculated, and ES and EDS hotspots and coldspots were identified. The study found that forests and water bodies provided the highest overall ES capacity, while the lowest scores were recorded for built-up and unused land areas. Built-up land and cropland provided the highest overall EDS capacity, while the lowest EDS scores were for water bodies. The forests and water bodies, which were widespread in the upper-middle reaches of the basin, were hotspots of provisioning services, regulating services, cultural services and ecological integrity, while the hotspots of EDS were concentrated in the built-up land areas and the croplands, which were mainly distributed in the downstream of the LRB. Modelling results indicated that the LRB was likely to experience agricultural (crop and livestock) intensification and urban growth under all four future scenarios. The cropland intensity and the urban growth rate were much higher under the historical trend (Trend) scenario compared to those with more planning interventions (Expansion, Sustainability, and Conservation scenarios). The most significant increase of livestock density in grassland was projected under the Expansion scenario. Unless the forest area and biodiversity conservation targets are implemented (Conservation scenarios), the forest areas are projected to decrease under three scenarios by 2030. The ESPI of all the ES declined from 1980 to 2018 and would continue to decline until 2030 without sustainable and conservation development strategies. Compared with the EDSPI in 1980, the EDSPI under all future scenarios in 2030 was projected to increase. This study calls for establishing and implementing sustainable environmental protection policies as well as cross-regional and trans-provincial eco-compensation schemes for minimising trade-offs in ES. The methodological framework and findings of this study can guide regional sustainable development and rational utilisation of land resources in the LRB and other comparable river basins, and will be valuable for policy and planning purposes to the pursuance of SDGs at the sub-national scale.

How to cite: Xu, J., Barrett, B., and Renaud, F.: Modelling dynamics of land use and ecosystem services changes in the Luanhe River Basin in China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1258, https://doi.org/10.5194/egusphere-egu21-1258, 2021.

EGU21-13567 | vPICO presentations | ERE1.5

Biosphere Reserves: Sustainable territories, Resilient communities – A conceptual model for the assessment of ecosystem services

Joana Alves, Jorge Duran, José Paulo Sousa, Paula Castro, Filipe Martinho, Miguel Pardal, Inger Måren, and Helena Freitas

Biosphere Reserves (BR) are territories recognized by UNESCO for their natural and cultural heritage and their role in promoting solutions to harmonize biodiversity conservation with the sustainable use of natural resources. Further, BRs are identified as “learning places for sustainable development”, emphasizing their importance to achieve the UN Sustainable Development Goals. However, Portuguese BRs lack recognition from society as well as from the local, regional or national entities as privileged instruments and areas for valuing and developing the territory.

To enhance the relevance and visibility of the BRs in society and among stakeholders, we designed a project based on the assessment of ecosystem services (ES), as they play fundamental roles in the mitigation and adaptation to climate change, and on the sustainability of the communities and their territories. Our project seeks to structure and foster collective dynamics in these social-ecological systems, respecting the autonomy and diversity of context and heritage that characterizes the Portuguese BRs. Our work is based on a conceptual model with three fundamental pillars. First, we will identify available geographical and biological information and combine it with remote sensing data (Landsat and Sentinel) to map the current and potential ES provided by Portuguese BRs. Second, in each BR, we will implement participatory multi-actor methodologies and focal groups to select the key ES to promote sustainable development and valorisation of natural endogenous resources. To do so, we will use a holistic assessment of the ecological, economic and social values of the different ES, as well as of their role in mitigating and adapting to climate change and environmental change. Finally, we will train local stakeholders on the valuing, promotion and sustainable production and consumption of ES, as to help these communities implementing the Sustainable Development Plans that will be prepared for each BR and in accordance with the UN’s Agenda 2030.

Through complementary initiatives and a comprehensive and networked programmatic action, “Biosphere Reserves: Sustainable territories, Resilient communities” seeks to add value to Portuguese BRs, increasing their resilience and sustainability, and to promote their unique territories and heritage, while showcasing them as model areas for the sustainable development.

How to cite: Alves, J., Duran, J., Sousa, J. P., Castro, P., Martinho, F., Pardal, M., Måren, I., and Freitas, H.: Biosphere Reserves: Sustainable territories, Resilient communities – A conceptual model for the assessment of ecosystem services, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13567, https://doi.org/10.5194/egusphere-egu21-13567, 2021.

EGU21-7204 | vPICO presentations | ERE1.5

Land change effects on ecosystem degradation across Nigerian agro-ecological zones from 1975 through 2020

Felicia Akinyemi and Chinwe Ifejika Speranza

Land system change is implicated in many sustainability challenges as its alteration impacts ecosystems and exacerbate the vulnerability of communities, particularly where livelihoods are largely dependent on natural resources. The production of a land use-cover map for year 2020 extended the time-series for assessing land use-cover dynamics over a period of 45 years (1975-2020). The case of Nigeria is examined as the land area encompass several agro-ecological zones. The classification scheme countries utilise for estimating Land Degradation Neutrality baseline and monitoring of the Sustainable Development Goal 15.3.1 indicator (proportion of degraded land over total land area) was used, based on seven land use-cover classes (tree-covered area, grassland, cropland, wetland, artificial surface area, otherland, and waterbody). Severity of land degradation, computed as changes in vegetation productivity using the Enhanced Vegetation Index (EVI), as well as changes in ecosystem service values were examined across the different land use-cover types, in areas of change and persistence. Land degradation is most severe in settlement areas and wetlands with declining trends in 34% of settlement areas and 29% in wetlands respectively. About 19% of tree-covered areas experienced increasing trends. In some areas of land use-cover persistence, vegetation productivity declined despite no land change occurring. For example, vegetation productivity declined in about 35% and 9% of persistent wetlands and otherland respectively between 2000 and 2020, whereas there was improvement in 22% of persistent grasslands, 18% of persistent otherlands and 12% of persistent croplands. In land change areas, about 12% and 8% of wetlands and tree-covered areas had declining vegetation trends respectively, whereas it improved the most in croplands (20%), and grasslands (16%). With some wetland, cropland and otherland areas degrading the most, protecting these critical ecosystems is required to sustain their functions and services. The finding that vegetation productivity may decline in areas of persistence underscores the importance of intersecting land use-cover (in terms of persistence and change) with vegetation productivity to identify pathways for enhancing ecological sustainability.

How to cite: Akinyemi, F. and Ifejika Speranza, C.: Land change effects on ecosystem degradation across Nigerian agro-ecological zones from 1975 through 2020, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7204, https://doi.org/10.5194/egusphere-egu21-7204, 2021.

EGU21-7415 | vPICO presentations | ERE1.5

Land users’ perceptions of land degradation and implications for sustainable land management and governance in Niger State, Nigeria 

Adenle Ademola, Sébastien Boillat, and Chinwe Ifejika Speranza

Declining land productivity remains a challenge for agricultural-based livelihoods and for achieving food security. This is particularly the case in social-ecological contexts where people are largely dependent on local food production for their livelihoods and food security, such as among rural communities in the Nigeria Guinea Savannah. Yet how land users perceive the problem of land degradation and their capacity to manage land in an environmentally sustainable manner, can influence the measures they can initiate to address land degradation. Using a case study of Niger state, Nigeria, this study examines land users’ experiences and land management measures to address land degradation in the Nigeria Guinea Savannah. 30 communities were purposively selected based on the validated mapping of the hotspots of degraded areas. We adapted the World Overview of Conservation Approaches and Technologies Sustainable Land Management questionnaires to also capture perceptions and administered 225 questionnaires to land users. Through, key informant interviews further insights and data on perspectives and motivations of land users and communities were collected to understand the land degradation situation and interpret the questionnaire surveys. Through qualitative and statistical analysis of differences in perceptions between socio-cultural strata, we show the relations between socio-demographic, socio-economic factors, and land degradation. We discuss land governance and sustainable land management practices for improving land productivity in the region.

 

 

How to cite: Ademola, A., Boillat, S., and Ifejika Speranza, C.: Land users’ perceptions of land degradation and implications for sustainable land management and governance in Niger State, Nigeria , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7415, https://doi.org/10.5194/egusphere-egu21-7415, 2021.

EGU21-6307 | vPICO presentations | ERE1.5

Crop transitions can drive economic and ecological shifts in an established farming landscape: a case study from California

Ariani Wartenberg, Diana Moanga, Matthew Potts, and Van Butsic

Meeting growing challenges to maintain food production and rural livelihoods while minimizing land degradation will require significant changes in the way existing farming landscapes are managed. A systemic understanding of the agroecological impacts of land-use change in established farming landscapes, and the identification of significant trade-offs or synergies, are crucial to inform farm management and land-use governance solutions. Here, we focus on land-use change impacts in an already established farming landscape. We investigate spatial and temporal dynamics of agricultural land-use change from 2002 to 2018, in Kern County, California. Our study region is one of the major agricultural production hotspots in the United States, and has undergone a recent agricultural land-use transition from annual to perennial cropping systems. In this study we analyzed parcel-level data documenting changes in the land-use footprint for individual crops, ranging from annual crops like wheat and cotton to perennial tree crops like almonds and pistachios. We assess how land-use change impacted ecosystem pressures and service indicators selected for their relevance in an agricultural context, including water-use, soil erosion, profit and carbon sequestration. Our results indicate no salient trade-offs or synergies among individual crops, and illustrate the possibility of limited economic-ecological trade-offs associated with a shift from annual to perennial crops in a well-established agricultural landscape. We further discuss the relevance of our findings in the context of land-ownership consolidation and changing export dynamics in the study area.

How to cite: Wartenberg, A., Moanga, D., Potts, M., and Butsic, V.: Crop transitions can drive economic and ecological shifts in an established farming landscape: a case study from California, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6307, https://doi.org/10.5194/egusphere-egu21-6307, 2021.

EGU21-16266 | vPICO presentations | ERE1.5

Post-Soviet changes in irrigated crop production in the Amu Darya Basin

Daniel Müller, Andrey Dara, Christopher Krause, Mayra Daniela Peña-Guerrero, Tillman Schmitz, Atabek Umirbekov, Yanbing Wei, and Philippe Rufin

Water withdrawals for irrigated crop production constitute the largest global consumer of blue water resources. Monitoring the dynamics of irrigated crop cultivation allows to track changes in water consumption of irrigated cropping, which is particularly paramount in water-scarce arid and semi-arid areas. We analyzed changes in irrigated crop cultivation along with occurrence of hydrological droughts for the Amu Darya river basin of Central Asia (534,700 km2), once the largest tributary river to the Aral Sea before large-scale irrigation projects have grossly reduced the amount of water that reaches the river delta. We used annual and seasonal spectral-temporal metrics derived from Landsat time series to quantify the three predominant cropping practices in the region (first season, second season, double cropping) for every year between 1988 and 2020. We further derived unbiased area estimates for the cropping classes at the province level based on a stratified random sample (n=2,779). Our results reveal a small yet steady decrease in irrigated second season cultivation across the basin. Regionally, we observed a gradual move away from cotton monocropping in response to the policy changes that were instigated since the mid-1990s. We compared the observed cropping dynamics to the occurrence of hydrological droughts, i.e., periods with inadequate water resources for irrigation. We find that areas with higher drought risks rely more on irrigation of the second season crops. Overall, our analysis provides the first fine-scale, annual crop type maps for the irrigated areas in the Amu Darya basin. The results shed light on how institutional changes and hydroclimatic factors that affect land-use decision-making, and thus the dynamics of crop type composition, in the vast irrigated areas of Central Asia.

How to cite: Müller, D., Dara, A., Krause, C., Peña-Guerrero, M. D., Schmitz, T., Umirbekov, A., Wei, Y., and Rufin, P.: Post-Soviet changes in irrigated crop production in the Amu Darya Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16266, https://doi.org/10.5194/egusphere-egu21-16266, 2021.

EGU21-7959 | vPICO presentations | ERE1.5

A land-based approach for climate change mitigation in the livestock sector

Maria Vincenza Chiriacò and Riccardo Valentini

The land sector plays a crucial role in the context of climate change, being both a contributor to the problem and part of its solution. On one side, greenhouse gas (GHG) emissions from agriculture, forestry and other land uses (AFOLU sector) cover the 24% of global emissions, representing the second hot spot in the contribution to climate change after the energy sector. On the other side, this sector offers the exclusive capacity to remove atmospheric carbon dioxide and store it in soils and biomass.

The challenge is to understand the extent to which sustainable land management can be a valuable solution to increase the mitigation potential of the land sector, particularly at small-scale rural landscape level. A land-based approach is developed and tested for application at small-scale rural landscape level, aiming at reducing and offsetting GHG emissions from the livestock activities, one of the main sources of GHG emissions of the whole agricultural sector. The proposed land-based approach builds on an ensemble of methodologies, including Geographic Information System (GIS) elaboration, Life Cycle Assessment (LCA) and methodologies from the Intergovernmental Panel on Climate Change (IPCC), that allow estimating livestock GHG emissions and the mitigation potential of sustainable land-use options applied in the same small-scale rural landscape (e.g. improvement of ruminants’ diet, biogas from manure, reduction of synthetic fertilizers, minimum/no-tillage, natural herbaceous cover, reuse of agricultural residues, new orchards and forests on marginal lands).

Results from a case study in Italy show that land-based mitigation options applied at small-scale rural landscape level can reduce and completely offset the GHG livestock emissions of the same area, leading to carbon neutral livestock systems, in line with the objectives of the EU Green Deal and the global climate commitments. Thus, this study confirms that the land sector can strongly contribute to climate change mitigation if sustainable land-use options are applied. Moreover, when sustainable land-use options are applied with a proximity approach in a small-scale, the results are not limited to the carbon neutrality of the livestock production but involve also other tangible environmental and socio-economic benefits in the territory (e.g. sustainable agriculture, biodiversity protection, water and air quality, new green areas, tourism, well-being etc.). 

A such sustainable land-based approach can be applied to all food systems (not only livestock) and can be scaled at global level involving an infinite number of districts (organized at local, regional or national level) with the potential to influence globally the food production toward a sustainable model of the whole land sector. The implementation of a such sustainable land management aiming to a carbon neutral food production can be supported at public policies level, under the EU Common Agricultural Policy (CAP) and the Carbon Farming schemes, but also by the private sector in the framework of voluntary carbon mechanisms.   

How to cite: Chiriacò, M. V. and Valentini, R.: A land-based approach for climate change mitigation in the livestock sector, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7959, https://doi.org/10.5194/egusphere-egu21-7959, 2021.

EGU21-3888 | vPICO presentations | ERE1.5

Societal vision vs. farmers’ reality: an approach to evaluate if agricultural intensification is sustainable

Julian Helfenstein, Matthias Bürgi, Vasco Diogo, Franziska Mohr, Beatrice Schüpbach, Rebecca Swart, Erich Szerencsits, Peter Verburg, and Felix Herzog

There is broad agreement that agriculture has to become more sustainable in order to provide enough healthy food at minimal economic, environmental and social costs. But what is “more sustainable”? More often than not, different stakeholders have opposing opinions on what a more sustainable future should look like. In this study, we present an approach to assess the sustainability of agricultural development based on societal visions. We illustrate the approach by linking observed changes in agricultural land use intensity in a Swiss case study area with desired change according to three contrasting visions. The three visions, from a liberal think-tank, the Swiss Farmer Association, and the agroecological movement, cover a wide spectrum of sociopolitical interest groups in Swiss agriculture. The observed developments aligned most closely with desired developments of the liberal think-tank. Farmer interviews revealed that farms increased in size (+ 57%), became more specialized, and more productive (+ 223%) over the past 20 years. In addition, interpretation of aerial photographs indicated that farming became more rationalized at the landscape level, with increasing field sizes (+ 34%) and removal of solitary field trees (-18%). The case study example highlights the potential of societal visions to assess changes in land use intensity and outcomes in various sustainability dimensions. The main advantages are that the approach accommodates multiple stakeholder goals, while explicitly addressing their narratives and respective systems of values and norms, thus being more informative to the wider public. For these reasons, we argue that future assessments of sustainability should focus on contrasting observed developments with desired change by various stakeholder groups. This could help identify mismatches between desired and actual development and pave the way for designing appropriate new policies.

How to cite: Helfenstein, J., Bürgi, M., Diogo, V., Mohr, F., Schüpbach, B., Swart, R., Szerencsits, E., Verburg, P., and Herzog, F.: Societal vision vs. farmers’ reality: an approach to evaluate if agricultural intensification is sustainable, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3888, https://doi.org/10.5194/egusphere-egu21-3888, 2021.

EGU21-13643 | vPICO presentations | ERE1.5

Pastoralists-farmers’ conflicts in Nigeria’s mid-Benue Trough: Socio-ecological drivers and pathways to addressing the conflicts.

Chukwudi Njoku, Francis Okpiliya, Joel Efiong, and Chinwe Ifejika Speranza

Violent conflicts related to pastoralists-farmers’ interactions in Nigeria have assumed an unprecedented dimension, causing loss of lives and livelihoods. The mid-Benue trough (Benue and Taraba States) has suffered most from the conflicts. This study aims to provide knowledge on the socio-ecological drivers of pastoralists-farmers’ conflicts in the mid-Benue trough from the year 2000 to 2020 and to identify pathways to solving them. First, data from the Armed Conflict Location and Event Data Project were used to map the conflicts. Second, to understand the nexus of climate change, land use and the conflicts, the study analyzed satellite data of Land Surface Temperature (LST) as a proxy for climate change, using data from the Moderate-Resolution Imaging Spectroradiometer (MODIS) satellite and Land Use Land Cover (LULC), using LandSat 7 ETM and LandSat 8 ETM+ data, then linked them to the mapped conflicts. Third, to understand causes and impacts of the conflict on pastoralists and farmers’ livelihoods, 100 interviews were conducted, 50 for each group and analyzed using content analysis and descriptive statistics. Results showed that there were 2532 fatalities from 309 conflict events between pastoralists and farmers. The incidents exhibited statistically significant clustering and were minimal between the year 2000 and 2012, increasing gradually until the year 2013 when it began to rise geometrically. The Getis-Ord Gi hotspot analysis revealed the conflict hotspots to include Agatu, Oturkpo, Gwer East and Gashaka Local Government Areas. The results from the LST analysis showed that the area coverage of high LST increased from 30 percent in 2000 to 38 percent in 2020, while extremely high LST area also increased from 14 to 16 percent. A significantly high percentage of the conflicts (87 percent) occurred in areas with high LST (>30⁰C). In addition, the LULC analyses showed that built-up land area increased by 35 km2 (0.1 percent) and dense forests reduced by 798 km2 (0.1 percent). Notably, shrublands and grasslands, which are the resource domains of the pastoralists reduced by 11,716 km(13.1 percent) and croplands of farmers increased by 12,316 km2 (13.8 percent). This presents an apparent transition of LULC from shrublands and grasslands to croplands in the area. Further analyses showed that 63 percent of the conflicts occurred in croplands and 16 percent in shrublands and grasslands. Hence, the reduction of land resource available to pastoralists and their subsequent cropland encroachment were identified as major causes of the conflict. It was therefore concluded that land development for other purposes is a major driver of pastoralists-farmers’ conflicts in the study area. There is thus a need to integrate conflict maps, LST and LULC dynamics to support dialogue, land use planning and policy formulation for sustainable land management to guide pastoral and farming activities.

How to cite: Njoku, C., Okpiliya, F., Efiong, J., and Ifejika Speranza, C.: Pastoralists-farmers’ conflicts in Nigeria’s mid-Benue Trough: Socio-ecological drivers and pathways to addressing the conflicts., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13643, https://doi.org/10.5194/egusphere-egu21-13643, 2021.

ERE2.1 – Energy Meteorology

EGU21-7581 | vPICO presentations | ERE2.1

Irradiance and atmospheric optical properties from photovoltaic power data: model improvements and first results

James Barry, Dirk Böttcher, Johannes Grabenstein, Klaus Pfeilsticker, Anna Herman-Czezuch, Nicola Kimiaie, Stefanie Meilinger, Christopher Schirrmeister, Felix Gödde, Bernhard Mayer, Hartwig Deneke, Jonas Witthuhn, Philipp Hofbauer, and Matthias Struck

Photovoltaic (PV) power data are a valuable but as yet under-utilised resource that could be used to characterise global irradiance with unprecedented spatio-temporal resolution. The resulting knowledge of atmospheric conditions can then be fed back into weather models and will ultimately serve to improve forecasts of PV power itself. This provides a data-driven alternative to statistical methods that use post-processing to overcome inconsistencies between ground-based irradiance measurements and the corresponding predictions of regional weather models (see for instance Frank et al., 2018). This work reports first results from an algorithm developed to infer global horizontal irradiance as well as atmospheric optical properties such as aerosol or cloud optical depth from PV power measurements.

Building on previous work (Buchmann, 2018), an improved forward model of PV power as a function of atmospheric conditions was developed. As part of the BMWi-funded project MetPVNet, PV power data from twenty systems in the Allgäu region were made available, and the corresponding irradiance, temperature and wind speed were measured during two measurement campaigns in autumn 2018 and summer 2019. System calibration was performed using all available clear sky days; the corresponding irradiance was simulated using libRadtran (Emde et al., 2016). Particular attention was paid to describing the dynamic variations in PV module temperature in order to correctly take into account the heat capacity of the solar panels.

PV power data from the calibrated systems were then used together with both the DISORT and MYSTIC radiative transfer codes (Emde et al., 2016) to infer aerosol optical depth, cloud optical depth and irradiance under all sky conditions.  The results were compared to predictions from the COSMO weather model, and the accuracy of the inverted quantities was compared using both a simple and more complex forward model. The potential of the method to extract irradiance data over a larger area as well as the increase in information from combining neighbouring PV systems will be explored in future work.

References
 
Buchmann, T., 2018: Potenzial von Photovoltaikanlagen zur Ableitung raum-zeitlich hoch aufgelöster Globalstrahlungsdaten. Heidelberg University, http://archiv.ub.uni-heidelberg.de/volltextserver/24687/.
Emde, C., and Coauthors, 2016: The libRadtran software package for radiative transfer calculations (version 2.0.1). Geosci. Model Dev., 9, 1647–1672, doi:10.5194/gmd-9-1647-2016. https://www.geosci-model-dev.net/9/1647/2016/.
Frank, C. W., S. Wahl, J. D. Keller, B. Pospichal, A. Hense, and S. Crewell, 2018: Bias correction of a novel European reanalysis data set for solar energy applications. Sol. Energy, 164, 12–24, doi:10.1016/j.solener.2018.02.012. https://doi.org/10.1016/j.solener.2018.02.012.

How to cite: Barry, J., Böttcher, D., Grabenstein, J., Pfeilsticker, K., Herman-Czezuch, A., Kimiaie, N., Meilinger, S., Schirrmeister, C., Gödde, F., Mayer, B., Deneke, H., Witthuhn, J., Hofbauer, P., and Struck, M.: Irradiance and atmospheric optical properties from photovoltaic power data: model improvements and first results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7581, https://doi.org/10.5194/egusphere-egu21-7581, 2021.

EGU21-14726 | vPICO presentations | ERE2.1

Deriving cloud information from all-sky images for intra-hour PV nowcasting

Philipp Gregor, Tobias Zinner, Bernhard Mayer, and Josef Schreder

Energy output from photovoltaics (PV) strongly depends on the respective weather situation. To ensure continuous energy availability in power grids with large PV contribution, flexibly manageable power plants have to compensate for variations in PV power production. Within the project NETFLEX, an intra-hour irradiance now-casting algorithm is developed as a basis for a PV power forecast used for management of a combined PV / biogas power plant.

The now-casting algorithm is designed around a cloud representation in a simplistic 2D advection model, which is updated with currently measured data and which projects cloud situations up to 15 minutes into the future. Main input to the model are images captured by two CMS Schreder all-sky imagers (ASI) installed at the PV plant in locations separated by about 530m. Captured images are processed to extract cloud masks, cloud base heights and cloud movement. To obtain cloud masks, ratios of red and blue channels as well as saturation and brightness are compared to reference data from a clearsky library. This library is composed from synthetic clearsky data computed by the radiative transfer model libRadtran (Mayer and Kylling, 2005), which are processed to resemble imager geometry and optics. The creation of synthetic references allows for any desired sun position and aerosol condition. Simultaneously captured images of both cameras are evaluated and corresponding pixels are matched. Exact calibration of the imager geometry then allows for cloud base height derivation using the method of miss-pointing vectors (Kölling et al., 2019). Consecutive images are evaluated for each ASI to estimate horizontal cloud motion by matching corresponding pixels. All cloud information computed from ASI images is assimilated into the 2D model as a base for cloud field predictions with information about cloud position, base height and velocity. The model-centered approach allows for flexible integration of additional data sources, e.g. satellite imagery and numerical weather prediction data.

Validation of image evaluation methods and now-casting model is done using synthetic all-sky images of LES cloud fields. Additionally, cloud base height from a ceilometer as well as global and direct integrated solar irradiance were measured on site of the PV power plant. This also allows for validation on real world cases.

Literature:

Kölling, T., Zinner, T., and Mayer, B.: Aircraft-based stereographic reconstruction of 3-D cloud geometry, Atmos. Meas. Tech., 12, 1155–1166, 2019.

Mayer, B. and Kylling, A.: Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use, Atmos. Chem. Phys., 5, 1855–1877, 2005.

How to cite: Gregor, P., Zinner, T., Mayer, B., and Schreder, J.: Deriving cloud information from all-sky images for intra-hour PV nowcasting, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14726, https://doi.org/10.5194/egusphere-egu21-14726, 2021.

EGU21-2867 | vPICO presentations | ERE2.1

New flexible retrieval for gusts and mean winds from Doppler wind lidars

Julian Steinheuer, Carola Detring, Frank Beyrich, Ulrich Löhnert, and Stephanie Fiedler

Phenomena in the atmospheric boundary layer are investigated in the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL, www.fesstval.de). Our aim is the retrieval of wind gusts from measurements of a Doppler wind lidar (DWL). DWLs allow the determination of wind vector profiles with high vertical resolution (∼30 m) and represent an alternative to classical meteorological tower observations. They can receive signals from altitudes higher than towers and are flexible in positioning. However, the retrieval of wind gusts from DWL measurements is not trivial because a monostatic lidar provides only one radial velocity, i.e., only one component of a three-dimensional vector, and measurements in three linearly independent directions are necessary to derive the wind vector. These have to be performed sequentially which limits the achievable time resolution, while wind gusts are short-lived phenomena. Therefore, we have developed a new wind retrieval that is applicable to different scanning configurations and various requested time resolutions. We tested several DWL configurations in autumn 2019 using DWL systems ’StreamLine’ from Halo Photonics and evaluated gust peaks and the 10min mean wind at 90 m height against data from a sonic anemometer at the meteorological tower. The most useful configuration for retrieving wind gusts is a fast continuous scan mode (CSM) that completes a full circulation cone within 3.4s. During this time interval, about eleven radial velocity measurements are completed. This fast CSM configuration was again successfully operated over a three-months period in summer 2020. We found that CSM paired with our new retrieval technique provides gusts which compare well to classical anemometer measurements from a meteorological tower. Future work includes the application of the new retrieval to DWL data during the FESSTVaL campaign in 2021 when DWL measurements are planned at different sites in order to study the sub-mesoscale variability of wind gusts.

How to cite: Steinheuer, J., Detring, C., Beyrich, F., Löhnert, U., and Fiedler, S.: New flexible retrieval for gusts and mean winds from Doppler wind lidars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2867, https://doi.org/10.5194/egusphere-egu21-2867, 2021.

EGU21-7656 | vPICO presentations | ERE2.1

Horizontal Wind Speed motion-induced error assessment on a floating Doppler Wind lidar

Andreu Salcedo-Bosch, Joan Farré-Guarné, Josep Sala-Álvarez, Javier Villares-Piera, Robin Tanamachi, and Francesc Rocadenbosch

A wind retrieval simulator of a floating Doppler Wind Lidar (DWL) with six Degrees of Freedom (DoF) in its motion is presented. The simulator considers a continuous-wave, conically scanning, floating DWL which retrieves the local wind profile from 50 line of sight (LoS) radial velocity measurements per scan. Rotational and translational motion effects over horizontal wind speed (HWS) measurements are studied parametrically. The 6 DoF motion framework as well as the most important buoy motion equations are based on the model presented in [1].

Each rotational and translational motion is simulated as 1 second sinusoidal signal defined by an amplitude, frequency and motion phase. In order to study the problem of motion-induced error on the retrieved HWS, a dimension reduction is needed (22 variables). A consideration followed in the literature [2] to alleviate the problem is to set the same motional frequency (f=0.3 Hz) for all DoF, a wind vector with constant HWS and null vertical wind speed (VWS). Moreover, the parametric study is carried out under certain constraints in order to finally reduce the problem dimensionality to three, which enables the generation of tri-dimensional colorplots of the error on the retrieved HWS.

Simulation results show that in the presence of motion, HWS error has a strong dependency on FDWL initial scan phase. Moreover, the directions of the rotation axis and translational velocity vector (with respect to wind direction, WD) show great impact on HWS error. For translational motion, a 3 DoF superposition principle is corroborated.

The simulator is as a useful tool for understanding particular lidar motion scenarios and their contributions to HWS measurements error. However, further analysis of the effect of lidar initial scan phase is needed. Additionally, these simulations are conducted under idealized assumptions of horizontally homogeneous wind profiles in the vicinity of the FDWL. Simulations using non-homogeneous wind fields (e.g., turbulence, air mass boundaries) would give insights on how well floating lidars can be expected to retrieve the wind profile in these common scenarios.

Acknowledgements

This work was supported via Spanish Government–European Regional Development Funds project PGC2018-094132-B-I00 and H2020 ACTRIS-IMP (GA-871115). The European Institute of Innovation and Technology (EIT), KIC InnoEnergy project NEPTUNE (Offshore Metocean Data Mea-suring Equipment and Wind, Wave and Current Analysis and ForecastingSoftware, call FP7) supported measurements campaigns. CommSensLab isa María-de-Maeztu Unit of Excellence funded by the Agencia Estatal de Investigación (Spanish National Science Foundation). The work of Andreu Salcedo-Bosch was supported by the “Agència de Gestió d’Ajuts Universitaris i de la Recerca (AGAUR)”, Generalitat de Catalunya, under Grant no. 2020 FISDU 00455.

References

[1] F. Kelberlau, V. Neshaug, L. Lønseth, T. Bracchi, and J. Mann, “Taking the Motion out of Floating Lidar: Turbulence Intensity Estimates with a Continuous-Wave Wind Lidar,” Remote Sens., vol. 12, no. 898, 2020.

[2] J. Tiana-Alsina, F. Rocadenbosch, and M. A. Gutierrez-Antunano, “Vertical Azimuth Display simulator for wind-Doppler lidar error assessment,” in 2017 IEEE Int. Geosci. Remote. Se. (IGARSS). IEEE, Jul. 2017.

How to cite: Salcedo-Bosch, A., Farré-Guarné, J., Sala-Álvarez, J., Villares-Piera, J., Tanamachi, R., and Rocadenbosch, F.: Horizontal Wind Speed motion-induced error assessment on a floating Doppler Wind lidar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7656, https://doi.org/10.5194/egusphere-egu21-7656, 2021.

EGU21-10881 | vPICO presentations | ERE2.1

Comparing large eddy simulations with sonic anemometer and LIDAR measurement data during Foehn events in complex terrain

Curdin T. Spirig, Stefan Fluck, Kenneth Vogt, and Julien G. Anet

Simulations of turbulent wind flows in complex, mountainous terrain prove to be challenging tasks for today’s numerical simulation models. However, knowing about these wind flow patterns and speeds would be beneficial to assess potential environmental risks for various stakeholders – aviation, wind farms, ski resorts, cable cars or others. With the PALM model system, a state-of-the-art turbulence resolving meteorological model for atmospheric boundary layer flows is available, that can be used to assess these types of questions. By treating topography on a cartesian grid, complex terrain can be accurately represented in simulations.

In this study, the complex local flow patterns in mountainous terrain were analyzed by means of high-resolution large eddy simulations with the PALM model system. This was conducted for the Rhine valley region focusing on a small peculiar topographic feature upstream of Balzers in the area of the border between the Principality of Liechtenstein and Switzerland, were flow splitting is known to occur. There, Foehn events lead to pronounced local wind maxima and pose a damaging risk to the upwind part of the village. The model results were compared with data from measurement masts equipped with sonic and cup-anemometers at the position of assumed wind speed maxima. As well, measurements of a continuous-wave LIDAR system located at the outflow of the side valley were integrated in our study. The validation measurements for the Foehn events in Balzers were taken in December 2020, during which two pronounced Foehn events took place.

In PALM, a nested simulation approach was chosen, with the smallest domain having a resolution of only a few meters. The simulation was forced by COSMO-1 model results in order to factor in the synoptic weather conditions of the respective days. We show model results of the flow patterns that occur in this complex topography, analyze the wind maxima present in the valley and compare the results with local measurement data. This study demonstrates how large eddy simulation tools like PALM can produce insights into complex flow structures in mountainous terrain, and how these insights can be used to make more informed decisions to protect residents from damaging outcomes of environmental risks.

How to cite: Spirig, C. T., Fluck, S., Vogt, K., and Anet, J. G.: Comparing large eddy simulations with sonic anemometer and LIDAR measurement data during Foehn events in complex terrain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10881, https://doi.org/10.5194/egusphere-egu21-10881, 2021.

Characterizing properties of wind speed variability and their dependence on the temporal scale is important: from sub-second intervals (for the design and monitoring of wind turbines) to longer time scales – months, years (for the evaluation of the wind power potential). Wind speed data are usually reported as averages over time intervals of various length (minutes, days, months, etc). The research project presented in this paper addressed the following questions: What aspects of the wind pattern are changed, in what ways and to what extent, in the process of producing time-averaged values? What precautions should be considered when time-averaged values are used in the assessment of wind variability? What are the conditions to be fulfilled for a meaningful comparison of wind pattern characteristics obtained in distinct studies? Our research started from wind speed records sampled at 0.14 second intervals, which were averaged over increasingly longer time intervals. Variability evaluation was based on statistical moments, L-moments, and detrended fluctuation analysis. We present the change suffered by characteristics of temporal variability as a function of sampling rate and the averaging time interval. In particular, the height dependence of wind speed variability, which is of theoretical and practical importance, is shown to be progressively erased when averaging intervals are increased. The paper makes recommendations regarding the interpretation of wind pattern characteristics obtained at different sites as a function of sampling rate and time-averaging intervals.

How to cite: Suteanu, C.: Time scale dependence of wind speed patterns - implications for wind power site assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1449, https://doi.org/10.5194/egusphere-egu21-1449, 2021.

EGU21-3117 | vPICO presentations | ERE2.1

Extreme wind speed climatology over Greece

Georgios Blougouras, Chris G. Tzanis, and Kostas Philippopoulos

Extreme wind speeds are a multifaceted environmental risk. They may cause considerable damage to infrastructure (e.g., bridges, private property), they can jeopardize maritime and aviation activities, and sometimes even human safety. Furthermore, the design of wind turbines for on and off-shore wind farms requires a study of the return periods of extreme wind speeds in combination with the lifespan of the wind turbines. Windstorms also result in major economic losses and cause up to 80 % of the natural hazards' long term insurance loss in Europe. The scope of this work is to identify location-specific extreme wind speed thresholds and obtain accurate estimates of exceedances for multiple future horizons. In this context, the Extreme Value Analysis framework is used for providing the return periods and the respective return levels of extreme wind speeds. The Peaks Over Threshold method is utilized for the 10 m wind speed for a domain centered over Greece, in Southeastern Mediterranean. Wind speed data at 10 m are extracted from the ERA5 reanalysis dataset that provides hourly estimates of surface wind speed with a horizontal resolution of 0.25°x0.25°, from 1979/01/01 up to 2019/12/31 (i.e., 41 years). The thresholds are selected using the Mean Residual Life plots, which is the most reliable method for identifying accurate threshold values. The seasonal analysis of the exceedances is discussed in terms of the physical mechanisms in the region. The exceedances are modelled using the Generalized Pareto Distribution, whose shape and scale parameters (ξ and σ, respectively) are estimated using the Maximum Likelihood Estimation method. The return levels and their confidence intervals are estimated for return periods up to 100 years. Geographic Information Systems are used for mapping future projections of extreme wind speeds and the corresponding confidence intervals. The results are discussed in terms of identifying high-risk areas and the findings could assist in informed decision-making in the wind energy industry. The proposed methodological framework could be extended to other areas characterized by particularly high wind speeds and the results can contribute towards sustainable investments and support adaptation mechanisms.

How to cite: Blougouras, G., Tzanis, C. G., and Philippopoulos, K.: Extreme wind speed climatology over Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3117, https://doi.org/10.5194/egusphere-egu21-3117, 2021.

EGU21-12303 | vPICO presentations | ERE2.1

Recovery processes in coastal wind farms

Tanvi Gupta and Somnath Baidya Roy

Wind turbines in a wind farm extract energy from the atmospheric flow and convert it into electricity, resulting in a localized momentum deficit in the wake that reduces energy availability for downwind turbines. Atmospheric momentum convergence from above, below, and sides into the wakes replenish the lost momentum, at least partially, so that turbines deep inside a wind farm can continue to function. In this study, we explore recovery processes in hypothetical offshore wind farms with particular emphasis on comparing the spatial patterns and magnitudes of horizontal and vertical recovery processes and understanding the role of mesoscale phenomena like sea breezes in momentum recovery in wind farms.

For this study, we use the Weather Research and Forecasting (WRF) model, a state-of-the-art mesoscale model equipped with a wind turbine parameterization, to simulate deep offshore and coastal wind farms with different wind turbine spacings under realistic initial and boundary conditions. The wind farms consist of 10000 turbines rated 3 MW spread over a 50 km x 50 km area. We conduct experiments with various background conditions, including low wind, high wind, and sea breeze cases identified using Borne’s method.

Results show that for deep offshore wind farms, power generation peaks at the upwind edge and monotonically decreases downwind into the interior due to cumulative wake effects of multiple rows of turbines. Vertical turbulent transport of momentum from aloft is the main contributor to recovery except in cases with strong background winds and high inter-turbine spacing where horizontal advective momentum transport can also contribute equally. Coastal wind farms behave similarly in the absence of sea-breezes.  However, under sea breeze conditions, the power production is high at the upwind edge and decreases thereafter but starts to increase again towards the downwind edge of the wind farm because of the sea breeze. The results further show that the contribution of horizontal (vertical) recovery in case of sea breeze conditions increases (decreases) to around 14% (86%) as compared to the non-sea breeze conditions where the horizontal (vertical) recovery contributes 9% (90%) to the momentum recovery in the wind farms. Vertical recovery shows a systematic dependence on wind farm density and wind speed. This relationship can be quantified using low-order empirical equations that can perhaps be used to develop parameterizations for replenishment in linear wake models. Overall, this study is likely to significantly advance our understanding of recovery processes in wind farms and wind farm-ABL interactions.

How to cite: Gupta, T. and Baidya Roy, S.: Recovery processes in coastal wind farms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12303, https://doi.org/10.5194/egusphere-egu21-12303, 2021.

EGU21-4888 | vPICO presentations | ERE2.1

A kinetic energy budget perspective to understand efficiency reductions of offshore wind generation in the German Bight in the North Sea

Jonathan Minz, Marc Imberger, Axel Kleidon, and Jake Badger

The European Commission’s net zero decarbonization scenarios estimate that up to 450GW of offshore wind capacity could be installed in Europe by 2050. German energy scenarios estimate that 50 to 70 GW of this could be installed in the German Bight in the North Sea and yield about 4000 full load hours (FLH) per year of power. However, these assume that wind speeds and yields are not reduced by the increased extraction of kinetic energy from the regional atmospheric flow by large wind farms. Our initial assessment of these assumptions, using two different approaches - the simple Kinetic Energy Budget of the Atmosphere model (KEBA) and the Weather Research and Forecasting model with Explicit Wake Parameterization (WRF-EWP), showed that emplacing such a large turbine capacity within the German Bight may lower expected yield down to 3300-3000 FLH. Here, we identify the major factors leading to this reduction. We use the two models to evaluate the role of atmospheric variables like wind directions, atmospheric stability, boundary layer height and surface friction in constraining large scale offshore wind energy generation. We test the KEBA model concept of limited kinetic energy fluxes through the boundary layer determining generation potential, and investigate deviations between the models to identify limitations of the simpler approach.The WRF model sets our ”best guess” of energy yield from regional wind turbine deployments (at scales of 104km2) since the scale of deployments that we assess are not in operation yet. Our analysis will provide insights about key atmospheric variables that shape regional offshorewind energy potential of the German Bight. We propose that estimating regional wind energy potential should account for atmospheric response.

How to cite: Minz, J., Imberger, M., Kleidon, A., and Badger, J.: A kinetic energy budget perspective to understand efficiency reductions of offshore wind generation in the German Bight in the North Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4888, https://doi.org/10.5194/egusphere-egu21-4888, 2021.

EGU21-15816 | vPICO presentations | ERE2.1

Train2Wind, or how large is an infinite wind farm?

Gregor Giebel, Tuhfe Göçmen, Jakob Mann, Anna Maria Sempreviva, Haakon Lund, Joachim Reuder, Jens Bange, and Fernando Porte-Agel

TRAIN2WIND is a PhD TRAINing school analysing enTRAINment in offshore WIND farms with computer models and experiments. By its very nature, a wind turbine extracts energy from the wind, which is replenished from the wind field on the sides and above due to the ambient turbulence. However, offshore the turbulence is lower, and wind farms are typically larger than onshore, therefore the wind can only be replenished from above in a process called entrainment. Train2Wind will investigate the entrainment process using advanced high-resolution computer modelling and wind tunnel models together with measurements of the wind field above, in and downstream of large wind farms, using lidars, radars, satellites and Unmanned Aerial Systems.

Besides the natural science package, one humanities PhD student at the University of Copenhagen will investigate the collaboration between the researchers from a social science and collaboration tools perspective.

The main work is done during the education of 18 fellows, where 13 embark on a PhD, while the other ones are employed for one year. The students will work with high-fidelity numerical simulations, lidars, unmanned aerial systems, wind tunnels and satellite data in order to understand entrainment of new momentum in very large wind farms. This changes the atmospheric boundary layer over a very extended wind farm, which becomes a wind turbine array boundary layer. The resulting change in wind resource is the main object of interest. The main planned activity is an experimental campaign at a major cluster of wind farms, probably in the North Sea. Another activity revolves around vertical axis turbines and their significantly different wake pattern, a potential mitigation measure.

So far we recruited the fellows and started with the simulations and the development of the hardware. We intend to employ a vertical take-off and landing model plane with a wing span of about 2m, which would allow to start and land from a helicopter pad offshore, and after the vertical start enjoy the advantage of a winged plane and its much larger range and endurance. Another instrument is a hexacopter mounted with a sonic anemometer, which allows to sample in a single point much akin a conventional met mast, but at any given point in or above a large wind farm. Lidar usage and development is part of the project as well, with a floating lidar in Bergen University and long-range lidars at DTU.

There are three numerical codes used in Train2Wind: Ellipsys3D, a Large Eddy Simulation (LES) high-fidelity code from DTU, WIRE-LES, another LES code from EPFL, and the Weather Research and Forecasting model run at DTU.

The outcome of the project is more knowledge of the entrainment process, and a guidance on how close to position clusters of wind farms in order not to exhaust the wind resource. The talk will give an overview of the project, highlighting the challenges.

How to cite: Giebel, G., Göçmen, T., Mann, J., Sempreviva, A. M., Lund, H., Reuder, J., Bange, J., and Porte-Agel, F.: Train2Wind, or how large is an infinite wind farm?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15816, https://doi.org/10.5194/egusphere-egu21-15816, 2021.

EGU21-6020 | vPICO presentations | ERE2.1

Ten years of the Wind Atlas of South Africa: Final results from WASA 3

Andrea Hahmann, Chris Lennard, Rogier Floors, Dalibor Cavar, Niels G. Mortensen, Bjarke T. Olsen, Leon Prinsloo, Andreas Bechmann, Neil Davis, and Jens Carsten Hansen

We present the evolution of the methods used to create and validate the various numerical wind atlases during the past ten years of the Wind Atlas for South Africa (WASA) project. In WASA 3, we improved on the previous numerical wind atlases by:

  • Creating an ensemble of 2-year simulations to find the optimal set of parameterisations and surface conditions for the wind climate of South Africa.
  • Using a new method of generalisation and downscaling of the WRF-derived wind climate using the PyWAsP engine.
  • Producing the most extensive to date wind climatology for South Africa, 30 years (1990–2019) simulation covering all South Africa at 3.33 km × 3.33 km spatial resolution and 30 minutes time output.

We will discuss these three areas and their improvements to the wind atlas' quality. The WASA 3 wind atlas' final error statistics show that the new WRF + PyWAsP method has a MAPE of 11.8% and 3.5% for the long-term mean power density and mean wind speed, respectively. These statistics are improved from those in WASA 1 and WASA 2.

When disregarding the two masts (WM09 and WM11) located in highly complex terrain, where the methodology was never designed, the use of the WRF and WRF + PyWAsP downscaling narrows the error distributions for both long-term wind speed and power density compared to the global reanalysis, ERA5.

The validated numerical wind atlas has further been used to model the wind resources of the entire land area of South Africa using the microscale WAsP model. Raster data exist with a horizontal resolution of 250 meters and three levels of 50, 100 and 150 meters a.g.l. of mean wind speed, power density, air density, Weibull A and k parameters, and ruggedness index.  These data sets and the WRF dataset will be made available in the public domain at the end of the project. Data sets for other heights above the ground and offshore can easily be added later.

How to cite: Hahmann, A., Lennard, C., Floors, R., Cavar, D., Mortensen, N. G., Olsen, B. T., Prinsloo, L., Bechmann, A., Davis, N., and Hansen, J. C.: Ten years of the Wind Atlas of South Africa: Final results from WASA 3, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6020, https://doi.org/10.5194/egusphere-egu21-6020, 2021.

EGU21-5829 | vPICO presentations | ERE2.1

Extreme gust atlas over South Africa

Xiaoli Larsén, Andries Kruger, Rogier Floors, Dalibor Cavar, and Andrea Hahmann

An atlas of the 50-year gust wind at a resolution of 3 s is calculated over South Africa, at a spatial resolution of 3.3 km at several heights, including 10 m and 60 m where measurements are available.

In developing the atlas, first, 30-year wind climate (1990 - 2019) is simulated using the Weather Research and Forecasting (WRF) model. The WRF model was initialized and forced with the ERA5 data, with three nested domains and the innermost one, covering the whole country, has a spatial resolution of 3.3 km. The model outputs include the wind time series at several heights (50 m, 100 m and 200 m) every 30 minutes. The 50-year 30-min winds at several heights are then obtained by application of a suitable extreme value distribution. Afterwards, the Kaimal turbulence model is applied, in connection with an assumption of Gaussian process for the time series in the time scale 30 min to 3 s, to obtain the corresponding 3 s gust value to the 30-min values of the 50-year winds.

There is a prevalence of a variety of strong wind events in South Africa, including mid-latitude cyclones, fronts and thunderstorms. The different physical mechanisms have different levels of challenges to the simple modeling approaches applied above. For more than 100 measurement stations, the 50-year gust values have also been calculated, mostly at 10 m, some at 60 m. They are used to validate the modeled values and identify regions and areas where our meso-to-turbulence modeling needs improvement or adjustment to eventually produce a verified extreme gust atlas.

How to cite: Larsén, X., Kruger, A., Floors, R., Cavar, D., and Hahmann, A.: Extreme gust atlas over South Africa, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5829, https://doi.org/10.5194/egusphere-egu21-5829, 2021.

EGU21-14402 | vPICO presentations | ERE2.1

Statistical calculation of thrust curve of a wind turbine based on available power curve and general specifications data

Evgeny Atlaskin, Irene Suomi, and Anders Lindfors

Power curves for a substantial number of wind turbine generators (WTG) became available in a number of public sources during the recent years. They can be used to estimate the power production of a wind farm fleet with uncertainty determined by the accuracy and consistency of the power curve data. However, in order to estimate power losses inside a wind farm due to wind speed reduction caused by the wake effect, information on the thrust force, or widely used thrust coefficient (Ct), is required. Unlike power curves, Ct curves for the whole range of operating wind speeds of a WTG are still scarcely available in open sources. Typically, power and Ct curves are requested from a WTG manufacturer or wind farm owner under a non-disclosure agreement. However, in a research study or in calculations over a multitude of wind farms with a variety of wind turbine models, collecting this information from owners may be hardly possible. This study represents a simple method to define Ct curve statistically using power curve and general specifications of WTGs available in open sources. Preliminary results demonstrate reasonable correspondence between simulated and given data. The estimations are done in the context of aggregated wind power calculations based on reanalysis or forecast data, so that the uncertainty of wake wind speed caused by the uncertainty of predicted Ct is comparable, or do not exceed, the uncertainty of given wind speed. Although the method may not provide accurate fits at low wind speeds, it represents an essential alternative to using physical Computational Fluid Dynamics (CFD) models that are both more demanding to computer resources and require detailed information on the geometry of the rotor blades and physical properties of the rotor, which are even more unavailable in open sources than power curves.

How to cite: Atlaskin, E., Suomi, I., and Lindfors, A.: Statistical calculation of thrust curve of a wind turbine based on available power curve and general specifications data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14402, https://doi.org/10.5194/egusphere-egu21-14402, 2021.

Solar Photovoltaic (PV) has the potential to fulfill a considerable amount of growing electricity demands worldwide.  In addition, being neat and clean, it can help to keep the greenhouse gases emission within safe limits. This resource needs a substantial amount of area for its sitting to supply the required amount of electricity. Such an area mainly depends on the available solar resource which is mainly the function of the local environment where PV is installed. Although some previous studies exist at the global scale, however, they have not comprehensively considered environmental (e.g., temperature, dust deposition, and snow) limiting factors that affect the actual solar PV yield. This study addresses such shortcomings and deals with all limiting factors simultaneously to provide a reliable assessment of potential PV performance at a global scale. PV cell efficiency is reduced due to an increase in resistance between cells at a temperature above a certain limit. Meanwhile, the accumulation of soil (dust) and snow on PV modules are also proven to limit the solar PV resources as it tends to block the incoming solar radiation. Lastly, the geomorphological parameter, which is an arrangement of a PV module to face the sun, is also shown to change its power output.

PV cell efficiency corrections for temperature changes, soil, and snow covers are applied using the biased corrected data from Global Soil Wetness Project 3 (GWSP3), CanSISE Observation-Based Ensemble of Northern Hemisphere Terrestrial Snow Water Equivalent, Version 2 from National Snow and Ice Data Center (nsidc), and TERRA/MODIS Aerosol Optical Thickness data available from NASA Earth Observations (NEO). The daily mean solar climatological values near the Earth’s surface for the last 14 years (2001–2014) with global coverage of 0.5º x0.5º are used in the analysis. The results have demonstrated that PV performance is affected by temperature increase, soil, snow, and varying tilt-angles. An annual maximum reduction of 5.7% in the total solar PV resource is seen in the Middle East due to the temperature changes. Likewise, a maximum loss of 6.45% in the total solar PV resource is witnessed for soil deposition for Sub-Saharan Africa. A higher reduction (~20%) is shown by snow covers for Russia and Canada in the upper Northern Hemisphere. In addition, a decline of 5–7% is observed for variation in the solar PV tilt-angles in comparison to optimum ones. As a whole, a maximum reduction of 19.45% in the total solar PV resource is found, which leads to a higher coefficient of determination (R2= 0.78) than uncorrected estimation (R2=0.67). This study will be helpful for household as well as large scale solar schemes and may contribute particularly to achieving the UN SDG No. 07 — Affordable and Clean Energy — and No. 13 — Climate Action — quantitatively.

How to cite: Ali, M. and Kim, H.: Global assessment for reduction of solar photovoltaic potential due to meteorological and geomorphological limiting factors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5773, https://doi.org/10.5194/egusphere-egu21-5773, 2021.

EGU21-15214 | vPICO presentations | ERE2.1

Estimation of photovoltaic energy generated in urban environments, case: Medellín Metropolitan Area (MMA) (Colombia)

Nathalia Correa Sánchez, Oscar José Mesa Sánchez, and Carlos David Hoyos Ortíz

This work considers photovoltaic solar energy as an alternative to promote the diversification of the energy matrix and contribute to improving access to the citizens of Medellín (MMA) Metropolitan Area,  Colombia. The objective is a more sustainable and resilient energy use.  To achieve this, we assess how much of the energy demand can be generated within the city, integrated into the urban morphology at the roofs of existing buildings. We use meteorological information and power measurements from three experimental solar panels. We analyze the photovoltaic energy potential in these Representative Urban Areas (RUA) and provide information relevant to the whole Valley's context to guide sustainable and resilient energy planning.  One particular result is about the energy reduction factor due to cloudiness, which quantifies how energy would vary under the region's cloud conditions.

How to cite: Correa Sánchez, N., Mesa Sánchez, O. J., and Hoyos Ortíz, C. D.: Estimation of photovoltaic energy generated in urban environments, case: Medellín Metropolitan Area (MMA) (Colombia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15214, https://doi.org/10.5194/egusphere-egu21-15214, 2021.

EGU21-7218 | vPICO presentations | ERE2.1

Assessment of a newly developed short-term forecasting system (nextSENSE) of Downwelling Surface Solar Irradiance (DSSI) and validation with ground-based measurements

Kyriakoula Papachristopoulou, Ilias Fountoulakis, Panagiotis Kosmopoulos, Dimitris Kouroutsidis, Panagiotis I. Raptis, Charalampos Kontoes, Maria Hatzaki, and Stelios Kazadzis

Monitoring and forecasting cloud coverage is crucial for nowcasting and forecasting of solar irradiance reaching the earth surface, and it’s a powerful tool for solar energy exploitation systems.

In this study, we focused on the assessment of a newly developed short-term (up to 3h) forecasting system of Downwelling Surface Solar Irradiation (DSSI) in a large spatial scale (Europe and North Africa). This system forecasts the future cloud position by calculating Cloud Motion Vectors (CMV) using Cloud Optical Thickness (COT) data derived from multispectral images from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) satellite and an optical flow motion estimation technique from the computer vision community. Using as input consecutive COT images, CMVs are calculated and cloud propagation is performed by applying them to the latest COT image. Using the predicted COT images, forecasted DSSI is calculated using Fast Radiative Transfer Models (FRTM) in high spatial (5 km over nadir) and temporal resolution (15 min time intervals intervals).

A first evaluation of predicted COT has been conducted, by comparing the predicted cloud parameter of COT with real observed values derived by the MSG/SEVIRI. Here, the DSSI is validated against ground-based measurements from three Baseline Surface Radiation Network (BSRN) stations, for the year 2017. Also, a sensitivity analysis of the effect on DSSI for different cloud and aerosol conditions is performed, to ensure reliability under different sky and climatological conditions.

The DSSI short-term forecasting system proposed, complements the existing short-term forecasting techniques and it is suitable for operational deployment of solar energy related systems

Acknowledgements

This study was funded by the EuroGEO e-shape (grant agreement No 820852).

How to cite: Papachristopoulou, K., Fountoulakis, I., Kosmopoulos, P., Kouroutsidis, D., Raptis, P. I., Kontoes, C., Hatzaki, M., and Kazadzis, S.: Assessment of a newly developed short-term forecasting system (nextSENSE) of Downwelling Surface Solar Irradiance (DSSI) and validation with ground-based measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7218, https://doi.org/10.5194/egusphere-egu21-7218, 2021.

EGU21-16091 | vPICO presentations | ERE2.1

Assessment of Alternative Ways to Integrate Weather Predictions in Photovoltaic Generation Forecasting. 

Kevin Bellinguer, Robin Girard, Guillaume Bontron, and Georges Kariniotakis

In recent years, the share of photovoltaic (PV) power in Europe has grown: the installed capacity increased from around 10 GW in 2008 to nearly 119 GW in 2018 [1]. Due to the intermittent nature of PV generation, new challenges arise regarding economic profitability and the safe operation of the power network. To overcome these issues, a special effort is made to develop efficient PV generation forecasting tools.

 

For short-term PV production forecasting, past production observations are typically the main drivers. In addition, spatio-temporal (ST) inputs such as Satellite-Derived Surface Irradiance (SDSI) provide relevant information regarding the weather situation in the vicinity of the farm. Moreover, the literature shows us that Numerical Weather Predictions (NWPs) provide relevant information regarding weather trends.

 

NWPs can be integrated in the forecasting process in two different ways. The most straightforward approach considers NWPs as explanatory input variables to the forecasting models. Thus, the atmosphere dynamics are directly carried by the NWPs. The alternative considers NWPs as state variables: weather information is used to filter the training data set to obtain a coherent subset of PV production observations measured under similar weather conditions as the PV production to be predicted. This approach is based on analog methods and makes the weather dynamics to be implicitly contained in the PV production observations. This conditioned learning approach permits to perform local regressions and is adaptive in the sense that the model training is conditioned to the weather situation.

The specialized literature focuses on spot NWPs which permits to find situations that evolve in the same way but does not preserve ST patterns. In this context, the addition of SDSI features cannot make the most of the conditioning process. Ref. [3] proposes to use geopotential fields, which are wind drivers, as analog predictors.

 

In this work, we propose the following contributions to the state of the art:

We investigate the influence of spot NWPs on the performances of an auto-regressive (AR) and a random forest models according to the two above-mentioned approaches: either as additional explanatory features and/or as analog features. The analogy score proposed by [2] is used to find similar weather situations, then the model is trained over the associated PV production observations. The results highlight that the linear model performs better with the conditioned approach while the non-linear model obtains better performances when fed with explanatory features.

Then, the similarity score is extended to gridded NWPs data through the use of a principal component analysis. This method allows to condition the learning to large-scale weather information. A comparison between spot and gridded NWPs conditioned approaches applied with AR model highlights that gridded NWPs improves the influence of SDSI over forecasting performances.

 

The proposed approaches are evaluated using 9 PV plants in France and for a testing period of 12 months.

 

References

[1]      IRENA - https://www.irena.org/Statistics/Download-Data

[2]      Alessandrini, Delle Monache, et al. An analog ensemble for short-term probabilistic solar power forecast. Applied Energy, 2015. https://doi.org/10.1016/j.apenergy.2015.08.011

[3]      Bellinguer, Girard, Bontron, Kariniotakis. Short-term Forecasting of Photovoltaic Generation based on Conditioned Learning of Geopotential Fields. 2020, UPEC. https://doi.org/10.1109/UPEC49904.2020.9209858

How to cite: Bellinguer, K., Girard, R., Bontron, G., and Kariniotakis, G.: Assessment of Alternative Ways to Integrate Weather Predictions in Photovoltaic Generation Forecasting. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16091, https://doi.org/10.5194/egusphere-egu21-16091, 2021.

EGU21-13850 | vPICO presentations | ERE2.1

Climate change impact on photovoltaic potential in Poland

Malgorzata Zdunek

Due to global warming and the worldwide depletion of fossil fuel resources, there is a growing need to transform the energy system toward greater use of renewable sources. In Poland, poor air quality constitutes an additional argument for the necessity of such transition. High levels of pollutants concentrations in many locations, especially in urban and suburban areas are caused by emissions from individual heating systems running on fossil fuels.

Data from recent years show that renewable generation forms the largest share of the total generation mix in Europe. Regarding new installation, solar and wind energy dominate renewable capacity expansion, jointly accounting for example in 2019 for 90% of all net renewable additions. However, along with the increase in the penetration of these energy sources also increases the sensitivity of the power system to weather and climatic conditions.

The study presents the impact of climate change up to the year 2100 on the photovoltaic power generation potential (Pvpot) in Poland. For determination of Pvpot index a set of high-resolution climate models projections, made available within the EURO-CORDEX initiative was used. Maps showing spatial distribution of absolute values of Pvpot in future climate (30-year average for 2071-2100) and relative changes with respect to current climate (30-year average for 2006-2035) are presented, separately for RCP4.5 and RCP8.5 scenario. The influence of meteorological conditions (temperature, wind and solar radiation) on PV module performance is taken into account by applying two different formula (Ciulla et. al, 2014 and Davy and Troccoli, 2012). Furthermore, two options for module orientation are considered: horizontal and inclined at an optimal angle.

How to cite: Zdunek, M.: Climate change impact on photovoltaic potential in Poland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13850, https://doi.org/10.5194/egusphere-egu21-13850, 2021.

EGU21-15646 | vPICO presentations | ERE2.1

Spatio-temporal ensemble predictions for wind and solar energy combining dispersion modelling methods and machine learning

Irene Schicker, Petrina Papazek, Elisa Perrone, and Delia Arnold

With the increasing usage of renewable energy systems to meet the climate agreement aims accurate predictions of the possible amount of energy production stemming from renewable energy systems are needed. The need for such predictions and their uncertainty is manifold: to estimate the load on the power grid, to take measures in case of too much/not enough renewable energy with reduced nuclear energy availability, rescheduling/adjusting of energy production,  maintenance, trading, and more. Furthermore, TSOs and energy providers need the information as finegrained, spatially and temporarily, as possible, on third level hub or even on solar farm / wind turbine level for a comparatively large area.

These needs pose a challenge to numerical weather prediction (NWP) post-processing methods. Typically, one uses selected NWP fields aswell as observations, if available, as input in post-processing methods. Here, we combine two post-processing methods namely a neural network and random forest approach with the Flex_extract algorithm. Flex_extract is the pre-processing algorithm for the langrangian particle dispersion model FLEXPART and the trajectory model FLEXTRA. Flex_extract uses the three-dimensional wind fields of the NWP model and calculates additionally the instantaneous surfaces fluxes. Thus, coupling Flex_extract with a machine learning post-processing algorithm enables the usage of native NWP fields with a higher vertical accuracy than pressure levels. To generate an ensmeble in post-processing from deterministic sources different tools are available. Here, we will apply the Schaake Shuffle. 

In this study a neural network and random forest approach for probabilistic forecasting with a high horizontal grid resolution (1 km ) as well as a high temporal forecasting frequency of wind speed and global horizontal irradiance for Austria will be presented. Evaluation will be carried out against gridded analysis fields and observations.

How to cite: Schicker, I., Papazek, P., Perrone, E., and Arnold, D.: Spatio-temporal ensemble predictions for wind and solar energy combining dispersion modelling methods and machine learning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15646, https://doi.org/10.5194/egusphere-egu21-15646, 2021.

EGU21-13417 | vPICO presentations | ERE2.1

IEA Wind Task 36 – International Collaboration on Forecast Improvements

Gregor Giebel, Will Shaw, Helmut Frank, Caroline Draxl, John Zack, Pierre Pinson, Corinna Möhrlen, George Kariniotakis, and Ricardo Bessa

The International Energy Agency (IEA) Wind Task 36 on Wind Power Forecasting organises international collaboration, among national weather centres with an interest and/or large projects on wind forecast improvements (NOAA, DWD, ...), forecast vendors and forecast users to facilitate scientific exchange to be prepared for future challenges.

The talk discusses the general setup of the Task, and the latest developments. Among those are decision making under uncertainty. To this aim, a series of forecasting experiments are being developed and one initial experiment was tested by a wide audience. The forecasting experiments took the form of a game, during which the participants could experience the benefit of probabilistic information on their decisions to trade.
Other results include an information portal for meteorological data, and the IEA Recommended Practice for Forecast Solution Selection which is divided into 3 parts:  (1) "Forecast Solution Selection Process", (2) "Designing and Executing Forecasting Benchmarks and Trials", and  (3) "Evaluation of Forecasts and Forecast Solutions". The Recommended Practice guideline encourages forecast users to establish a framework of metrics that help identify, whether the user's forecast performance criteria effectively incentivize the forecast provider to optimize towards the forecast target variable that has the most value for the user's application(s). For this year, we intend to update the guideline in the light of the experiences throughout the industry in its initial application, and after collecting this experience at 3 Open Space workshops.

Collaboration is open to IEA Wind member states; 12 countries are already actively collaborating.

The Task is divided in three work packages: Work Package (WP) 1 is a collaboration on the improvement of the scientific basis for the wind predictions themselves. This includes numerical weather prediction (NWP) model physics, but also widely distributed information on accessible datasets. This WP also currently organises a benchmark for NWP models, based on the Wind Forecast Improvement Project 2 (WFIP2) datasets. WP2 deals with the power conversion from the wind speed forecasts and the associated vendor issues. Amongst other things, WP2 published the IEA Recommended Practice on how to select an optimal wind power forecast solution for a specific application. The focus of WP3 is on the engagement of end users to disseminate the best practice in the use of wind power predictions, especially probabilistic forecasts and also what kind of measurements are required in real-time environments

A major activity of the Task is the organisation of workshops and special sessions at conferences, like this one. Previous workshops on e.g. forecasting on the minute scale including lidars, a workshop on the value of forecasts, or special sessions on the Wind Energy Science Conference, the Wind Integration Workshop, the ESIG Meteorology and Market Design for Grid Services workshops are still visible online from the IEAWindForecasting YouTube channel.

How to cite: Giebel, G., Shaw, W., Frank, H., Draxl, C., Zack, J., Pinson, P., Möhrlen, C., Kariniotakis, G., and Bessa, R.: IEA Wind Task 36 – International Collaboration on Forecast Improvements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13417, https://doi.org/10.5194/egusphere-egu21-13417, 2021.

EGU21-5642 | vPICO presentations | ERE2.1

Strength and Challenges of global model MPAS with regional mesh refinement for mid-latitude storm forecasting: A case study

Marc Imberger, Xiaoli Guo Larsén, and Neil Davis

Mid-latitude storms are large-scale weather patterns. They involve a large range of spatial and temporal atmospheric scales of motion. Their characteristic extreme precipitation, wind gusts and high surface winds can significantly impact wind farms (e.g. shutdowns of turbines due to exceedance of cut-off wind speed) affecting grid performance and safety. Adequate storm forecasting, which relies on high spatial model resolution, is crucial. Traditional methods usually involve the use of limited area models (LAMs). While the performance of LAMs is generally satisfactory, challenges arise when large-scale storm structures enter near the the lateral boundaries of the LAM. In this case, insufficient update intervals of the forcing data at the lateral boundaries and spatial and temporal interpolation can deteriorate the storm structure that cause insufficient storm deepening. The global Model for Prediction Across Scales (MPAS) with regional mesh refinement avoids lateral boundary conditions and allows refinement with smooth transition zones. Based on a case study of storm “Christian”, MPAS’ capabilities in simulating key storm characteristics are explored in this work. Buoy measurements of sea level pressure, reanalysis and forecast products from the Climate Forecast System (CFSv2) and simulations with the Weather Research and Forecasting (WRF) model are used to evaluate the forecast performance with respect to storm intensity, storm arrival time and storm duration. A mesh configuration with refinement from 54-km to 18-km (further referred to as variable-resolution mesh) is compared with quasi-uniform mesh configurations to examine the impact of transition zone and mesh refinement on the storm structure and forecast performance. It is found that MPAS is generally able to predict the storm intensity based on the local minimum sea level pressure, while the estimation of storm arrival time and storm duration have been negatively influenced by model drifts in MPAS and by impacts of the transition zone on the storm development in the variable-resolution configuration. An additional low pressure system emerged in the variable-resolution mesh whereby its presence is sensitive to model physics. The investigation highlights the importance of the transition zone design in MPAS and the need for additional strategies like data assimilation techniques to prevent model drifts for storm forecasting.

How to cite: Imberger, M., Larsén, X. G., and Davis, N.: Strength and Challenges of global model MPAS with regional mesh refinement for mid-latitude storm forecasting: A case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5642, https://doi.org/10.5194/egusphere-egu21-5642, 2021.

EGU21-11009 | vPICO presentations | ERE2.1

Parametrizing wind farms in mesoscale models: review of existing approaches, applications and future advancements

Jana Fischereit, Roy Brown, Xiaoli Guo Larsén, Jake Badger, and Graham Hawkes

With the expansion of wind energy on- and offshore, large-scale wind farm flow effects in a temporal and spatially heterogeneous atmosphere become increasingly relevant. Mesoscale models equipped with a Wind Farm Parametrization (WFP) can be used to study these effects. In the past, different WFPs have been developed and were applied with different aims. The aim of this study is to provide a better overview on existing WFPs, their development stage and application areas. 

Through a systematic literature review based approach, 617 potentially relevant publications were identified, out of which 59 were reviewed in detail. From these studies, 10 different explicit WFPs have been identified along with three main application areas: (1) the characterizations of wind farm flow effects, (2) the environmental impact of wind farms and (3) the implication for wind energy planning.

In this presentation, we will review differences between the identified WFPs including their description of the turbine-induced forces and turbulent kinetic energy production as well as their treatment of sub-grid scale effects. In addition, we will summarize the literature findings on existing validation of the WFPs and on the sensitivity of the WFPs to the mesoscale model set-up. Reviewing the results for the different application areas indicated that wind farm wakes can last for several 10s of kilometers downstream depending on stability, surface roughness and terrain. Therefore, neighbouring wind farms need to be taken into account for regional planning of wind energy. Yet, their environmental impact, in terms of other reviewed parameters than wind, is mostly confined to areas close to the farm.

Based on these findings, we suggest that future work should include, among other things, benchmark-type validation studies with long-term measurements for different WFPs, further developments of WFPs and mesoscale model physics and more interactions between the mesoscale and microscale community.

How to cite: Fischereit, J., Brown, R., Guo Larsén, X., Badger, J., and Hawkes, G.: Parametrizing wind farms in mesoscale models: review of existing approaches, applications and future advancements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11009, https://doi.org/10.5194/egusphere-egu21-11009, 2021.

EGU21-7692 | vPICO presentations | ERE2.1

Modelling windfarm wakes in operational forecasting model HARMONIE-AROME

Natalie Theeuwes, Bart van Stratum, Bert van Ulft, Jan Barkmeijer, Sukanta Basu, and Ine Wijnant

Wind power production in the European Union (EU) is steadily increasing, specifically on the North-Sea. Wind farms are growing both in number and size, while weather models evolve to higher resolutions. This means that the effect of wind farms can no longer be ignored by weather prediction models. Wind farms essentially decelerate the wind (blockage and wake effects) and increase turbulence, indirectly influencing temperature and humidity. In this study, we have included the widely used Fitch et al. (2012) windfarm parameterisation in the operational mesoscale model HARMONIE-AROME. Using our method, we are able to include individual turbines both on- and offshore. The model is evaluated using various datasets, e.g. production data from Elia (Belgium), floating lidar measurements at Borssele Wind Farm, and anemometer measurements from the FINO-towers. The inclusion of the windfarm parameterisation improves the wind forecast near wind farms, also improving the estimate in power production. In addition, we are able to model the effects of wind farms on the boundary-layer temperature and humidity.

Fitch, A. C., Olson, J. B., Lundquist, J. K., Dudhia, J., Gupta, A. K., Michalakes, J., & Barstad, I. (2012). Local and mesoscale impacts of wind farms as parameterized in a mesoscale NWP model. Monthly Weather Review, 140(9), 3017–3038.

How to cite: Theeuwes, N., van Stratum, B., van Ulft, B., Barkmeijer, J., Basu, S., and Wijnant, I.: Modelling windfarm wakes in operational forecasting model HARMONIE-AROME, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7692, https://doi.org/10.5194/egusphere-egu21-7692, 2021.

EGU21-13132 | vPICO presentations | ERE2.1

Wind Energy Forecast Conditioned on Großwetterlage (large scale weather situation)

Greta Denisenko, Markus Abel, Detlef Siebert, Paul Seidler, and Thomas Seidler

Obtaining a quantitative measure for the uncertainty of forecasts for renewable energy has proven to be a challenging problem in the past. We present results on predicting uncertainty of a forecast conditioned on the large weather situation (Großwetterlage). As a first attempt, we use the objective weather classification by the German Meteorological Service (DWD), which sorts the weather into 40 situations based on wind direction, cyclonality and moisture in the atmosphere.

The considered forecasts concern the day-ahead production of solar power for two exemplary solar parks. To quantify the uncertainty, we define five different metrics (based on normalized absolute error and probability distribution), where each one is trained individually using machine learning. As a result, we obtain measures for over- and underprediction conditioned on the said Großwetterlage.

We consider this to be a very promising yet accessible approach to derive a quantitative measure for uncertainties based on the current, day-to-day weather situation. Future work may concern an improvement of the Großwetterlagencharacterization and a general, probabilistic formulation of the problem, e.g. using Bayesian inference.

How to cite: Denisenko, G., Abel, M., Siebert, D., Seidler, P., and Seidler, T.: Wind Energy Forecast Conditioned on Großwetterlage (large scale weather situation), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13132, https://doi.org/10.5194/egusphere-egu21-13132, 2021.

EGU21-16219 | vPICO presentations | ERE2.1

Smart4RES: Improved weather modelling and forecasting dedicated to renewable energy applications.

George Kariniotakis and Simon Camal and the Smart4RES team

In this paper we present the research directions and innovative solutions developed in the European Horizon 2020 project Smart4RES (http://www.smart4res.eu) for better modelling and forecasting of weather variables necessary to optimise the integration of renewable energy (RES) production (i.e. wind, solar, run-of-the-river hydro) into power systems and electricity markets. Smart4RES gathers experts from several disciplines, from meteorology and renewable generation to market- and grid-integration. It aims to contribute to reach very high RES penetrations in power grids of 2030 and beyond, through thematic objectives including:
•    Improvement of weather and RES forecasting (+10-15% in performance),
•    Streamlined extraction of optimal value through new forecasting products, data market places, and novel business models,
•    New data-driven optimization and decision-aid tools for market and grid management applications.
•    Validation of new models in living labs and assessment of forecasting value vs costly remedies to hedge uncertainties (i.e. storage). 

Smart4RES focuses both on improving forecasting models of weather (e.g. physical models, data assimilation, Large Eddy Simulation) and RES production (e.g. seamless models, highly resolved predictions), and on addressing applications in power grids. Developments in the project have been formalized in Use Cases that cover a large range of time frames, technologies and geographical scales. For example, use-cases on power grids refer to the provision of ancillary services to the upper-level grid (e.g., balancing power) and the local grid (e.g., voltage control and congestion management), where the accurate forecasts of variable generation are key for accurate decision-making. A grid state forecasting will quantify dynamically the flexibility potential of RES in distribution grids. Collaborative forecasting investigates the improvement associated to local data sharing between distributed RES plants. This data sharing paves the way to a data market where agents exchange measurements, predictions or other types of valuable data. Lastly, data-driven approaches will streamline decision-making by simplifying the model chain of bidding RES production, storage dispatch or predictive management electricity grids. They will also provide interpretable hindsight to decision-makers by integrating the decisions of experts (human-in-the-loop) and will be tested in realistic laboratory conditions (software-in-the-loop).

In this paper we focus on the work done for improving modelling and forecasting of weather variables; i.e. through innovative measuring set-ups (i.e. a network of sky cameras in Germany); through the development of seamless numerical weather prediction (NWP) approaches to be able to couple outputs of NWP models with different resolutions; through ultra high resolution NWPs based on Large Eddy Simulation. We present results using data from real world test cases considered in the project. Finally we assess how the new forecasting products may bring value to the applications. 

How to cite: Kariniotakis, G. and Camal, S. and the Smart4RES team: Smart4RES: Improved weather modelling and forecasting dedicated to renewable energy applications., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16219, https://doi.org/10.5194/egusphere-egu21-16219, 2021.

EGU21-2228 | vPICO presentations | ERE2.1

Evaluation of S2S forecasts over India for renewable energy applications

Aheli Das and Somnath Baidya Roy

This study evaluates S2S forecasts of meteorological variables relevant for the renewable energy sector from six global coupled forecast models: ECMWF-SEAS5, DWD- GCFS 2.0, Météo-France’s System 6, NCEP-CFSv2, UKMO- GloSea5-GC2-LI, and CMCC-SPS3. The variables include 10m wind speed, incoming shortwave radiation, 2 m temperature, and relative humidity because these variables are critical for estimating the supply and demand of renewable energy. The study is conducted over seven homogenous climate regions of India for 1994-2016 April and May when energy demand peaks throughout the country. The evaluation is done by comparing the forecasts at 1, 2, 3, 4, and 5-months lead-times with ERA5 reanalysis data. In order to assess the forecast quality, deterministic metrics such as bias and correlation and probabilistic metrics such as Ranked Probability Score (RPS) and Continuous Ranked Probability Score (CRPS) are calculated by spatially averaging the forecasts and reanalyses over each region. The tercile limits for each variable are determined separately for each homogenous region from the ERA5 reanalysis using leave-one-out cross-validation. The forecasts show the highest skill at 1-month lead-time and the skill reduces with the increase in lead-time. However, deviations from this pattern are observed in some cases. For example, the 2 m temperature forecasts tend to perform better at longer lead-times over the western Himalayas perhaps because the slowly-varying snow dynamics aids in long-term predictability. The 2 m temperature and relative humidity forecasts generally show high correlations with observations over the western coast of the Indian peninsula in May at all lead-times, indicating the ability of the models to simulate presence of moisture prior to monsoon onset. Results show that the model performance depends on time-period of initialisation, better representation of surface fluxes, interaction between radiation and microphysics schemes, land-surface processes and factors governing radiative forcing such as greenhouse gases and aerosols. Overall, the SEAS5 model performs better than other models, although the Météo-France’s System 6 and UKMO- GloSea5-GC2-LI models also perform well in some regions.

How to cite: Das, A. and Baidya Roy, S.: Evaluation of S2S forecasts over India for renewable energy applications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2228, https://doi.org/10.5194/egusphere-egu21-2228, 2021.

EGU21-7671 | vPICO presentations | ERE2.1

Long-term climate change effects in the European offshore wind energy 

Stefano Susini and Melisa Menendez

Climate change and offshore renewable energy sector are connected by a double nature link. Even though energy generation from clean marine sources is one of the strategies to reduce climate change impact within next decades, it is expected that large scale modification of circulation patterns will have in turn an impact on the spatial and temporal distribution of the wind fields. Under the WINDSURFER project of the ERA4CS initiative, we analyse the climate change impact on marine wind energy resource for the European offshore wind energy sector. Long-term changes in specific climate indicators are evaluated over the European marine domain (e.g. wind power density, extreme winds, operation hours) as well as local indicators (e.g. gross energy yield, capacity factor) at several relevant operating offshore wind farms.

Adopting an ensemble approach, we focus on the climate change greenhouse gases scenario RCP8.5 during the end of the century (2081-2100 period) and analyze the changes and uncertainty of the resulting multi-model from seven high resolution Regional Climate Models (RCM) realized within Euro-Cordex initiative (EUR-11, ~12.5km). ERA5 reanalysis and in-situ offshore measurements are the historical data used in present climate.

Results indicate a small decrease of wind energy production, testified by reduction of the climatological indicators of wind speed and wind power density, particularly in the NW part of the domain of study. The totality of the currently operating offshore windfarms is located in this area, where a decrease up to 20% in the annual energy production is expected by the end of the century, accompanied by a reduction of the operation hours between 5 and 8%. Exceptions are represented by Aegean and Baltic Sea, where these indicators are expected to slightly increase. Extreme storm winds however show a different spatial pattern of change. The wind speed associated to 50 years return period decreases within western Mediterranean Sea and Biscay Bay, while increases in the remaining part of the domain (up to 15% within Aegean and Black Sea). Finally, the estimated variations in wind direction are relevant on the Biscay Bay region.

How to cite: Susini, S. and Menendez, M.: Long-term climate change effects in the European offshore wind energy , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7671, https://doi.org/10.5194/egusphere-egu21-7671, 2021.

EGU21-10141 | vPICO presentations | ERE2.1 | Highlight

Optimal design and Levelized Cost of Electricity of 100% solar power microgrids in Africa: robustness and sensitivity to meteorological and economical drivers. 

Théo Chamarande, Benoit Hingray, Sandrine Mathy, and Nicolas Plain

Autonomous micro-grids based on solar photovoltaic (PV) are one of the most promising solution to bring electricity access in many off-grid regions worldwide. The sizing of these microgrids is not straightforward. It is especially highly sensitive to the multiscale variability of the solar resource, from sub-daily to seasonal times scales (cf. Plain et al. 2019). Because of this, achieving a given level of service quality requires to provision 1) storage and 2) extra PV production capacity, the main challenge being to also deliver electricity during times with no solar resource (night) and during periods with low solar resource (e.g. winter). Different storage / PV panel sizes can produce the same level of service quality. The optimal design is typically identified to minimize the levelized cost of electricity (LCOE). The cost optimization however obviously relies on a number of technical and economic hypothesis that come with large uncertainties, such as the installation and maintenance costs of both PV and batteries, the system lifetime or the temporal profile of the electricity load.

This work explores the robustness of the optimal sizing to variations of different such parameters. Using irradiance data from Heliosat SARAH2 and temperatures from ERA5 reanalysis, we simulate the hourly solar PV production of a generic array of PV panels for 200 locations in Africa over a 8-years period. We then identify the configurations (storage, PV panel surface) for which 95% of demand hours are satisfied. For different PV/storage costs’ ratios and different electrical demand profiles, we then identify the configuration with the lowest LCOE.

Our result show that the optimal configuration is highly dependent on the characteristics of the resource, and especially on its co-variability structure with the electric demand on different timescales (seasonal, day-to-day, infra-day). It is conversely very robust to changes to costs hypotheses.

These results have important practical implications. They especially allow us to propose simple design rules that are based on the only characteristics of the solar resource and electrical demand. The storage capacity can be estimated from the 20% percentile of the daily nocturnal demand and the PV surface area can be estimated from the mean daily demand and the standard deviation of the mean daily solar energy.

These rules are very robust. They allow to guess the optimal configuration for different costs’ ratios with a good precision. The normalized root mean square error is 0.17 for the PV capacity, 0.07 for storage capacity and 0.02 for LCOE.

Plain, N., Hingray, B., Mathy, S., 2019. Accounting for low solar resource days to size 100% solar microgrids power systems in Africa. Renewable Energy. https://doi.org/10.1016/j.renene.2018.07.036

How to cite: Chamarande, T., Hingray, B., Mathy, S., and Plain, N.: Optimal design and Levelized Cost of Electricity of 100% solar power microgrids in Africa: robustness and sensitivity to meteorological and economical drivers. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10141, https://doi.org/10.5194/egusphere-egu21-10141, 2021.

Spatial and temporal characteristics of simulated wind fields - stemming from the high-resolution weather model WRF with boundary conditions from ERA5 reanalysis data had been validated against the respective data stemming from measurements regarding annual characteristics as reported by [1]. As one result, the tendency of the WRF sets showed some overestimation of the coherency and underestimation of the power spectral density (PSD).

Here, this investigation is deepened to look on the capability of the modelled data to reflect the variability of the PSD and coherencies of the wind speed fluctuations on a monthly and seasonal (three- monthly) scale.

The intra annual variation of the PSD and the coherence functions are well captured by the WRF-generated wind speeds.  No seasonal dependency can be detected for the underestimation of the spectra from the modelled data. The shape can well be modelled by the approach of [Larsén et al., 2013].  Concerning the coherences, the tendency of an overestimation as detected in the analysis of annual sets, shows up in the seasonal scale in similar magnitude, reflecting a systematic shortcoming of the simulated sets to reflect the spatial inhomogeneity of the field.

[1] Poulsen, T, Beyer, H.G., Cross spectral characteristics of  modelled and measured sets of spatially distributed wind in the Faroe Islands, poster presentation  EGU 2020 (2020)

[2] Larsén, X., Vincent, C., and Larsen, S. (2013). Spectral structure of mesoscale wind over the water. Quarterly Journal of the Royal Meteorological Society, 139:685–700. (2013)

How to cite: Beyer, H. G. and Poulsen, T.: How well do ERA5/WRF generated wind fields reflect the seasonal variability of the spatio-temporal characteristics of wind field, tested for North-Atlantic conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7759, https://doi.org/10.5194/egusphere-egu21-7759, 2021.

EGU21-9125 | vPICO presentations | ERE2.1

Low wind spells characterization over Europe as seen from ERA5 reanalysis

Enrique Sanchez, Claudia Gutierrez, Maria Ofelia Molina, and María Ortega

Light wind conditions can be a very relevant feature from the wind power perspective. If such values are below a certain threshold (fixed or relative to some percentile), from the renewable energy production perspective, the amount of such energy is then strongly reduced or even suppressed. Frequency and intensity of such conditions is therefore of high interest, and a characterization of how these conditions can remain in time (during several hours, or days) can be even more important. From a climatic perspective, those episodes could be named as spells. This is the case of dry or wet ones, when referring to precipitation and its absence, or hot or cold ones, when focusing on temperatures. There is plenty of literature focused on that extreme conditions, for example in the set of indices to define extreme events developed by the ETCCDI (the CCl/CLIVAR/JCOMM Expert Team (ET) on Climate Change Detection and Indices: http://etccdi.pacificclimate.org/). However, no mention is made to wind there. Here, we will explore the application of those indices for temperature and precipitation, but now applied to wind values, when they remain below normal values during a certain period of time. Several considerations will first be made to define light wind thresholds. Then, the statistical characterization of the persistence of those conditions will be inspected. ERA5 reanalysis over Europe for the last 40 years is used as the database to perform such analysis, at a resolution of 0.25 degrees for the whole region. From ERA5 time frequency, we are able to analyze hourly scales, due to the high time variability of wind, which can be also of quite relevant interest from the energetic resource perspective. We also analyze daily scales, which is more typical from a climatic focus, and see how these results can be related to mean wind conditions at each point. Time climatic variability and spatial obtained patterns are also studied. Results from this work will be useful to advance in a more systematic and rigorous climatic description of such wind conditions, that would be very important from the energy perspective, for example. In particular, we are interested in exploring the recently developed concept of energy droughts (Raynaud et al., 2018).

How to cite: Sanchez, E., Gutierrez, C., Molina, M. O., and Ortega, M.: Low wind spells characterization over Europe as seen from ERA5 reanalysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9125, https://doi.org/10.5194/egusphere-egu21-9125, 2021.

Low production of renewable energy for up to several days can cause stress on the electricity system, especially when such events coincide with high demand. Meteorological conditions leading to extremely low production of wind and PV power are known. These are periods of relatively little irradiance and anomalously weak winds. Past work underlined the importance of high-pressure systems over Central Europe during winter for causing such conditions. However, there is less known about low-production periods in other seasons and their regional scale characteristics from a climatological perspective. Despite being probably less severe in summer, low-production events can nevertheless be problematic. One example is the higher electricity demand for cooling systems in summer, which is especially relevant in the context of climate change.

Here we statistically analyse the synoptic meteorological conditions causing low-production events of wind and solar power in Europe for winter and summer. To this end, we use a daily weather regime classification for Europe from the German Weather Service, known as “Grosswetterlagen” (GWL). Our simulation of the production of wind and PV power is based on the reanalysis data COSMO-REA6 for Europe with a horizontal resolution of 6 km, and an established wind and PV power model, developed in the research area “Climate Monitoring and Diagnostics” of the Hans-Ertel Centre for Weather Research. Scenarios of gridded installed capacity of PV and wind power plants in Europe for 2050 are taken from the CLIMIX model to calculate hourly power production. Our composite analysis of the PV and wind power production associated with the different GWLs highlight (1) the regional differences in the power production in Europe across country borders and (2) different regional patterns of anomalies in power production depending on  GWLs. Based on our simulations, we derive an atlas of potential PV and wind production associated with different GWLs. This atlas will be helpful to understand which GWLs lead to regionally low-production events, and to what extend the severity of such events can be forecasted in different seasons. Such knowledge is important since the share of wind and solar power continues to increase in the European electricity grid.

How to cite: Ho, L. and Fiedler, S.: Climatology of low wind and solar power production events in Europe with Grosswetterlagen classification, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10164, https://doi.org/10.5194/egusphere-egu21-10164, 2021.

EGU21-15368 | vPICO presentations | ERE2.1

Wind Energy Assessment in Southwestern Europe in December months 2017 to 2020

Ana Gonçalves, Margarida L.R. Liberato, and Raquel Nieto

Renewable resources are dependent on the variability of weather conditions and thus on the availability of the resource as it is the case of wind energy. The huge expansion of the worldwide wind power capacity to produce electricity makes this technology vulnerable to extreme weather conditions such as those associated with extratropical cyclones and extreme weather events (Gonçalves et al., 2020). This work aims to assess the wind resources available and the wind energy potential (WEP) during recent December months (the years 2017 to 2020) in the southwestern Europe. These winter months were characterized by high impact storms with strong winds associated which caused extensive damage. In this region, a total of 10 intense named storms occurred in December: 2017 (Ana, Bruno, and Carmen); 2018 (Etienne and Flora); 2019 (Daniel, Elsa, and Fabien); 2020 (Dora and Ernest) (IPMA; AEMet; Météo France; 2021). To understand the effect of the strong winds associated with the passage of the storms during these months, the ERA5 Reanalysis 10m wind components (10-meter U and V wind components) are retrieved from the European Centre for Medium Range Weather Forecasts (ECMWF) (Hersbach et al., 2019).  The fields were extracted at 00, 06, 12 and 18 UTC (6-hourly data), for the 2017, 2018, 2019 and 2020 December months over a geographical sector that covers the southwestern Europe region (30°N–65°N; 40°W–25°E) and compared to climatological values for the 1981-2010 period. Moreover, the wind energy potential was calculated for the respective December months and the values compared and associated with the values of renewable energy reports available for the Iberian Peninsula and the countries of southwestern Europe. Obtained results show an increase of wind intensity of up to 2 m.s-1 in southwestern Europe during December 2017 and 2019 and a decrease of 2 m.s-1 in December 2018, when compared with the respective climatology for the 1981-2010 period. In December 2020, a significant increase of wind intensity reaching up to 2.8 m.s-1 in the Bay of Biscay region, affecting the Iberian Peninsula and the west coast of France. The increase in wind resource resulted in an increase in wind potential in the months under study. These values are in line with the values of wind energy produced during the months analyzed for the EU-28 countries. Finally, it is shown that the highest values of wind production occurred during the days when the storms hit southwestern Europe.

Acknowledgements

This work is supported by Fundação para a Ciência e a Tecnologia – FCT through the projects PTDC/CTA-MET/29233/2017 (WEx-Atlantic) and UID/GEO/50019/2020. Partial support was also obtained from the Xunta de Galicia under the Project ED431C 2017/64-GRC Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas (Grupos de Referencia Competitiva) and Consellería de Educación e Ordenación Universitaria, cofunding from the ERDF, in the framework of the Operational Program Galicia 2014–2020.

 

References

Agencia Estatal Meteorología, 2021. Online: http://www.aemet.es/es/conocermas/borrascas 

Gonçalves et al., 2020. ECAS 2020, doi:10.3390/ecas2020-08132

Hersbach et al.,  2019. ECMWF Newsletter, Vol 159, pp. 17–24, doi: 10.21957/vf291hehd7

Instituto Português do Mar e da Atmosfera, 2021. Online: https://www.ipma.pt/en/index.html 

Météo France, 2021. Online: http://www.meteofrance.com/accueil 

How to cite: Gonçalves, A., L.R. Liberato, M., and Nieto, R.: Wind Energy Assessment in Southwestern Europe in December months 2017 to 2020, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15368, https://doi.org/10.5194/egusphere-egu21-15368, 2021.

EGU21-550 | vPICO presentations | ERE2.1

A century of European wind and solar power generation variability

Jan Wohland, David J. Brayshaw, and Stefan Pfenninger

To reach its goal of net greenhouse gas neutrality by 2050, the European Union seeks to massively expand wind and solar power. Relying on weather-dependent power generation, however, poses substantial risks if climate variability is not adequately understood and accounted for in energy system design. Through informed combination of centennial reanalyses that have been tested for agreement with large scale climate phenomena, we here quantify European wind and solar generation variability over the last century. We report that wind and solar generation vary on a multidecadal scale, but wind more strongly. We identify hotspots and study dominant patterns of (co-)variability, finding that solar generation varies mostly uniformly across Europe while the leading wind variability modes reveal cross-border balancing potential. Continental scale transmission thus proves useful in balancing wind power variability also on multidecadal timescales. Evaluating local solutions to balance generation variability, we find that combined wind and solar systems optimized for minimal seasonal variability exhibit multidecadal variability of around 10% in many European countries. This amplitude can be reduced three-fold through wind shares optimised for minimal multidecadal variability. Thus, with improved spatial planning only, multiple options to mitigate long-term renewable generation variability exist.

How to cite: Wohland, J., Brayshaw, D. J., and Pfenninger, S.: A century of European wind and solar power generation variability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-550, https://doi.org/10.5194/egusphere-egu21-550, 2021.

EGU21-4692 | vPICO presentations | ERE2.1

Analysis of wind resource under heat wave conditions in southern Europe

María Ofelia Molina, Enrique Sánchez, Claudia Gutiérrez, and María Ortega

In recent years, renewable energy is gaining importance in the energy mix, increasing the dependence of the energy system on weather. Atmospheric patterns that affect wind energy production focusing on the winter months have been studied in previous works, as wind resource in Europe is higher for this season, but also because it is when there is a greater and more stable heating demand in Europe. Southern European countries, however, present summer demand increases due to the cooling needs of these countries (Spain, Portugal , Italy and Greece). These increases have been seen with real daily demand data from ENTSO-E (the European Network of Transmission System Operators for Electricity). Demand in Spain is even higher on days of heat waves in the 2015-2018 period, reaching in that case the annual maxima. The objective of this work is to study the wind patterns in these episodes of heat waves. Reduced overall summer wind power supply coupled with high energy demand under these conditions could be compromised. We will analyse means of daily wind anomalies on days of heat waves (composites) using data from the ERA5 reanalysis and the E-OBS temperature observations. The study of the wind resource in conditions of high energy demand due to extreme climate events, can help in the energy supply strategic planning and control to minimize the impact of these events on an electricity system with high penetration of renewables.

 

How to cite: Molina, M. O., Sánchez, E., Gutiérrez, C., and Ortega, M.: Analysis of wind resource under heat wave conditions in southern Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4692, https://doi.org/10.5194/egusphere-egu21-4692, 2021.

Storm Anatol impacted the North Sea and northern Europe on 3-4 December 1999. It brought hurricane force winds to Denmark and northern Germany, and high winds also in Sweden and the Baltic states.  For many meteorological stations in Denmark, the wind speeds were the highest on record, and the storm was ranked as a century event.  The storm impacts included extensive forest damage, fatalities, hundreds of injuries, power outages, transportation interruptions, as well as storm surge flooding on the west coast of Denmark.  At the time of the storm, Denmark was strongly committed to wind energy, and approximately 10 onshore wind turbines were destroyed during the storm.  An important industry insurer noted that this was a remarkably low number considering the storm intensity and the large number of turbines (>3500) installed in Denmark.  In 1999, offshore wind energy was just getting started in Europe.  Denmark had just started an environmental monitoring program at Horns Rev off the Danish North Sea coast in advance of an offshore wind farm that would be installed in 2002.  The offshore meteorological mast at Horns Rev survived the storm, but the wave field was significant, and it partially disabled the measurement system.
 
This contribution takes a closer look at the regional met-ocean conditions during the storm.  A brief overview is made of the wind field and available wave measurements from the North Sea.  A closer examination is made of water level meaurements from around the North Sea to characterize the storm surge and identify possible meteotsunamis and infragravity waves.  Offshore accidents are briefly discussed to assess if there had been unusual wave strikes on shipping or platforms.  At the time of the storm in 1999, there was a growing awareness in the scientific community of possible changes in sea state conditions in the North Atlantic area and the increasing threat of rogue waves.  The offshore wind energy research platform FINO1 near Borkum in the southern North Sea experienced large wave damage during Storm Britta on 1 November 2006.  There was a repetition of the wave damage during storms in 2007 and 2013.  Storm Anatol in 1999 was a major North Sea storm, and this contribution presents a survey to assess if there was unusual wave phenomena during the event. 

How to cite: Kettle, A.: Storm Anatol over Europe in December 1999: impacts on societal and energy infrastructure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3427, https://doi.org/10.5194/egusphere-egu21-3427, 2021.

ERE2.2 – Spatial and temporal modelling of renewable energy systems

EGU21-1271 | vPICO presentations | ERE2.2 | Highlight

Assessing the impact of land-use change for solar park development in the UK: implications for biodiversity and ecosystem services

Fabio Carvalho, Alona Armstrong, Mark Ashby, Belinda Howell, Hannah Montag, Guy Parker, Joana Cruz, Piran White, and Simon Smart

According to the latest IPCC report, 70 to 85% of electricity generation worldwide will need to come from renewable sources of energy by 2050 if countries are to meet internationally agreed greenhouse gas emissions targets. In the rush to decarbonise energy supplies to meet such targets, solar parks (SPs) have proliferated around the world, with uncertain implications for the biodiversity and ecosystem service (ES) provision of hosting ecosystems. SPs necessitate significant land-use change that could disproportionately affect the local environment compared to other low-carbon sources.

In Britain, SPs are commonly built on intensive arable land and managed as grasslands. This offers both risks and opportunities for ecosystem health, yet evidence for assessing ecosystem consequences is scarce. Therefore, there is an urgent need to understand how net environmental gains can be integrated into land-use change for solar energy development to address the current biodiversity and climate crises.

We used vegetation data from over 70 SPs and 50 countryside survey plots (1 km2) in England and Wales to assess the effects of land-use change for SPs on plant diversity and ES provision. We assessed ten habitat indicator variables (e.g., species richness, larval food plants, forage grasses, bird food plants) associated to functionally important plant species that have the potential to enhance ecosystem service delivery.

SPs showed higher diversity of habitat indicator species than arable land and improved grasslands, with vegetation between solar arrays showing higher numbers of species important for ES provision (e.g., N-fixing species important for nutrient cycling) than vegetation under solar panels. Overall, the diversity of habitat indicator species seemed highly dependent on former land-use, showing SPs have the potential to enhance ecosystem services provision if built on degraded agricultural land.

Developing this understanding will enable optimisation of SP design and management to ensure delivery of ecosystem co-benefits from this growing land-use.

How to cite: Carvalho, F., Armstrong, A., Ashby, M., Howell, B., Montag, H., Parker, G., Cruz, J., White, P., and Smart, S.: Assessing the impact of land-use change for solar park development in the UK: implications for biodiversity and ecosystem services, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1271, https://doi.org/10.5194/egusphere-egu21-1271, 2021.

EGU21-15348 | vPICO presentations | ERE2.2

Land-use impacts of variable renewable energy in Brazil

Olga Turkovska and Johannes Schmidt

Brazil has seen more than a ten-fold increase in wind power capacity in the last decade and in the past few years, the development of solar PV increased as well. However, little is known about the impacts of variable renewable generation (VRES) in Brazil compared to other world regions, although Brazilian wind power infrastructure is concentrated in the least protected ecosystems that are prone to degradation, desertification and species extinction.  Even less is known about solar PV. This study focuses on land-use impacts of past VRES generation development in Brazilian federal states, which cover most of the country's VRES installed capacity. We assessed and compared their spatial installation patterns associated land-use and land cover change in the period before installation until 2019, using a detailed wind turbine and solar PV location database in combination with a high-resolution land-use and land cover map. Also, we explored which drivers contributed to the existing allocation of VRES in Brazil. We found that 62% of the studied wind park area was covered by native vegetation and coastal sands. Overall, 3.2% of the total wind park area was converted from native vegetation to anthropogenic use. Wind parks installed mainly on native vegetation, on average, underwent higher land-use change compared to other wind parks. Similar to wind power, solar PV in some regions e.g., Bahia, occupied mostly native vegetation land, however being installed in closer proximity to anthropogenic land activities than wind power.

How to cite: Turkovska, O. and Schmidt, J.: Land-use impacts of variable renewable energy in Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15348, https://doi.org/10.5194/egusphere-egu21-15348, 2021.

EGU21-2199 | vPICO presentations | ERE2.2

Optimising solar park design and management to boost pollinator abundance

Hollie Blaydes, Alona Armstrong, Duncan Whyatt, Simon Potts, and Emma Gardner

Solar photovoltaics (PV) is projected to become the dominant renewable, with much capacity being installed as ground-mounted solar parks. Land use change for solar can affect ecosystems across various spatial scales and solar parks offer a unique opportunity for ecological enhancement. One compelling potential benefit put in practice by the solar industry is management for insect pollinators. Specifically, solar parks can provide refuge for pollinators through the provision of suitable habitat, potentially contributing to halting and reversing widespread declines recorded in a number of pollinator groups. There is scope to both manage and design solar parks for pollinators, but understanding is limited. Using a combination of GIS and a process-based pollinator model, we explore how solar park size, shape and management could affect ground-nesting bumblebee abundance inside solar parks and surrounding landscapes in the UK. We show that within solar parks, the floral resources provided by different management practices is a key factor affecting bumblebee abundance, but the impacts are dependent on landscape context. In comparison, solar park size and shape have a lesser impact. Moreover, the effects of both solar park management and design extend into the surrounding landscape, affecting bumblebee abundance up to 1 km away from the solar park. If designed and managed optimally, solar parks therefore have the potential to boost local pollinator abundance and pollination services to surrounding land. Our results demonstrate how incorporating biodiversity into solar park design and management decisions could benefit groups such as pollinators and contribute to the wider environmental sustainability of solar parks.

How to cite: Blaydes, H., Armstrong, A., Whyatt, D., Potts, S., and Gardner, E.: Optimising solar park design and management to boost pollinator abundance, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2199, https://doi.org/10.5194/egusphere-egu21-2199, 2021.

EGU21-16017 | vPICO presentations | ERE2.2

How clean is your ‘clean’ energy? The ENVIRO module for energy system models

Nicholas Martin, Cristina Madrid-López, Laura Talens-Peiró, and Bryn Pickering

A decarbonized, renewable energy system is generally assumed to represent a cleaner and more sustainable one. However, while they do promise day-to-day reductions in carbon emissions, many other environmental impacts could occur, and these are often overlooked. Indeed, in the two documents that form the EU Energy Union Strategy (COM/2015/080) the words ‘water’, ‘biodiversity’ or ‘raw materials’ do not appear. This ‘tunnel vision’ is often also adopted in current energy systems models, which do not generally provide a detailed analysis of all of the environmental impacts that accompany different energy scenarios. Ignoring the trade-offs between energy systems and other resources can result in misleading information and misguided policy making.

The environmental assessment module ENVIRO combines the bottom up, high resolution capabilities of life cycle assessment (LCA) with the hierarchical multi-scale upscaling capabilities of the Multi-Scale Integrated Assessment of Socioecosystem Metabolism (MuSIASEM) approach in an effort to address this gap. ENVIRO also takes the systemic trade-offs associated with the water-energy-food-(land-climate-etc.) nexus from MuSIASEM while considering the supply chain perspective of LCA. The module contains a built-in set of indicators that serve to assess the constraints that greenhouse gas (GHG) emissions, pollution, water use and raw material demands pose to renewable energy system scenarios. It can be used to assess the coherence between energy decarbonization targets and water or raw material targets; this can be extended to potentially any economic or political target that has a biophysical component.

In this work, we introduce the semantics and formalization aspects of ENVIRO, its integration with the energy system model Calliope, and the results of a first testing of the module in the assessment of decarbonization scenarios for the EU. The work is part of the research developed in the H2020 Project SENTINEL: Sustainable Energy Transition Laboratory (contract 837089).

How to cite: Martin, N., Madrid-López, C., Talens-Peiró, L., and Pickering, B.: How clean is your ‘clean’ energy? The ENVIRO module for energy system models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16017, https://doi.org/10.5194/egusphere-egu21-16017, 2021.

EGU21-13096 | vPICO presentations | ERE2.2

pyam - an open-source Python package for energy system scenario analysis & visualization

Daniel Huppmann and Matthew Gidden

Background: Transparency, reproducibility and reusability of scientific analysis

Researchers are now widely expected to share the data and source code of their work to foster transparency, reproducibility and reusability.
Alas, the quality of data documentation and scientific software scripts can vary substantially. In many instances, metadata and information on the provenance of data are missing or incomplete, and source code often does not include a clear list of dependencies (including version information) or systems requirements. Finally, the source code does not include sufficient inline documentation to be easily understood. As a consequence, even though the data and related scripts may be released under an open-source license, analysis too often cannot be reproduced or adapted with reasonable effort by other researchers.

The pyam package

This talk presents the open-source Python package pyam for energy system scenario analysis and visualization. The aim of pyam is not to provide any ground-breaking new methods or analysis routines. Instead, it provides a reliable, well-tested interface
similar in feel & style to the widely used pandas package, but geared for data formats and applications often used in energy systems analysis
and integrated assessment modelling.

By using pyam for their scenario input data processing and analysis workflows, researchers can reduce standard tasks like unit conversion and data validation from a 5-minute effort to 30 seconds - and have the knowledge that their scripts won't break if pandas or another dependency change their APIs, because the pyam community will work to ensure forward-compatibility and continuity. As another side benefit, the pyam package will raise meaningful errors when input data doesn't make sense, whereas own ad-hoc scripts may fail silently or - even worse - return non-sensical values.

Spatial, temporal and sectoral aggregation & downscaling features

To highlight the applicability of the pyam package for the EGU community and energy & climate modellers at large, this talk will focus on the features for spatial, temporal and sectoral aggregation and downscaling. The package include several often-used methods like weighting by proxy variables or deriving indicators based on minimum or maximum values of timeseries data.

Building a community

The pyam package follows best-practice of version control, continuous-integration and scientific-software documentation. This facilitates building on the package by other researchers. The community uses several tools for communication and discussion, including a Slack channel, an email list and a Github repository for issues & pull requests. And of course, we appreciate contributions by colleagues to extend the scope of features and methods based on their own use cases and requirements!

More information

ReadTheDocs: https://pyam-iamc.readthedocs.io/
GitHub repo: https://github.com/iamconsortium/pyam

How to cite: Huppmann, D. and Gidden, M.: pyam - an open-source Python package for energy system scenario analysis & visualization, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13096, https://doi.org/10.5194/egusphere-egu21-13096, 2021.

EGU21-4505 | vPICO presentations | ERE2.2 | Highlight

Regional impacts of electricity system transition in Central Europe until 2035

Jan-Philipp Sasse and Evelina Trutnevyte

Achieving current electricity sector targets in Central Europe (Austria, Denmark, France, Germany, Poland and Switzerland) will redistribute regional benefits and burdens at sub-national level. Limiting emerging regional inequalities would foster the implementation success. We model one hundred scenarios of electricity generation, storage and transmission for 2035 in these countries for 650 regions and quantify associated regional impacts on system costs, employment, greenhouse gas and particulate matter emissions, and land use. We highlight tradeoffs among the scenarios that minimize system costs, maximize regional equality, and maximize renewable electricity generation. Here, we show that these three aims have vastly different implementation pathways as well as associated regional impacts and cannot be optimized simultaneously. Minimizing system costs leads to spatially-concentrated impacts. Maximizing regional equality of system costs has higher, but more evenly distributed impacts. Maximizing renewable electricity generation contributes to minimizing regional inequalities, although comes at higher costs and land use impacts.

How to cite: Sasse, J.-P. and Trutnevyte, E.: Regional impacts of electricity system transition in Central Europe until 2035, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4505, https://doi.org/10.5194/egusphere-egu21-4505, 2021.

EGU21-16205 | vPICO presentations | ERE2.2

Decision support for renewables deployment through spatially explicit energy system alternatives

Bryn Pickering, Francesco Lombardi, and Stefan Pfenninger

A decarbonised European energy system will require a number of potentially contested decisions on where best to locate renewable generation capacity. Typically, modellers determine the “best” system based on the least cost to society, focussing on a cost-minimising energy system model result to inform planning and policy. This approach neglects potentially more desirable alternative results which might, for example, avoid problematic concentrations of onshore wind power deployment, increase national supply security, or lower the risk of system failure in adverse weather conditions.

In response, we have developed a method to generate spatially explicit, practically optimal results (SPORES) in the context of energy system optimisation. SPORES can be used to explore energy systems which may offer more socially, politically, or environmentally acceptable alternatives. Furthermore, we have developed metrics to aid identification of interesting alternatives, like those which maximise the spatial distribution of wind generation capacity or minimise exposure to multi-year demand and weather uncertainty.

In this presentation, we will detail the application of the SPORES method in two cases of energy system decarbonisation:  the Italian power system and the European energy system. We will present technology deployment strategies which are prevalent across SPORES, such as solar photovoltaics coupled with battery storage, as well as those which offer flexibility of choice in location and extent of deployment. To help with the urgent task of planning socially and politically acceptable energy system decarbonisation strategies, our implementation of SPORES in the open-source energy systems modelling framework Calliope makes it accessible to a wide range of potential users; we will also discuss how other research groups can further build on this to accelerate the energy transition.

How to cite: Pickering, B., Lombardi, F., and Pfenninger, S.: Decision support for renewables deployment through spatially explicit energy system alternatives, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16205, https://doi.org/10.5194/egusphere-egu21-16205, 2021.

EGU21-716 | vPICO presentations | ERE2.2 | Highlight

Quantifying the trade-off between public acceptance and cost efficiency in decentralized energy systems

Jann Weinand, Russell McKenna, Max Kleinebrahm, and Fabian Scheller

Renewable energy technologies are most economical when planned at a large scale in a coordinated manner. But local resistance often hinders developments, especially for onshore wind. In these decentralized energy systems, the beauty of landscapes is particularly relevant for acceptance of wind turbines or transmission lines. Thus, by using the scenicness as a proxy for public acceptance, we quantify its impact on optimal energy systems of around 11,000 municipalities. In municipalities with high scenicness, it is likely that onshore wind will be rejected, leading to higher levelized costs of energy up to about 5 €-cent/kWh. Onshore wind would be replaced mainly by solar photovoltaics and the cost-optimal energy systems would be associated with higher CO2 emissions of up to about 120%. The quantitative basis that we have created can be used to first identify municipalities where public resistance to onshore wind could be particularly high. Second, the results regarding the increase in costs and CO2 emissions can be used to convince the citizens in these municipalities towards accepting onshore wind installations.

How to cite: Weinand, J., McKenna, R., Kleinebrahm, M., and Scheller, F.: Quantifying the trade-off between public acceptance and cost efficiency in decentralized energy systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-716, https://doi.org/10.5194/egusphere-egu21-716, 2021.

EGU21-185 | vPICO presentations | ERE2.2

The Sensitivity of Power System Expansion Models on Climate Scenarios

Bruno Schyska, Alexander Kies, Markus Schlott, Lueder von Bremen, and Wided Medjroubi

Power system expansion models are a widely used tool for planning power systems, especially considering the integration of renewable resources. Studies using these models form the basis for far-reaching political decisions. The backbone of power system models is an optimization problem, which depends on a number of economic and technical parameters. Although these parameters contain significant uncertainties, a consistent way to quantify the sensitivity to these uncertainties does not yet exist. Here, we analyze and quantify the sensitivity of a power system expansion model to the meteorological parameter time series based on a novel misallocation metric. We find that the sensitivity to the weather data is in the same order of magnitude as the sensitivity to the definition of cost. By comparing different climatic periods both from a meteorological perspective and with respect to the impacts on the optimal power system design we can, additionally, identify representative weather years and periods which should rather not be used for expansion planning.

How to cite: Schyska, B., Kies, A., Schlott, M., von Bremen, L., and Medjroubi, W.: The Sensitivity of Power System Expansion Models on Climate Scenarios, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-185, https://doi.org/10.5194/egusphere-egu21-185, 2021.

EGU21-10011 | vPICO presentations | ERE2.2

Unravelling the opposing effects of network clustering on electricity system models with high shares of renewables

Martha Frysztacki, Jonas Hörsch, Veit Hagenmeyer, and Tom Brown

Energy systems are typically modeled with a low spatial resolution that is based on administrative boundaries such as countries, which eases data collection and reduces computation times. However, a low spatial resolution can lead to sub-optimal investment decisions for renewable generation, transmission expansion or both. Ignoring power grid bottlenecks within regions tends to underestimate system costs, while combining locations with different renewable capacity factors tends to overestimate costs. We investigate these two competing effects in a capacity expansion model for Europe’s future power system that reduces carbon emissions by 95% compared to 1990s levels, taking advantage of newly-available high-resolution data sets and computational advances. We vary the model resolution by changing the number of substations, interpolating between a 37-node model where every country and synchronous zone is modeled with one node respectively, and a 512-node model based on the location of electricity substations. If we focus on the effect of renewable resource resolution and ignore network restrictions, we find that a higher resolution allows the optimal solution to concentrate wind and solar capacity at sites with higher capacity factors and thus reduces system costs by up to 10.5% compared to a low resolution model. This results in a big swing from offshore to onshore wind investment. However, if we introduce grid bottlenecks by raising the network resolution, costs increase by up to 19% as generation has to be sourced more locally where demand is high, typically at sites with worse capacity factors. These effects are most pronounced in scenarios where transmission expansion is limited, for example, by low social acceptance.

How to cite: Frysztacki, M., Hörsch, J., Hagenmeyer, V., and Brown, T.: Unravelling the opposing effects of network clustering on electricity system models with high shares of renewables, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10011, https://doi.org/10.5194/egusphere-egu21-10011, 2021.

EGU21-6563 | vPICO presentations | ERE2.2

Machine learning-based allocation of renewable power production

Marianne Zeyringer, Natalia Sirotko-Sibirskaya, and Fred Espen Benth

The integration of renewable energy sources into the power grid is of the utmost importance for achieving the goal of zero carbon emission. Although there are feasibility studies showing that renewable energy might be able to cover 2050 global energy demand using less than 1 % of the world's land for footprint and spacing, see Jacobson and Delucchi (2011), nowadays renewable energy production is known to be highly intermittent due to substantial uncertainties in the weather conditions. One possibility to reduce such uncertainty (besides storage and employing hydrogen technologies) is spatiotemporally diversified allocation of renewable power capacities which (alongside with the transmission infrastructure) should guarantee that the power demand is met at any given time with a certain (high) probability. We treat the question of spatiotemporal diversification of renewable capacities as a Markowitz portfolio problem with the difference that instead of n = 1, …, N stocks we have geographical locations each with a certain expected level of renewable power production (instead of expected returns for stocks) and the corresponding variance. Another difference to a classical Markowitz portfolio problem is that we require additionally that at each given time point t = 1, …, T, we can reach a predetermined level of renewable power production with a certain probability, i. e. we solve so called chance-constrained problem. Finally, instead of solving one-step problem as it is the case with a Markowitz portfolio we reformulate our problem in the optimal control framework in continuous time and solve it with a reinforcement learning algorithm as suggested in Lillicrap et al. (2019). The advantage of this approach is that the optimal capacities (control) are updated continuously as a response to changing weather conditions (state). We exemplify our approach with the data from ERA5 data, see Hersbach et al. (2020), and suggest possible allocation of renewable energy sources across the European Union.

How to cite: Zeyringer, M., Sirotko-Sibirskaya, N., and Benth, F. E.: Machine learning-based allocation of renewable power production, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6563, https://doi.org/10.5194/egusphere-egu21-6563, 2021.

EGU21-12166 | vPICO presentations | ERE2.2

Optimizing the Norwegian power grid to meet European climate targets

Maximilian Roithner, James Price, Johannes Schmidt, and Marianne Zeyringer

The energy provided by sun or wind changes with time and cannot be regulated. This creates problems currently because society demands energy when it needs it, largely ignoring availability. Transmission grid or energy storage capacity expansion and demand management are proposed strategies to deal with this. They can be used in a mix or can at least partially substitute for one another. By 2050, large amounts of wind and solar power capacity is expected to be deployed in an effort to meet the goals of the EU’s “Green Deal” . Norway is in a position to contribute to a stable European grid due to its hydropower resources as well as excellent wind resources allowing for spatial diversification with wind in the rest of Europe and technological diversification with solar in the South of Europe. Spreading out wind over a larger area or combining it with other technologies can reduce the variability. Yet, a conflict of interest is possible from the Norwegian perspective, as increased interconnection might lead to higher power prices in the country.

Previous research has taken transmission capacity expansion into account. A frequent conclusion was that improved transmission capacity requires less energy storage. Yet to our knowledge, no study has examined the optimal level of Norwegian transmission capacities to reach Europe’s climate goals in a model that embeds Norway into a representation of the whole European system. Also, the above mentioned tension between the European and the Norwegian perspective has not been discussed.

This work closes the gap by improving the representation of Norway in the MIT licensed European investment and dispatch power system model (highRES-Europe).

Using it, we study the cost-optimal transmission grid in Norway and interconnection to neighbouring countries to meet European Climate targets. This novel approach, allows investigating spatial diversification  and technological diversification effects over a large geographical area. The process includes power generation estimates from reanalysis weather data and demand estimates based on historic electricity demand statistics. Being an optimization model, highRES then takes these inputs to design a power system that satisfies the demand at least cost.

The cost-optimal amount of transmission grid expansion to reach European Climate targets is the main expected conclusion.

When looking at the development of system costs in different countries, conclusions about the benefits from grid expansion are expected. Here we also compare the Norwegian perspective to the European perspective to identify possible target conflicts. 

It is anticipated that the larger spatial coverage of the model leads to a lower need for storage expansion and that investment into interconnection between Norway and its neighbours are proposed to allow for import and storage of renewable overproduction in other countries.

Further insights into the amount and duration of electricity stored in Norway, supporting the deployment of renewable energy in Europe, are expected.

How to cite: Roithner, M., Price, J., Schmidt, J., and Zeyringer, M.: Optimizing the Norwegian power grid to meet European climate targets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12166, https://doi.org/10.5194/egusphere-egu21-12166, 2021.

EGU21-11085 | vPICO presentations | ERE2.2

Replacing Coal with Wind and Solar in South Korea’s electricity system

Jonas Hörsch, Tina Aboumahboub, Gaurav Ganti, Matthew Gidden, Himalaya Bir Shrestha, Lara Welder, and Anne Zimmer

South Korea’s current energy system heavily relies on fossil fuels in particular coal-fired generation followed by nuclear. Currently, the country is defining its long-term energy strategy and latest Basic Electric Power Supply and Demand Plan proposes to increase the share of renewable energies to 26% by 2034, while converting most of their older half of coal plants to LNG. However, to be consistent with Paris Agreement compatible pathways, more ambitious coal phase out schedules to retire the entire coal fleet until 2030 are also discussed. We consolidate such a schedule with an expansion plan for wind and solar capacities derived from open-source renewable resource and energy system models.

For the analysis of integrating renewable energies into South Korea’s future energy system, we perform a detailed assessment of the technical potential of renewable energy sources by applying a temporally and spatially resolved modelling. A comprehensive set of geographical constraints and land exclusion factors are applied to derive the suitable area for placement of wind onshore and offshore turbines as well as PV installations. The land eligibility analysis is followed by the simulation of generation profiles from wind turbines and PV units from ERA-5 weather data, deriving the hourly capacity factors and the corresponding levelized cost of electricity for each location.

We optimize the expansion and operation of renewable energies and storage in South Korea’s electricity system for a Paris Agreement compatible coal phase out until 2030. The model chooses from the renewable expansion potentials and their cost characteristics derived in the resource assessment to balance an hourly-resolved demand scenario for each year. Flexibility needs are met with an optimized dispatch of the existing gas power plants and additional short-term and long-term storage capacities. The detailed modelling approach at a high temporal and spatial resolution allows to have a realistic assessment of the power system integration impacts of varying renewable sources and to evaluate the system adaptation needs in terms of required storage capacities.

How to cite: Hörsch, J., Aboumahboub, T., Ganti, G., Gidden, M., Bir Shrestha, H., Welder, L., and Zimmer, A.: Replacing Coal with Wind and Solar in South Korea’s electricity system, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11085, https://doi.org/10.5194/egusphere-egu21-11085, 2021.

EGU21-6783 | vPICO presentations | ERE2.2

Analysis of the operational benefits of hybrid hydropower-floating solar photovoltaic systems

Sika Gadzanku, Ana Dyreson, and Nathan Lee

Floating solar photovoltaics (FPV) systems have become an attractive RE option due to their potential energy, environmental, and social benefits. FPV systems have been deployed as standalone systems and hybridized with other generation or energy storage technologies. Hybrid FPVs, especially those paired with hydropower plants, are of specific interest because of potential cost and performance benefits such as improved system operation at different time scales, additional energy storage opportunities, improved transmission utilization, reduced solar PV curtailment, and water conservation. Despite the interest in hybrid hydropower-FPV systems, there is limited research quantifying the operational benefits of these hybrid systems. To help address this research gap, this study analyzes the potential grid-level operational benefits of a generic hybrid hydropower-FPV system through a modeling exercise. Using a solar resource time-series and resource data for an example hydropower plant, we quantify the potential curtailment reduction, increased transmission utilization, and changes in seasonal and diurnal electricity generation for the hybrid FPV system compared to stand alone systems. Results suggest that depending on the seasonality of hydropower resources and the ratio of the size of the FPV system to hydropower plant sizes, the hybrid hydropower-FPV system could reduce curtailment and lead to more optimal use of limited water resources.

How to cite: Gadzanku, S., Dyreson, A., and Lee, N.: Analysis of the operational benefits of hybrid hydropower-floating solar photovoltaic systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6783, https://doi.org/10.5194/egusphere-egu21-6783, 2021.

Concentrated Solar Power (CSP) can shift electricity over time using cheap Thermal Energy Storage (TES). However, the cost of CSP is still high. Conversely, the cost of Photovoltaic (PV) systems have fallen. However, the Battery Energy Storage (BES) used to mitigate the generation variability is uneconomical to utilize as a grid-scale storage. Moreover, in order to increase the operating hours of both solar technologies, one has to increase both TES capacity and CSP solar field compared to the electricity-generating turbine, as measured by the Solar Multiple (SM), and increase the BES capacity and PV module size relative to a fixed inverter capacity, as measured by the Inverter Loading Ratio (ILR). This increase the investment costs although the Levelized Cost of Electricity tends to be lowered by the higher capacity factor (CF). These differences between solar technologies must be accounted when designing an optimal prospective power supply system based on renewable energies (RE). Particularly, the utilization of CSP and PV with storage is widely suggested within the Moroccan strategy that aims at deploying 20% of its electrical capacity from solar energy by 2030. However, the share between PV and CSP and the amount of storage associated is still to be found. This study discuss objectively scenarios for solar integration in the electricity mix by evaluating the impact of rental cost and storage of CSP [1] and PV on the optimal mixes together with the role of time-space complementarity in reducing the adequacy risk. To do so, we simulate hourly CFs and load curves adjusted to observations for the four Moroccan electrical zones. We analyze mixes along Pareto fronts using the Mean-Variance approach -implemented in the E4CLIM model - in which the total cost of a mix is constrained to be lower than that of the actual 2018 mix [1].  We find that wind gains a higher shares compared to solar technologies because wind is regular on average which involves less capacity to install. However, at low penetrations, the addition of TES to CSP decreases the risk – the more as SM is increased keeping the mean CF fixed – which makes CSP less variable than wind and favors its installation compared to PV. To prevent reaching the maximum-cost sooner at high penetrations, the share of CSP decreases compared to PV and wind. However, the larger the ILR, the larger the share of PV compared to wind and CSP-TES, particularly for SM<4 and CSP tends to replace PV with high ILRs at high penetrations. We also show that a strong RE variability reduction is achieved through spatial diversification and by taking into account correlations between PV and CSP capacities, but less so as the surplus of energy available for TES and BES is increased.

[1]: Bouramdane, A.-A.; Tantet, A.; Drobinski, P. Adequacy of Renewable Energy Mixes with Concentrated Solar Power and Photovoltaic in Morocco: Impact of Thermal Storage and Cost. Energies 2020, 13, 5087.

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How to cite: Bouramdane, A., Tantet, A., and Drobinski, P.: Sensitivity of the Moroccan mix to the integration of Thermal and Battery Storage combined with Concentrated Solar Power and Photovoltaics: Design, Dispatch and Optimal Mix analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8755, https://doi.org/10.5194/egusphere-egu21-8755, 2021.

EGU21-13411 | vPICO presentations | ERE2.2

Assessment of hybrid urban renewable energy potential through sector coupling of photovoltaic electricity and geothermal heat

Alina Walch, Romain Sibuet, Roberto Castello, and Jean-Louis Scartezzini

To fulfil ambitious targets for reducing CO2-emissions in the building sector, the design of new neighbourhoods or the retrofitting of existing buildings requires an increasingly high use of renewable energy (REN). The coupling of heat and electricity in hybrid energy systems hereby plays a key role, as it allows to cover the needs of both sectors using renewable sources. Existing case studies of hybrid energy systems for individual buildings or neighbourhoods are often highly specific to a given location, and it is difficult to draw generalisable conclusions. This work hence aims at the development of a hybrid energy systems model based on large-scale databases of renewable energy potential with high spatial and temporal resolution, in this case for Switzerland. The resulting model may be used to obtain comparable results for case studies across the country or scaled up to the national level. For this, our approach integrates national-scale databases of hourly solar photovoltaic (PV) potential [1] and ground-source heat pump (GSHP) potential [2] for individual buildings with their modelled heat and electricity demand.

The presented work consists of three steps. First, hourly energy demand for heat and electricity of the residential and service sectors is derived for the entire Swiss building stock. The hourly demand model combines a top-down modelling of annual energy demand with a bottom-up mapping of hourly demand profiles. Second, the energy demand profiles are matched with the renewable energy potentials in hybrid energy systems, at the scale of individual buildings and neighbourhoods. We further add flexibility options to these systems, such as thermal energy storage. Third, the size of the renewable technologies and the storage options are optimised such as to maximise the autonomy level of the resulting hybrid energy systems. The autonomy level is obtained through the modelling of the system dynamics at monthly-mean-hourly temporal resolution, i.e. at hourly resolution for a typical day per month. This reduces the computational complexity of the approach and assures its scalability to the national level.

The above workflow is tested on a neighbourhood in Geneva, Switzerland, and the resulting optimal system configurations are compared across different building types in the residential and service sector, and for different shares of REN generation. We show how different system configurations, such as the combined use of PV and GSHPs, as well as the addition of flexibility through the use of a thermal energy storage, impact the self-sufficiency and autonomy level of buildings and neighbourhoods. While the presented work focuses on one neighbourhood only, future extensions will aim at applying the model to the Swiss national scale using all data in the national REN databases. This will allow to compare the feasibility of different system configurations with high REN shares across the country.

 

[1] Alina Walch, Roberto Castello et al. ‘Big Data Mining for the Estimation of Hourly Rooftop Photovoltaic Potential and Its Uncertainty’. Applied Energy 262 (2020).

[2] Alina Walch, Nahid Mohajeri, et al. ‘Quantifying the Technical Geothermal Potential from Shallow Borehole Heat Exchangers at Regional Scale’. Renewable Energy 165 (2021).

How to cite: Walch, A., Sibuet, R., Castello, R., and Scartezzini, J.-L.: Assessment of hybrid urban renewable energy potential through sector coupling of photovoltaic electricity and geothermal heat, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13411, https://doi.org/10.5194/egusphere-egu21-13411, 2021.

EGU21-11266 | vPICO presentations | ERE2.2

Driving factors of the growth of US wind power generation - A decomposition of historical on-shore wind power generation data

Peter Regner, Katharina Gruber, Sebastian Wehrle, and Johannes Schmidt

US Wind power generation has grown significantly over the last decades, driven by more and larger turbines being installed. However, less is known about how other factors affect the expansion of wind power. In this study, we use historical wind power generation time series, data on installed wind turbines and wind speed time series from the ERA5 data set to quantify driving factors of the growth of US wind power generation. By use of index-decomposition techniques and a regression analysis, we show how different factors affect the output of wind power generation in the US. These include changes in the number of installed turbines, average swept area, park efficiency, location choice, and hub height. Based on this, we discuss potential consequences for the future expansion of wind energy. As expected, the total rotor swept area is responsible for the largest part of the increase in generated power, due to a larger number of installed turbines and larger rotor sizes in particular. Unexpectedly, turbine efficiency slightly declined in the last decades. Wind speeds available to wind turbines have slightly increased. This is a result of larger hub heights, but also of new wind turbines being installed at windier locations.

How to cite: Regner, P., Gruber, K., Wehrle, S., and Schmidt, J.: Driving factors of the growth of US wind power generation - A decomposition of historical on-shore wind power generation data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11266, https://doi.org/10.5194/egusphere-egu21-11266, 2021.

EGU21-2796 | vPICO presentations | ERE2.2

Determinants of the global distribution of solar PV parks 

Joyce Bosmans, Mirza Cengic, Aafke Schipper, David Gernaat, Detlef van Vuuren, and Mark Huijbregts

Suitability maps for solar photovoltaic (PV) parks are key in estimating potential supply of these resources. These maps are typically created based on expert judgement using variables such as resource availability (irradiation), topography (e.g. slope), socio-economic factors (e.g. distance to urban areas), infrastructure (e.g. distance to roads and transmission lines), land cover type, and / or ecological functions (e.g. protected areas). However, such  priori expert-based suitability maps do not necessarily match up with the actual spatial distribution of solar PV or wind parks. 

Here we aim to understand the determinants of the actual global distribution of solar PV parks by relating the locations of utility-scale solar PV parks worldwide to the above-mentioned variables. Specifically, we develop a generalized linear mixed-effects model to predict the probability of occurrence of a PV park at a certain location, based on variable values at each PV location as well as randomly selected locations where PV parks are absent. We furthermore include country as random effect to take into account inter-country differences in renewable energy policies. We then use the model to create a global 1km resolution map of the likelihood of finding a solar PV park and identify the most important determinants of their distribution. 

Finally, we compare our findings to the suitability maps currently used by the integrated assessment model IMAGE, which are based on expert judgement using land cover, ecological functions, infrastructure, socio-economic factors and topography. From this comparison and our identification of the most important determinants, we can deduce what drives geographical patterns in the actual distribution of renewable energy facilities, which can be used to improve suitability maps in future integrated assessments of the energy transition. 

How to cite: Bosmans, J., Cengic, M., Schipper, A., Gernaat, D., van Vuuren, D., and Huijbregts, M.: Determinants of the global distribution of solar PV parks , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2796, https://doi.org/10.5194/egusphere-egu21-2796, 2021.

Keywords: Market value, Technological diversification, Geographical diversification, Spatial value factor distribution

Ambitious climate and energy targets require environmentally compatible energy generation with a high utilisation of renewable energy sources. However, due to the intermittent appearance of wind and PV feed-in, variable renewable energy (VRE) reveals significantly lower market values than conventional dispatchable power (Joskow, 2011). Additionally, with higher VRE shares a significant market value drop of wind and solar power has been observed in recent years as a result of the merit order effect (Hirth, 2013). Moreover, results by Engelhorn and Müsgens (2018) and Becker and Thrän (2018) have indicated regional disparities in empirical market values for Germany.  This poses interest on what exactly drives and how to quantify the development and spatial distribution of VRE market values.

Against this background, an electricity market model is applied to trace the development of spatial market values based on model-endogenous electricity prices. A special feature of the model is the inclusion of highly regionally disaggregated weather data which allows to investigate effects of different geographical and technological VRE diversification strategies in Germany until 2035 (Eising et al., 2020). The results of this research are threefold:

  • Technological diversity: results show a significant decrease in PV and onshore wind value factors as VRE shares increase. Replacing onshore wind energy by offshore wind energy reduces the volatility and counteracts the value drop of onshore wind, offshore wind and PV.
  • Geographical diversity: results indicate that geographical diversification does not necessarily mitigate decreasing VRE value factors. Under specific circumstances, a higher concentration at sites with lower full-load hours and corresponding higher feed-in volatility potentially mitigates positive effects from more spatially distributed generation.
  • Spatial distribution of value factors: for all mitigation strategies and for wind and PV the spatial value factor distribution shows future increases in regional disparities. However, regional value factor disparities are most distinct in case of onshore wind. The analysis reveals two significant drivers: first, a negative relationship between the regional wind capacity density and their regional value factors can be observed. Second, results indicate a negative relationship between site-specific wind feed-in volatility and the value factor.

 Summarising, the analysis highlights the importance of considering spatial market values in efficiently designing future electricity markets.  

 

References

Becker, R., Thrän, D., 2018. Optimal Siting of Wind Farms in Wind Energy Dominated Power Systems. Energies 11, 978. https://doi.org/10.3390/en11040978

Eising, M., Hobbie, H., Möst, D., 2020. Future wind and solar power market values in Germany — Evidence of spatial and technological dependencies? Energy Econ. 86, 104638. https://doi.org/10.1016/j.eneco.2019.104638

Engelhorn, T., Müsgens, F., 2018. How to estimate wind-turbine infeed with incomplete stock data: A general framework with an application to turbine-specific market values in Germany. Energy Econ. 72, 542–557. https://doi.org/10.1016/j.eneco.2018.04.022

Hirth, L., 2013. The market value of variable renewables: The effect of solar wind power variability on their relative price. Energy Econ. 38, 218–236.

Joskow, P.L., 2011. Comparing the Costs of Intermittent and Dispatchable Electricity Generating Technologies. Am. Econ. Rev. 101, 238–241.

How to cite: Eising, M., Hobbie, H., and Möst, D.: Effects of geographical and technological diversification on the development of spatially disaggregated wind and solar power market values  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14563, https://doi.org/10.5194/egusphere-egu21-14563, 2021.

EGU21-16021 | vPICO presentations | ERE2.2

Spatial economic potential of post feed-in tariff wind turbines in Germany

Christine Dede and Manuel Eising

Keywords: direct marketing, post-FiT, wind, spatial analysis

Within the coming ten years, more than 25 GW of onshore wind will reach the end of 20 year feed-in tariff (FiT) scheme according to the German Renewable Energy Law (EEG). This urges operators to take decision on repowering, lifetime extension or shutdown. In order to support the operators’ decision this study discusses and analyses the economic potential of lifetime extension or shutdown. Due to the limited lifetime extension of post-FiT turbines, rather short-term alternative revenue schemes on the day-ahead market, either via direct marketing or via a merchant PPA, appear as a reasonable option.

For these post-FiT business models, the methodology at hand introduces a revenue and cost cascade. The value and cost categories derive from a power system perspective cascade introduced by Hirth et al. (2015) complemented by transaction costs and additional revenue streams, e.g. from Guaranties of Origin (GoO).

The applied spatial economic analysis calculates region-specific contribution margins for post-FiT wind turbines in Germany in two steps:

  • Calculation of regionally dispersed value factors [%], market values [€/MWhel] and annual market revenues [€/MW] using hourly day-ahead price time series and hourly wind feed-in time series for German NUTS2 regions.
  • Identifying the distribution of wind turbine operational expenditures (OPEX) from the literature and analysing their regional-specific magnitude. Capital expenditures from the initial wind turbine investment or grid connection are considered as sunk costs and can be neglected.

Subtracting spatial OPEX from spatial market values reveals region-specific contribution margins and the economic potential for continuing wind turbine operation. The conclusion is threefold:

  • Location-specific market values strongly affect the contribution margin: year-to-year evolution of day-ahead price levels translates into high volatility of contribution margin. Capacity-dense regions show lower empirical market values. This trend of regional disparities will increase (Eising et al., 2020) due to increasing cannibalisation effect at ever-increasing wind market shares.
  • Variation in OPEX assumptions influence the locational contribution margins: the literature review on wind turbine OPEX levels reveals a wide assumption range between 21,4 – 46 €/MWhel and a data gap on actual OPEX for post-FiT wind turbines. In addition, the level distribution of cost causation in energy driven [€/MWhel] and capacity driven [€/MW] OPEX together with the regional variation in wind speeds leads to a significant regional OPEX sensitivity.
  • In general, wind-intense sites nowadays deliver higher contribution margins. This overperformance arises from higher absolute market revenues [€/MW] and relatively lower OPEX [€/MWhel]. However, relatively lower market values already appear in the observed timeframe 2006 - 2016 at capacity-dense regions in central-northern Germany.

Overall, this study highlights the importance of acknowledging the spatial distribution of market values for analysis of business models, in particular for post-FiT wind turbines, instead of power system analysis as in the vast majority of market value studies.

References

Eising, Hobbie, Möst, 2020. Future wind and solar power market values in Germany — Evidence of spatial and technological dependencies? Energy Econ. 86. https://doi.org/10.1016/j.eneco.2019.104638

Hirth, Ueckerdt, Edenhofer, 2015. Integration costs revisited – An economic framework for wind and solar variability. Renew. Energy 74. https://doi.org/10.1016/j.renene.2014.08.065

How to cite: Dede, C. and Eising, M.: Spatial economic potential of post feed-in tariff wind turbines in Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16021, https://doi.org/10.5194/egusphere-egu21-16021, 2021.

EGU21-813 | vPICO presentations | ERE2.2

The impact of policy measures on the spatial and temporal expansion of wind energy: a classification of instruments and modeling recommendations

Anselm Eicke, Stefanie Mieth, Carsten Pape, Klara Reder, and Silvana Tiedemann

Policy measures influence the spatial and temporal deployment of wind energy often more than the geo-economical potential. On the national level, the design of renewable energy support schemes mostly determines the most promising locations for investments. These national instruments also interplay with regulation on the local and municipal level, including land development plans, licensing regimes, and local renewable energy targets. While modeling sometimes focuses on the national level, local regulations are most often absent from the analysis. Controversially, measures at the different administrative levels simultaneously foster and hinder the deployment of wind energy in some regions.

The contribution of this paper is threefold. First, we categorize policy measures at different administrative levels that influence the spatial expansion of wind energy. We uncover at which stage of the planning process these instruments play a role and by which mechanism they influence the spatial distribution and the development time. Second, we present and evaluate techniques to reflect such policy measures in spatial and temporal scenario models and discuss how to generalize them across countries and/or jurisdictions. Third, we apply these modelling techniques on the German case to gain insights on the pros and cons of different modelling approaches. The case study incorporates first scenarios from the Kopernikus project Ariadne.

How to cite: Eicke, A., Mieth, S., Pape, C., Reder, K., and Tiedemann, S.: The impact of policy measures on the spatial and temporal expansion of wind energy: a classification of instruments and modeling recommendations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-813, https://doi.org/10.5194/egusphere-egu21-813, 2021.

EGU21-14368 | vPICO presentations | ERE2.2

Desirable vs. likely: modeling feasible wind power potentials

Johannes Schmidt, Michael Klingler, Olga Turkovska, and Sebastian Wehrle

Assessments of the potential for wind turbine deployment have become a very active research field in spatial and temporal modeling. Initially, such studies assessed geographical, technical and wind resource potentials, with the objective to identify where wind turbines could in principle be erected. Together with further assumptions, for example on grid connection cost, this served as a prime input for power system models, which used results from studies of feasible potentials as upper limits on deployable capacities.

However, increasing opposition against new wind power projects has demonstrated the limitations of such assessments. In response, the research community developed novel methods to include social constraints in assessments of wind energy potentials. In many instances, this amounted to predicting whether wind turbines could be installed at a specific location, ultimately indicating the eligibility of a location for wind power by a binary categorization.

Another strand of literature sought to determine (socially) desirable allocations of wind turbines rather than predicting possible ones. While these attempts also respect binary geographical and technical constraints on wind power deployment, the desirability of a certain allocation of wind turbines results from the trade-off between corresponding benefits and (negative) impacts, assessed either implicitly in a welfare-framework or explicitly within a multi-criteria analysis.

We argue that predictive approaches are not suitable as a basis for further normative analysis in energy system models. Predictive analysis does not consider effects that are external to the modelled agents’ decisions and is thus not compatible with weighing benefits and cost, arising for example from impacts on the environment, in a broader perspective.

To facilitate analysis, we see several avenues for improvement:

  • Assessments should clearly state if they aim at predicting the spatial allocation of wind parks or if they model desirable allocations. If resulting wind potentials are used in energy system models, which are designed to model desirable future states of the energy system, we understand that predictive modeling on the side of spatial wind power allocations is incompatible with a general normative modeling approach.
  • Binary land-eligibility studies may suffer from conceptual flaws if continuous measures are mapped to binary categorizations. We therefore propose to use binary indicators only in cases when wind turbine deployment is ruled out with high degrees of certainty (such as technical or legal restrictions). This helps to decrease the computational complexity. To integrate trade-offs of different spatial allocations of wind parks in normative energy system models, continuous indicators such as wind resources or impacts of wind parks need to be assessed separately.
  • Standard criteria for wind potential assessments should be amended by (i) largely neglected issues of human land-use and land-tenure, which are particularly important in countries where land tenure rights are insecure and different land use interests compete and (ii) assessments of wind park impacts on the quality of neighboring ecosystems. Integrating these insights into prospective modeling studies is of high relevance as climate change mitigation and biodiversity preservation should go hand in hand when modeling the energy transition.

How to cite: Schmidt, J., Klingler, M., Turkovska, O., and Wehrle, S.: Desirable vs. likely: modeling feasible wind power potentials, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14368, https://doi.org/10.5194/egusphere-egu21-14368, 2021.

EGU21-15227 | vPICO presentations | ERE2.2

The contribution of spatiotemporal modelling to spatial planning instruments on the local level

Peter Lichtenwoehrer, Georg Neugebauer, Lore Abart-Heriszt, Franz Suppan, and Gernot Stoeglehner

In the course of the energy transition, spatial and temporal aspects of energy demand and renewable energy supply are increasingly coming to the forefront of scientific studies and political debates. In this context, the use of spatiotemporal models has been identified as a decisive methodology for integrated spatial and energy planning. However, the transformation of spatiotemporal results into concrete spatial planning instruments has not yet been sufficiently discussed. Therefore, this research aims to provide answers by using specific results of a case study in Austria. In the case study evaluation, energy demand is considered in high spatial resolution using statistic data in 250m raster cells as a basis. The results are supplemented with an assessment of high spatio-temporal solar energy potentials. Taking these results as a basis, the following questions are addressed: How can spatial and temporal evaluations of energy demand and supply support the energy transition by means of spatial planning on the local level? What measures with respect to renewable energy generation, storage and grid capacity can be derived and which effects are expected to be achieved? With respect to renewable energy provision, initial results reveal added value for the spatial delimitation of district heating supply areas. Further, building integrated solar energy generation reveals high shares of excess energy – both thermal and electric – which has to be properly used, taking into account different sectors of energy demand. As a consequence, the results of this research also offer the opportunity to reflect on the benefits of sector coupling, as well as the new organization of energy supply via energy communities.

How to cite: Lichtenwoehrer, P., Neugebauer, G., Abart-Heriszt, L., Suppan, F., and Stoeglehner, G.: The contribution of spatiotemporal modelling to spatial planning instruments on the local level, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15227, https://doi.org/10.5194/egusphere-egu21-15227, 2021.

EGU21-1805 | vPICO presentations | ERE2.2

Energy landscapes resulting from climate protection goals – a GIS-based approach to carbon neutrality

Stephan Bosch and Dominik Kienmoser

To date, the spatio-temporal patterns of renewable energies brought about by a deployment that corresponds to internationally agreed climate protection goals, have been neither exactly analysed nor visualised. It is also unknown what land uses would be incorporated into these new energy landscapes due to a lack of spatial restrictions, and what social conflicts these land use changes may give rise to. Moreover, the extent to which existing land use, which is the product of a capitalist order, affects the achievement of a carbon-neutral society, has not been grasped at all. There is no knowledge about the feasibility of altering spatial restrictions for renewable energies in order to identify alternative spatial patterns of sustainable energy transition. Our objective is therefore to model and visualise a regional energy landscape whose greenhouse gas balance in the electricity sector corresponds to the target of the UN Climate Conference. The study provides a detailed analysis of the landscape transformations in rural spaces that would be caused if those forces which strive to link the energy transition to the values of the Paris Agreement were to win through. It is revealed that a precise alignment of the expansion of renewable energies with international climate protection targets would strongly mechanise rural areas and significantly transform their land use patterns.

How to cite: Bosch, S. and Kienmoser, D.: Energy landscapes resulting from climate protection goals – a GIS-based approach to carbon neutrality, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1805, https://doi.org/10.5194/egusphere-egu21-1805, 2021.

EGU21-14722 | vPICO presentations | ERE2.2

Identifying land cover suitability factors for photovoltaic installations with focus on cropland and urban areas

Madhura Yeligeti, Wenxuan Hu, Yvonne Scholz, and Kai von Krbek

Solar photovoltaic (PV) systems will foreseeably be an integral part of future energy systems. Land cover area analysis has a large influence on estimatiin of long-term solar photovoltaic potential of the world in high spatial detail. In this regard, it is often seen in contemporary works, that the suitability of various land cover categories for PV installation is considered in a yes/no binary response. While some areas like natural parks, sanctuaries, forests are usually completely exempted from PV potential calculations, other land over categories like urban settlements, bare, sparsely vegetated areas, and even cropland can principally support PV installations to varying degrees. This depends on the specific land use competition, social, economic and climatic conditions, etc. In this study, we attempt to evaluate these ‘factors of suitability’ of different land cover types for PV installations.

As a basis, the openly available global land cover datasets from the Copernicus Land Monitoring Service were used to identify major land cover types like cropland, shrubland, bare, wetlands, urban settlements, forests, moss and snow etc. For open area PV installations, with a focus on cropland, we incorporated the promising technology of ‘Agri-voltaics’ in our investigation. Different crops have shown to respond positively or negatively, so far, to growing under PV panels according to various experimental and commercial sources. Hence, we considered 18 major crops of the world (covering 85% of world cropland) individually and consequently, evaluated a weighted overall suitability factor of cropland cover for PV, for three acceptance scenarios of future.

For rooftop PV installations in urban areas, various socio-economic and geographical influences come in play. The rooftop area available and further usable for PV depends on housing patterns (roof type, housing density) which vary with climate, population density and socio-economic lifestyle. We classified global urban areas into several clusters based on combinations of these factors. For each cluster, rooftop area suitability is evaluated at a representative location using the land cover maps, the Open Street Map and specific characteristics of the cluster.

Overall, we present an interdisciplinary approach to integrate technological, social and economic aspects in land cover analysis to estimate PV potentials. While the intricacies may still be insufficient for planning small localized energy systems, this can reasonably benefit energy system modelling from a regional to international scale.

How to cite: Yeligeti, M., Hu, W., Scholz, Y., and von Krbek, K.: Identifying land cover suitability factors for photovoltaic installations with focus on cropland and urban areas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14722, https://doi.org/10.5194/egusphere-egu21-14722, 2021.

EGU21-5648 | vPICO presentations | ERE2.2 | Highlight

Photovoltaics in Austria - open space and rooftop potential analysis on a high spatial resolution

Christian Mikovits, Thomas Schauppenlehner, Patrick Scherhaufer, Johannes Schmidt, Lilia Schmalzl, Nina Hampl, and Robert Sposato

Austria aims to meet 100% of its electricity demand from domestic renewable sources by 2030 which means, that an additional 30 TWh per year are required. Solar energy will play a significant role to reach this goal, meaning the need for a substantial increase in photo-voltaic capacity. While some federal states and municipalities released a solar roof-top cadastre, there is lacking knowledge on the estimation of the potential of both, open space installations and roof-top modules, on a national level with a high spatial resolution. Results show significant differences between urban and rural areas, as well as between the Alpine regions and the Prealpine- and Easter Plain areas.

The work includes a framework to automatically process solar PV data and land-use data was developed and openly available for usage. The framework is able to fetch solar data automatically from a defined source, and join, manipulate and alter it with geodata applying various spatial methods.

How to cite: Mikovits, C., Schauppenlehner, T., Scherhaufer, P., Schmidt, J., Schmalzl, L., Hampl, N., and Sposato, R.: Photovoltaics in Austria - open space and rooftop potential analysis on a high spatial resolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5648, https://doi.org/10.5194/egusphere-egu21-5648, 2021.

EGU21-13081 | vPICO presentations | ERE2.2

Prospecting urban rooftop solar farm potential in Dublin, Ireland

Ankit Verma, John Connolly, and Noel O'Connor

The development of a sustainable and renewable energy system is a significant challenge for Ireland. In line with UN and EU policies, Ireland aims to transition to a competitive, low carbon, climate-resilient and environmentally sustainable economy by 2050 (Project Ireland 2040 National Planning Framework). Ireland is committed to an aggregate reduction in CO2 emissions of at least 80% (compared to 1990 levels) by 2050 across the electricity generation, built environment and transport sectors. Renewable energy can help Ireland reduce GHG emissions and carbon footprint as energy demands grow. It also reduces dependencies on fossil fuels as well as increases energy supply security.

According to the Sustainable Energy Authority of Ireland’s “Energy in Ireland 2020” report, 36.5% of electricity demand was met by renewable energy sources in 2019. Wind energy contributes 32% while solar energy contributes to <1%. Significant investment has been made in Ireland’s wind sector; however, the solar energy sector is relatively new. Ireland has the second-lowest total installed and cumulated solar photovoltaic (PV) capacity in the EU with just 36 MW or 7.3 W per inhabitant. (EurObserv'ER 2019).

Solar prospecting is necessary to identify optimum locations where solar farms can be established. Commercial and industrial building rooftops in urban areas offer a suitable location for establishing rooftop solar farms due to good connectivity with the electricity grid and proximity to users. Here we present an urban solar prospecting study in Dublin, Ireland.

A very high-resolution geospatial dataset was acquired for 47 industrial areas covering 53.3 km2. The data comprises of very high-resolution aerial images (12.5 cm/pixel) and digital surface model (DSM) (25 cm/pixel).

The high-resolution DSMs were used to model solar irradiation on building rooftops in ArcGIS Pro using the area solar analyst tool. These models were optimised for Irish conditions using Met Éireann solar radiation data for Dublin. The maximum solar insolation received in Dublin is 1000-1050 kWh/m2. The results demonstrate that there is potentially a large amount of commercial and industrial rooftop surface area available for PV installation in Dublin. These rooftops can generate a significant amount of electricity and help to offset CO2 emissions.

 

How to cite: Verma, A., Connolly, J., and O'Connor, N.: Prospecting urban rooftop solar farm potential in Dublin, Ireland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13081, https://doi.org/10.5194/egusphere-egu21-13081, 2021.

EGU21-4935 | vPICO presentations | ERE2.2

Modeling public charging infrastructure considering spatial distribution of e-car ownership and points of interests

Philip Gauglitz, David Geiger, Jan Ulffers, and Evamaria Zauner

Considering climate change, it is essential to reduce CO2 emissions. The provision of charging infrastructure in public spaces for electromobility – along with the substitution of conventional power generation with renewable energies – can contribute to the energy transition in the transport sector. Scenarios for the spatial distribution of this charging infrastructure can help to exemplify the need for charging points and their impact, for example, on power grids. We present an approach based both on the usage frequency of points of interest (POIs) and on the need for charging points in residential areas. This approach is validated in several steps and compared with alternative methods, such as a machine learning model trained with existing charging point utilization data.

Our approach uses two drivers to model the demand for public charging infrastructure. The first driver represents the demand for more charging stations to compensate for the lack of home charging stations and is derived from a previously developed and published model addressing electric-vehicle ownership (with and without home charging options) in households. The second driver represents the demand for public charging infrastructure at POIs. Their locations are derived from Open Street Map (OSM) data and weighted based on an evaluation of movement profiles from the Mobilität in Deutschland survey (MiD, German for “Mobility in Germany”). We combine those two drivers with the available parking spaces and generate distributions for possible future charging points. For computational efficiency and speed, we use a raster-based approach in which all vector data is rasterized and computations are performed on the full grid of a municipality. The presented application area is Wiesbaden, Germany, and the methodology is generally applicable to municipalities in Germany.

The method is compared and validated with alternative approaches on several levels. First, the allocation of parking space based on the raster calculation is validated against parking space numbers available in OSM. Second, the modeling of charging points supposed to compensate for the lack of home charging opportunities is contrasted with a simplified procedure by means of an analysis of multifamily housing density. In the third validation step, the method is compared to an existing machine learning model that estimates spatial suitability for charging stations. This model is trained with numerous input datasets such as population density and POIs on the one hand and utilization data of existing charging stations on the other hand. The objective of these comparisons is both to generally verify our model’s validity and to investigate the relative influence of specific components of the model.

The identification of potential charging points in public spaces plays an important role in modeling the future energy system – especially the power grid – as the rapid adoption of electric vehicles will shift locations of demand for electricity. With our investigation, we want to present a new method to simulate future public charging point locations and show the influences of different modeling methods.

How to cite: Gauglitz, P., Geiger, D., Ulffers, J., and Zauner, E.: Modeling public charging infrastructure considering spatial distribution of e-car ownership and points of interests, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4935, https://doi.org/10.5194/egusphere-egu21-4935, 2021.

EGU21-8001 | vPICO presentations | ERE2.2

Development of a dynamic European residential building stock typology for energy system analysis

Max Kleinebrahm, Elias Naber, Jann Weinand, Russell McKenna, and Armin Ardone

In recent years, different approaches have been developed with the aim of defining representative buildings that can be used as a basis for residential building energy system analyses. Due to the coupling of different sectors at the household level, the analysis of future residential energy systems is becoming increasingly complex. On the European level a large amount of data has been published over the last years. This study combines multiple different data sets relevant for energy system analysis at the building level and presents a dynamic methodology for the derivation of representative building/household combinations, which can be used as a basis for residential energy system analyses on a European level. The approach enables representative buildings to be generated dynamically taking into account the parameters relevant to the respective research question. In a first step, various data sets are combined to describe local building properties, weather conditions, economic and ecological framework conditions as well as socio-demographic parameters on NUTS3 level. Based on the developed database, a two-step procedure for the derivation of building household combinations is presented. In the first step, a synthetic European population is generated by using iterative proportional fitting. In the second step different cluster approaches are compared for the derivation of case specific archetype buildings. Finally, the developed methodology is used in an exemplary way for the analysis of the potential of energy self-sufficient single-family buildings in the future European building stock by using a mixed integer linear programming optimization model for the optimal energy system design and dispatch of residential buildings, taking into account relevant framework conditions such as weather conditions, regulatory framework conditions and site-specific building properties.

How to cite: Kleinebrahm, M., Naber, E., Weinand, J., McKenna, R., and Ardone, A.: Development of a dynamic European residential building stock typology for energy system analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8001, https://doi.org/10.5194/egusphere-egu21-8001, 2021.

EGU21-16111 | vPICO presentations | ERE2.2

Bioenergy potentials from recently abandoned cropland under the land-energy-water nexus

Jan Sandstad Næss, Otavio Cavalett, and Francesco Cherubini

Bioenergy plays a key role in scenarios limiting global warming below 2°C in 2100 relative to pre-industrial times. Land availability for bioenergy production is constrained due to competition with agriculture, nature conservation and other land uses. Utilizing recently abandoned cropland to produce bioenergy is a promising option for gradual bioenergy deployment with lower risks of potential trade-offs on food security and the environment. Up until now, the global extent of abandoned cropland has been unclear. Furthermore, there is a need to better map bioenergy potentials, taking into account site-specific conditions such as local climate, soil characteristics, agricultural management and water use.

Our study spatially quantify global bioenergy potentials from recently abandoned cropland under the land-energy-water nexus. We integrate a recently developed high-resolution satellite-derived land cover product (European Space Agency Climate Change Initiative Land Cover) with an agro-ecological crop yield model (Global Agro-Ecological Zones 3.0). Abandoned cropland is mapped as pixels transitioning from cropland to non-urban classes. We further identify candidate areas for nature conservation and areas with increased pressure on water resources. Based on climatic conditions, soil characteristics and agricultural management levels, we spatially model bioenergy yields and irrigation water use on abandoned cropland for three perennial grasses. We compute and analyze bioenergy potentials for 296 different variants of management factors and land and water use constraints. By assessing key energy, water and land indicators, we identify optimal bioenergy production strategies and site-specific trade-offs.

We found 83 million hectares of abandoned cropland between 1992 and 2015, equivalent of 5% of today’s cropland area. Bioenergy potentials range between 6-39 exajoules per year (EJ yr-1) (11-68% of today’s bioenergy demand), depending on agricultural management, land availability and irrigation water use. We further show and extensively discuss site-specific trade-offs between increased bioenergy production, land-use and water-use. Our high-end estimate (39 EJ yr-1) relies on complete irrigation and land availability. When acknowledging site-specific trade-offs on water resources and nature conservation, a potential of 20 EJ yr-1 is achievable without production in biodiversity hotspots or irrigation in water scarce areas. This is equal to 8-23% of median projected bioenergy demand in 2050 for 1.5°C scenarios across different Shared Socio-economic Pathways. The associated land and water requirements are equal to 3% of current global cropland extent and 8% of today’s global agricultural water use, respectively.

How to cite: Næss, J. S., Cavalett, O., and Cherubini, F.: Bioenergy potentials from recently abandoned cropland under the land-energy-water nexus, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16111, https://doi.org/10.5194/egusphere-egu21-16111, 2021.

EGU21-7180 | vPICO presentations | ERE2.2

The Texas 2021 cold spell in a climate-power system perspective

Katharina Gruber, Tobias Gauster, Luis Ramirez-Camargo, Gregor Laaha, and Johannes Schmidt

Between February 15th and 16th 2021 a cold spell reached Texas, causing large-scale rolling blackouts in the Texan power system. These were driven in part by a significant increase in electricity demand for heating, and in part by the loss of power generation capacity in the system.

We use (i) ERA-5 temperatures weighted according to population to predict load, (ii) temperatures weighted according to power plant locations, and (iii) temperatures weighted according to Texas gas fields, together with (iv) data on outages of gas and coal power plants, to (a) study the event in February, and (b) estimate the severity of this event based on seven decades of data (1950-2021). To characterise the power demand, we used population weighted temperature and time variables as surrogates.

We find that the February of 2021 event was a very cold year compared to other winters in the period of 2004-2020, from which we use observations of load on the electricity network. There were, however, colder events before 2004. Predicted electricity demand was higher than in any other winter in our simulation, although deeper temperatures were observed before. This is due to the particular timing of temperature fluctuations, with cold episodes coinciding with daily and weekly demand patterns in an unfortunate way. Predicted demand in February 2021 was, however, never higher than the highest observed load during hot hours in summer.

From synoptic signal analysis, we further estimate that a catastrophic failure of gas power plants occurred at temperatures below -7.3°C, and of coal power plants at -9.2°C. However, lower temperatures before 2004 did not cause any catastrophic failures. In contrast, the problems at gas power plants started when the gas field output weighted temperature fell to -10.2°C. This is a temperature never observed since 2004, indicating that the reason for outage may be related to gas and not power production. In the period since 1950-2003, temperatures as low or lower have been observed. However, the 2021 event is exceptional in terms of how long temperatures were below 0°C before the system failed.

Wind power plants also failed to operate due to icing conditions. This seems to be, however, a very rare event. We did not find any other significant difference in wind power generation simulated from ERA5 wind data to observed wind generation in Texas in the period 2016-2019 under freezing conditions. This also points to very special conditions in the 2021 winter event. We find however, that in lower temperatures, capacity factors of the installed wind park tend to decrease.

How to cite: Gruber, K., Gauster, T., Ramirez-Camargo, L., Laaha, G., and Schmidt, J.: The Texas 2021 cold spell in a climate-power system perspective, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7180, https://doi.org/10.5194/egusphere-egu21-7180, 2021.

EGU21-4581 | vPICO presentations | ERE2.2

Wind of change: predicting wind potentials for the energy transition

Federico Amato, Fabian Guignard, and Alina Walch

Wind energy is a promising renewable resource to contribute to the energy transition in many parts of the world. In contrast to solar power, it is available at any time of the day; however, it is highly variable and complex to model. This poses challenges for the planning of future energy systems with high shares of wind power. The quantification of the spatial and temporal variation of wind power and the related uncertainty may hence provide valuable information for energy planners and policymakers. Here we propose an estimation of hourly wind energy potential at the Swiss national scale for pixels of 200 x 200 m2. To this aim, this research is structured into two parts. First, ten years of wind speed measurement collected at an hourly frequency on a set of 208 monitoring stations are interpolated using advanced spatio-temporal techniques, allowing the estimation of wind speed at unsampled locations. Second, the resulting wind field is used to estimate hourly wind power potential on a national scale.

Because of its turbulent nature and its very high variability, wind speed modelling is a challenging task, especially in complex mountainous regions. To face these challenges, the interpolation task is solved as follows. The wind speed data are decomposed through Empirical Orthogonal Functions (EOFs) in temporal basis and spatially dependent coefficients. Then, the spatial coefficients are interpolated. While any regression model could be used to model these coefficients, Extreme Learning Machine (ELM) - a single layer feed-forward neural network with random input weights – was chosen to perform this task, profiting of its high computation speed and of its ability to retrieve reliable and rigorous model uncertainty assessments. Finally, the wind speed time series are reconstructed at any location adopting the interpolated coefficients in the EOFs equation. Uncertainty is quantified by taking advantage of the ELM uncertainty estimates for the spatial coefficients’ models and of the orthogonality of the basis.

In the second part of the research, the modelled spatio-temporal wind field is used to estimate wind power potential, taking into account technical characteristics of horizontal-axis wind turbines as well as national regulatory planning limitations for the installation of power plants. The limitations include restrictions for noise abatement and landscape, natural, ecological and cultural heritage protection plans as provided in the Swiss national wind atlas. The resulting wind power potential represents the first dataset of its type for Switzerland, which may be used to model future energy systems with increased wind power production. Considering the spatial and temporal variability of wind hereby permits to assess the complementarity with other forms of renewables such as photovoltaics, which play a key role in Switzerland’s Energy Strategy.

 

References:

Amato, Federico, et al. "A novel framework for spatio-temporal prediction of environmental data using deep learning." Scientific Reports 10.1 (2020): 1-11.

Guignard, Fabian, et al. "Uncertainty Quantification in Extreme Learning Machine: Analytical Developments, Variance Estimates and Confidence Intervals." arXiv preprint arXiv:2011.01704 (2020).

Walch, Alina, et al. "Big Data Mining for the Estimation of Hourly Rooftop Photovoltaic Potential and Its Uncertainty". Applied Energy 262 (2020): 114404.

How to cite: Amato, F., Guignard, F., and Walch, A.: Wind of change: predicting wind potentials for the energy transition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4581, https://doi.org/10.5194/egusphere-egu21-4581, 2021.

EGU21-1838 | vPICO presentations | ERE2.2

Spatio-temporal Modelling of Significant Wave Height and Wave Energy Potential Estimation in the Aegean and Ionian Sea

Georgios Kozyrakis, Katerina Spanoudaki, and Emmanouil Varouchakis

The continuous search for affordable and renewable energy resources is a topic of interest for decades. Many large-scale measuring campaigns have been conducted and various different tools have been developed over the years (both numerical and statistical in nature), in order to locate regions with high wind, wave and solar energy potential. Depending on the energy resource, not all regions are performing equally, as expected. To pinpoint regions with high energy gain requires state-of-the-art tools and unremitting research efforts.

The objective of the current research effort is the spatio-temporal wave data analysis, originated from satellite data, and sensor buoy data scattered in the Aegean and Ionian Sea, with the use of geostatistical and dynamic downscaling methods, for estimating the wave energy potential for the Hellenic region. The main areas of interest are the Aegean and Ionian islands, with unsustainable energy production.

WRF model is used to  dynamically downscale coarse global climate model output to provide the regional wind forcing for a 40-year hindcast period on a 3 x 3 km grid over the Aegean and Ionian Seas. The calculated wind forcing is used as a driver for the WAVEWATCH-III wave model to calculate the significant wave height and period in the region and subsequently achieve a high-resolution estimation of the wave energy potential spatial distribution and temporal evolution. Model results have been validated with mooring time series of wave parameters in the Aegean Sea and satellite-based along track Significant Wave Height data available through CMEMS Wave Thematic Assembly Center (CMEMS WAVE TAC). To strengthen the results outcome, a spatio-temporal geostatistical methodology has been introduced to validate the computational results and provide a fast and robust estimation of the wave and energy fields. The results between the two different approaches are compared in order to establish either spatial or temporal correlation patterns.

 Acknowledgements

This project has received funding from the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under grant agreement No [1237].

How to cite: Kozyrakis, G., Spanoudaki, K., and Varouchakis, E.: Spatio-temporal Modelling of Significant Wave Height and Wave Energy Potential Estimation in the Aegean and Ionian Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1838, https://doi.org/10.5194/egusphere-egu21-1838, 2021.

EGU21-9226 | vPICO presentations | ERE2.2

Beneficial role of diurnal smoothing for grid integration of wind power

Anasuya Gangopadhyay, Ashwin K Seshadri, and Ralf Toumi

Smoothing of wind generation variability is important for grid integration of large-scale wind power plants. One approach to achieving smoothing is aggregating wind generation from plants that have uncorrelated or negatively correlated wind speed. It is well known that the wind speed correlation on average decays with increasing distance between plants, but the correlations may not be explained by distance alone. In India, the wind speed diurnal cycle plays a significant role in explaining the hourly correlation of wind speed between location pairs. This creates an opportunity of “diurnal smoothing”. At a given separation distance the hourly wind speeds correlation is reduced for those pairs that have a difference of +/- 12 hours in local time of wind maximum. This effect is more prominent for location pairs separated by 200 km or more and where the amplitude of the diurnal cycle is more than about  0.5 m/s. “Diurnal smoothing” also has a positive impact on the aggregate wind predictability and forecast error. “Diurnal smoothing” could also be important for other regions with diurnal wind speed cycles.

How to cite: Gangopadhyay, A., Seshadri, A. K., and Toumi, R.: Beneficial role of diurnal smoothing for grid integration of wind power, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9226, https://doi.org/10.5194/egusphere-egu21-9226, 2021.

EGU21-7013 | vPICO presentations | ERE2.2

Spatiotemporal wind energy potential estimation and analysis in Japan

Taichi Matsuoka, Tetsushi Amano, Remi Delage, and Toshihiko Nakata

For an efficient integration of wind and solar resources toward sustainable energy systems, it is crucial to consider their fluctuations in space and time. Current spatial wind potential estimations in Japan are limited to the annual average of wind speed. In this study, we evaluate the spatial and temporal evolution of both onshore and offshore wind energy potential in Japan based on 5 km mesh and 1-hour sampling weather forecast data. We then demonstrate the benefits of cross-border sharing on the power output stability and identify important sites having high average potential and low average correlation with other sites for the temporal smoothing of power output.

How to cite: Matsuoka, T., Amano, T., Delage, R., and Nakata, T.: Spatiotemporal wind energy potential estimation and analysis in Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7013, https://doi.org/10.5194/egusphere-egu21-7013, 2021.

EGU21-7945 | vPICO presentations | ERE2.2

Spatial and temporal variability in PV generation with respect to consumption patterns

Natasa Vulic, Martin Rüdisüli, and Kristina Orehounig

In efforts to reduce the carbon intensity of electricity generation, optimizing the use of renewable energy necessitates an understanding of its spatial and temporal variability with respect to the corresponding consumption patterns. Their coupled analysis leads to identifying existing and anticipated discrepancies in supply and demand that can help to guide both the implementation of monitoring and control strategies to balance loads through demand-side management (e.g. shifting space heating, domestic hot water, EV charging) and storage (e.g. battery, thermal, and chemical), as well as plans for further expansion of renewable energy generation. In this study, we analyze PV production and consumption patterns (daily/weekly/seasonal) within and across different utilities for the case study in Switzerland. We analyze three utilities using (1) indicators to assess their PV production and utilization, (2) visualization techniques to observe the varying patterns in consumption and production across day/week/year, and (3) computational methods to balance production surpluses and deficits, estimating the necessary load-shifts for different PV production levels (regardless of the means of shifting this demand). In the first case, we assess balancing areas of different scales---from a handful of prosumers to a residential neighborhood to the full utility area---demonstrating an improvement in their capacity to accommodate higher shares of PV production. We attribute this improvement to reduced variability in aggregated supply and demand, together with the increased diversity in building use (residential, office, retail/restaurant, industrial, etc.). When comparing the production and consumption patterns across the three utilities, similarities in the shapes of the daily profiles, weekday/weekend consumption, seasonal variations (e.g. heating demand) and load-scheduling practices (e.g. domestic hot water charging) are observed. Nevertheless, we observe large differences in their ability to consume the produced PV electricity locally, which appear related to their building stock composition, PV installation types (residential vs commercial), as well as access to higher grid hierarchy levels. These differences demonstrate the need for locally tailored strategies to expand PV production while ensuring their adequate utilization.  The general methods and approach presented here aim to assess these differences and inform more effective implementation strategies needed to reach ambitious national renewable energy targets.

How to cite: Vulic, N., Rüdisüli, M., and Orehounig, K.: Spatial and temporal variability in PV generation with respect to consumption patterns, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7945, https://doi.org/10.5194/egusphere-egu21-7945, 2021.

EGU21-7386 | vPICO presentations | ERE2.2

Comparison of PV potential models for africa and their potential cost implications.

Arnold Wasike and Catherina Cader

We currently have more than 7500 planned mini grids, most of them in Africa. These will soon connect more than 27 million people and cost about 12 billion dollars [1]. Africa is in a good position for Photo voltaic (PV) mini grid optimization, receiving more than 1800 KWh/m2 Global Horizontal Irradiation (GHI) every year [2], for most parts of the continent. However, the lack of a coordinated renewable energy monitoring and distribution network works against optimization of PV potential models [3]. This study shows the accuracy of existing photo voltaic potential estimators like renewables ninja [3], the National Renewable Energy Laboratory (NREL), International Renewable Energy Agency (IRENA), and the global solar atlas [2], by comparing the modeled values with long term measurements from ground solar stations. This is done for more than 20 stations distributed over Africa. Our results show best correlations [4] of up to 65.3% from version 2 of the Surface Radiation Data Set from Heliosat (SARAH) derived from the Photovoltaic Geographical Information System (PVGIS). However, we also have correlations as low as 16.2% for models commonly used in off grid simulations. The sensitivities of the modeled cost of a mini grid to the variation in PV potential were tested [5][6] using the statistical range in sourced PV potential from the different estimators, giving us cost variation of more than 2.8% that may arise from the different sources.

References

1. World Bank, ESMAP - Mini grids for half a billion people

2. https://globalsolaratlas.info/map

3. doi: 10.1016/j.energy.2016.08.060

4. Wikipedia contributors. (2021, January 7). Pearson correlation coefficient. In Wikipedia, The Free Encyclopedia. Retrieved 09:00, January 20, 2021, from https://en.wikipedia.org/w/index.php?title=Pearson_correlation_coefficient&oldid=998963119

5. Cader. 2018

5. Hoffmann. 2019

7. https://doi.org/10.2136/vzj2018.03.0062

How to cite: Wasike, A. and Cader, C.: Comparison of PV potential models for africa and their potential cost implications., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7386, https://doi.org/10.5194/egusphere-egu21-7386, 2021.

ERE2.5 – Exploration, utilization and monitoring of conventional and unconventional geothermal resources

EGU21-549 | vPICO presentations | ERE2.5

A multidisciplinary study for geothermal energy sources identification in the Baia Mare area (Romania)

Ionelia Panea, Carmen Gaina, Victor Mocanu, Ioan Munteanu, Lucian Petrescu, Liviu Matenco, Daniel Scradeanu, Florina Tuluca, Mihaela Scradeanu, Florin Nache, Alexandru Zlibut, Catalin-Florin Bouaru, Alexander Minakov, and Valentina Magni

Geothermal energy is known as a renewable source that has little effect on environment, since no burning process is involved in the producing of thermal and electric energy. Geothermal water is considered an environmentally friendly energy source which is valuable especially in polluted areas. Our study area, the Baia Mare region, is located in the northwestern part of Romania, a region known as one of the most polluted environment in Romania due to its long-lasting local mining and metallurgical activities. Additional quantities of CO2 emissions resulted from the use of various, relatively cheap, heating sources by the local population. The main goals of our study are to evaluate the subsurface geothermal potential of the Baia Mare area and to identify promising geothermal exploitation sites. Heat flow values in this area are among the highest in Romania. We therefore plan to combine geological, geophysical, geochemical and hydrogeological data (geo-data) in order to provide a geoscientific solution for increasing the geothermal energy production in this part of Romania. Our research program contains surface geological mapping, geophysical surveys (active and passive seismic, magnetic, magnetotelluric and geothermal), geochemical analysis, hydrogeological surveys, modeling of geo-data and joint interpretation of geo-data. An initial 3D geothermal model will be built using existent geo-data. This model will help us to identify subsurface structures which show high potential for geothermal exploration. Interpretation of existent active seismic data collected during previous hydrocarbon exploration will provide information about the subsurface structural geology. The results of the new interpretation will be compared and correlated with the existent geological maps and sections for the study area. The magnetic data available in the public domain will be used to identify subsurface igneous bodies. The temperature data available from previous measurements will be used to build temperature-versus-depth distributions. These results will be analysed within a larger geodynamic framework. A pilot site will be selected after the analysis of the initial 3D geothermal model on which we plan to collect and record new geo-data. Data processing, inversion and modeling will be performed in order to create the final geothermal model with locations of promising exploitation wells. 

How to cite: Panea, I., Gaina, C., Mocanu, V., Munteanu, I., Petrescu, L., Matenco, L., Scradeanu, D., Tuluca, F., Scradeanu, M., Nache, F., Zlibut, A., Bouaru, C.-F., Minakov, A., and Magni, V.: A multidisciplinary study for geothermal energy sources identification in the Baia Mare area (Romania), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-549, https://doi.org/10.5194/egusphere-egu21-549, 2021.

In the fast-growing economies around the world, the demand for energy as well as environmental concerns make geothermal energy a potential renewable energy source. Most geothermal provinces across the world have the capacity to generate enormous amounts of hydrothermal energy, and hot springs in these areas are generally associated with active volcanic or tectonic activity. With modern technical advancement, low enthalpy geothermal systems (< 100°C) are also being considered for geothermal energy production. In non-volcanic hot springs, the water temperature remains low compared to volcanic hot springs. We study two such hot springs located within Neoproterozoic granulites of the tectonically stable Eastern Ghats Belt (EGB) of the Indian shield. The source of heat for these amagmatic hot springs may either be deep-seated fracture zones, or alternative heat sources at shallow crustal levels. A combination of geological, geochemical, hydrological and geophysical techniques has been applied to characterize non-volcanic hot springs in India. The hot springs at Atri and Tarbalo are located to the south of the Mahanadi Shear Zone within the EGB. Penetrative granulite facies planar structural fabrics in rocks of the northern EGB are reoriented within an E-W striking, northerly dipping ductile shear zone that is subsequently dissected by WNW-ESE trending, sub-vertical pseudotachylite-bearing faults and fractures. Tube and dug wells around the shear zone yield both hot (~ 60°C) and cold (~ 28°C) water, sometimes spatially only 20 metres apart. Chemical analyses indicate both have distinct compositions, with hot waters rich in Na+, K+ and Cl- while cold-waters have higher Ca2+ and HCO3- concentration. Stable isotope analyses (δ2H and δ18O) of both waters indicate that both are meteoric in origin. Tritium (3H) and 14C analyses indicate that hot spring waters are much older than the non-thermal groundwater. The hot water is 17714 years old, while the non-thermal groundwater indicates modern day recharge. This suggests that both waters come from different reservoirs. VLF-electromagnetic studies indicate that water exists in isolated pockets beneath the crystalline country rocks, but also circulated through WNW-ESE trending fracture systems. Heat production studies reveal that the EGB is a high radiation zone, and some host rocks have exceptionally high heat producing element (HPE) concentrations (primarily thorium) within the minerals monazite and thorite. Hence, meteoric water is entrapped in those “perched aquifers” near HPE-rich pockets for a long duration and has sufficient time to undergo radiogenic heating, shielded from the non-thermal groundwater circulating within the fracture system. These isolated pockets act as sources for the hot springs,with HPE being the source of heat. The high HPE distribution in the crust resulting from Neoproterozoic geological events has, thus, elevated the present-day equilibrium geotherm in the EGB, forming sources for shallow-level, non-volcanic hot springs within a tectonically inactive terrane. Therefore, the hot springs in these regions, as well as the hot dry rocks of these areas can be considered as potential geothermal resources.

How to cite: Maitra, A., Gupta, S., Singh, A., and Kessari, T.: Geological, geochemical and geophysical studies on the non-volcanic hot springs, Atri and Tarbalo in the Indian shield: potential unconventional renewable energy sources, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2783, https://doi.org/10.5194/egusphere-egu21-2783, 2021.

EGU21-8657 | vPICO presentations | ERE2.5

Regional groundwater flow conditions and preliminary geothermal potential in asymmetric basins

Ádám Tóth, Attila Galsa, and Judit Mádl-Szőnyi

Fluid, as an elemental component of a geothermal system, transports and distributes underground heat according to the topographic driving force within a groundwater basin. As the water table configuration has diverse and distinct forms in real-life basins, asymmetric hydraulic head variation may occur from basin to basin in accordance with real physiographic characteristics. Therefore, the effects of an asymmetric water table distribution in groundwater basins were investigated in several model sets with special emphasis on the temperature field and with the help of five response parameters: maximum temperature of outflowing water, average temperature, the portion of the thermal water reservoir, Péclet number and location and extent of thermal water discharge.

Our simulation results showed that in the absence of thermal springs, the extent of the thermal water reservoir might be larger and the temperatures might be higher. Sedimentary basin fill fosters the formation of heat accumulation under and within this unit. As a new “parameter” in the basin-scale groundwater and geothermal studies, basin asymmetry was introduced which has a critical role in discharge and accumulation patterns, thus it controls the location of basin parts bearing the highest geothermal potential. So if thermal water can reach the ground surface, the discharge might not take place exactly above the thermal water reservoir due to the asymmetric driving forces of groundwater flow. Furthermore, the extent and temperature of thermal water reservoirs are also influenced by local-scale anisotropy, heterogeneities, i.e. faults, fault zones and fractures, and, of course, basal heat flux.

Therefore, the application of asymmetric basin-scale models in preliminary geothermal potential assessment would be beneficial for understanding heat distribution. The results also have further implications on the identification of prospective areas and planning of shallow and deep geothermal energy utilization, the interplay between basin-parts and rejuvenation of geothermal resources.

This research is part of the ENeRAG project that has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 810980.

How to cite: Tóth, Á., Galsa, A., and Mádl-Szőnyi, J.: Regional groundwater flow conditions and preliminary geothermal potential in asymmetric basins, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8657, https://doi.org/10.5194/egusphere-egu21-8657, 2021.

EGU21-12196 | vPICO presentations | ERE2.5

Revised hydrogeological model of the hydrothermal system Waiwera (New Zealand)

Andreas Grafe, Thomas Kempka, Michael Schneider, and Michael Kühn

The geothermal hot water reservoir underlying the coastal township of Waiwera, northern Auckland Region, New Zealand, has been commercially utilized since 1863. The reservoir is complex in nature, as it is controlled by several coupled processes, namely flow, heat transfer and species transport. At the base of the aquifer, geothermal water of around 50°C enters. Meanwhile, freshwater percolates from the west and saltwater penetrates from the sea in the east. Understanding of the system’s dynamics is vital, as decades of unregulated, excessive abstraction resulted in the loss of previously artesian conditions. To protect the reservoir and secure the livelihoods of businesses, a Water Management Plan by The Auckland Regional Council was declared in the 1980s [1]. In attempts to describe the complex dynamics of the reservoir system with the goal of supplementing sustainable decision-making, studies in the past decades have brought forth several predictive models [2]. These models ranged from being purely data driven statistical [3] to fully coupled process simulations [1].

Our objective was to improve upon previous numerical models by introducing an updated geological model, in which the findings of a recently undertaken field campaign were integrated [4]. A static 2D Model was firstly reconstructed and verified to earlier multivariate regression model results. Furthermore, the model was expanded spatially into the third dimension. In difference to previous models, the influence of basic geologic structures and the sea water level onto the geothermal system are accounted for. Notably, the orientation of dipped horizontal layers as well as major regional faults are implemented from updated field data [4]. Additionally, the model now includes the regional topography extracted from a digital elevation model and further combined with the coastal bathymetry. Parameters relating to the hydrogeological properties of the strata along with the thermophysical properties of water with respect to depth were applied. Lastly, the catchment area and water balance of the study region are considered.

The simulation results provide new insights on the geothermal reservoir’s natural state. Numerical simulations considering coupled fluid flow as well as heat and species transport have been carried out using the in-house TRANSport Simulation Environment [5], which has been previously verified against different density-driven flow benchmarks [1]. The revised geological model improves the agreement between observations and simulations in view of the timely and spatial development of water level, temperature and species concentrations, and thus enables more reliable predictions required for water management planning.

[1] Kühn M., Stöfen H. (2005):
      Hydrogeology Journal, 13, 606–626,
      https://doi.org/10.1007/s10040-004-0377-6

[2] Kühn M., Altmannsberger C. (2016):
      Energy Procedia, 97, 403-410,
      https://doi.org/10.1016/j.egypro.2016.10.034

[3] Kühn M., Schöne T. (2017):
      Energy Procedia, 125, 571-579,
      https://doi.org/10.1016/j.egypro.2017.08.196

[4] Präg M., Becker I., Hilgers C., Walter T.R., Kühn M. (2020):
      Advances in Geosciences, 54, 165-171,
      https://doi.org/10.5194/adgeo-54-165-2020

[5] Kempka T. (2020):
      Adv. Geosci., 54, 67–77,
      https://doi.org/10.5194/adgeo-54-67-2020

How to cite: Grafe, A., Kempka, T., Schneider, M., and Kühn, M.: Revised hydrogeological model of the hydrothermal system Waiwera (New Zealand), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12196, https://doi.org/10.5194/egusphere-egu21-12196, 2021.

Drilling boreholes during exploration and development of geothermal reservoirs not only involves high cost, but also bears significant risks of failure. In geothermal reservoir engineering, techniques of optimal experimental design (OED) have the potential to improve the decision making process. Previous publications explained the formulation and implementation of this mathematical optimization problem and demonstrated its feasibility for finding borehole locations in two- and three-dimensional reservoir models that minimize the uncertainty of estimating hydraulic permeability of a model unit from temperature measurements. Subsequently, minimizing the uncertainty of the parameter estimation results in a more reliable parametrization of the reservoir simulation, improving the overall process in geothermal reservoir engineering.

Various OED techniques are implemented in the Environment for Combining Optimization and Simulation Software (EFCOSS). To address problems arising from geothermal modeling, this software framework links mathematical optimization software with SHEMAT-Suite, a geothermal simulation code for fluid flow and heat transport through porous media. This contribution shows how to determine experimental conditions such that the uncertainty when estimating different parameters of model units from temperature measurements in the borehole is minimized. Numerical simulations of synthetic geothermal reservoir scenarios are presented to demonstrate the OED workflow and its applicability to geothermal reservoir modeling

How to cite: Fink, J. and Seidler, R.: Predicting Optimal Borehole Locations for Parameter Estimation in Geothermal Reservoirs Using Optimal Experimental Design, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12419, https://doi.org/10.5194/egusphere-egu21-12419, 2021.

EGU21-12456 | vPICO presentations | ERE2.5

HyTheC - Multidisciplinary approach to conceptual modelling of hydrothermal systems in Croatia

Mirja Pavić, Staša Borović, Maja Briški, Tihomir Frangen, and Kosta Urumović

The increase in thermal water utilisation is foreseen by many European and Croatian strategic documents regulating energetics, tourism, environmental protection and sustainable development. Croatian Geological Survey wishes to establish a multidisciplinary group for hydrothermal systems research which will contribute to responsible geothermal development in our country through a 5-year research project HyTheC which started in 2020.

Pannonian part of Croatia has favourable geothermal characteristics and natural thermal water springs emerge at two dozen localities, with temperatures up to 65 °C. These waters have been used for millennia, and in the past fifty years they are a basis for the development of tourism and health care centres which use the thermal water resource for heating, therapy and recreation (Borović & Marković, 2015). As their water demand increased, higher quantities were abstracted and additional intake structures and wells were constructed.

Thermal springs are part of hydrothermal systems which include: recharge areas in the mountainous hinterlands of the springs; geothermal aquifers - in Croatia mostly fractured and karstified Mesozoic carbonate rocks (Borović et al., 2016) - in which water resides and gets heated due to heat flow from the Earth; and discharge areas in places with favourable structural characteristics of higher permeability. The continuous functioning of such systems depends on a delicate balance between groundwater flow velocities, precipitation/dissolution processes and structural framework.

In order to maintain that balance and use thermal water resources in a sustainable manner, a system-level understanding is required. Multidisciplinary methodology (structural geology, hydrogeology, geothermal, hydrogeochemical and geophysical research and remote sensing) will be used to construct conceptual models of systems, perform 3D geological modelling, hydrogeological and thermal parametrisation of the geological units involved in the thermal fluid flow, and conduct numerical simulations of system functioning in undisturbed conditions and with different extraction scenarios.

This methodology will be tested in three pilot areas in Croatia where thermal water is being utilized (Daruvar, Hrvatsko zagorje and Topusko). These three areas have significantly different levels of initial data availability and it shall therefore be determined which methodology and order of application of different methods should be applied while researching the systems with considerable existing data, medium amount of data and very scarce data, respectively.

Keywords : hydrothermal system, natural thermal spring, multidisciplinary research, Croatia

References

Borović, S. & Marković, T. 2015 : Utilization and tourism valorisation of geothermal waters in Croatia. Renewable and Sustainable Energy Reviews, 44, pp. 52-63.

Borović, S., Marković, T., Larva, O., Brkić, Ž. & Mraz, V. 2016 : Mineral and Thermal Waters in the Croatian Part of the Pannonian Basin. U: Papić, P., ur., Mineral and Thermal Waters of Southeastern Europe. Cham: Springer, pp. 31-45.

 

ACKNOWLEDGMENT

The Installation Research project HyTheC (UIP-2019-04-1218) is funded by the Croatian Science Foundation.

How to cite: Pavić, M., Borović, S., Briški, M., Frangen, T., and Urumović, K.: HyTheC - Multidisciplinary approach to conceptual modelling of hydrothermal systems in Croatia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12456, https://doi.org/10.5194/egusphere-egu21-12456, 2021.

EGU21-14465 | vPICO presentations | ERE2.5

Characterisation of the Dogger and Trias deep ressources in Orléans Métropolis, Centre-Val de Loire region, France : 3D geomodel and first geothermal potential assessment

Virginie Hamm, Laure Capar, Perrine Mas, Philippe Calcagno, and Séverine Caritg-Monnot

In Ile-de-France region, in the center of Paris Basin, geothermal energy contributes to a large extent to the supply of heating networks with about 50 of the 70 deep geothermal installations dedicated to district heating in France. Those installations mainly exploit the Dogger limestones between 1500-2000 m deep, which are present throughout the Paris Basin. In the case of Centre Val-de Loire region, south of Paris Basin, deep geothermal energy is very little developed, only one geothermal well is currently in operation and targeting the Triassic aquifer at Chateauroux on the southern edge of the basin. A former doublet had also targeted the Trias at Melleray (Orléans metropolis) in the 1980’s but was shut down after one year due to reinjection problem.

In 2019, Orléans metropolis, in collaboration with BRGM, has launched a program in order to investigate its deep geothermal resources like the Dogger and Trias aquifers between 900 m and 1500 m deep. This action is in line with Orléans métropolis Territorial Climate Air Energy Plan (PCAET) and master plan for the heating networks adopted which foresee 65 000 additional dwellings to be connected using geothermal energy based heating networks.

In order to reduce the risks of failure of deep geothermal drilling, one of the prerequisites is a better knowledge of the subsurface. This requires the development of an accurate 3D subsurface geomodel as well as the most reliable possible hydrodynamic and thermal parameters to assess the geothermal potential. The purpose of this work was to produce a 3D geological model of the Dogger and Triassic units, on the scale of Orléans Metropolis, based on hydrocarbon and geothermal well data as well as interpretation of 2D seismic data. Seismic data acquired in the 1960s and the 1980s were processed and interpreted. A particular attention was paid to the Sennely fault and its geometry. It crosses the study area and was interpreted as a relay fault segmented in three parts. The horizon picking points were then converted from two-way time to depth and integrated in the GeoModeller software for the development of the 3D geomodel. It was then used for first hydrothermal simulations in order to assess the theorical potential of the Dogger and Trias aquifers at Orléans metropolis.

The 3D geomodel and first geothermal potential assessment have allowed defining areas of interest for geothermal development into the Dogger or Trias. However an initial exploratory drilling well or additional exploration techniques will be necessary to confirm/specify the reservoir properties (useful thickness, porosity, permeability) and the connectivity of the reservoir(s) and the flow rates that can actually be exploited, which cannot be predicted by the current geological model.

How to cite: Hamm, V., Capar, L., Mas, P., Calcagno, P., and Caritg-Monnot, S.: Characterisation of the Dogger and Trias deep ressources in Orléans Métropolis, Centre-Val de Loire region, France : 3D geomodel and first geothermal potential assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14465, https://doi.org/10.5194/egusphere-egu21-14465, 2021.

EGU21-12254 | vPICO presentations | ERE2.5

DIG: A New Project to De-risk Ireland’s Geothermal Energy Potential 

Brian O’Reilly, Duygu Kiyan, Javier Fullea, Sergei Lebedev, Christopher J. Bean, Patrick Meere, and Emma L. Chambers and the DIG team

Potential deep (greater > 400 m) geothermal resources, within low to medium temperature settings remain poorly understood and largely untapped in Europe. DIG (De-risking Ireland’s Geothermal Potential) is a new academic project started in 2020, which aims to develop a better understanding of Ireland’s (all-island) low-enthalpy geothermal energy potential through the gathering, modelling and interpretation of geophysical, geological, and geochemical data.

The overarching research objectives, are to (i) determine the regional geothermal gradient with uncertainty estimates across Ireland using new and existing geophysical and geochemical-petrophysical data, (ii) investigate the thermochemical crustal structure and secondary fracture porosity in Devonian/Carboniferous siliciclastic and carbonate lithologies using wide-angle seismic, gravity and available geochemical data, and (iii) identify and assess the available low-enthalpy geothermal resources at reservoir scale within the Upper Devonian Munster Basin, i.e. the Mallow warm springs region, using electromagnetic and passive seismic methods, constrained by structural geological mapping results. A new hydrochemistry programme to characterise deep reservoir water composition will add further constraints.

In the island-scale strand of the project, we are using Rayleigh and Love surface waves in order to determine the seismic-velocity and thermal structure of the lithosphere, with crustal geometry. Together with the legacy surface heat flow, gravity, and newly available long-period MT data, this will place bounds on the shape of regional geotherms. Radiogenic heat production and thermal conductivity measurements for Irish rocks will be incorporated into an integrated geophysical-petrological model, within a scheme able to provide critical temperature uncertainties. Regional-scale research will exploit legacy wide-angle seismic data across the Laurentian and Avalonian geological terranes. Geochemical and petrophysical databases will guide in-house Bayesian inversion tools, to estimate probabilities on model outcomes.

Local-scale research will derive subsurface electrical conductivity and velocity images from electromagnetic and passive seismic surveys from the northern margin of the Munster Basin, where the thermal waters tend to have a distinctive chemical fingerprint and a meteoric origin based on available geochemical and isotopic compositions. This local focus aims to directly image fault conduits and fluid aquifer sources at depth, within a convective/conductive region associated with warm springs. This will determine the scale of the geothermal anomaly and hence will evaluate the potential for local- and industrial-scale space heating in the survey locality.

This presentation will give an overview of this new research project and will deliver preliminary multi-parameter crustal models produced by the thermodynamic inversions that fit the surface-wave and surface elevation data. The project is funded by the Sustainable Energy Authority of Ireland under the SEAI Research, Development & Demonstration Funding Programme 2019 (grant number 19/RDD/522) and by the Geological Survey Ireland.

How to cite: O’Reilly, B., Kiyan, D., Fullea, J., Lebedev, S., Bean, C. J., Meere, P., and Chambers, E. L. and the DIG team: DIG: A New Project to De-risk Ireland’s Geothermal Energy Potential , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12254, https://doi.org/10.5194/egusphere-egu21-12254, 2021.

EGU21-2216 | vPICO presentations | ERE2.5

An integrated approach to assess both risk and impacts related with geo-resources exploration and exploitation

Maria Vittoria Gargiulo, Alexander Garcia, Ortensia Amoroso, and Paolo Capuano

To the welfare of both economy and communities, our society widely exploits geo-resources. Nevertheless, with benefits come risks and even impacts. Understanding how a given project intrinsically bares such risks and impacts is of critical importance for both industry and society. In particular, it is fundamental to distinguish between the specific impacts related to exploiting a given energy resource and those shared with the exploitation of other energy resources. In order to do so, it is useful to differentiate impacts in two categories: routine impacts – caused by ordinary routine operations, investigated by Life-cycle assessment with a deterministic approach – and risk impacts – caused by incidents due to system failure or external events, investigated by risk assessments with a probabilistic approach. The latter category is extremely interesting because it includes low probability/high consequences events, which may not be completely independent or unrelated, causing the most disastrous and unexpected damages. For this reason, it is becoming more and more crucial to develop a strategy to assess not only the single risks but also their possible interaction and to harmonize the result obtained for different risk sources. Of particular interest for this purpose is the Multi-Hazard/Multi-Risk Assessment.

The aim of our work is to present an approach for a comprehensive analysis of impacts of geo-resource development projects. Routine operations as well as risks related to extreme events (as e.g.,seismic or meteorological) are linked using a Multi-Hazard Risk (MHR) approach built upon a Life-Cycle analysis (LCA). Given the complexity of the analysis, it is useful to adopt a multi-level approach: (a) an analysis of routine operations, (b) a qualitative identification of risk scenarios and (c) a quantitative multi-risk analysis performed adopting a bow-tie approach. In particular, after studying the two tools, i.e. LCA and MRA, we have implemented a protocol to interface them and to evaluate certain and potential impacts.

The performance of the proposed approach is illustrated on a virtual site (based on a real one) for geothermal energy production. As a result, we analyse the outcome of the LCA, identify risk-bearing elements and events, to finally obtain harmonised risk matrices for the case study. Such approach, on the one hand, can be used to assess both deterministic and stochastic impacts, on the other hand, can also open new perspective in harmonizing them. Using the LCA outputs as inputs of the MRA can allow the analyst to focus on particular risk pathways that could otherwise seem less relevant but can open new perspective in the risk/impact evaluation of single elements, as we show in this case study.

This work has been supported by S4CE ("Science for Clean Energy") project, funded from the European Union’s Horizon 2020 - R&I Framework Programme, under grant agreement No 764810 and by PRIN-MATISSE (20177EPPN2) project funded by Italian Ministry of Education and Research.

How to cite: Gargiulo, M. V., Garcia, A., Amoroso, O., and Capuano, P.: An integrated approach to assess both risk and impacts related with geo-resources exploration and exploitation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2216, https://doi.org/10.5194/egusphere-egu21-2216, 2021.

EGU21-977 | vPICO presentations | ERE2.5

Assessment of the fracture networks controlling geothermal fluids in the northern part of the Malawi Rifted Zone

Estefanny Davalos-Elizondo and Daniel Lao Davila

We investigated the relationship between the geothermal fluids and the fracture networks that control the storage and fluid pathways of geothermal systems in the northern part of the Malawi Rifted Zone (MRZ). The MRZ is a magma-poor rift located in the Western Branch, where potential geothermal energy is postulated from elevated heat flow and the emergence of hot springs through fracture zones. However, there is a lack of knowledge about the fracture networks that control fluid pathways and storage of the geothermal systems in the region.

Preliminary geothermometer calculation studies of hot springs in the MRZ suggested that the highest geothermal reservoir temperatures (200 °C) are found in the northern region. Additionally, the hot springs are associated with the local meteoric water that seeps through deep fracture zones. These structurally-controlled geothermal systems are characterized by geothermal fluids stored in fracture zones with vertical fluid rise (upflows) and/or in shallow sedimentary rocks with  horizontal geothermal circulation (outflows) deposited in basins along the MRZ. 

The guiding hypothesis is that interconnected regional joints, inherited reactivated structures, and Quaternary faults comprise a complex fracture network that controls the geothermal fluid transport and storage of geothermal systems in the northern part of the MRZ. Therefore, this study aims to quantify the relationship between complex fracture networks and geothermal fluids in this region. Here the term “complexity” means fracture networks that show a wider range of orientations and higher intensity than other areas. We use digital elevation models to map structures, density maps of fracture intensity, and topology characterization to identify surface level connectivity. Additionally, we use high-resolution aeromagnetic data to identify possible conductive structures at depth and the relationship between Precambrian structures and geothermal systems. 

The preliminary results show that most of the hot springs in the Karonga area are located in Permian-Triassic and Quaternary basins with ~NNW-SSE fault trends. Also, the hot springs are focused on a region of higher fracture intensity with a favorable setting related to terminations of ~NNW-SSE faults and intersections with reactivated Precambrian foliations (NW-SE). The Chiweta hot spring, the highest reservoir temperature in Malawi, is located at an intersection between NE-SW, N-S, and NW-SE fault systems. Aeromagnetic data shows that most of the hot springs are aligned with the deep conductive structures ~NW-SE oriented of the Karonga Fault Zone (KFZ). The KFZ has been associated with the reactivation of the Precambrian Mughese Shear Zone.

The expectations of this research are: 1) to provide a better understanding of the fracture networks that transport the geothermal fluids, 2) to identify permeable areas to mitigate the high-risk of drilling non-productive wells, and 4) the low-cost methodology used in this study can be applied in similar areas of the Western Branch.

How to cite: Davalos-Elizondo, E. and Lao Davila, D.: Assessment of the fracture networks controlling geothermal fluids in the northern part of the Malawi Rifted Zone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-977, https://doi.org/10.5194/egusphere-egu21-977, 2021.

The European Water Framework Directive (WFD) commits EU member states to achieve a good qualitative and quantitative status of all their water bodies.  WFD provides a list of actions to be taken to achieve the goal of good status.  However, this list disregards the specific conditions under which deep (> 400 m b.g.l.) groundwater aquifers form and exist.  In particular, deep groundwater fluid composition is influenced by interaction with the rock matrix and other geofluids, and may assume a bad status without anthropogenic influences. Thus, a new concept with directions of monitoring and modelling this specific kind of aquifers is needed. Their status evaluation must be based on the effects induced by their exploitation. Here, we analyze long-term real-life production data series to detect changes in the hydrochemical deep groundwater characteristics which might be triggered by balneological and geothermal exploitation. We aim to use these insights to design a set of criteria with which the status of deep groundwater aquifers can be quantitatively and qualitatively determined. Our analysis is based on a unique long-term hydrochemical data set, taken from 8 balneological and geothermal sites in the molasse basin of Lower Bavaria, Germany, and Upper Austria. It is focused on a predefined set of annual hydrochemical concentration values. The data range dates back to 1937. Our methods include developing threshold corridors, within which a good status can be assumed, and developing cluster analyses, correlation, and piper diagram analyses. We observed strong fluctuations in the hydrochemical characteristics of the molasse basin deep groundwater during the last decades. Special interest is put on fluctuations that seem to have a clear start and end date, and to be correlated with other exploitation activities in the region. For example, during the period between 1990 and 2020, bicarbonate and sodium values displayed a clear increase, followed by a distinct dip to below-average values and a subsequent return to average values at site F. During the same time, these values showed striking irregularities at site B. Furthermore, we observed fluctuations in several locations, which come close to disqualifying quality thresholds, commonly used in German balneology. Our preliminary results prove the importance of using long-term (multiple decades) time series analysis to better inform quality and quantity assessments for deep groundwater bodies: most fluctuations would stay undetected within a < 5 year time series window, but become a distinct irregularity when viewed in the context of multiple decades. In the next steps, a quality assessment matrix and threshold corridors will be developed, which take into account methods to identify these fluctuations. This will ultimately aid in assessing the sustainability of deep groundwater exploitation and reservoir management for balneological and geothermal uses.

How to cite: Dietmaier, A. and Baumann, T.: Long term variations of the hydrochemical composition of deep thermal ground water in the Lower Bavarian Molasse Basin – Causes and Perspectives, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4127, https://doi.org/10.5194/egusphere-egu21-4127, 2021.

EGU21-8170 | vPICO presentations | ERE2.5

Gas bubble induced scalings in geothermal systems

Lilly Zacherl and Thomas Baumann

Scalings in geothermal systems are affecting the efficiency and safety of geothermal systems. An operate-until-fail maintenance scheme might seem appropriate for subsurface installations where the replacement of pumps and production pipes is costly and regular maintenance comprises a complete overhaul of the installations. The situation is different for surface level installations and injection wells. Here, monitoring of the thickness of precipitates is the key to optimized maintenance schedules and long-term operation.

A questionnaire revealed that operators of geothermal facilities start with a standardized maintenance schedule which is adjusted based on local experience. Sensor networks, numerical modelling and predictive maintenance are not yet applied. In this project we are aiming to close this gap with the development of a non-invasive sensor system coupled to innovative data acquisition and evaluation and an expert system to quantitatively predict the development of precipitations in geothermal systems and open cooling towers.

Previous investigations of scalings in the lower part of production pipes of a geothermal facility suggest that the disruption of the carbonate equilibrium is triggered by the formation of gas bubbles in the pump and subsequent stripping of CO2. Although small in it's overall effect on pH-value and saturation index, significant amounts of precipitates are forming at high volumetric flow rates. To assess the kinetics of gas bubble induced precipitations laboratory experiments were run. The experiment addresses precipitations at surfaces and at the gas bubbles themselves.

How to cite: Zacherl, L. and Baumann, T.: Gas bubble induced scalings in geothermal systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8170, https://doi.org/10.5194/egusphere-egu21-8170, 2021.

EGU21-8715 | vPICO presentations | ERE2.5

Preliminary geochemical and isotopic characterization of the warm and cold waters of the Cotronei (Ponte Coniglio), Bruciarello and Repole thermal areas, (Calabria - Southern Italy).

Giovanni Vespasiano, Francesco Muto, Rosanna De Rosa, Mara Cipriani, Elissavet Dotsika, and Carmine Apollaro

The geochemical characteristics of the Calabrian thermal waters have already been investigated in several studies which adopted a sort of ‘‘regional’’ approach.  On the other hand, the recent works by Vespasiano et al., 2014 and Apollaro et al. 2019 were focused to specific thermal sites with the aim to investigate the geochemistry and to reconstruct the local geothermal conceptual model. In this study, was adopted the same ‘‘local’’ approach to investigate the geochemistry of the warm and cold-water discharges from the Cotronei and Caccuri thermal area. Bruciarello, Cotronei (Ponte Coniglio) and Repole thermal areas fall in the proximity of the western side of the Crotone Basin made up of terrains structured between the middle Miocene and Holocene, transgressive on the crystalline basement belonging to the Sila massif. The Basin, located on the Ionian side of the PCO (Peloritan Calabrian Orogen), was interpreted like a forearc basin in the inner portion of the Calabrian accretion wedge.

Geochemical and hydrogeological data allow to identify the presence of (i) a deep primary geothermal endmember hosted into the crystalline basement (Cotronei system), and (ii) secondary shallow systems developed in the Miocene sedimentary successions (Bruciarello and Repole). All thermal waters have shown different composition: Na(Ca)-Cl composition for Ponte Coniglio-Cotronei (EC 3.57 ± 0.22 mS/cm), Na(Ca)-Cl(SO4) composition for Bruciarello (EC 8.17 ± 0.76 mS/cm) and Na-SO4(Cl) composition for Repole (EC 4.15 mS/cm). The water-rock interaction between primary fluids and evaporitic succession leads to the formation of the secondary Bruciarello and Repole systems. In these sites, the thermal endmember, hosted in the crystalline basement, infiltrates within Miocene evaporitic successions and undergone important compositional changes due to Anhydrite (or gypsum) and sodium Al-silicates dissolution (e.g. Albite) followed by precipitation of phases such as calcite and clay minerals (e.g. Caolinite).

The silica geothermometers indicated temperatures of 55 ± 2 °C for the endmember and slightly lower temperatures for the remaining two systems. Furthermore, δ18O and δ2H values highlight a meteoric origin for all thermal systems and provide infiltration altitude of about 1650 – 1850 m a.s.l. that agree with the Sila plateau heights.

Assuming a geothermal gradient of about 33°C/km, a temperature for the deep thermal reservoir of ⁓55 °C and an average atmospheric temperature of 6°C in the recharge area (Sila plateau), it can be assumed that the meteoric waters descend to depths of 1500 m, where the thermal aquifer is located. This data would confirm the location of the primary geothermal reservoir within the crystalline basement.

Apollaro C., Tripodi V., Vespasiano G., De Rosa R., Dotsika E., Fuoco I., Critelli S., Muto F. 2019. Chemical, isotopic and geotectonic relations of the warm and cold waters of the Galatro and Antonimina thermal areas, southern Calabria, Italy. Marine and Petroleum Geology. 109, 469–483. https://doi.org/10.1016/j.marpetgeo.2019.06.020

Vespasiano G., Apollaro C., Muto F., Dotsika E., De Rosa R., Marini L. 2014 - Chemical and isotopic characteristics of the warm and cold waters of the Luigiane Spa near Guardia Piemontese (Calabria, Italy) in a complex faulted geological framework. Applied Geochemistry, 41, 73-88.

How to cite: Vespasiano, G., Muto, F., De Rosa, R., Cipriani, M., Dotsika, E., and Apollaro, C.: Preliminary geochemical and isotopic characterization of the warm and cold waters of the Cotronei (Ponte Coniglio), Bruciarello and Repole thermal areas, (Calabria - Southern Italy)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8715, https://doi.org/10.5194/egusphere-egu21-8715, 2021.

EGU21-13261 | vPICO presentations | ERE2.5

Exploration of orogenic, fault-hosted geothermal systems using an integrated, multi-disciplinary approach.

Carbajal-Martínez Daniel, Loïc Peiffer, Larryn W. Diamond, John M. Fletcher, Claudio Inguaggiato, and Christoph Wanner

Non-magmatic, orogenic geothermal systems are recognized as significant energy resources for electricity production or direct uses. This study focuses on the non-magmatic geothermal system hosted by the Agua Blanca fault, Ensenada, Mexico. The Agua Blanca fault is a 140 km long transtensional structure with segments recording up to 11 km of dextral strike-slip displacement and normal throws of up to 0.65 km. We have identified at least seven geothermal areas manifested by hot springs discharging at temperatures ranging from 38 °C to 107 °C. These systems involve topography-driven infiltration of meteoric water deep into the Agua Blanca fault and exfiltration of the heated water at valley floors and along a local beach known as La Jolla.

For this contribution, we present recent and ongoing exploration activities aiming to (i) obtain a fundamental understanding of the governing thermal-hydraulic-chemical processes controlling the circulation of meteoric water in the hydrothermally active fault system and (ii) quantify the natural discharge rate and its respective advective heat output. Chemical and isotopic analyses of thermal springs and seismic epicenters' location reveal that meteoric water penetrates between 5 to 10 km deep into the brittle orogenic crystalline basement and thereby attains temperatures between 105 and 215 °C. Interestingly, the deepest circulation and hottest reservoir temperatures occur where the extensional displacement along the fault shows maximum values. However, our data provide no evidence that meteoric water infiltrates beyond the brittle-ductile zone in the crust (12-18 km).

For the La Jolla beach thermal area, we have quantified the advective heat output from thermal images acquired with an unmanned aerial vehicle equipped with a thermal camera and from water flow and direct temperature measurements. The total thermal water discharge is 330 ± 44 L s-1 and occurs over a surface area of 2804 m2 at temperatures up to 52 °C. At 20 cm depth, the temperature is as high as 93 °C. These observations collectively imply a current heat output of 40.5 ± 5.2 MWt (Carbajal-Martínez et al., 2020). We are currently estimating the shape and magnitude of the subsurface thermal anomaly at La Jolla beach by performing coupled thermal-hydraulic-chemical simulations using the code Toughreact.

We conclude that meteoric water circulation through the Agua Blanca fault system reflects the interplay between the permeability distribution along the fault system and the rugged regional topography. Under ideal conditions such as at La Jolla beach, such circulation generates rather large thermal outputs that could supply the thermal energy for a multi-effect distillation desalinization plant and contribute to cover the shortage of fresh water in Ensenada.

How to cite: Daniel, C.-M., Peiffer, L., Diamond, L. W., Fletcher, J. M., Inguaggiato, C., and Wanner, C.: Exploration of orogenic, fault-hosted geothermal systems using an integrated, multi-disciplinary approach., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13261, https://doi.org/10.5194/egusphere-egu21-13261, 2021.

EGU21-15066 | vPICO presentations | ERE2.5

A detailed soil gas physical-chemical survey for geothermal exploration at Tenerife, Canary Islands.

Alba Martín-Lorenzo, Fátima Rodríguez, Mar Alonso, Cecilia Amonte, Gladys V. Melián, María Asensio-Ramos, Eleazar Padrón, Pedro A. Hernández, and Nemesio M. Pérez

There is no evidence of hydrothermal fluid discharges in the surficial environment of the Canary Islands, the only Spanish territory with potential high enthalpy geothermal resource, with the exception of the Teide fumaroles.

In 2011 and 2014 several geochemical and geophysical studies were carried out across 4 mining licenses on the island of Tenerife (Abeque, Berolo, Guayafanta, Garehagua) for geothermal exploration purposes. The geothermal exploration licenses known as Garehagua and Abeque, located on the south ridge and on the northwest ridge of the island of Tenerife respectively, showed the highest geothermal potential of the studied areas. It was decided to carry out several more detailed studies in the areas with the most significant anomalies to better characterize the potential for economic exploitation.

Three surface geochemical surveys each with an average measurement spacing of ~40 m were conducted, and allowed for a mesh resolution of 10 m x 10 m: a mesh size of a much higher spatial resolution than typical grids for surveys of potentially prospective or known geothermal areas. An area called ‘’Madre del Agua’’, located in the northern zone of the Gareagua mining license was prioritised for attention due to i) observed geochemical anomalies at the soil surface; ii) the prominent low-resistivity structure interpreted as a clay alteration cap, and; iii) the positive correlation between thickness of clay alteration cap and helium emission. This study area covers ~0.7 km2. The second area selected for detailed study is located inside the Abeque mining license. The spatial correlation between the helium enrichment and the endogenous CO2 component of Abeque motivated the selection of this study area called ‘’Abeque Detalle’’, which covers ⁓0.8 km2. The third study area called ‘’Fuente del Valle’’ (⁓0.6 km2) was motivated by the observation of significant values ​​of helium anomalies in the Garehagua study area that were measured on the surface in the vertical of a bubbling of endogenous gases at depth, ~2,850 m from the entrance of the Fuente del Valle gallery.

The studies were completed from July to September 2018 (Madre del Agua and Abeque Detalle) and from January to March 2019 (Fuente del Valle). During the survey 1065 sampling sites were made, distributed among the three surveys: 362 points in Madre del Agua, 377 in Abeque Detalle and 326 in Fuente del Valle. At each sampling site the soil CO2 efflux and 222Rn activity were measured in-situ and He and H2 were sampled at 40 cm depth and analysed in the lab. The spatial distribution of soil gases of the three study areas confirm the presence of relative enrichment of non-reactive and/or highly mobile gases in the soil gas atmosphere such as He and CO2, that suggests the existence of a significant contribution of deep-seated gases.

How to cite: Martín-Lorenzo, A., Rodríguez, F., Alonso, M., Amonte, C., Melián, G. V., Asensio-Ramos, M., Padrón, E., Hernández, P. A., and Pérez, N. M.: A detailed soil gas physical-chemical survey for geothermal exploration at Tenerife, Canary Islands., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15066, https://doi.org/10.5194/egusphere-egu21-15066, 2021.

EGU21-15875 | vPICO presentations | ERE2.5

Deep geothermal energy from the Cornubian Batholith: preliminary lithological and heat flow insights from the United Downs Deep Geothermal Power Project. 

Christopher Dalby, Robin Shail, Tony Batchelor, Lucy Cotton, Jon Gutmanis, Gavyn Rollinson, Frances Wall, and James Hickey

SW England is the most prospective region in the UK for the development of deep geothermal energy as it has highest heat flow values (c. 120 mW m-2) and predicted temperatures greater than 190 oC at 5 km depth. The United Downs Deep Geothermal Project (UDDGP), situated near Redruth in Cornwall, is the first deep geothermal power project to commence in the UK. Two deviated geothermal wells, UD-1 (5058 m TVD) and UD-2 (2214 m TVD), were completed in 2019 and intersect the NNW-SSE-trending Porthtowan Fault Zone (PTFZ) within the Early Permian Cornubian Batholith.

The Cornubian Batholith is composite and can be divided into five granite types that were formed by variable source melting and fractionation [1]. These processes were the primary control on the heterogeneous distribution of U, Th and K that underpins heat production in the granite. Previous high resolution airborne gamma-ray data has demonstrated the spatial variation of near-surface granite heat production [2], and the CSM Hot Dry Rock Project (1977-1991) provided U, Th and K distributions to depths of 2600 m in the Carnmenellis Granite [3]. However, uncertainties in: (i) U, Th and K content in the deeper batholith, (ii) thermal conductivity are still challenges to modelling the high heat flow.

Preliminary evaluation of UD-1 downhole spectral gamma data (900-5057 m) indicates the presence of three major granite types on the basis of contrasting U and Th characteristics. QEMSCAN mineralogical analysis of cuttings (720 – 5057 m) demonstrates the overwhelming dominance of two mica (G1) and muscovite (G2) granites and little expression of biotite (G3) granites. U- and Th- bearing accessory minerals include monazite, zircon and apatite, with the appearance of allanite and titanite in the deeper granites. Representivity analysis between various cutting fractions show no systematic bias in the major mineral components.

There is a substantial increase in Th below 3000 m that indicates the deeper parts of the batholith are likely to contribute substantially to overall heat production. Monazite is the primary source for Th and has a close association with micas. Mineralogical, mineral chemical, whole-rock geochemical and coupled thermal conductivity analysis is ongoing to improve understanding of the construction of this part of the Cornubian Batholith and its implications for the regional thermal resource and sub-surface temperature evaluation.

References:
[1]Simons B et al. (2016) Lithos, 260: 76-94
[2]Beamish D and Busby J (2016) Geothermal Energy, 4.1:4
[3]Parker R (1989) Pergamon, 621.44

How to cite: Dalby, C., Shail, R., Batchelor, T., Cotton, L., Gutmanis, J., Rollinson, G., Wall, F., and Hickey, J.: Deep geothermal energy from the Cornubian Batholith: preliminary lithological and heat flow insights from the United Downs Deep Geothermal Power Project. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15875, https://doi.org/10.5194/egusphere-egu21-15875, 2021.

EGU21-1101 | vPICO presentations | ERE2.5

NMR contribution in sub-horizontal well for porosity-permeability heterogeneity characterization in limestones: implications for 3D reservoir prediction and flow simulation in a world class geothermal aquifer

Maxime Catinat, Benjamin Brigaud, Marc Fleury, Miklos Antics, Pierre Ungemach, Melanie Davaux, Julien Gasser Dorado, Hadrien Thomas, Codjo Thomas Florent Essou, Simon Andrieu, and Emmanuel Mouche

With around 50 heating networks today operating, the aera around Paris is the European region which concentrates the most heating network production units in terms of deep geothermal energy. In France, the energy-climate strategy plans to produce 6.4TWh in 2023, compared to 1.5TWh produced in 2016. Despite an exceptional geothermal potential, the current average development rate of 70MWh/year will not allow this objective to be achieved, it would be necessary to reach a rate of 6 to 10 times higher. The optimization of the use of deep geothermal energy is a major challenge for France, and in Ile-de-France, which has a population of nearly 12 million inhabitants. This project aims to reconstruct and simulate heat flows in the Paris Basin using an innovative methodology (1) to characterize, predict and model the properties of reservoirs (facies, porosity, permeability) and (2) simulate future circulations and predict the performance at a given location (sedimentary basin) on its geothermal potential. This study focuses on a high density area of well infrastructures around Cachan, (8 doublets, 1 triplet in 56 km2). A new sub-horizontal doublet concept has been recently (2017) drilled at Cachan to enhance heat exchange in medium to low permeability formations. Nuclear Magnetic Resonance (NMR T2) logs have been recorded in the sub-horizontal well (GCAH2) providing information on pore size distribution and permeability. We integrated all logging data (gamma ray, density, resistivity, sonic, NRM T2) of the 19 wells in the area and 120 thin section observations from cuttings to derive a combined electrofacies-sedimentary facies description. A total of 10 facies is grouped into 5 facies associations coded in all the 19 wells according to depths and 10 3rd order stratigraphic sequences are recognized. The cell size of the 3D grid was set to 50 m x 50 m for the XY dimensions. The Z-size depends on the thickness of the sub-zones, averaging 5 m. The resulting 3D grid is composed of a total of nearly 8.105cells. After upscaled, facies and stratigraphic surfaces are used to create a reliable model using the “Truncated Gaussian With Trends” algorithm. The petrophysical distribution “Gaussian Random Function Simulation” is used to populate the entire grid with properties, included 2000 NMR data, considering each facies independently. The best reservoir is mainly located in the shoal deposits oolitic grainstones with average porosity of 12.5% and permeability of 100 mD. Finally, hydrodynamic and thermal simulations have been performed using Pumaflow to give information on the potential risk of interference between the doublets in the area and advices are given in the well trajectory to optimize the connectivity and the lifetime of the system. NMR data, especially permeability, allow to greater improve the simulations, defining time probabilities of thermal breakthrough in an area of high density wells.

How to cite: Catinat, M., Brigaud, B., Fleury, M., Antics, M., Ungemach, P., Davaux, M., Gasser Dorado, J., Thomas, H., Thomas Florent Essou, C., Andrieu, S., and Mouche, E.: NMR contribution in sub-horizontal well for porosity-permeability heterogeneity characterization in limestones: implications for 3D reservoir prediction and flow simulation in a world class geothermal aquifer, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1101, https://doi.org/10.5194/egusphere-egu21-1101, 2021.

EGU21-2205 | vPICO presentations | ERE2.5

Characterisation of a highly heterogeneous geothermal reservoir based on geophysical well logs

Johanna Bauer, Daniela Pfrang, and Michael Krumbholz

For successful exploitation of geothermal reservoirs, temperature and transmissibility are key factors. The Molasse Basin in Germany is a region in which these requirements are frequently fulfilled. In particular, the Upper Jurassic Malm aquifer, which benefits from high permeability due to locally intense karstification, hosts a large number of successful geothermal projects. Most of these are located close to Munich and the “Stadtwerke München (SWM)” intends to use this potential to generate most of the district heating demands from geothermal plants by 2040.

We use geophysical logging data and sidewall cores to analyse the spatial distribution of reservoir properties that determine porosity, permeability, and temperature distribution. The data are derived from six deviated wells drilled from one well site. The reservoir rocks are separated by faults and lie in three different tectonic blocks. The datasets include image logs, GR, sonic velocities, temperature, flowmeter- and mud logs. We not only focus on correlations between rock porosity and matrix permeability, but also on how permeability provided by fractures and karstification correlate with inflow zones and reservoir temperature. In addition, we correlate individual parameters with respect to their lithology, dolomitisation and the rock’s image fabric type, adapted from Steiner and Böhm (2011).  

Our results show that fracture intensity and orientations vary strongly, between and within individual wells. However, we observed local trends between fracture systems and rock properties. For instance fracture intensities and vp velocities (implying lower porosities) are higher in rock sections classified as dolomites without bedding contacts. As these homogeneous-appearing dolomites increase, from N to S, the mean fracture intensities and vp velocities also increase. Furthermore, we observed most frequently substantial karstification in dolomites and dolomitic limestones. Nevertheless, an opposing trend for the percentage of substantial karstification can be also found, i.e., the amount of massive karstification is higher in the northern wells. The interpretation of flowmeter measurements show that the main inflow zones concentrate in those Upper Malm sections that are characterised by karstification and/or intense fracturing.

In the next step, we will correlate laboratory measurements of outcrop- and reservoir samples (e.g. porosity, permeability, and mechanical rock properties) with the logging data. The aim is to test the degree to which analogue samples can contribute to reservoir characterization in the Upper Jurassic Malm Aquifer (Bauer et al., 2017).

This work is carried out in the research project REgine "Geophysical-geological based reservoir engineering for deep-seated carbonates" and is financed by the German Federal Ministry for Economic Affairs and Energy (FKZ: 0324332B).

Bauer, J. F., Krumbholz, M., Meier, S., and Tanner, D. C.: Predictability of properties of a fractured geothermal reservoir: The opportunities and limitations of an outcrop analogue study, Geothermal Energy, 5, 24, https://doi.org/10.1186/s40517-017-0081-0, 2017.

Steiner, U., Böhm, F.: Lithofacies and Structure in Imagelogs of Carbonates and their Reservoir Implications in Southern Germany. Extended Abstract 1st Sustainable Earth Sciences Conference & Exhibition – Technologies for Sustainable Use of the Deep Sub-surface, Valencia, Spain, 8-11 November, 2011.

How to cite: Bauer, J., Pfrang, D., and Krumbholz, M.: Characterisation of a highly heterogeneous geothermal reservoir based on geophysical well logs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2205, https://doi.org/10.5194/egusphere-egu21-2205, 2021.

EGU21-3044 | vPICO presentations | ERE2.5

Deconvolution well test analysis applied to the Waiwera geothermal reservoir (New Zealand)

Michael Kühn and Leonard Grabow

The geothermal reservoir in Waiwera has been subject to active exploitation for a long time. It is located below the village on the Northern Island of New Zealand and was used commercially since 1863. The continuous production of geothermal water, to supply hotels and spas, had a negative impact on the reservoir. Until the year 1969 from all wells drilled the warm water flow was artesian. Due to overproduction the water had to be pumped from the 1970s on. Further, within the years 1975 to 1976 the warm water seeps on the beach of Waiwera ran dry. In order to protect the reservoir and the historical and tourist site in the early 1980s a water management plan was deployed. The "Auckland Council" established guidelines to enable sustainable management of the resource [1]. However, shortly after the recent shutdown of the primary user (Waiwera Thermal Resort & Spa) renewed artesian activity was reported by locals and newly obtained observation data indicate revived activity of the hot springs on the beachfront of Waiwera [2].

So far, the physical relation between abstraction rates and water level change of the hydrogeological system is only fairly understood [3]. The aim of this work was to link the influence of rates to actual reservoir properties and measured water level data. For this purpose, the daily abstraction history was investigated by means of a variable-rate well test analysis. For the analysis, a modified deconvolution algorithm of Von Schroeter et al. was implemented [4]. The algorithm derives the reservoir response function by solving a least square problem with the unique feature of imposing only implicit constraints on the solution space. To investigate the theoretical performance of the algorithm with respect to stability and error propagation a sensitivity analysis was conducted. The results for Waiwera were obtained by subjecting the implementation to a bootstrapping method which selected time periods to analyse on a random base.

Results throughout all years show radial flow during middle-time behaviour and a leaky flow boundary during late-time behaviour. As opposed to the expected model, a double-porosity flow or a constant head boundary were not determined. For middle-time behaviour, the findings agree very well with prior results of a pumping test. The late-time behaviour cannot be observed during the short pumping test but is in accordance with the expected model.

[1] Kühn M., Stöfen H. (2005) A reactive flow model of the geothermal reservoir Waiwera, New Zealand. Hydrogeology Journal 13, 606-626, doi: 10.1007/s10040-004-0377-6
[2] Präg M., Becker I., Hilgers C., Walter T.R., Kühn M. (2020) Thermal UAS survey of reactivated hot spring activity in Waiwera, New Zealand. Adv. Geosci. 54, 165-171, doi: 10.5194/adgeo-54-165-2020
[3] Kühn M., Schöne T. (2017) Multi variate regression model of the water level and production rate time series of the geothermal reservoir Waiwera (New Zealand). Energy Procedia 125, 571-579, doi: 10.1016/j.egypro.2017.08.196
[4] Schroeter T., Hollaender F., Gringarten A.C. (2004) Deconvolution of well-test data as a nonlinear total least-squares problem. SPE Journal, 9, Society of Petroleum Engineers.

How to cite: Kühn, M. and Grabow, L.: Deconvolution well test analysis applied to the Waiwera geothermal reservoir (New Zealand), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3044, https://doi.org/10.5194/egusphere-egu21-3044, 2021.

EGU21-5185 | vPICO presentations | ERE2.5

Ground motions induced by pore pressure changes at the Szentes geothermal area, SE Hungary

Eszter Békési, Peter Fokker, Thibault Candela, János Szanyi, and Jan-Diederik van Wees

The long-term sustainable exploitation of geothermal resources requires cautious planning and regulation. Exploitation in excess of natural recharge can result in reservoir pressure decline, causing a decrease in production rates. Furthermore, such “overexploitation” of geothermal reservoirs may lead to compaction and land subsidence. Understanding of such phenomena is critical for the assessment of societal-environmental risks, but can also be used for optimization by constraining reservoir processes and properties.

Excessive thermal water volumes have been extracted from porous sedimentary rocks in the Hungarian part of the Pannonian Basin. Thermal water production in Hungary increased significantly from the early 70’s. Regional-scale overexploitation of geothermal reservoirs resulted in basin-scale pressure drop in the Upper Pannonian sediments, leading to compaction and ground subsidence.

We investigated surface deformation at the Szentes geothermal filed, SE Hungary, where the largest pressure decline occurred. We obtained data from the European Space Agency’s ERS and Envisat satellites to estimate the ground motions for the periods of 1992-2000 and 2002-2010. We applied inverse geomechanical modelling to understand the compaction behaviour of the reservoir system and to estimate the subsurface properties. We constrained the model parameters using the Ensemble Smoother with Multiple Data Assimilation, which allowed us to incorporate large amounts of surface movement observations in a computationally efficient way. The model requires pressure time series as input parameters, therefore, the lack of regular pressure measurements in geothermal wells of Szentes resulted in significant uncertainties. Still, we managed to identify a potential delay in pressure drop and subsidence, implying a time-decay compaction behaviour of the reservoir system,  and we arrived at realistic estimates for the compaction coefficient of the reservoir. The improved parametrization enables better forecasting of the reservoir behaviour and facilitates the assessment of future subsidence scenarios. This study thus demonstrates the effectiveness of InSAR-based ground motion data and inverse geomechanical modelling for the monitoring of geothermal reservoirs and the establishment of a sustainable production scheme.

How to cite: Békési, E., Fokker, P., Candela, T., Szanyi, J., and van Wees, J.-D.: Ground motions induced by pore pressure changes at the Szentes geothermal area, SE Hungary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5185, https://doi.org/10.5194/egusphere-egu21-5185, 2021.

The Molasse Basin is one of the most promising areas for deep geothermal exploration in Germany and a very ambitious project in this region is to power the entire district heating system of the city of Munich with renewable energies by 2040; a major part of this will consist of geothermal energy. As part of a joint project (financed by the German Federal Ministry For Economic Affairs And Energy; FKZ 0324332B) the Leibniz Institute for Applied Geophysics (LIAG) works together with the Munich City Utilities (Stadtwerke München), to improve reservoir characterization and sustainable reservoir exploration within the German Molasse Basin. The target horizon for hydrothermal exploration is the aquifer in the Upper Jurassic carbonates. A major problem is the strong heterogeneity of the carbonates. Compared to quantity and quality of the structural data of the reservoir, the database of reservoir properties such as density, porosity and permeability, which describe the geothermal potential, is insufficient. Therefore, it is necessary to generate such data in order to improve the value of the structural information. A 3D seismic survey cannot only provide structural information, but also important reservoir properties such as elastic parameters and seismic attributes. One of the most important attributes is the acoustic impedance, which can be determined with a seismic inversion and used to estimate a porosity volume.

The data basis for this study was the 170km² GRAME-3D seismic survey measured in Munich, a structural geological model, and drilling and logging data from the geothermal site “Schäftlarnstraße”.

The inversion results show low impedance values at the top of the reservoir, but also at the middle part. Spatially, the intermediate block of the Munich fault shows low values but also the eastern part of the hanging wall block and the western part of the footwall block. Based on a well correlation a relationship between acoustic impedance and porosity could be determined and a 3D porosity volume was calculated. In the upper part but also in the middle part of the reservoir areas with increased porosity (>10%) are shown, which might indicate a high geothermal potential.

For a better classification, an attribute analysis was performed. The intermediate block and the eastern part of the hanging wall block show strongly fractured rocks. In contrast, there are hardly any conspicuous features in the western part of the footwall block, although high porosities are also expected here. This suggests that the presence of faults is not the only factor favoring high porosities in carbonates. More likely is a combination with karstification processes, which is why even areas that do not show enhanced tectonic deformation have high porosities.

How to cite: Wadas, S. and von Hartmann, H.: Porosity estimation and characterization of a geothermal carbonate reservoir in the South German Molasse Basin based on seismic inversion and attribute analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7028, https://doi.org/10.5194/egusphere-egu21-7028, 2021.

EGU21-748 | vPICO presentations | ERE2.5

Heat transfer estimation through a high-temperature geothermal field in New Zealand quantified by multi-channel data modelling

Alberto Ardid, Rosalind Archer, and David Dempsey

EGU21-3525 | vPICO presentations | ERE2.5

Transport of Heat by Hydrothermal Circulation in a Young Rift Setting:  Observations from the Auka and JaichMaa Ja'ag' vent Field in the Pescadero Basin, Southern Gulf of California.

Raquel Negrete-Aranda, Florian Neumann, Juan Contreras, Robert N. Harris, Ronald M. Spelz, Robert Zierenberg, and David W. Caress

New heat flow measurements collected throughout the Auka and JaichMaa Ja' ag' hydrothermal vent fields in the central graben of the Southern Pescadero Basin, southern Gulf of California, indicate that upflow of hydrothermal fluids associated with active rifting dissipate heat in excess of 10 W/m2 around faults that have a few tens-of-meters of displacement. Heat flow anomalies slowly decay to background values of ~2 W/m2 at distances of ~1 km from these faults following an inverse square-root distance law. We develop a physical model of the Auka vent field based on the fundamental Green's function solution of the heat equation. The model includes the effects of circulation in the porous networks of faults and the lateral seepage of geothermal brines through the fault walls to surrounding hemipelagic sediments.  We use an optimal fitting method to estimate the reservoir depth, permeability, and circulation rate. Our model indicates the heat source is at a depth of ~5.7 km; permeability and flow rates in the fracture system are ~10-14 m2 and 10-7 m/s, respectively, and ~10-16 m2 and 10-8 m/s in the basin aquitards, respectively. Model scaling laws point to the importance of faults in controlling sediment-hosted vent fields and slow circulation throughout low permeability sediments in controlling the brine's chemistry. Although the fault model seems appropriate and straightforward for the Pescadero vents, it does seem to be the exception to the other known sediment-hosted vent fields in the Pacific.

How to cite: Negrete-Aranda, R., Neumann, F., Contreras, J., Harris, R. N., Spelz, R. M., Zierenberg, R., and Caress, D. W.: Transport of Heat by Hydrothermal Circulation in a Young Rift Setting:  Observations from the Auka and JaichMaa Ja'ag' vent Field in the Pescadero Basin, Southern Gulf of California., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3525, https://doi.org/10.5194/egusphere-egu21-3525, 2021.

EGU21-1688 | vPICO presentations | ERE2.5

The potential for geothermal lithium in Italy

Pierfranco Lattanzi, Andrea Dini, Giovanni Ruggieri, and Eugenio Trumpy

Italy has never been a lithium (Li) producer, and the potential for “hard rock” deposits is moderate at best. On the other hand, the increasing demand for Li-based rechargeable batteries fostered new interest in this metal, and prompted the quest for alternative resources. The extraction of Li from geothermal brines (“geothermal lithium”) is currently considered in several countries, including, in Europe, France, Germany, and UK (EGEC, 2020).

Italy has vast geothermal resources, and there is a potential for “geothermal lithium” as well. A preliminary survey of literature data pointed out several occurrences of fluids with Li contents up to hundreds of mg/L. Among high-enthalpy fluids, we point out those of Cesano, Mofete, and Latera. At Cesano, geothermal fluids contain about 350 mg/L lithium (Calamai et al., 1976). Early studies conducted in the past century (Pauwels et al., 1990) suggested the feasibility of lithium recovery from these fluids. Even higher contents (480 mg/L) occur in the deep reservoir at Mofete (Guglielminetti, 1986), whereas fluids in the shallow and intermediate reservoir in the same field contain 28 to 56 mg/L. Geothermal fluids at Latera have somewhat lower contents (max 13.5 mg/L; Gianelli and Scandiffio, 1989). Several low-enthalpy thermal waters in Emilia-Romagna, Sardinia, Sicily and Tuscany also show significant (> 1 mg/L) Li contents (max 96 mg/L at Salsomaggiore; Boschetti et al., 2011). There are no published Li data for high-enthalpy fluids at Larderello; however, evidence of Li-rich fluids was found in fluid inclusions in hydrothermal minerals (Cathelineau et al., 1994). Moreover, the shallow (ca. 3.5 km) granitoid body underlying the field contains a Li-rich (about 1,000 ppm) biotite (A. Dini, unpublished data); it has been estimated that such rock may contain as much as 500 g Li per cubic meter.

 

References

Boschetti T., et al. - Aquat Geochem (2011) 17:71–108

Calamai A., et al. - Proc. U.N. Symp. Development Use Geotherm. Energy, S. Francisco, USA (1976), 305-313

Cathelineau M., et al. – Geochim. Cosmochim. Acta (1994) 58: 1083-1099

EGEC (European Geothermal Council). https://www.egec.org/time-to-invest-in-clean-geothermal-lithium-made-in-europe/. Accessed December 2, 2020.

Gianelli G., Scandiffio G. - Geothermics (1989) 18: 447-463

Guglielminetti M. - Geothermics (1986) 15: 781-790

Pauwels H., et al. - Proc. 12th New Zealand Geothermal Workshop (1990), 117-123

How to cite: Lattanzi, P., Dini, A., Ruggieri, G., and Trumpy, E.: The potential for geothermal lithium in Italy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1688, https://doi.org/10.5194/egusphere-egu21-1688, 2021.

EGU21-6189 | vPICO presentations | ERE2.5

Cosmovision and geothermal: proposal for direct uses of the geothermal resource

Karla Elizalde, Mariana Patricia Jácome Paz, and Alma Adriana Zárate Arroyo

Cosmovision and geothermal: proposal for direct uses of the geothermal resource in El Carrizal, Veracruz, México

Keywords:  Geothermy, direct uses, resource, social analisis.

Currently there is a wide epistemological repertoire that tells us about the man-natural environment relationship, the close relationship that exists between these two entelechies has been the subject of controversy within scientific disciplines, and it is not possible to speak of man without a time and space, just as you cannot talk about space and its components without mentioning at some point the presence of man.

This close relationship between man and nature has evolved over time, going from a static concept to a dynamic one in response to the need to offer an explanation of how the natural environment with anthropic presence has been modified and used.

Geothermal energy plays a very important role, from the energy field to the tourist, forming part of our civilization and history, with which it has a wide historical and cultural background. That is why, at present, geothermal energy appears as an important solution for obtaining renewable, sustainable, accessible and low-cost ecological energy throughout its temperature range.

 

The main limiting cause for planning and carrying out an integral project of direct uses of the thermal resource is the lack of research work on thermal manifestations, where the geological and geochemical characteristics are described and which are integrated into a social analysis that tells us about perception of geothermal resources and the cultural and identity value that the adjacent population grants.

This panorama is repeated throughout the Mexican territory, and in particular, in the vicinity of the state of Veracruz and its various thermal springs, an example of this are: Los Baños Carrizal (Apazapan, Ver., 19 ° 19´ 15.69” N - 96 37´43.94” W), Hotel Chichaki (Apazapan, Ver., 19 ° 19´31.54” N - 96 ° 43´24.11” W), Isabelass Spa (Loc.Tinajitas, Actopan, Ver., 19 ° 37´ 38.07” N - 96 ° 27´31.87” W), among others.

In this work will present  the preliminary results of the project that leads to the realization of a geochemical characterization and the elaboration of a social study that manages to understand the role that the different thermal manifestations play around the history and culture of the population and with this to reach the proposal of a project of direct uses of the geothermal resource.

How to cite: Elizalde, K., Jácome Paz, M. P., and Zárate Arroyo, A. A.: Cosmovision and geothermal: proposal for direct uses of the geothermal resource, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6189, https://doi.org/10.5194/egusphere-egu21-6189, 2021.

EGU21-9442 | vPICO presentations | ERE2.5

CROWDTHERMAL – A vision for citizens’ empowerment in geothermal projects

Gauthier Quinonez, Isabel Fernandez, Jan Hildebrand, Georgie Friederichs, Christina Baisch, and Ottó Elíasson

CROWDTHERMAL is an EU Horizon 2020 project, developing alternative funding schemes for geothermal energy. CROWDTHERMAL supports the European Green Deal aiming at reaching carbon neutrality by 2050. To reach this goal the involvement of society is needed. In 2017, renewable energy accounted for 17.5% of the European gross energy consumption, of which only 3% were geothermal energy – despite its upsides and positive impact regarding decarbonization and heating and cooling in Europe. Geothermal is green, available 24 hours a day. CROWTHERMAL contributes to decrease dependency on fossil fuels in Europe by empowering local communities to directly participate in the development of geothermal projects via alternative financing schemes and engaging communication strategies.

 

To support the participation in geothermal projects, CROWDTHERMAL is analysing the perception of geothermal energy and will develop a public engagement approach making extensive use of social media. Since our project started in September 2019, the CROWDTHERMAL team has developed a set of reports, addressing social, environmental and financial aspects of community financed geothermal projects.

 

With regards to finance, CROWDTHERMAL formulates new financing models for community funding at national and international levels covering Member States and the EU alike. Community funding will enable citizens to collectively finance geothermal projects that will not only benefit them but also the society as a whole. The positive effect of citizens’ participation in energy projects was showcased by a report on renewable energy projects in Europe using alternative financing methods at different stages of their development published in 2020. Furthermore, an alternative finance risk inventory and potential mitigation tools have been developed. The deliverables compile the advantages, potential risks and possible risk mitigation measures for different alternative finance methods, each from a project developer’s and from a community investor’s perspective. The financial models are currently being developed and will be validated with the help of three geothermal Case Studies in Iceland, Hungary and Spain and through an European survey conducted by European Federation of Geologists’ (EFG) Third Parties.

 

For the remaining 1.5 years of its funded period, CROWDTHERMAL will create Core Services and a social media powered platform that will support the deployment of integrated development schemes for geothermal energy utilising alternative finance and community engagement tools. It is targeted at project developers and citizens with an interest in energy empowerment. The aim is to connect the new approaches brought forwardhighlighted by CROWDTHERMAL with conventional financing, public engagement and risk mitigation schemes. It is also planned to launch a European mobilisation campaign via social media and conferences and workshops and by mobilising EFG Third Parties and the Altfinator Network. The CROWDTHERMAL Core Services will be designed to be operated after the EC-funded period helping geothermal projects tapping into alternative finance during the years to come.

 

 

Finally, CROWDTHERMAL started to strengthen ties with the Cost Action Geothermal-DHC and lately organised two joint meetings to identify synergies and potential opportunities for cooperation. The goal is to further expand the CROWTHERMAL network to provide opportunities to test CROWDTHERMAL concepts in a growing European geothermal energy market.

 

 

How to cite: Quinonez, G., Fernandez, I., Hildebrand, J., Friederichs, G., Baisch, C., and Elíasson, O.: CROWDTHERMAL – A vision for citizens’ empowerment in geothermal projects, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9442, https://doi.org/10.5194/egusphere-egu21-9442, 2021.

EGU21-10763 | vPICO presentations | ERE2.5

CDGP, a data center of EPOS TCS Anthropogenic Hazards, to help analysis of geothermal anthropogenic seismicity

Marc Schaming, Mathieu Turlure, Jean Schmittbuhl, Beata Orleka-Sikora, and Stanislaw Lasoki

The Data Centre for Deep Geothermal Energy (CDGP – Centre de Données de Géothermie Profonde, https://cdgp.u-strasbg.fr) was launched in 2016 by the LabEx G-Eau-Thermie Profonde - now ITI Géosciences pour la transition énergétique GeoT, https://iti-geot.unistra.fr/ - to preserve, archive and distribute data acquired on geothermal sites in Alsace. At the moment, it archives and gives access to data from Soultz-sous-Forêts (1988-2010), Rittershoffen (2012-2014) and Vendenheim (2016-2021).

Access to patrimonial data like those from Soultz-sous-Forêts (SSF, 1993, 2000) or from Rittershoffen allows reprocessing of data, validation of new ideas. Cauchie et al. (2020) reinvestigated earthquakes during SSF 1993 stimulation and discussed implications for detecting the transition between events related to pre-existing faults and the onset of fresh fractures. Vallier et al. (2019) used a simplified 2D thermo-hydro-mechanical model of SSF reservoir to infer that the sediments–granite interface has a weak influence on the hydrothermal circulation, or that the brine viscosity has a huge impact on the hydrothermal circulation. Koepke et al. (2020) applied pseudo-probabilistic fracture network method to the seismicity induced during the SSF 2000 stimulation to confirm the existence of a large prominent fault. Drif et al. (2020) used data from Vendenheim area to determine the seismic moment, the source size, the average stress drop and the focal mechanism associated to the M3 event in November 2019.

Some of the CDGP data are also available on the EPOS Thematic Core Service Anthropogenic Hazards platform (https://tcs.ah-epos.eu/, Orlecka-Sikora et al., 2020), with other geothermal episodes, and with applications to process and analyse the data. This platform is a functional e-research infrastructure that allows free experimentations in a virtual laboratory, promoting interdisciplinary collaborations between stakeholders (the scientific community, industrial partners and society).

Cauchie, L., Lengliné, O. & Schmittbuhl, J., 2020 - Seismic asperity size evolution during fluid injection: case study of the 1993 Soultz-sous-Forêts injection. Geophysical Journal International 221, 968–980.
Drif, K., Lengline, O., Lambotte, S., Kinscher, J. & Schmittbuhl, J., 2020 - Source parameters of the Ml3.0 StrasbourgEarthquake (12th November 2019). Communication at EGW2020, http://labex-geothermie.unistra.fr/wp-content/uploads/2020/12/abstracts-egw2020-en.pdf#page=68.
Koepke, R., Gaucher, E. & Kohl, T., 2020 - Pseudo-probabilistic identification of fracture network in seismic clouds driven by source parameters. Geophys J Int 223, 2066–2084.
Orlecka-Sikora B., Lasocki S., Kocot J., Szepieniec T., Grasso J-R., Garcia-Aristizabal A., Schaming M., Urban P., Jones G., Stimpson, I., Dineva S., Sałek P., Leptokaropoulos K., Lizurek G., Olszewska D., Schmittbuhl J., Kwiatek G., Blanke A., Saccorotti G., Chodzińska K., Rudziński Ł., Dobrzycka I., Mutke G., Barański A., Pierzyna A., Kozlovskaya E., Nevalainen J.,  Kinscher J., Sileny J., Sterzel M., Cielesta, S., Fischer T., 2020 -An open data infrastructure for the study of anthropogenic hazards linked to georesource exploitation. Scientific Data 7, 89. doi:10.1038/s41597-020-0429-3.
Vallier, B., Magnenet, V., Schmittbuhl, J. & Fond, C, 2019 - Large scale hydro-thermal circulation in the deep geothermal reservoir of Soultz-sous-Forêts (France). Geothermics 78, 154–169.

How to cite: Schaming, M., Turlure, M., Schmittbuhl, J., Orleka-Sikora, B., and Lasoki, S.: CDGP, a data center of EPOS TCS Anthropogenic Hazards, to help analysis of geothermal anthropogenic seismicity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10763, https://doi.org/10.5194/egusphere-egu21-10763, 2021.

EGU21-15437 | vPICO presentations | ERE2.5

EASYGO - Efficiency and Safety in Geothermal Operations – A new Innovative Training Network

Maren Brehme, Martin O Saar, Evert Slob, Paola Bombarda, Hansruedi Maurer, Florian Wellmann, Phil J Vardon, David Bruhn, and Easygo Team

How to operate a geothermal system in the most efficient and safe manner? This is the most important and urgent question after a geothermal resource has been identified. The recently funded Innovative Training Network ‘EASYGO‘ will answer that question from different perspectives and give high-level training for early stage researchers (ESR; here PhD candidates) in geothermal operations.

Tackling the challenges of sustainable geothermal operations requires an interdisciplinary and intersectoral approach. To achieve the main objective, researchers will work on the whole chain of geothermal operations, from production to power-plant engineering to injection. They will develop novel monitoring concepts, perform real-time simulations, develop system components, assess novel concepts for operations and test operational parameters at the field scale. The major strength and originality of the programme is that it is developed around large-scale infrastructure. Researchers will have access to the infrastructure in all countries for testing equipment and doing real-time measurements.

EASYGO graduates will be a new generation of multidisciplinary experts in geothermal operations, trained to achieve standardised efficient and safe operations of geothermal systems to enable the ambitious international expansion plans. The mobility plan of EASYGO envisages each ESR to have at least one academic secondment and one industrial secondment.

EASYGO consists of an intersectoral team of experts from academic and non-academic institutions. All academic participants are members of the IDEA League, a strategic alliance of leading European universities of technology. The members of the IDEA League with a strong research profile in geothermal energy, TU Delft (The Netherlands), RWTH Aachen (Germany), ETH Zurich (Switzerland) and Politecnico di Milano (Italy), constitute the academic consortium of EASYGO. Additionally, ten industry partners from all countries drive the research from an applied point of view. Our ambition is to contribute to making Europe a world leader in geothermal science, operational technology and education, thereby accelerating the energy transition.

How to cite: Brehme, M., Saar, M. O., Slob, E., Bombarda, P., Maurer, H., Wellmann, F., Vardon, P. J., Bruhn, D., and Team, E.: EASYGO - Efficiency and Safety in Geothermal Operations – A new Innovative Training Network, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15437, https://doi.org/10.5194/egusphere-egu21-15437, 2021.

EGU21-4140 | vPICO presentations | ERE2.5

Curie point depth and heat flow maps deduced from magnetic data of Gonghe Basin, China

Zhuo Wang and Zhaofa Zeng

Most recently, energy consumption around the world steps into a new situation divided by petroleum, natural gas, coal and new energy. Fossil fuels are disputed for pollution and CO2 emission, and geothermal energy is popular as a clean, ecofriendly and renewable new energy, which can be used for power generation or direct application (e.g. bathing, building heating).

Gonghe Basin, located in the western part of China, has been thought as a potential geothermal field since 1989. To investigate geothermal distribution in Gonghe Basin and adjacent area, magnetic data is used in this paper. Firstly, we proposed an improved magnetic interface inversion method based on traditional Park-Oldenburg method. This improved method introduces dual geological interfaces instead of one interface, variable magnetic susceptibility instead of constant magnetic susceptibility and upward continuation in a form equivalent to inversion iteration in the Fourier domain instead of the divergent, downward continuation term, to improve suitability and precision of the inversion method. Then Curie point depth (CPD) map and heat flow map could be deduced from magnetic data through the improved Park-Oldenburg method.

The CPDs range from 16 to 25.5 km and heat flow values range from 61 to 91 mW/m2. What's more, we take faults and seismic activities into account, we find that study area has greater geothermal potential in eastern part with shallower CPD, higher heat flow values and more active subsurface structure. Considering with known geothermal value in actual measurement, the results indicate high heat flow value in Gonghe Basin is coaction of high thermal background, radiogenic heat and partial geothermal anomalous heat source. 

How to cite: Wang, Z. and Zeng, Z.: Curie point depth and heat flow maps deduced from magnetic data of Gonghe Basin, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4140, https://doi.org/10.5194/egusphere-egu21-4140, 2021.

EGU21-13290 | vPICO presentations | ERE2.5

Joint inversion of converted and surface waves for characterization of geothermal fields

Ivan Granados Chavarria, Marco Calò, Thomas Bodin, and Angel Figueroa Soto

Joint inversion of surfaces and teleseismic converted waves is commonly used to retrieve seismic structures beneath a seismic station. Currently, this approach is routinely applied at global and regional scale to probe the structures of the mantle and the lower-crust. However, the difficulty to retrieve reliable converted waves at high frequencies (> 1 Hz) makes challenging to apply this technique to resolve structures at shallow depths (<20 km). Here we explore the feasibility of using a trans-dimensional Bayesian scheme based on a reversible jump Markov Chains Monte Carlo method, to resolve shallow structure at local scale. We use phase and group velocity dispersion curves for Love and Rayleigh waves, from 0.5 to 10 s and tele-seismic converted waves in a distance range from 30o to 95o. We explore the ability of different approaches to retrieve high frequency converted phases that will be used in the framework of the Bayesian inversion. We present preliminary tests of the reliability of the method and applications to experimental data collected in the super-hot geothermal field of Los Humeros, México. This work is performed in the framework of the Mexican European consortium GeMex (Cooperation in Geothermal energy research Europe-Mexico, PT5.2 N: 267084 funded by CONACyT-SENER: S0019, 2015-04, and Horizon 2020, grant agreement No. 727550).

How to cite: Granados Chavarria, I., Calò, M., Bodin, T., and Figueroa Soto, A.: Joint inversion of converted and surface waves for characterization of geothermal fields, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13290, https://doi.org/10.5194/egusphere-egu21-13290, 2021.

EGU21-12741 | vPICO presentations | ERE2.5

Ambient seismic noise monitoring and imaging at the Theistareykir geothermal field (Iceland)

Tania Toledo, Anne Obermann, Philippe Jousset, Arie Verdel, Joana Martins, Kemal Erbas, Egill Júlíusson, Anette Mortensen, and Charlotte Krawczyk

The Theistareykir geothermal field is located at the intersection between the active Northern Rift Zone and the active Tjörnes Fracture Zone in NE Iceland, and its study is of vital importance for further development of local and regional geothermal resources. Since autumn 2017, a seismic network consisting of 21 stations was deployed to monitor the high temperature Theistareykir geothermal field (Iceland). This seismic network belongs to a set of multiparameter networks installed to better understand the underlying structure and behavior of the geothermal reservoir under exploitation.

In this framework, we use the continuous ambient noise seismic records between October 2017 and October 2019 to compute a 3D shear wave velocity model of the geothermal field and to detect possible stress changes due to the injection and production activities. We compute the phase auto- and cross-correlations of the vertical component recordings, measure the Rayleigh wave group velocity dispersion curves, and obtain 2D group velocity maps between 1 and 5 s.  The 2D group-velocity maps are used to construct regionalized dispersion curves which are then inverted using a Neighborhood Algorithm to retrieve the 3D Vs model of Theistareykir. We observe various underground structures and identify the locations of possible magmatic or hydrothermal bodies in light of available and newly acquired geological and geophysical data. In addition, we analyze the short and long term temporal evolution of the phase auto-correlations using coda wave interferometry and discuss their relationship to the geothermal field operations. We notice a slightly stronger velocity reduction around the production site in comparison to the surrounding regions.

How to cite: Toledo, T., Obermann, A., Jousset, P., Verdel, A., Martins, J., Erbas, K., Júlíusson, E., Mortensen, A., and Krawczyk, C.: Ambient seismic noise monitoring and imaging at the Theistareykir geothermal field (Iceland), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12741, https://doi.org/10.5194/egusphere-egu21-12741, 2021.

EGU21-7036 | vPICO presentations | ERE2.5

Benefits of Global Sensitivity Analysis and Reduced Order Modeling for Basin-Scale Process Simulations

Denise Degen, Mauro Cacace, Cameron Spooner, Magdalena Scheck-Wenderoth, and Florian Wellmann

Geophysical process simulations pose several challenges including the determination of i) the rock properties, ii) the underlying physical process, and iii) the spatial and temporal domain that needs to be considered.

Often it is not feasible or impossible to include the entire complexity of the given application. Hence, we need to evaluate the consequences of neglecting certain processes, properties, etc. by using, for instance, sensitivity analyses. However, this evaluation is for basin-scale application non-trivial due to the high computational costs associated with them. These high costs arise from the high-dimensional character of basin-scale applications in the parameter, spatial, and temporal domain.

Therefore, this evaluation is often not performed or via computationally fast algorithms as, for example, the local sensitivity analysis. The problem with local sensitivity analyses is that they cannot account for parameter correlations. Thus, a global sensitivity analysis is preferential. Unfortunately, global sensitivity analyses are computationally demanding.

To allow the usage of global sensitivity analysis for a better evaluation of the changes in the influencing parameters, we construct in this work a surrogate model via the reduced basis method.

The reduced basis method is a model order reduction technique that is physics-preserving.  Hence, we are able to retrieve the entire state variable (i.e. temperature) instead of being restricted to the observation space.

To showcase the benefits of this methodology, we demonstrate with the Central European Basin System how the influences of the thermal rock properties change when moving from a steady-state to a transient system.

Furthermore, we use the case study of the Alpine Region to highlight the influences of the spatial distribution of measurements on the model response. This latter aspect is especially important since measurements are often used to calibrate and validate a given geological model. Thus, it is crucial to determine which amount of bias is introduced through our commonly unequal data distribution.

How to cite: Degen, D., Cacace, M., Spooner, C., Scheck-Wenderoth, M., and Wellmann, F.: Benefits of Global Sensitivity Analysis and Reduced Order Modeling for Basin-Scale Process Simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7036, https://doi.org/10.5194/egusphere-egu21-7036, 2021.

EGU21-9766 | vPICO presentations | ERE2.5

Fluid Flow Modeling using Geochemistry to Characterize the Songwe Medium Temperature Geothermal System - Tanzania

Sitti Nur Asnin, Martha Nnko, Sadock Josephat, Albano Mahecha, Elisante Mshiu, Giovanni Bertotti, and Maren Brehme

A geothermal area with only bicarbonate thermal water discharges at medium temperature requires a more integrated analysis than used in classical geochemical exploration. This signature is typical for steam-heated water, which commonly occurs at the margins of a geothermal system. However, these waters can also rise from carbonate rich layers in the central part of the field. Our study shows that fluid flow modeling can identify the exact source, flow pathways and temperatures of reservoir fluids based on water-rock interaction. For the first time, we present a conceptual geothermal fluid flow model based on geochemical data for the Songwe geothermal system in Tanzania.

Thermal springs discharge along NW-SE fracture zones in two separate areas: the central Songwe graben (Iyola, Main springs, Rambo and Kaguri) and eastern Songwe graben (Ikumbi). The discharge temperatures of springs range between 37 and 85 oC with Na-HCO3 type, and carbonate deposits surrounding most of the springs. We estimated fluid temperatures for a depth of 2.5km by applying K-Mg and Na-K-Ca (Mg correction) geothermometers, suggesting that reservoir fluids reach temperatures between 125 and 148 oC. We reconstructed reservoir fluid characteristics for that temperatures and propose oversaturated minerals (volcanics, clays, carbonates, apatites, weathered metamophics and hydrothermal minerals) as a model result of interaction between the deep fluids and certain lithologies. Comparison between the modeled oversaturated minerals with minerals in the springs (calcite, aragonite, analcime, muscovite, and smectite) suggests that Kaguri spring water is a result of interaction between deep reservoir fluids with all lithologies, passed on the way to the surface (Metamorphics, Karoo group and Red Sandstone). The fluid signature of Kaguri springs suggest an upflow zone of the geothermal system. Further, our model with oversaturated minerals shows that the thermal water from the reservoir flows laterally along the Red Sandstone layer to the eastern part of study area. It appears as Rambo springs, south of Kaguri springs, and as Main springs and Iyola to the west. The outflow zone might be continuing towards Ikumbi springs, where the fluids also interact with volcanic units. The proposed model shows that carbonate dissolution from the Red sandstone layer is the most common water-rock interaction. The carbonate is embedded in pores and fractures and occurs as matrix in the sandstone. The water-rock interaction is dominated by HCO3- and Na and seen in carbonate depositions at all springs.

How to cite: Asnin, S. N., Nnko, M., Josephat, S., Mahecha, A., Mshiu, E., Bertotti, G., and Brehme, M.: Fluid Flow Modeling using Geochemistry to Characterize the Songwe Medium Temperature Geothermal System - Tanzania, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9766, https://doi.org/10.5194/egusphere-egu21-9766, 2021.

EGU21-10114 | vPICO presentations | ERE2.5

Grid-Free Surface-Based Geological Modelling using Subdivisions Surfaces and NURBS – Advantages for Geothermal Applications

S. Mohammad Moulaeifard, Denise Degen, and Florian Wellmann

Pragmatic and cost-effective representations of geological structures and features (e.g., heterogeneities, faults and folds) in full 3-D geological models are challenging. Implementations are highly dependent on the flexibility of the representation method. We investigate the use of parametric surface-based geological modelling methods for the purpose of low-dimensional model representations. Specifically, we focus on two grid-free and controllable parametric surfaced-based modelling methods: NURBS and subdivision surfaces. NURBS are the standard method in Computer-Aided Design (CAD) and have been used in geological reservoir modelling before. Subdivision surfaces are a common representation in the gaming and animation industry. They are very interesting as they can support watertight modelling and arbitrary topology (preserving the relationship between different parts of the model). However, this method is, to date, rarely used in geological modelling.

Unlike implicit modelling, parametric surfaced-based modelling is a grid-free representation and exploits the boundary surfaces of the model. Also, the geological features (e.g., heterogeneities, faults, folds) can be represented by there bounding surfaces instead of grid-cells. Therefore, they do not suffer from the limitation of grid cells (e.g., Stair-stepping), which are often present in implicit representations.

We discuss the advantages and shortcomings of both NURBS and subdivision surfaces for geological modelling. Furthermore, we investigate the approximation of geological structures by subdivision surfaces in this presentation. The approximated models are watertight (closed), controllable with few control points, smooth, and have less than 5% of the number of the vertices of the original model. Reducing the number of vertices of the model while preserving the topology can decrease the cost of both modelling and simulations. As the final step, we present the advantages of grid-free surface-based geological modelling for thermal finite element analyses by using a state-of-the-art finite-element solver, namely the MOOSE framework

How to cite: Moulaeifard, S. M., Degen, D., and Wellmann, F.: Grid-Free Surface-Based Geological Modelling using Subdivisions Surfaces and NURBS – Advantages for Geothermal Applications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10114, https://doi.org/10.5194/egusphere-egu21-10114, 2021.

Chemical stimulation of geothermal wells to remove drilling mud and to increase the connection to the reservoir are state of the art. There is hardly any deep geothermal well in the carbonates of the upper jurassic in the pre alpine foreland basin which was not developed using one or more pulses of acid. Several tons of acid are injected into the borehole and followed by a chaser to push the acid into the reservoir. Given the wide use of chemical stimulation measures, mass balance data for the stimulation is rare. This might be due to a rather simple reaction mechanism and the assumption that there is a full stoichiometric reaction and all injected acid is recovered. The efficiency of the stimulation is assessed based on the hydraulic properties derived from the short-term pumping tests following the stimulation. This project compares the full mass balance for chemical stimulation measures and the temporal development of the concentration of relevant ions during the pumping test after stimulation. The data was collected at several sites with a temporal resolution of down to 30 mins. The data includes multiple stimulations as well as stimulation with varying acids and different setup. Using this data set we want to answer the questions whether the acid is fully recovered, whether the assumption of full stochiometric reaction is valid, whether there is a difference in the transport of reactive and conservative ions, what additional value a hydrochemical analysis could add and whether on-site measurements could substitute costly measurements. The evaluation shows a distinct behaviour of the temporal development of the chloride concentration (after stimulation with hydrochloric acid) which can be described by a bi-exponential fit. The fitting parameters of the two exponential terms are getting closer with each stimulation indicating a reduced heterogeneity along the accessible flow paths around the borehole. A comparison of the full scale analysis with on-site sensors was sometimes not possible because the sensors showed a drift during the experiment or were poorly calibrated. As calcium, magnesium, and chloride ion concentrations showed different behaviour, electrical conductivity is not able to cover the full development. The mass balance indicates that a full recovery of the injected acid might take significantly longer than the short term pumping tests. Hydrochemical monitoring provides additional and relevant data about the reservoir in the surrounding of the borehole and allows important predictions about the long-term behaviour, especially if the borehole is used as injection well. For routine applications improved sensors and fast (and cheap) on-site analysis is required.

How to cite: Kaplar, F. and Baumann, T.: Comparative study of chemical stimulation at geothermal wells in the carbonates of the upper jurassic in the Bavarian Molasse Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13172, https://doi.org/10.5194/egusphere-egu21-13172, 2021.

The geothermal environment is an assembly of heterogeneous geological settings and complex interactions among different phases of rock and fluid medium. The artificial activities of energy production could further interplay with the on-going natural processes within volcanos, hotspots, and other geothermal areas to result in spatiotemporal signatures of displacements near the surface. Here, we study the temporal ground deformation near a geothermal site through processing Interferometric Synthetic Aperture Radar (InSAR) time-series data obtained over the past decades, as reconciled with the nearby GPS station. To interpret these signals and potentially reveal the reservoir’s temporal activity, we employ state-of-art finite element models (FEMs) to simulate a more realistic crustal domain near the energy-production zone with irregular reservoir geometry, distributed rock materials, and surface topography. Linear Bayesian geodetic inversion and Green’s function library area were adopted to quantify the cause of surface subsidence, as compared to the documented production history. Our study demonstrates an unprecedented approach to precisely simulate the elastic deformation caused by geothermal energy extraction and pumping, providing an important platform to further explore the in-depth evolving stress state and its relation to surrounding induced and natural seismicity.

How to cite: Tung, S. and Feigl, K.: Modeling surface deformation of geothermal environments with high-fidelity finite element models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13413, https://doi.org/10.5194/egusphere-egu21-13413, 2021.

EGU21-15084 | vPICO presentations | ERE2.5

SHEMAT-Suite: a parallel open source simulator for flow, heat and mass transport in porous media

Johannes Keller, Johanna Fink, and Norbert Klitzsch

We present SHEMAT-Suite, a numerical code for simulating flow, heat, and mass transport in porous media that has been published as an open source code recently. The functionality of SHEMAT-Suite comprises pure forward computation, deterministic Bayesian inversion, and stochastic Monte Carlo
simulation and data assimilation. Additionally, SHEMAT-Suite features a multi-level OpenMP parallelization. Along with the source code of the software, extensive documentation and a suite of test models is provided.

SHEMAT-Suite has a modular structure that makes it easy for users to adapt the code to their needs. Most importantly, there is an interface for defining the functional relationship between dynamic variables and subsurface parameters. Additionally, user-defined input and output can be implemented without interfering with the core of the code. Finally, at a deeper level, linear solvers and preconditioners can be added to the code.

We present studies that have made use of the code's HPC capabilities. SHEMAT-Suite has been applied to large-scale groundwater models for a wide range of purposes, including studying the formation of convection cells, assessing geothermal potential below an office building, or modeling submarine groundwater discharge since the last ice age. The modular structure of SHEMAT-Suite has also led to diverse applications, such as glacier modeling, simulation of borehole heat exchangers, or Optimal Experimental Design applied to the placing of geothermal boreholes.

Further, we present ongoing developments for improving the performance of SHEMAT-Suite, both by refactoring the source code and by interfacing SHEMAT-Suite with up-to-date HPC software. Examples of this include interfacing SHEMAT-Suite with the Portable Data Interface (PDI) for improved data management, interfacing SHEMAT-Suite with PetSC for MPI-parallel solvers, and interfacing SHEMAT-Suite with PDAF for parallel EnKF algorithms.

The goal for the open source SHEMAT-Suite is to provide a rigorously tested core code for flow, heat and transport simulation, Bayesian and stochastic inversion, while at the same time enabling a wide range of scientific research through straightforward user interaction.

How to cite: Keller, J., Fink, J., and Klitzsch, N.: SHEMAT-Suite: a parallel open source simulator for flow, heat and mass transport in porous media, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15084, https://doi.org/10.5194/egusphere-egu21-15084, 2021.

EGU21-15793 | vPICO presentations | ERE2.5

Thermal modeling in active poly-phased calderas: case study of Los Humeros, Mexico 

Paromita Deb, Guido Giordano, Xiangyun Shi, Federico Lucci, Christoph Clauser, and Philippe Calcagno

The Los Humeros Volcanic Complex (LHVC) is an active Quaternary caldera system in the Trans Mexican Volcanic Belt, characterized by two major caldera-forming events, Los Humeros (164 000 years ago) and Los Potreros (69 000 years ago). This site is also subjected to numerous episodes of post-caldera bi-modal volcanism during Holocene period (8 000 years – 3 000 years old). The volcanic complex hosts an active geothermal field which has been under commercial exploitation for the last 30 years. Latest geochemical, petrological and geochronological investigations consider the geothermal activity in the LHVC to be the result of an underlying complex magma plumbing system, characterized by numerous short-lived, shallow magma storage zones. Geothermal wells in the LHVC have encountered variable temperatures within depths of 2000 m, ranging from 170 °C at some areas to above 350 °C in the neighboring areas. To explain this anomalous temperature distribution and evaluate the thermal footprint of different volcanic episodes, we reconstructed the thermal history of the LHVC for a period of 182 000 years considering the spatially and temporally-varying nature of the heat sources. Our numerical model is constrained by information of depths, ages and volumes of the magma reservoirs, obtained from the geochemical and thermo-barometric modeling of the erupted material. The simulated present-day temperature state agrees well with the measured temperature data in the Los Humeros geothermal wells and can be used for identifying locations with anomalous temperature distribution. This integrated modeling approach, whereby numerical model is constrained by field-based geochemical information is essential in exploration geothermal fields, where limited borehole data is available, and promising for identifying potential locations of super-hot geothermal fluids.

How to cite: Deb, P., Giordano, G., Shi, X., Lucci, F., Clauser, C., and Calcagno, P.: Thermal modeling in active poly-phased calderas: case study of Los Humeros, Mexico , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15793, https://doi.org/10.5194/egusphere-egu21-15793, 2021.

EGU21-16033 | vPICO presentations | ERE2.5

Modelling Mineral-Scaling in Geothermal Reservoirs Using Both a Local Equilibrium and a Kinetics Approach

Ahmed Hussain, Negar Khoshnevis, Bernard Meulenbroek, Wouter Van der Star, Hans Bruining, Johan Claringbould, Ayla Reerink, and Karl-Heinz Wolf

              When producing heat from a geothermal well, the produced water cools down in the heat exchanger, and experiencing a lower pressure in the surface processing-facility (1 – 10 bar) than in the reservoir (100 – 300 bar). The decrease in pressure may cause gas to come out of solution. This decrease in temperature and degassing of the produced water may cause precipitation and dissolution (mineralization) to occur. After the produced water is cooled down, it is reinjected into the reservoir through an injection well. Mineralization in the reservoir restricts the flow path of the injected water, resulting in reduced injectivity. Consequently, more energy is required by the injection pump, which results in additional costs, and thereby reduces the project’s economic return.            
              When numerically modeling mineralization in a geothermal reservoir, accounting for the reaction kinetics can be computationally expensive. The simulations can be made less expensive by assuming local equilibrium between the reactants and reaction-products; but using this approach might give results that are not in agreement with experimental findings.
              Here we present an analytical model for mineral precipitation in a low-enthalpy geothermal reservoir. We compare the kinetics of the relevant reaction terms with respect to the transport terms (heat and flow) to determine whether the local equilibrium approach (LEA) or kinetics approach (KA) is appropriate for modeling a specific reaction. We focus on the near-wellbore region in the reservoir, where precipitation can behave as a ‘skin’; when assuming radial-flow, precipitation in the near-wellbore region has a more dramatic impact on the injectivity than precipitation further downstream in the reservoir.      
              Using numerical simulations we validate the approach to use different methods of geochemical modelling based on the reaction speed and its potential impact on computation time.
              Based on our analysis on mineralization in the near-wellbore-region, the three different reaction regimes can be distinguished when comparing the time-scale of reaction to the time-scale of transport, viz.: (1) fast reactions (mineralization can be considered instantaneous and modelling these reactions using LEA or KA does not lead to significantly different simulation results); (2) very slow reactions (no significant change in ion concentrations in the region of interest, whether these reactions are modelled using LEA or KA); (3) reaction/transport intermediate zone (using LEA leads to significantly different simulation results compared to KA).
              Accounting for these classifications allows simplification of the current numerical geochemical-models, while still accounting for relevant kinetics of mineralization. This approach was tested using a numerical model of precipitation in a geothermal reservoir.              

How to cite: Hussain, A., Khoshnevis, N., Meulenbroek, B., Van der Star, W., Bruining, H., Claringbould, J., Reerink, A., and Wolf, K.-H.: Modelling Mineral-Scaling in Geothermal Reservoirs Using Both a Local Equilibrium and a Kinetics Approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16033, https://doi.org/10.5194/egusphere-egu21-16033, 2021.

EGU21-16182 | vPICO presentations | ERE2.5

Thermodynamic modelling and simulation of geothermal power plants: case studies and environmental impact

Vitantonio Colucci, Angelo Damone, Giampaolo Manfrida, and Daniele Fiaschi

The emissions associated with Geothermal power plant (GTPP) due to geothermal fluids represents a compelling challenge addressed in the last decades. The on-line measuring of pollutants generated by GTPP might result in a complicated task to handle. Simulation of GTPP has become an excellent tool to monitor and control the emission of pollutants. In the present work, the pollutant emissions of GTPP of Hellisheidi (Island), Chiusdino, and Castelnuovo (Italy) are modelled and developed with Unisim Design R480 using well understood thermodynamical models implemented in OLI. The presence of brine in the thermodynamical models has been taken into account. Carbon dioxide, methane, and hydrogen sulfide are the chemical pollutants considered for the process simulation. The AQ framework model in OLI is being used for binary mixtures and non-condensable gas. Furthermore, for liquid mixtures containing more than two components, the MSE-SRK Thermodynamic model is desirable depending on the original geothermal fluid source. The simulation process outcome agrees with experimental data for pressure between 30 and 100 bar within 5% deviation. A systematic study of the spatial distribution of the emissions has been made for the area surrounding the GTPP. Furthermore, an economic evaluation overview has been performed to highlight the equipment needed for maintenance and tool substitution.

How to cite: Colucci, V., Damone, A., Manfrida, G., and Fiaschi, D.: Thermodynamic modelling and simulation of geothermal power plants: case studies and environmental impact, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16182, https://doi.org/10.5194/egusphere-egu21-16182, 2021.

ERE2.6 – Shallow geothermal systems for heating and cooling: geoscience and engineering approaches

Shallow geothermal energy is a renewable energy source that will play an important role in future energy management plans. Densely populated areas are often developed on alluvial plains, which consist of unconsolidated sediments. These have different thermal properties, so their accurate determination is important for planning subsurface heat utilization for heating and cooling of buildings in urban areas. Bulk thermal conductivity (λb) is one of the most important ground thermal properties for estimating shallow geothermal potential, as it controls the ability of sediments to transfer heat. The λb can be determined with empirical bulk thermal conductivity estimation models (λb EM), which define λb as a function of the measured physical parameters of the sediment (water content, bulk density) and the fluid. In this contribution, we present a preliminary study of three empirical evaluation models for determining the thermal conductivity of sediments – the Kersten (1949), the Johansen (1975) and the Cote & Conrad model (2005). Validation was carried out with laboratory-measured λb using 30 unconsolidated sediment samples classified into 2 different groups (cohesive, non-cohesive) and by water content. The modelled results were evaluated using the coefficient of determination (R2) and root mean square error (RMSE). The modelled λb for non-cohesive sediments has the highest λb with the Johansen model. The lowest RMSE was obtained with the Kersten model. For cohesive sediments, the highest λb and lowest RMSE, and consequently the best model, are based on the saturation of the sediments. It varies between the Cote & Conrad and the Kersten model. By dividing the sediment samples based on shear strength and water content, we obtained the better agreement of individual groups with estimation models. This showed the importance of the physical parameters in better predicting the modelled results. In the future, we will need to upgrade results with the use of more estimation models, that could improve the modelled results. With such an approach the estimation models can become a useful tool for a faster determination of the shallow geothermal potential.

How to cite: Adrinek, S. and Janža, M.: A preliminary study of empirical evaluation models for determining the thermal conductivity of sediments , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8777, https://doi.org/10.5194/egusphere-egu21-8777, 2021.

EGU21-12488 | vPICO presentations | ERE2.6

Thermal properties evaluation of granitoid rocks by using Digital Imaging Analysis (DIA) and 2D modelling simulation

Raffaele Sassi, Chiara Coletti, Alessandro Borghi, Roberto Cossio, Maria Chiara Dalconi, Giorgia Dalla Santa, Luca Peruzzo, Arianna Vettorello, and Antonio Galgaro

Seven granitoid rocks were selected due to the well-defined mineralogical content, the typical the holocrystalline texture, their absent (or very poor) Crystal Preferred Orientations (CPOs), and very-low porosity in order to apply a predictive approach that quantifies and simulates the rock thermal properties by considering the contributions of the mineral phases content. For this purpose, thermal properties of granodiorite, tonalite, granite, and gabbro rock samples were analysed and compared by (i) direct measurements on the bulk rock samples, (ii) by applying Quantitative Phase Analysis (QPA) on Digital Imaging Analysis (DIA) and Xray diffraction Rietveld method, and (iii) by 2D numerical modelling.

The results confirm the good accuracy of DIA-QPA method by the good according with data refined by X-Ray diffraction Rietveld method, and indicate the potential reliability of the more attractive approach in terms of prediction of the 2D modelling starting by the Quantitative Phase Analysis (QPA) based on Digital Imaging Analyses (DIA). This method, indeed, permits to observe concurrently different mineralogical and textural parameters (such as mineral abundance, grain size and grain size distribution), and it also provides a deep knowledge of the rock’s thermal behaviour.

Numerical modelling results indicate that a steady-state condition (SSC) is reached by the combination of thermal contribution given both in terms of modal mineral abundance (mainly controlled by mineralogical phase content related to the quartz occurrence) and in terms of rock texture (by the grain-size dimensions and the geometrical distribution of minerals), considering negligible the porosity.

The use of predictive models for the evaluation of the rocks thermal properties can find many important applications (e.g., in deep and shallow geothermal systems, as well as in building construction materials), and also permits to evaluate the expected energy performance of borehole heat exchange probes, involving granitoid lithologies, representing a suitable alternative also in cases where direct measures are not possible.

How to cite: Sassi, R., Coletti, C., Borghi, A., Cossio, R., Dalconi, M. C., Dalla Santa, G., Peruzzo, L., Vettorello, A., and Galgaro, A.: Thermal properties evaluation of granitoid rocks by using Digital Imaging Analysis (DIA) and 2D modelling simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12488, https://doi.org/10.5194/egusphere-egu21-12488, 2021.

EGU21-2838 | vPICO presentations | ERE2.6

Advanced investigations of hydro-geothermal ground properties using a geothermal experimental platform

Valériane Gigot, Bertrand François, Marijke Huysmans, and Pierre Gerard

Although vertical Ground Heat Exchangers (GHE) is a booming technology for both cooling and heating buildings, several improvements could still be proposed in the dimensioning of such systems. Nowadays, most of the dimensioning methods consider only radial heat flux around GHE using a homogeneous ground thermal conductivity, averaged along the depth of the borehole and determined from thermal response tests (TRT) or tables. Impacts of layered ground and groundwater flows on the heat refurbishment around GHE are thus generally neglected.  

Many numerical or analytical studies have investigated and quantified the positive impact of groundwater flows on the efficiency of GHE (Dehkordi & Schincariol, 2014; Funabiki et al., 2014). However, those results are rarely compared with in-situ temperature measurements around GHE. Indeed, such experimental data requires (i) the installation of temperature sensors in the heat ground reservoir around GHE and (ii) the characterization of groundwater flows (magnitude and direction) at great depths, which can be complex and expensive.

In this work, an experimental platform composed of 4 vertical GHE drilled at depths of 85 m has been exploited to provide in-situ temperature measurements characterizing heat transfers around GHE. The 4 vertical GHE are located at the 4 corners of a 4-m square and cross a succession of horizontal geological layers. The study focuses on the heat transfers in a 30-m thick sand unconfined aquifer layer, whose 17 m are saturated. A piezometer has been drilled in this unit and allows the characterization of groundwater flows with advanced hydrogeological tests (Brouyère et al., 2008). Each GHE is equipped with both PT100 (installed at the extremities of the unconfined aquifer and just below the groundwater table level) and optical fibres (OF) along the borehole. This experimental platform allows to perform innovative characterization of the geothermal properties of the site. In particular, performing a comparative analysis of the temperature measurement in the GHE between PT100 and OF and several Distributed Thermal Response Tests (D-TRT) under different conditions. In addition, it has been possible to follow the heat transfers around GHE during a long-term activation of a single GHE through heat plume temperature measurement in the non-activated GHE. Anisotropic temperature distribution highlights the impact of groundwater flows on heat reservoir refurbishment.

In this contribution, D-TRT results characterizing the ground geothermal properties, the pre-design of the long-term TRT using an existing analytical solution (Erol et al., 2015) and preliminary experimental results of the long-term TRT will be presented and discussed.

 

References

  • Funabiki, A. et al. (2014). The effects of groundwater flow on vertical-borehole ground source heat pump systems. In Engineering Systems Design and Analysis. American Society of Mechanical Engineers.
  • Dehkordi, S.E., & Schincariol, R.A. (2014). Effect of thermal-hydrogeological and borehole heat exchanger properties on performance and impact of vertical closed-loop geothermal heat pump systems. Hydrogeology Journal.
  • Erol, S. et al. (2015). Analytical solution of discontinuous heat extraction for sustainability and recovery aspects of borehole heat exchangers. International journal of thermal sciences.
  • Brouyère, S. et al. (2008). A new tracer technique for monitoring groundwater fluxes: The Finite Volume Point Dilution Method. Journal of contaminant hydrology.

How to cite: Gigot, V., François, B., Huysmans, M., and Gerard, P.: Advanced investigations of hydro-geothermal ground properties using a geothermal experimental platform, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2838, https://doi.org/10.5194/egusphere-egu21-2838, 2021.

EGU21-11059 | vPICO presentations | ERE2.6

Comparison between traditional and enhanced Thermal Response Test for ground thermal properties estimation

Antonio Galgaro, Alberto Carrera, and Eloisa Di Sipio

For the design and implementation of an efficient Ground Source Heat Pump (GSHP) system, the local
subsoil represents the core element. Since the thermal performance of Borehole Heat Exchangers (BHEs) is
site-specific, its planning typically requires the knowledge of the thermal proprieties of the ground, which
are influenced by the local stratigraphic sequence and the hydrogeological conditions. The evaluation of
the variations of the ground thermal conductivity (TC) along the depth, as well as its undisturbed
temperature, are essential to correctly plan the BHEs field and improve the performance of the ground
heat exchangers themselves.
Thermal Response Test (TRT) is a well-known experimental procedure that allows to obtain the thermal
properties of the ground. However, the traditional method provides a single value of the equivalent TC and
the undisturbed temperature, which can be associated with the average value over the entire BHE length,
with no chance to detect the thermo-physical parameters variations with depth and to discriminate the
contributions of the different geological levels crossed by the geothermal exchange probe. Indeed,
different layers within a stratigraphic sequence, may have different thermal properties, according to the
presence and to the flow rate of groundwater, as well as to granulometry and mineralogical composition,
density, and porosity of the lithologies. The identification of the different contributions to the thermal
exchange provided by each geological unit, in practice, can further support BHE design, helping to
determine the most suitable borehole length and number, achieving the highest heat exchange capability
at the lower initial cost of implementing of the entire geothermal plant.
In the last years, new improved approaches to execute an enhanced thermal response test have been
developed, as the pioneer wireless data transmission GEOsniff technology (enOware GmbH) tested in this
study. This measurement method is characterized by its sensors, 20mm-diameter marbles equipped by
pressure and temperature transducers combined with a system of data storing and wireless data
transmission. Released at regular intervals down the testing BHE, infilled with water, each marble freely
floats allowing the measurement of the water temperature variations over time at different depths, in
order to identify areas with particular values of thermal conductivity related to distinctive hydrogeological
conditions or lithological assessment. This way, the GEOsniff technology allows a high-resolution spatially-
distributed representation of the subsoil thermal properties along the BHE.
In this work, we present the test outputs acquired at the new humanistic campus of the University of
Padova, located in the Eastern Po river plain (Northern Italy). The thermal conductivity data obtained by
the GEOsniff method have been compared and discussed, by considering the standard TRT outputs. This
innovative technique looks promising to support the optimization of the borehole length in the design
phase, even more where the complexity of the treated geological setting increases.

How to cite: Galgaro, A., Carrera, A., and Di Sipio, E.: Comparison between traditional and enhanced Thermal Response Test for ground thermal properties estimation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11059, https://doi.org/10.5194/egusphere-egu21-11059, 2021.

EGU21-9948 | vPICO presentations | ERE2.6

Wireless probes for measuring vertical temperature profiles in borehole heat exchangers (BHEs)

Simon Schüppler, Roman Zorn, Hagen Steger, and Philipp Blum

The measurement of the undisturbed ground temperature (UGT) serves to design low-temperature geothermal systems, in particular borehole heat exchangers (BHEs), and to monitor shallow aquifers. Wireless and miniaturized probes such as the Geosniff (GS) measurement sphere, which are characterized by an autarkic energy supply and equipped with pressure and temperature sensors, are increasingly being used for the measurement of highly resolved vertical temperature profiles. The measurement probe sinks along the course of the BHE with a selectable measurement frequency to the bottom of the BHE and is useable for initial measurements as well as long term groundwater monitoring. To ensure quality assurance and further improvement of this emerging technology, the analysis of measurement errors and uncertainties of wireless temperature measurements (WTMs) is indispensable. Thus, we provide an empirical laboratory analysis of random, systematic, and dynamic measurement errors, which lead to the measurement uncertainty of WTMs using the GS as a representative device. We subsequently transfer the analysed uncertainty to measured vertical temperature profiles of the undisturbed ground at a BHE site in Karlsruhe, Germany. The precision and accuracy of 0.011 K and -0.11 K, respectively, ensure a high reliability of the GS measurements. The largest measurement uncertainty is obtained within the first five meters of descent resulting from the thermal time constant τ of 4 s. The measured temperature profiles are qualitatively compared with common Distributed Temperature Sensing (DTS) using fiber optic cables and punctual Pt-100 sensors. Wireless probes are also suitable to correct temperature profiles recorded with fiber optics with systematic errors of up to -0.93 K. Various boundary conditions such as the inclination of the BHE pipes or changes of the viscosity and density of the BHE fluid effect the descent rate of the GS of up to 40 %. We additionally provide recommendations for technical implementations of future measurement probes and contribute to an improved understanding and further development of WTMs.

How to cite: Schüppler, S., Zorn, R., Steger, H., and Blum, P.: Wireless probes for measuring vertical temperature profiles in borehole heat exchangers (BHEs), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9948, https://doi.org/10.5194/egusphere-egu21-9948, 2021.

EGU21-8234 | vPICO presentations | ERE2.6

New borehole heat exchanger thermal enhanced grout formulations

Eloisa Di Sipio, Enrico Garbin, Laura Fedele, Davide Menegazzo, Ludovico Mascarin, Giorgia Dalla Santa, Sergio Bobbo, Gilberto Artioli, Adriana Bernardi, and Antonio Galgaro

In shallow geothermal systems, especially ground source heat pumps (GSHP), cementitious grouts play a decisive role in guaranteeing an efficient heat transfer between the probe and the surrounding ground. Several studies have been devoted to understand the effect of different additives (silica sand, graphite, fluorspar, glass and fly ash …) in improving especially the thermal conductivity of such mixtures, maintaining at the same time physical properties as viscosity and workability suitable for in situ application. In fact, when continuous operation mode is running, thermal conductivity shows a positive effect on the mean heat exchange rate of vertical borehole heat exchangers (BHE). However, when an intermittent operation mode is selected, the BHE performance improves when a high thermal conductivity is coupled with a high specific heat capacity.

This research focus on assessing the contribution of two specific thermal additives (silica sand and molybdenum disulphide powder) to the thermal properties’ improvements of a specific commercial cementitious grout. These components are added in different proportion to the grout, up to the creation of 6 different mixtures. For each mixture 3 specimens are prepared, in order to perform the thermo-physical analyses. In addition, other 3 commercial grouts are considered. A total of 10 mixtures, leading to the creation of 30 specimens, have been analyzed. Then, thermal conductivity, thermal diffusivity and specific heat capacity of each specimen measured in anhydrous and saturated conditions are considered.

The commercial grouts prepared as stated by the producers show, as expected, a minimum variation of their thermal properties in wet and anhydrous conditions. Instead, when the additives are used, a noticeable improvement of the thermal properties is observed in saturated conditions, where the effect of silica sand seems dominant. The best thermal properties improvement obtained by combining the two additives is also considered.

However, the grouts suitability to be easily managed on site must be considered because, even if the new mixtures show a general gain of the thermal properties, these can be difficult to apply going from laboratory to full scale.

Anyway, the characterization of the grouts thermal properties based on composition and saturation variations is important not only in numerical simulations, but also in analytical approaches, typical of the heat exchange probe fields sizing processes. In fact, the cementitious grouts play a key role in determining the shallow geothermal systems efficiency in transient mode operation, often neglected by sizing programs. In fact, those characterized by better thermal performances will contribute to the reduction of the borehole thermal resistances, interposed in the heat exchange processes between the heat transfer fluid and the ground. Finally, this research contributes to fill the gap between numerical simulation and experimental data, providing real data to be used as database for further numerical modelling analysis improvement.

 

GEO4CIVHIC project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 792355.

How to cite: Di Sipio, E., Garbin, E., Fedele, L., Menegazzo, D., Mascarin, L., Dalla Santa, G., Bobbo, S., Artioli, G., Bernardi, A., and Galgaro, A.: New borehole heat exchanger thermal enhanced grout formulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8234, https://doi.org/10.5194/egusphere-egu21-8234, 2021.

The actual heat demand of a building depends on various building-specific parameters, such as building age, insulation type, housing volume, but also external parameters, e.g. outdoor temperature. Being able to dynamically model the thermal power demand of a specific building can increase the robustness of coupled borehole heat exchanger simulations (BHE-simulations), as the transient heat demand models of a building / consumer can be used to simulate the thermal response of the subsurface to the prescribed consumer demand.

We present results of coupling results of Building Performance Simulation (BPS) with simulations of Borehole Heat Exchangers. BPS are carried out using TEASER (Tool for Energy Analysis and Simulation for Efficient Retrofit) which models the thermal power demand of a building based on parameters, such as year of construction, net-lease area, and outdoor-temperature.

Using annual temperature curves, we model the thermal power demand of buildings from the 1950s, once in original state and in retrofitted state. The thermal response of a connected BHE-field is simulated using SHEMAT-Suite, an open-source simulator for heat- and mass-transfer in porous media. In our BHE simulations, thermal plumes develop as a result of heat-extraction and regional groundwater flow.

To improve the forecast of, e.g. the magnitude of these plumes, realistic knowledge of the heat demand is important, which can be achieved by the presented coupling of BPS- and BHE-modelling.

 

How to cite: Niederau, J., Fink, J., and Lauster, M.: Building Performance Simulations coupled to Borehole Heat Exchanger Simulations: a tool for realistic monitoring and forecast, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14502, https://doi.org/10.5194/egusphere-egu21-14502, 2021.

EGU21-14021 | vPICO presentations | ERE2.6

Non stationary combination for the simulation of time-varying flow rates in closed-loop ground heat exchangers

Gabrielle Beaudry, Philippe Pasquier, and Denis Marcotte

Ground source heat pump systems are among the most energy-efficient heating and cooling technologies. Their performance is strongly related to the accuracy of the ground heat exchanger sizing, hence requiring the forecast of the system’s temperature evolution in response to the anticipated thermal loads. Through this process, simulation techniques that make use of the superposition principle are commonly used to reduce the computational burden. In their current state, these techniques are however only suitable for addressing linear and stationary problems and do not apply to fundamental non stationary situations related to ground source heat pumps operation that involve time-variant parameters.

The present work addresses this issue by introducing a novel method based on the principle of superposition that tackles the fast evaluation of the temperature of a closed-loop ground heat exchanger operating with a dynamic heat load as well as time-variant circulation flow rates. The developed method relies on the non stationary combination, a technique borrowed from the field of seismic data processing. This technique achieves discontinuous transitions of convolution products that can be smoothened near transition times by realizing a linear interpolation over the duration of the fluid residence time.

The accuracy and efficiency of the proposed method are verified by comparing its results with those provided by reference 3D finite-elements models developed in the Comsol Multiphysics environment. For this purpose, comparative simulations representing the non stationary operation of a closed-loop system having time-variant circulation flow rates are conducted. The case of a single well is first investigated, followed by a borefield of eight wells to demonstrate the validity of the method in both scenarios.

Findings indicate that the proposed method can reproduce the reference results with a mean absolute error that is lower than 0.02 °C, and that it is faster than the numerical models by several orders of magnitude. These findings suggest that a broader range of operating scenarios can be handled by highly efficient simulation tools based on the superposition principle, which could foster the development of optimal operating strategies and lead to enhanced overall performances of ground source heat pump systems.

How to cite: Beaudry, G., Pasquier, P., and Marcotte, D.: Non stationary combination for the simulation of time-varying flow rates in closed-loop ground heat exchangers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14021, https://doi.org/10.5194/egusphere-egu21-14021, 2021.

EGU21-10117 | vPICO presentations | ERE2.6

Thermal Active Zone space-time evolution: a small-scale monitoring of thermal and electrical conductivity

Alberto Carrera, Jacopo Boaga, Paolo Scotton, and Antonio Galgaro

The growing demand for renewable energy leads to an increase in the development of alternative energy applications. In this way, shallow geothermics assumes an important role in the global energy transition of building air conditioning. The design of Ground Source Heat Pumps (GSHP) requires a multidisciplinary approach including a good understanding of the underground geological setting, such as hydrogeological aspects and heat flow conditions. Classic monitoring strategies often rely on local and point-based measurements to monitor changes of underground temperature in time, with the limit of not succeeding in a whole delimitation of the Thermal Active Zone (TAZ). In this context, Electrical Resistivity Tomography (ERT) can bring relevant information on the temperature distribution for monitoring the induced thermal plume within BHEs (Borehole Heat Exchangers) systems. Geophysics helps the understanding of the thermal processes, in order to front the difficulties arising from Ground Source Heat Pumps (GSHP) implementation. Thermal conductivity and electrical resistivity depend equally in a complex way on different common subsurface and environmental attributes such as, among the main, mineralogical composition, grain size, density, porosity and saturation. Besides, thermal conductivity increases significantly with temperature in wet ground, by making it clear a relationship between both parameters.

ERT is particularly sensitive to the porous medium temperature and, when applied in time-lapse (TL), could provide spatially distributed information on the changes over time of water content, salinity or temperature. For this reason, in this work we monitored the complex TAZ temporal evolution during a heat injection experiment using a 3D time-lapse ERT survey, arranged in a reduced scale physical model. For a better understanding of measured electrical resistivity values, focused on mapping the extent of a geothermal plume around a borehole, a specific laboratory device was utilized. Grain size distribution, bulk density and saturation of the porous medium are known and established, as well as reliable temperature values acquired through sensors with which calibrate the ERT results. Thus, changes in resistivity can be interpreted to track the evolution of the plume of heated water and used to estimate the temperature change. The propagation of the heat plumes into the ground is also highly sensitive to interstitial water flow rate, thus also this condition was recreated and monitored varying the hydraulic gradient in the experimental device.

The present work aims to demonstrate the ability of ERT to provide complementary insights about the sub-surface spatio-temporal dynamic for monitoring the extension of TAZ caused by BHEs probes. In addition, the detailed scale adopted and the variable control within a laboratory setup ease the study of the interaction between thermal and electrical properties.

How to cite: Carrera, A., Boaga, J., Scotton, P., and Galgaro, A.: Thermal Active Zone space-time evolution: a small-scale monitoring of thermal and electrical conductivity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10117, https://doi.org/10.5194/egusphere-egu21-10117, 2021.

EGU21-12377 | vPICO presentations | ERE2.6

Analysis of novel shallow geothermal system in coastal fractured limestone aquifer

Nicola Pastore, Claudia Cherubini, and Concetta Immacolata Giasi

In shallow geothermal systems natural and forced groundwater movement as well as the temperature driven flow plays an important role on the borehole heat exchanger efficiency.

The analysis of the efficiency of innovative heat exchangers installed in a fractured limestone aquifer was carried out through three-dimensional numerical simulations and experimental investigations on physical models.

The coastal fractured limestone aquifer of the industrial area of Bari (Italy) was chosen as benchmark field site in order to identify the aquifer parameter range and the respective combinations. The role of seawater intrusion on the borehole heat exchanger efficiency was deepen .

The results disclosed that the efficiency of the innovative heat exchangers is strictly dependent on the aquifer transmissivity and groundwater flow under natural and forced groundwater conditions.

Discussion on the performance of the seasonal heat storage and the occurrence of the thermal interference between the borehole heat exchanger was presented.

How to cite: Pastore, N., Cherubini, C., and Giasi, C. I.: Analysis of novel shallow geothermal system in coastal fractured limestone aquifer, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12377, https://doi.org/10.5194/egusphere-egu21-12377, 2021.

EGU21-10010 | vPICO presentations | ERE2.6

Shallow geothermal energy potential of south-west Germany

Johannes Miocic

A large-scale transformation of the heating and cooling sector is needed to achieve the climate neutrality goals by 2050 as outlined in the European Green Deal. One frequently discussed option for reducing the greenhouse gas emissions is the widespread use of ground source heat pumps (GSHPs) for heating and cooling living spaces. Here, the technical potential of GSHPs to supply heat to buildings in the state of Baden-Württemberg, Germany, is analysed. This study is based on the yearly demand for heating energy at a building block scale, geological conditions, mean annual surface temperatures, as well as legal restrictions such as temperature differences at the heat pump, maximum monthly heat extraction rates as well as areas restricted from drilling. It is shown that for many densely populated areas many GSHPs would be needed to supply all the energy needed for heating. However, in less densely populated areas GSHPs can be used for heating. If future heating demand is lower due to wide-spread insulation retrofitting, GSHPs could supply most of the energy needed for heating even in densely populated areas.

How to cite: Miocic, J.: Shallow geothermal energy potential of south-west Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10010, https://doi.org/10.5194/egusphere-egu21-10010, 2021.

EGU21-10082 | vPICO presentations | ERE2.6 | Highlight

Modeling Neighborhood-Scale Shallow Geothermal Energy Utilization - A Case Study in Berlin

Shuang Chen, Jakob Randow, Katrin Lubashevsky, Steve Thiel, Tom Reinhardt, Rüdiger Grimm, Anke Bucher, Olaf Kolditz, and Haibing Shao

Nowadays, utilizing shallow geothermal energy for heating and cooling buildings has received increased interest in the energy market. Among different technologies, large borehole heat exchanger (BHE) arrays are widely employed to supply heat to various types of buildings and districts. Recently, a 16-BHE array was constructed to extract shallow geothermal energy to provide heat to the newly-developed public building in Berlin. According to the previous geological survey, different non-homogeneous sedimentary layers exist in the subsurface, with variating groundwater permeabilities and thermal parameters. To estimate the performance of the BHE array system, and its sensitivity to different subsurface conditions, as well as to determine its thermal impact to the surrounding area, a comprehensive 3D numerical model has been set up according to the Berlin BHE array project. The model is simulated for 25 years with two finite element simulators, the open source code software OpenGeoSys (OGS) and the well-known commercial software FEFLOW. In the model, an annual thermal load curve is assigned to each BHE according to the real monthly heating demand. Although the way of the implementing parameters in the two programs differs from each other and some assumptions had to be made in the model comparison, the comparison result shows that both OpenGeoSys and FEFLOW produce in good agreement. Different parameters, e.g. the Darcy velocity, the thermal dispersivity of the aquifer, the surface temperature and the geothermal heat flux are investigated with respect to their impact on the underground and BHE circulation temperature. At last, the computed underground temperature and the brine fluid temperature evolution from OGS is benchmarked with the results from the model simulated in FEFLOW. The numerical experiments show that the the ground water field has the strongest influence on the brine fluid temperature within the BHEs. When the thermal dispersivity of the aquifer is considered, the mixing effect in the aquifer leads to a higher brine fluid temperature in the BHE, indicating a better thermal recharge of the system.

How to cite: Chen, S., Randow, J., Lubashevsky, K., Thiel, S., Reinhardt, T., Grimm, R., Bucher, A., Kolditz, O., and Shao, H.: Modeling Neighborhood-Scale Shallow Geothermal Energy Utilization - A Case Study in Berlin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10082, https://doi.org/10.5194/egusphere-egu21-10082, 2021.

EGU21-603 | vPICO presentations | ERE2.6

Numerical Modelling of a District Scale Groundwater Heat Pump Operation: Case Study from Colchester, UK

Taha Sezer, Abubakar Kawuwa Sani, Rao Martand Singh, and David P. Boon

Groundwater heat pumps (GWHP) are an environmentally friendly and highly efficient low carbon heating technology that can benefit from low-temperature groundwater sources lying in the shallow depths to provide heating and cooling to buildings. However, the utilisation of groundwater for heating and cooling, especially in large scale (district level), can create a thermal plume around injection wells. If a plume reaches the production well this may result in a decrease in the system performance or even failure in the long-term operation. This research aims to investigate the impact of GWHP usage in district-level heating by using a numerical approach and considering a GWHP system being constructed in Colchester, UK as a case study, which will be the largest GWHP system in the UK. Transient 3D simulations have been performed pre-construction to investigate the long-term effect of injecting water at 5°C, into a chalk bedrock aquifer. Modelling suggests a thermal plume develops but does not reach the production wells after 10 years of operation. The model result can be attributed to the low hydraulic gradient, assumed lack of interconnecting fractures, and large (>500m) spacing between the production and injection wells. Model validation may be possible after a period operational monitoring.

How to cite: Sezer, T., Sani, A. K., Singh, R. M., and Boon, D. P.: Numerical Modelling of a District Scale Groundwater Heat Pump Operation: Case Study from Colchester, UK, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-603, https://doi.org/10.5194/egusphere-egu21-603, 2021.

The performance of a GroundWater Heat Pump (GWHP) is critically influenced by the thermal recycling between wells, i.e. the proportion of thermally affected injected water that is pumped back by the extraction well. The use of the complex potential theory, assuming a homogeneous aquifer and a uniform regional flow, to assess the evolution of the extraction temperature from a doublet is presented. One major limitation in the available models in the literature is that they assume a constant extraction flow rate and constant heat extraction. This is unrealistic since buildings energy loads vary naturally with time during the day, the month and the year. To overcome this, the present paper develops a semi-analytical model to dynamically determine the extraction temperature of a doublet GWHP taking into account a variable extraction heat flow. Results obtained are benchmarked to a finite-element Comsol Multiphysics numerical model under different conditions, which enlightens the limitations of the proposed model. The developed model can be easily used to assess the technical potential of a GWHP.

How to cite: Jaafar, M. A. and Maragna, C.: Semi-analytical model for dynamical modeling thermal recycling in a doublet well of open-loop groundwater heat pump with variable heat extraction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7332, https://doi.org/10.5194/egusphere-egu21-7332, 2021.

EGU21-12076 | vPICO presentations | ERE2.6

Geo.KW, a coupled hydrothermal and infrastructure model at urban scale

Thilo Schramm, Fabian Böttcher, Viktoria Pauw, Leonhard Odersky, Smajil Halilovic, and Kyle Davis

To reduce anthropogenic climate change, our energy demand needs to be met by renewable energies, wherever possible. So far, only a minor part of heating and cooling is met by such sources. Shallow geothermal energy, powered by green electricity, can close this gap at a high level of efficiency, while reducing intermittency problems current renewables have. As there are various competing uses of the underground in urban environments, e.g. drinking water protection and infrastructure, local authorities are more and more restrictive in granting licenses for new shallow geothermal systems.

In the project Geo.KW we created a coupling approach, which combines hydrothermal and infrastructure modeling to efficiently position shallow geothermal systems between existing uses and other conflicting groundwater usage, optimized by economical and ecological constraints. This should act as a planning tool for water authorities and policymakers.

We are using PFLOTRAN, a finite volume Darcy-Richards model as our flow and heat transport model.
The energy infrastructure optimization is done with urbs, a linear optimization model for distributed energy systems.
For our iterative coupling, we are using preCICE, a multi-physics coupling library, which facilitates fully parallel peer-to-peer exchange between these modeling domains.

The city of Munich is the pilot-region for the implementation of our tool, supported by local government and water authorities. The size and complexity of the model makes it necessary to run the optimization approach on a supercomputer, i.e. the SuperMUC-NG of the Leibniz Supercomputing Centre. Even there, the model needs to be partitioned for the energy infrastructure optimization to be feasible.

How to cite: Schramm, T., Böttcher, F., Pauw, V., Odersky, L., Halilovic, S., and Davis, K.: Geo.KW, a coupled hydrothermal and infrastructure model at urban scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12076, https://doi.org/10.5194/egusphere-egu21-12076, 2021.

EGU21-12890 | vPICO presentations | ERE2.6

Centrifuge modelling of a non-symmetrically heated concrete energy pile group with raft

Badr Ouzzine, Jean de Sauvage, Iheb Ghandri, Giulia Viggiani, and Gopal Madabhushi

The growing energy needs of urban areas and the current environmental context have led to the development of new energy technologies. Since the 1980s, energy geo-structures have been developed and applied, in which heat exchanger pipes are attached to the reinforcement cages of geotechnical structures such as pile foundations or diaphragm walls. By circulating a heat transfer fluid in these pipes, and using a heat pump, these low-enthalpy solutions make it possible to produce heating and cooling with significantly reduced CO2 emissions. However, the cyclic thermal loading generates stresses and strains in the geo-structure and in the surrounding soil, due to thermal expansion. Research on the behaviour of energy pile groups is rather limited, particularly for piled foundations in which only a few piles within a group are thermally activated. Indeed, the implementation of this type of energy technology is slow because of the many concerns about the impact of thermal cycles on the mechanical behaviour of the piles. The complexity of this problem is increased if a natural groundwater flow is present, as this has the potential to affect significantly heat transfer between piles in the group.

To tackle these questions, the stresses induced in pile groups by thermal activation were studied by geotechnical centrifuge modelling.  Two reduced scale models of 2*2 pile groups were examined, one in dry and one in saturated Hostun sand. In the tests, only one pile was subjected to cyclic thermal loading, but all the pile heads were connected to the same raft. The model piles were cast in cement and copper pipes were used to model simultaneously the reinforcement cages and the heat exchanger pipes. This modelling highlighted that, when heated, the energy pile goes into additional compression along with the diagonally opposite pile, due to the raft rotation. The other two thermally inactive piles showed a decrease of axial load. The saturation of the sand layer displayed a strong role not only on the transient response, but also on the thermal equilibrium due to additional thermal inertia.

In order to make relevant comparisons between the observations made on the reduced scale models and those made at prototype scale, scaling laws must be respected, so that the model and the full-scale structure undergo the same physical phenomena. Therefore, preliminary theoretical work was carried out to examine the various thermal phenomena involved. For each phenomenon of interest, the quantities that allow keeping dimensionless numbers identical or at least of the same order of magnitude are studied. Some phenomena were verified also numerically or experimentally. This work is presented in the form of a catalog of scaling laws derived for both mechanical and thermal behaviour of pile foundations.

How to cite: Ouzzine, B., de Sauvage, J., Ghandri, I., Viggiani, G., and Madabhushi, G.: Centrifuge modelling of a non-symmetrically heated concrete energy pile group with raft, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12890, https://doi.org/10.5194/egusphere-egu21-12890, 2021.

EGU21-7084 | vPICO presentations | ERE2.6

Geothermal Geotechnics development program as a commonly used solution in D-wall.

Grzegorz Kacprzak, Tomasz Stasiukiewicz, Rafał Bagiński, Mateusz Frydrych, and Marcin Piotrowski

The project relates to an idea consisting in the use of diaphragm walls constituting a substructure system most often used during the foundation of a large volume building structure in tight urban fabric. Additionally, it offers the possibility of using this substructure as near-surface geothermal geotechnics and in conjunction with adjacent soil as an interseason heat storage in the form of enclosed box. The effect of the following development program is expected to provide a product in the form of concrete elements, that are already required for structural reasons, as diaphragm walls and barrettes with an integrated geothermal installation that allows obtaining part of the heat energy necessary for the operation of a renewable energy building. The accumulated energy, in the form of a lower energy source will be used to heat the building in winter. In summer,  the reduced temperature of diaphragm walls in relation to weather conditions will allow the building to cool down, and thus will power air conditioning systems. This will feature not only concerns about environment aspects but also provides a long-term cost-saving solution that will limit building maintenance.

Presented, currently running, two years program is an effect of cooperation between experienced deep foundation contractor and The Institute of Heat Engineering, scientific unit. The development program, presented below, is based on the industrial research phase in which the lower heat source systems are modelled in Ansys Fluent and then the calculation results are reproduced under laboratory conditions on small physical 3x2x0.7m models. The results from measurements with temperature sensors and IR cameras are used to calibrate the FEM models and to determine the most optimal distribution of the pipes with the fluid carrier.  Stage 2 will allow the analysis of the impact of thermal stress generated by the geothermal installation on the construction of the diaphragm walls and the entire building using deformation sensors.  Development works in stage 3 will allow verification of the above assumptions using real commercial construction in the interseasonal cycle.

The most significant effect of the development programme, stage 4,  will be the creation of a simple tool, on the basis of empirical data collected during model works and prototype tests, to commonly determine the thermal balance for building structures under given ground conditions for commercial buildings. The aim of the tool, being acquired by a deep foundation contractor, is a popularization of the thermo-active ground structures solutions and promotion of geothermal energy utilization.

How to cite: Kacprzak, G., Stasiukiewicz, T., Bagiński, R., Frydrych, M., and Piotrowski, M.: Geothermal Geotechnics development program as a commonly used solution in D-wall., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7084, https://doi.org/10.5194/egusphere-egu21-7084, 2021.

EGU21-14107 | vPICO presentations | ERE2.6

Experimental investigation of thermal interactions in high-temperature borehole thermal energy storage using cyclic heat loads 

Murat Aydin, Bo Wang, Jens Lingenauer, and Sebastian Bauer

High temperature and short-term subsurface heat storage using BTES is a promising option and emerging technology for increasing the fraction of renewable energy in the heat sector and supplying stored heat at high and directly usable temperatures. For this, investigation of thermal interactions of multiple BHEs employed for high-temperature cyclic storage operations is required to understand the system behavior and the relevant thermal processes involved. This work therefore presents highly controlled meso-scale experiments for high temperature borehole thermal energy storage.

The experiment is set up at Kiel University, using a sand pit with two meters depth and a volume of 30 m³ filled with partially saturated fine sand. Five BHEs are constructed, with four positioned at the edges of a square of 0.7 m side length and the fifth one in the center.  Temperatures were measured at 224 locations at varying distances and depths to the center BHE. For the tests, inflow temperatures of the BHEs were set to mimic a high temperature storage system for both stationary and cyclic heat loads by using 70°C and 10-15°C inflow temperature for heating and cooling cycles, respectively. Cycles ranged from 12 to 120 hours.

Thermal characteristics of the boreholes and the sand medium have been determined using constant temperature Thermal Response Tests for the individual boreholes, yielding an average thermal conductivity of about 1.8 W/m/K and typical heat injection/extraction rates of 0.2 kW per meter of BHE length. Subsequently, all BHEs were jointly operated using the same inflow temperatures, in order to determine their thermal interactions in a storage operation. Thermal interaction due to the simultaneous operation of the other BHEs reduced the heat transfer rate by about 30% after 12 hours of continuous heating in the center BHE, while for the outer BHEs the heat transfer rate was reduced by approximately 24%. After about three days of continuous heating, heat transfer rates have stabilized at about 60% in the outer and 40% in the center BHE.  Based on these values, a thermal recovery factor of 55% is obtained. For the cyclic heat storage experiments, similar utilization ratios were found, although average heat transfer rates for the individual BHEs increase with decreasing cycle time. Furthermore, although heat transfer rates are lower in the joint operation of the BHEs, temperatures in the sand are actually higher. Temperatures in the sand at 0.2 m from the center BHE increase from 30°C for individual BHE operation to 57 °C in the joint operation, thus providing higher storage temperatures.

How to cite: Aydin, M., Wang, B., Lingenauer, J., and Bauer, S.: Experimental investigation of thermal interactions in high-temperature borehole thermal energy storage using cyclic heat loads , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14107, https://doi.org/10.5194/egusphere-egu21-14107, 2021.

EGU21-14929 | vPICO presentations | ERE2.6 | Highlight

Optimising the thermal use of groundwater for a decentralized heating and cooling supply in the city of Munich, Germany

Fabian Böttcher, Kyle Davis, Smajil Halilovic, Leonhard Odersky, Viktoria Pauw, Thilo Schramm, and Kai Zosseder

Shallow geothermal energy can contribute to a regenerative supply of urban heating and cooling loads and hence, reduce primary energy consumption and greenhouse gas emissions. In the city of Munich, which hosts a very productive shallow aquifer, conditions are outstanding for the thermal use of groundwater. Therefore, already more than 2800 shallow geothermal systems are installed and due to better economic incentives, numbers are rising. Thus, the future development of this already intensely used urban aquifer holds challenges to avoid conflicting uses, but also opportunities to build synergies and balance the energy budget.

However, fostering a sustainable development is only possible with knowledge about the dynamic hydraulic and thermal behaviour of the groundwater and its anthropogenic and natural influences. Currently, this information is missing on a city scale as a decision basis for the responsible growth of thermal groundwater use. As a consequence, water authorities have to become increasingly restrictive when granting licenses to cope with preventive drinking water protection. Therefore, tools for the thermal management of aquifers are needed to enable resilient decision making.

The project GEO.KW (2019-2021), funded by the German Ministry for Economic Affairs and Energy, took up this challenge and develops a flexible management and optimisation tool for the thermal use of groundwater. As pilot area for an implementation, Munich offers a dynamic and well-monitored hydrogeology. The tool’s core element is the coupling between a thermal-hydraulic groundwater model and a linear optimisation model for distributed energy systems. This interdisciplinary approach, allows us to include the heat storage potential of the aquifer and study the coverable heating and cooling demand depending on the thermal resource at high temporal and spatial resolution. The optimisation integrates all regulatory restrictions of water resource management, like temperature or extraction limits, and comparatively analyses conventional heating and cooling systems alongside with thermal groundwater use. As cost factor in the optimisation, greenhouse gas emissions and economic cost is evaluated.

The development focuses on using highly parallelised open-source codes and efficient code coupling. The numerical groundwater simulation is performed with PFLOTRAN, a code specifically built for scalability on supercomputers. It is coupled to the linear optimiser urbs through the minimally invasive coupling library preCICE and the simulations are performed on the SuperMUC-NG in Garching, Germany. Since the parallelisation of optimisation problems is not straightforward, a decomposition procedure is introduced to assure performance with high resolution models.

The optimisation tool and associated methods will also be applicable to other urban areas. Thus, it will offer the decision support for an optimised growth of thermal groundwater use to assure its contribution to emission-free and decarbonised heating and cooling of cities.

How to cite: Böttcher, F., Davis, K., Halilovic, S., Odersky, L., Pauw, V., Schramm, T., and Zosseder, K.: Optimising the thermal use of groundwater for a decentralized heating and cooling supply in the city of Munich, Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14929, https://doi.org/10.5194/egusphere-egu21-14929, 2021.

EGU21-1977 | vPICO presentations | ERE2.6

Mine water heat and heat storage research opportunities at the UK Geoenergy Observatory in Glasgow, UK

Alison Monaghan, Vanessa Starcher, Hugh Barron, Fiona Fordyce, Helen Taylor-Curran, Richard Luckett, Kirsty Shorter, Kyle Walker-Verkuil, Jack Elsome, Oliver Kuras, Corinna Abesser, David Boon, Barbara Palumbo-Roe, Rachel Dearden, and Michael Spence

Mine water geothermal heat production and storage can provide a decarbonised source of energy for space heating and cooling, however the large resource potential has yet to be exploited widely. Besides economic, regulatory and licensing barriers, geoscientific uncertainties such as detailed understanding of thermal and hydrogeological subsurface processes, resource sustainability and potential environmental impacts remain.

The UK Geoenergy Observatory in Glasgow is a research infrastructure for investigating shallow, low-temperature coal mine water heat energy resources available in abandoned and flooded mine workings at depths of around 50-90 m. It is an at-scale ‘underground laboratory’ of 12 boreholes, surface monitoring equipment and open data. The Glasgow Observatory is accepting requests for researchers and innovators to undertake their own experiments, test sensors and methods to increase the scientific evidence base and reduce uncertainty for this shallow geothermal technology.

How to cite: Monaghan, A., Starcher, V., Barron, H., Fordyce, F., Taylor-Curran, H., Luckett, R., Shorter, K., Walker-Verkuil, K., Elsome, J., Kuras, O., Abesser, C., Boon, D., Palumbo-Roe, B., Dearden, R., and Spence, M.: Mine water heat and heat storage research opportunities at the UK Geoenergy Observatory in Glasgow, UK, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1977, https://doi.org/10.5194/egusphere-egu21-1977, 2021.

EGU21-5052 | vPICO presentations | ERE2.6

Greenhouse gas emissions of aquifer thermal energy storage (ATES)

Ruben Stemmle, Philipp Blum, Simon Schüppler, Paul Fleuchaus, Melissa Limoges, Peter Bayer, and Kathrin Menberg

Aquifer Thermal Energy Storage (ATES) is an open-loop geothermal system enabling seasonal storage of thermal energy in groundwater. It is a promising technology for environmentally friendly energy generation that can overcome the seasonal mismatch between demand and supply of heating and cooling and helps to reduce greenhouse gas (GHG) emissions. Yet, there are only few studies quantifying GHG emissions caused by ATES systems over their entire life cycle. This study presents a novel life cycle assessment (LCA) regression model focusing on the GHG emissions that is a fast alternative to conventional time-consuming LCA. Due to its parametric structure, the regression LCA model can be used to perform Monte Carlo simulations of a wide range of different ATES configurations. Accordingly, it allows the environmental evaluation of the technology as a whole.

The application of the model reveals that the median value of investigated ATES configurations is 83.2 gCO2eq/kWhth with most of the emissions resulting from electricity consumption during the operational phase. Compared to conventional heating systems based on heating oil and natural gas, this value reveals potential GHG savings of up to 74 %. In terms of cooling, ATES can save up to about 59 % of GHG emissions compared to conventional, electricity-based technologies. Specific GHG emissions from a modified LCA regression model considering a projected electricity mix for the year 2050 add up to 10.5 gCO2eq/kWhth forecasting even higher emission savings of up to 97 %. A sensitivity analysis reveals that in particular the operational time for cooling and the coefficient of performance (COP) of the heat pump should be carefully considered when planning or optimizing new systems under current conditions. In contrast, when considering the projected 2050 electricity mix, the most important system parameter is the number of wells. This reflects the decreasing importance of the electrical power necessary for ATES operation due to the much lower specific GHG emissions of the projected 2050 electricity mix.

How to cite: Stemmle, R., Blum, P., Schüppler, S., Fleuchaus, P., Limoges, M., Bayer, P., and Menberg, K.: Greenhouse gas emissions of aquifer thermal energy storage (ATES), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5052, https://doi.org/10.5194/egusphere-egu21-5052, 2021.

ERE3.1 – Petroleum exploration and production and their impact on the environment

EGU21-14 | vPICO presentations | ERE3.1

Environmental impact and treatment of hydraulic fracturing in shale gas

Heng Wang and Lifa Zhou

Hydraulic fracturing is one of the key technologies to stimulate shale gas production and may have some environmental impacts while enhancing shale gas development. Through the introduction of hydraulic fracturing technology from the design and construction aspects, analysis of its potential adverse environmental impacts in water resource consumption, surface water and groundwater pollution, geological disasters, and other aspects, and based on the existing problems to form targeted solutions.

According to EIA report, during the stimulation process of shale gas fracturing, the amount of water resources is about 10,000m3, of which 20%-80% can be returned, and the flowback rate of Shale gas in China is 20%-60%, which means that at least 20%-40% polluted water containing various chemical raw materials will be hidden in the formation for a long time. The shale flowback rate in China is significantly lower than that in the United States, not only due to formation conditions, but also due to equipment and technology. In view of this situation, it is necessary to control the whole process from design to construction.

In the design process of hydraulic fracturing of shale gas, real-time control of the fracture range is carried out in conjunction with seismic monitoring and software simulation fitting, so as to reduce the consumption of water resources on the premise of achieving the purpose of increasing production. Especially, to reducing the fracturing program as much as possible in the water-scarce areas, so as to ensure the security of public water resources. Reduce the use of chemical additives to alleviate the pollution of surface water and groundwater. After detection of possible pollution, determine the amount of pollution sources on site and carry out comprehensive pollutant recovery and treatment. Strictly prohibit high-risk pollution sources from entering the fracturing fluid process. At the same time, the fracturing fluid is used to recycled and purified. In terms of geological disasters caused by fracturing, high-risk geological disaster zones should be identified and monitored in advance to prevent large-scale geological activities caused by micro-earthquakes caused by fracturing from causing uncontrollable geological disasters.

How to cite: Wang, H. and Zhou, L.: Environmental impact and treatment of hydraulic fracturing in shale gas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14, https://doi.org/10.5194/egusphere-egu21-14, 2021.

Currently, oil and gas industry dispose the produced water under the ground without treatment and with minimal consideration on the beneficial reuse applications. Yet, in recent years and in response to the worldwide water shortage concerns, produced water management and treatment has gained more attention and interest. Managing produced water is subject to different limitations specially if it is done for offsite applications. This includes the consideration of transportation cost and removal of dispersed and dissolved oil, metals, ammonia, salinity, alkalinity and ion toxicity for human and agricultural use which can result in a greater economic cost in terms of chemical usage and desalination operations. The importance of properly managing produced water is mainly rely on the clear vision of the treating method used which must be defined based on regulatory parameters and reuse standards. This study investigates mathematical modelling and optimisation to include the reuse specification into the produced water quality management and discusses its implication.

How to cite: AlEdan, A. and Erfani, T.: Produced water treatment and reuse in oil and gas industry- Mathematical modelling and optimisation for infrastructure utilisation  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16235, https://doi.org/10.5194/egusphere-egu21-16235, 2021.

In order to finely describe the hydrocarbon generation and expulsion process of source rocks and provide reasonable key parameters for quantitative evaluation of oil and gas resources, we carried out a simulation research under semi-open system on hydrocarbon generation and expulsion for the dark mudstone with Type-Ⅲ kerogen in the Eocene Pinghu Formation in the Xihu Sag, East China Sea Shelf Basin. The results show that the process of hydrocarbon generation and expulsion can be divided into five stages as follows:

  • Ro = 0.5%~0.7%, oil was generated slowly without expulsion;
  • Ro = 0.7%~1.0%, oil was generated and expelled rapidly;
  • Ro = 1.0%~1.5%, oil began to be cracked into hydrocarbon gas;
  • Ro = 1.5%~2.3%, gas generation predominated;
  • Ro > 2.3%, only dry gas was generated.

Oil expulsion threshold (Ro) of the source rock of this type is about 0.7% (Ro = 0.7%), having a wide gas-window of Ro = 1.0%~3.0%. So it can maintain relatively strong gas generation ability at high- and over-mature stages, belonging to gas-prone source rock. Following the study on experimental results and the characteristics of hydrocarbon generation and expulsion in samples, we established a set of mathematical models for the evaluation of the process and potential of gas generation and oil generation and expulsion of the dark mudstone with Type-Ⅲ kerogen in the study area. Compared with the thermal simulation experiment in a closed system, the cumulative yield of oil in the semi-open system is higher and closer to that under actual geological conditions. Accordingly, we may conclude that more oil and gas resources may exist in the Xihu Sag.

How to cite: Xu, C.: Simulation of hydrocarbon generation and expulsion for the dark mudstone with Type-Ⅲ kerogen in the Pinghu Formation of Xihu Sag in East China Sea Shelf Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-291, https://doi.org/10.5194/egusphere-egu21-291, 2021.

Determining the timings of oil charge in sedimentary basins are essential to understand the evolutionary histories of petroleum systems, especially in sedimentary basins with complicated tectonic evolution and thermal histories. The Ordovician carbonate reservoir in the Tahe Oilfield, which is located in the northern Tarim Basin, comprises the largest marine reservoirs in China with reserves up to 3.2×108 t. This study aims to determine the timings of oil charge in the Ordovician carbonate reservoir in the Tahe Oilfield, Tarim Basin, which basin is subjected to multiple phases of tectonic deformations and oil charge. The phases of calcite veins that contain oil inclusions were systematically investigated by cathodoluminescence observation, in situ rare earth element, C, O, and Sr isotope analyses. The homogenization temperatures of aqueous inclusions that are coeval with oil inclusions were measured to determine the timings of oil charge by combining the burial and geothermal histories. Two phases of calcite veins were judged by the differences in cathodoluminescence color, Ce anomaly, δ18O, and 87Sr/86Sr values, which might be caused by variations in the water-rock interaction processes during different calcite phases. Primary oil inclusions with yellow fluorescence were observed in the two phases of calcite veins, suggesting two phases of oil charge. By combining the homogenization temperatures of aqueous inclusions with the burial and geothermal histories, the timing of phase I oil charge was inferred to be 336–312 Ma, and the timing of phase II oil charge was inferred to be 237–217 Ma.

How to cite: Chen, J. and Guo, X.: Determination of oil charge timing in the Ordovician carbonate reservoir of the Tahe Oilfield, Tarim Basin, NW China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1547, https://doi.org/10.5194/egusphere-egu21-1547, 2021.

      Element geochemical analysis of 94 ditch cutting samples of the shale source rock from the Wenchang Formation in the Zhuyi sub-basin and the Liushagang Formation in the Weixinan sub-basin was conducted to determine their palaeoenvironment and main controlling factors and to further establish development models. The results indicate that freshwater and a warm and humid climate were characteristics of the depositional palaeoenvironment between Wenchang and Liushagang formations. During the deposition of Wenchang Formation, the parent rocks mainly consisted of felsic volcanic rocks, the water was characterized by a high palaeoproductivity, shallow-deep water depths, and weakly reducing conditions, whereas during the deposition of Liushagang Formation, the parent rocks mainly consisted of mafic volcanic rocks, and the palaeoproductivity, palaeowater depth, and reducing conditions of the water were better than during the deposition of Wenchang Formation. The formation of high-quality source rocks in the Liushagang Formation were mainly controlled by two factors: (1) the mafic igneous rock provenance and strong weathering provided macronutrients (e.g. P, Fe) for water; (2) high palaeoproductivity provided the source of organic matter, which played a much important role than preservation condition of organic matter. For Wenchang Formation, the good preservation of organic matter which was created by the reducing environment in deep water was also necessary. Accordingly, two models were briefly summarized: a productivity and preservation model for the Wenchang Formation source rocks and a productivity model for the Liushagang Formation source rocks, both of them can develop high-quality source rocks, but the source rock quality of the former were lower than of the latter, this was mainly attributed to the difference in the nutrients and palaeoproductivity. This study provides valuable guidance for oil and gas exploration in the northern South China Sea and the study of lacustrine source rocks in other areas.

How to cite: Zhao, N.: Depositional Palaeoenvironment and Models of the Eocene Lacustrine Source Rocks in the Northern South China Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-298, https://doi.org/10.5194/egusphere-egu21-298, 2021.

EGU21-13228 | vPICO presentations | ERE3.1

Modelling dynamic fault slip and seismic wavefield for production-induced seismicity in Groningen

Jingming Ruan, Ranajit Ghose, and Wim Mulder

Induced seismicity from a gas-producing region such as Groningen is believed to be caused by reservoir depletion due to long-term gas production. However, because of the complexity and uncertainty regarding the underground structure and composition, it is difficult to quantify the effect on induced seismicity due to gas production. Here we use finite-element modelling to investigate the seismogenic potential of a pre-existing fault reactivated due to fluid depletion, considering different model settings. By applying quasi-static poroelastic loading representing reservoir depletion, the stress and strain fields are derived from the resulting displacement field. The equilibrium of the fault is then evaluated using either rate-and-state or slip-weakening behaviour for friction. When the critical state is reached on the fault, where the shear stress is greater than the friction, the reactivation of the fault takes place. This reactivation is simulated by using a dynamic solver to observe the propagation and the arrest of the dynamic faulting, as well as the resultant wavefield due to seismic slip. By comparing the depletion value at both aseismic and seismic ruptures, and looking at the stress distribution on the fault, the pattern of rupture nucleation, and the resulting seismic wavefield, we are able to evaluate separately the effect of different model settings, including the geometry and material property of both caprock and reservoir, reservoir depletion pattern, and the friction law. Furthermore, by combining our study with the observed seismic wavefield, it is possible to obtain useful insights on the spatial variation in the source region.

How to cite: Ruan, J., Ghose, R., and Mulder, W.: Modelling dynamic fault slip and seismic wavefield for production-induced seismicity in Groningen, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13228, https://doi.org/10.5194/egusphere-egu21-13228, 2021.

The overpressure has a significant effect on hydrocarbon migration and accumulation. Scholars have gradually focused on the quantitative characterization of overpressure, which proposes many overpressure quantitative models suitable for different overpressure mechanisms. However, there are few studies on quantitative characterization of overpressure in crude oil cracking. In view of this, taking the south of Aman transition zone in Tarim Basin as the research object, recovered the overpressure characteristics of the research area in the reservoir forming period, and established the quantitative model of crude oil cracking pressurization.

Firstly, according to the data about fluid inclusions tested by some experimental apparatus, the paleo-pressures were calculated by PVTx simulation method and basin simulation method. Next, based on the volume increment of crude oil cracking is equal to the volume reduction caused by overpressure compression, established the quantitative model for pressurization of total crude oil cracking. Moreover, equaled to the mass of residual oil plus the quality of cracked gas and pyrobitumen, put forward the quantitative model for pressurization of partial crude oil cracking and proposed these two model combined with some parameters, which included density and compressibility of oil, gas ,water and pyrobitumen and conversion rate of crude oil cracking and so on. Then, using these two models, calculated the intensity of pressurization of Shunnan gas reservoir. At last, the accuracy of the model was tested by restored paleo-pressure values.

The study shows that the southwest of Shunnan slope is a typical overpressure area. The formation pressure coefficients of Yijianfang formation and Yingshan formation are between 1.15 and 1.48, and those of Penglaiba formation are as high as 1.94. Based on the homogenization temperature of the inclusions and combined with burial history and thermal history, the paleo-pressure in Shunnan is restored through fluid inclusion method. There were two periods of overpressure in Cisuralian (292-280ma) and Neogene (21-2ma). The paleo-pressure coefficient of Neogene is 1.57-1.64, which is generally higher than that of Cisuralian(1.39~1.48). The main mechanism of overpressure in Shunnan area is the cracking of crude oil and the author tried to establish the quantitative characterization of crude oil cracking. The overpressure of crude oil cracking during Neogene reaches around 30 MPa, of which the contributions is respectively 66.7 %.

How to cite: Zhang, H. and Liu, H.: Quantitative characterization of crude oil cracking pressurization in the south of transition zone of Aman, Tarim Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-354, https://doi.org/10.5194/egusphere-egu21-354, 2021.

EGU21-396 | vPICO presentations | ERE3.1

Prospects of oil-bearing in the Rhine Rift (Germany)

Yuri Galant, Yuri Pikovskiy, and Pavel Čížek

Searching for oil in Germany is an urgent task, since from its own reserves Germany can cover only four percent of the total volume of oil required for the country's economy. In this regard, we have conducted research with the aim of assessing the prospects of the Rhine Rift oil potential. Were analyzed in basalts Polycyclic Aromatic Hydrocarbons (PAH). The PAH Petroleum Association clearly indicates the presence of petroleum hydrocarbons in rocks and are an indicator of the oil content of deep horizons. The previous report (EGU2020) highlighted the positive factors of oil   potential in the Rhine Rift. There are favorable geological settings of Rhine Rift, such as seismic activity, new tectonic movements, and presence of basalt, decompressed rocks of mantle, rift stretching mode, and favorable geochemical indications, such as existence of typomorphic oil-associated PAH (Phenanthrene, Chrysene, Pyrene, Benz(a)pyren), presence the components resembling on compositions of Moravia oil . For detailing research conducted mathematical correlation between the non-hydrocarbon components PAH (Naftalen + Homologus, Difenil, Benz (ghi) perylene, Fluorene, Perilen, Antracen, Tetraphen) and hydrocarbon components PAH (Phenanthrene, Pyrene, Chrysene, Benz(a)pyren). Mathematical correlation is 0.041, which is a weak positive relationship on the Chaddock scale. The weak positive relationship between the oil components of PAHs and non-oil components probably indicates that the sources of the oil components of PAHs and non-oil components of PAHs are different. And the source of the oil PAHs is probably the oil fields. Thus the geological-geochemical-mathematical factors point to favorable oil-bearing entrails Rhine Rift! For prospecting   cluster of oil   in the first instance recommended at areas: Bad Urah, Kaizertuhl-Shellingen !

 

How to cite: Galant, Y., Pikovskiy, Y., and Čížek, P.: Prospects of oil-bearing in the Rhine Rift (Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-396, https://doi.org/10.5194/egusphere-egu21-396, 2021.

Tectonic evolution of Thrace Basin in the offshore area surrounding the Gokceada island has been widely studied except for pressure and temperature conditions. This study aims to fill this scientific gap while introducing the discovery of NW-SE oriented Gokceada Volcanic Zone, represented by extinct volcano geometries and chaotic seismic facies on seismic sections. Presence of such a significant heat source causes inevitable effects on pressure-temperature behaviour that might manifest itself as abrupt changes and makes the understanding of petroleum system essential. Hence, an integrated workflow involving seismic & well log interpretation, post-drill ppfg & temperature analysis, conversion of interval velocities into a 3D pore pressure model and 1D basin modelling has been conducted for the first time. 1D models focus especially on the oldest sedimentary unit of gas prone Thrace Basin, known as Early-Mid Eocene aged Karaagac Formation in the Northern Aegean region.


Basin analysis has yielded unique results by providing clues to better understand pore pressure mechanism and maturity rate of the Karaagac Formation, including type-III Eocene shales. The shallower parts of the Karaagac Formation, dominated by the Eocene deltaic succession, is in main oil window. On the other hand, between 4-5 km. depth at where the Eocene shales exist, maturity rate reaches late oil-wet gas. Maturity profile also suggests that entrance to the early oil window is at 38-35 Ma, corresponding to the Oligocene. It can be claimed that high burial rates caused fast maturation which can also be supported by the sedimentation rates, calculated approximately as 450 m/Ma. The post-collisional extensional regime in the Early-Mid Eocene, characterised by wedge-shaped growth strata on seismic sections, can be considered as the main reason for the high sedimentation rates. Thus, it can be proposed that the main causes for increasing pore pressures are disequilibrium compaction and possibly hydrocarbon generation process.


Gokceada Volcanic Zone can be suggested as another driving force of fast maturation. Temperature profiles of two wells exhibit a significant increase towards the volcanic zone. In terms of geothermal gradients, the abrupt changes resulted with temperature fluctuations. Gradient values change between 35-45 0C/km during Eocene-Oligocene at when the basin has experienced severe volcanism due to the crustal thinning. By the ongoing burial, values decrease and approach present-day conditions, ranging between 25-35 0C/km. Present day temperatures reach at least 150-160 0C interval for the deepest part of the basin.


Unlike the temperatures, pore pressures slightly decrease along the volcanic zone. This trend can be related to low porosities of products of intrusions and extrusions. For a better comparison of pressure conditions, a pore pressure cube has been reflected on the seismic sections. According to the model, present-day pressure values range between 5000-12000 psi in the Karaagac Formation. A very similar pressure profile has been illustrated by burial history charts and post-drill ppfg graphs as well. Although different inputs were used, outcomes of all methods validate each other. Therefore, findings of this study can act as a reliable foundation for pore pressure prediction and static temperature prognosis in the area.

How to cite: Uyanik, A.: Uncovering the impact of Gokceada Volcanic Zone on pressure and temperature conditions of Thrace Basin in the Northern Aegean Sea using 1D basin modelling and seismic velocity extraction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-567, https://doi.org/10.5194/egusphere-egu21-567, 2021.

In recent years, new models of continuum mechanics, generalizing the classical theory of elasticity, have been intensively developed. These models are used to describe composite and statistically heterogeneous media, new structural materials, as well as in complex massifs in mine conditions. The paper presents an algorithm for the propagation of longitudinal acoustic waves in the framework of active well monitoring of elastic layered block media with inclusions of hierarchical type of L-th rank. Relations for internal stresses and strains for each hierarchical rank are obtained, which constitute the non local theory of elasticity. The essential differences between the non local theory of elasticity and the classical one and the connection between them are investigated. A characteristic feature of the theory of media with a hierarchical structure is the presence of scale parameters in explicit or implicit form. This work focuses on the study of the effects of non locality and internal degrees of freedom, reflected in internal stresses, which are not described by the classical theory of elasticity and which can be potential precursors of the development of a catastrophic process in a rock massif. Thanks to the use of a model of a layered block medium with hierarchical inclusions, it is possible, using borehole acoustic monitoring, to determine the position of the highest values ​​of internal stresses and, with less effort, to implement the method of unloading the rock massif. If it is necessary to conduct short-term predictive monitoring of geodynamic regions and determine a more accurate position of the source of a dynamic phenomenon using borehole active acoustic observations, it is necessary to use the values ​​of the tensor of internal hierarchical stresses as a monitored parameter.

How to cite: Hachay, O. and Khachay, A.: Study of internal stresses in rock massif within the framework of elastic layered block models with inclusions of the hierarchical structure of the L-rank., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-300, https://doi.org/10.5194/egusphere-egu21-300, 2021.

The Ordos Basin is located in the central and western part of China, which is rich in oil resources in Mesozoic strata. Huanxian area is located in the west of the Ordos Basin, covering an area of about 3000 km2. With the wide distribution of Jurassic low resistivity reservoir, it is difficult to identify reservoir fluid by logging, which restricts the efficient promotion of oil resources exploration and development in this area to a certain extent.

Based on the basic geological law, this study makes full use of the data of oil test conclusion, production performance and formation water analysis to deeply analyze the genesis of low resistivity reservoir in this area. The average formation water salinity of Jurassic in Huanxian area is 63.5g/l. Through the correlation analysis of mathematical methods such as fitting and regression, the formation water salinity and reservoir apparent resistivity show a good negative correlation in the semi logarithmic coordinate, and the correlation coefficient is 0.78. Therefore, it is considered that the main controlling factor for the widespread development of low resistivity reservoir in this area is the high formation water salinity. Irreducible water saturation, clay mineral content and nose bulge structure amplitude are the secondary controlling factors for the development of low resistivity reservoir in this area, and their correlation coefficients with apparent resistivity are 0.23, 0.25 and 0.31, respectively.

On the basis of clarifying the genesis of Jurassic low resistivity reservoir in Huanxian area, the comprehensive identification of reservoir fluid type by logging is carried out. For the whole area, there are obvious differences in geological characteristics, so conventional methods such as cross plot method of acoustic time difference and apparent resistivity can not effectively identify reservoir fluid. According to the main controlling factors of reservoir apparent resistivity, the salinity of formation water is combined with apparent resistivity and resistivity index of reservoir respectively to establish the cross plot. Using these two kinds of cross plot, the accuracy of reservoir fluid type identification is 62.9% and 88.6% respectively. This method can meet the accuracy requirements of reservoir fluid identification, realize the rapid identification of reservoir fluid types in the whole area, and provide technical support for efficient exploration and development of Jurassic low resistivity reservoir in this area.

How to cite: Guo, J. and Zhou, L.: Analysis of main controlling factors and identification method of Jurassic low resistivity reservoir in Huanxian area, Ordos Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-664, https://doi.org/10.5194/egusphere-egu21-664, 2021.

EGU21-564 | vPICO presentations | ERE3.1

Analysis on the heterogeneity of reservoir Chang 6 in D district of Ordos Basin

Guilin Yang and Zhanli Ren

This study is designed to evaluate the heterogeneity of the Chang 6 reservoirs in Study area, and to analyze the effect of heterogeneity on the distribution of oil. Mainly based on the sedimentary microfacies of the chang 6 reservoir, to calculate the mudstone by using the gamma curve in the logging curve, the separation layer and the interlayer were separated by 2 meters, then analyse the data of intercalation and interlayer by means of sedimentary facies, core and thin etc. We believe that the distribution of the sand in the plane and the heterogeneity of the reservoir is the main control factor of the oil distribution in the area, and it has a good area of oil, which own better properties, and the grain size more coarse; The main control factors of the Chang 6 reservoir in D area is the distribution and physical property of the sand body plane, the better the continuity and physical property of the sand body plane, and the better display of the oil-bearing property of the reservoir; The migration will occur in the vertical direction When the oil and gas meet the thinner interlayer, which will have a great influence on the distribution of oil and gas in the vertical direction; The full extent of oil and gas in the reservoir is controlled by the microscopic heterogeneity of the reservoir. In the study area, the reservoir heterogeneity influence the oil and gas distribution by the physical and lithologic characteristics, the distribution of sand body surface and the distribution of layer interval etc mainly. The study on the relationship between the heterogeneity and reservoir distribution of the Chang 6 reservoirs in the research area can be reasonably evaluated for the favorable areas of oil and gas reservoirs and prediction research areas, so as to guide the development of rational development plans in the next step.

How to cite: Yang, G. and Ren, Z.: Analysis on the heterogeneity of reservoir Chang 6 in D district of Ordos Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-564, https://doi.org/10.5194/egusphere-egu21-564, 2021.

We investigate the influence of the microscopic displacement processes on optimal gas flooding strategies. We couple a 1-D compositional reservoir model with an economic model of the flooding to assess profitability of the strategies. In general, we aim at the net present value maximisation, although the oil recovery and COstorage efficiencies are also estimated. Under certain assumptions, we reduce the number of parameters controlling selection of optimal strategy to just a few dimensionless quantities characterising both physical and economic processes. We show that the production life of oil fields should not be fixed in optimisation studies, especially at low oil prices. A significantly larger net present value can be achieved by varying the reservoir lifetime in addition to the injection rates and volumes and other well controls. Herewith, the optimal strategy can differ from that in the case of a presumed production time. We conclude that waterflooding is the optimal recovery method if the injection rate is low, whereas gas (WAG) flooding applied as a primary method and followed by waterflooding is most optimal for large injection rates. Gas flooding applied as the tertiary recovery method is most optimal for an intermediate range of the rates. In the latter case, gas injection should begin much earlier than water breaks through to producing wells. Finally, we investigate how oil price influences the range of parameters suitable for gas injection.

The authors acknowledge funding from the Russian Foundation for Basic Research under grant # 20-31-80009.

How to cite: Chernova, A., Afanasyev, A., and Andreeva, A.: Influence of oil field production life on optimal CO2 flooding strategies: Insight from the microscopic displacement efficiency, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6217, https://doi.org/10.5194/egusphere-egu21-6217, 2021.

Advances in the field of nanoscience and nanotechnology have resulted in the development of engineered nanoparticles, with unique physico-chemical properties, and their applications to all the sectors of industry, including the petroleum industry. This presentation will discuss several advances and applications of silica-based nanofluids in chemical enhanced oil recovery (EOR) processes related to interfacial phenomena in multiphase systems and physics of multiphase flow in porous media, and in particular the oil recovery characteristics resulting from nanofluids based low-salinity water flooding and chemical EOR processes. Laboratory experiments were carried out using homogeneous sandpack columns simulating oil-wet and water-wet reservoirs. To simulate oil-wet reservoirs, the sandpack columns were saturated with a light crude oil (West Texas Intermediate) at first. While in the case of the simulated water-wet reservoirs, these reservoirs were made by saturating the sandpack columns initially with a 1.0 wt% brine (NaCl) and then followed by an injection of the light crude oil. The subsequent oil-saturated (oil-wet system) and oil-brine mixture (water-wet system) within the sandpack columns were then subject to water flooding (non-sequenced recovery) or EOR processes (sequenced recovery) utilizing brine and/or surfactant as controls as well as low (0.01 wt%) and high (0.1 wt%) silica-based nanofluids. When compared with the high concentration of silica-based nanofluid, the low silica-based nanofluid concentration produced low fractional and cumulative oil recovery results in the water flooding process of oil recovery for both oil-wet and water-wet reservoir systems; however, the low silica-based nanofluid concentration was found to be the most effective with EOR process for both oil-wet and water-wet reservoir systems. Our findings permit to choose optimal concentrations of silica nanoparticles to be employed for either water flooding or EOR processes in order to increase the oil extraction efficiency.

How to cite: Darnault, C., Phibbs, B., McCarroll, C., and Blanton, B.: Chemical Enhanced Oil Recovery and Nanotechnology: Effects of Silica-Based Nanofluids on Low-Salinity Water Flooding and Enhanced Oil Recovery Processes in Oil-Wet and Water-Wet Reservoirs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13079, https://doi.org/10.5194/egusphere-egu21-13079, 2021.

EGU21-14198 | vPICO presentations | ERE3.1

Depth and composition dependent nanopore structures of Indian shale gas reservoirs: An implication on storage potential

Abinash Bal, Santanu Misra, and Manab Mukherjee

We investigated the nanopore structures of shale samples obtained from Cambay and Krishna-Godavari (KG) basins in India using low-pressure N2 sorption method. The samples occurred at variable depths (1403-2574m and 2599-2987m for Cambay and KG basins, respectively) and have wide ranges of clay contents (56-90%) both in volume and mineralogy. The results of this study indicate the specific surface area (SSA) and pore diameters of the samples share a non-linear negative correlation. The SSA is a strong function of the clay content over the samples’ depth. The specific micropore volumes of the KG basin have relatively higher (8.29-24.4%) than the Cambay basin (0.1-3.6%), which leads to higher SSA in the KG basin. From different statistical thickness equations, the Harkins Jura equation was found to be most suitable for the computation of BJH pore size distribution and t-plot inversion in shale. Shale samples from Cambay basin show unimodal pore size distribution, with a modal diameter of 4-5nm, while in the KG basin, show bi-modal to multimodal pore size distribution, mostly ranges from 3-12 nm. In the fractal FHH method, fractal exponent Df-3 provides a better realistic result than fractal dimensions calculated from (Df-3)/3. In our samples, pore surface fractal dimension (Df1) show a positive correlation with SSA and a negative correlation with pore diameter, and pore structure fractal dimension (Df2) shows a negative correlation both with clay(%) and depth. The experimental data obtained in this study are instrumental in developing the pore-network model to assess the hydrocarbon reserve and recovery in shale.

How to cite: Bal, A., Misra, S., and Mukherjee, M.: Depth and composition dependent nanopore structures of Indian shale gas reservoirs: An implication on storage potential, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14198, https://doi.org/10.5194/egusphere-egu21-14198, 2021.

EGU21-4504 | vPICO presentations | ERE3.1

Alternative energy resources in Lithuania - shale gas perspective

Saulius Lozovskis, Saulius Šliaupa, Jurga Lazauskienė, and Rasa Šliaupienė

In Worlds practice it is known that shale gas can be viable source of energy. Lithuania is situated in the central and eastern parts of the pericratonic Baltic Sedimentary Basin. The Lower Silurian shales are considered as a most prospective formation for gas exploration due to high amount of organic matter (more than 2%) and large thickness (120-200 m). Mineralogical composition and related petrophysical and mechanical properties were assessed for west Lithuanian shales that occur at the depths of 1500-2000 m. Thermal maturity of organic matter Tmax ranges from 432 to 455oC (oil window). Shales contain 37–57% of clay minerals. Illite predominates and chlorite is less abundant mineral. Quartz and feldspars compose about 35–45% of shale volume. The carbonate content ranges from 1% to 28%. TOC content is about 2%, while interpretation of well logs show higher average amount of TOC ranging from 2.5 to 8%. The Middle Llandovery “hot” shales of 4-11m thick show anomalous TOC content up to 20%. The mineral brittleness index was calculated to range mainly from 0.35 to 0.40 (bellow the lower exploitation limit), while logging brittleness index varies from 0.40 to 0.60 (good quality). This difference is explained by logging coverage of the whole Lower Silurian section by contrast to selective drill coring of wells. The bulk porosity decreases with depth from 16% to 3% (linear correlation Depth=-0.0107×Porosity+25.7). The low cation exchange capacity (0.2-8.8 meq/100g) is accounted to specific mineral composition. The low erodibility (Roller Oven technique) is related to high shale compaction. The capillary suction time method was used to estimate the swelling capacity of shales. Rather low values are explained in terms of predominance of illite in clay fraction and high amount of detrital grains. In summary, the exploitation parameters estimated for west Lithuanian shales are classified as good and excellent and can be used to minimize the impact on the environment.

How to cite: Lozovskis, S., Šliaupa, S., Lazauskienė, J., and Šliaupienė, R.: Alternative energy resources in Lithuania - shale gas perspective, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4504, https://doi.org/10.5194/egusphere-egu21-4504, 2021.

EGU21-2328 | vPICO presentations | ERE3.1

Prediction of feasible synthesis gas compositions at three European coal deposits

Christopher Otto and Thomas Kempka

In the present study, we apply our validated stoichiometric equilibrium model [1], based on direct minimisation of Gibbs free energy, to predict the synthesis gas compositions produced by in-situ coal conversion at three European coal deposits. The applied modelling approach is computationally efficient and allows to predict synthesis gas compositions and calorific values under various operating and geological boundary conditions, including varying oxidant and coal compositions. Three European coal deposits are assessed, comprising the South Wales Coalfield (United Kingdom), the Upper Silesian Coal Basin (Poland) and the Ruhr District (Germany). The stoichiometric equilibrium models were first validated on the basis of laboratory experiments undertaken at two different operating pressures by [2] and available literature data [3]. Then, the models were adapted to site-specific hydrostatic pressure conditions to enable an extrapolation of the synthesis gas composition to in-situ pressure conditions. Our simulation results demonstrate that changes in the synthesis gas composition follow the expected trends for preferential production of specific gas components at increased pressures, known from the literature, emphasising that a reliable methodology for estimations of synthesis gas compositions for different in-situ conditions has been established. The presented predictive approach can be integrated with techno-economic models [4] to assess the technical and economic feasibility of in-situ coal conversion at selected study areas as well as of biomass and waste to synthesis gas conversion projects.

[1] Otto, C.; Kempka, T. Synthesis Gas Composition Prediction for Underground Coal Gasification Using a Thermochemical Equilibrium Modeling Approach. Energies 2020, 13, 1171.

[2] Kapusta et al., 2020

[3] Kempka et al., 2011

[4] Nakaten and Kempka, 2019

How to cite: Otto, C. and Kempka, T.: Prediction of feasible synthesis gas compositions at three European coal deposits, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2328, https://doi.org/10.5194/egusphere-egu21-2328, 2021.

ERE4.1 – Secure subsurface storage for future energy systems

EGU21-10327 | vPICO presentations | ERE4.1

Geologic carbon storage resource requirements of climate change mitigation targets in Europe

Yuting Zhang, Samuel Krevor, and Chris Jackson

To limit global warming to well below 2oC, integrated assessment models have projected that gigaton-per-year-scale carbon capture and storage is needed by c. 2050. These scenarios are unconstrained by limiting growth rates or historical data due to the limited existing deployment of the technology. A new approach using logistic growth models identifies a coupling between storage resource base (pore space underground) and minimum growth rates necessary to meet global climate change mitigation targets (Zahasky & Krevor, 2020). However, viable growth trajectories consistent with carbon storage targets remain unexplored at the regional level. Here, we show the application of logistic modelling constrained by climate change targets and assessed storage resources for the European Union (EU), the United Kingdom (UK), and Norway. This allows us to identify plausible growth trajectories of CCS development and the associated discovered storage resource base requirement in these regions. We find that the EU storage resource base is sufficient to meet storage targets of 80 MtCO2/year and 92 MtCO2/year suggested in the European Commission climate change mitigation strategy to 2050, ‘A Clean Planet for All’. However, the more ambitious goals of 298 MtCO2/year and 330 MtCO2/year are likely to require additional storage resources based predominantly in the North Sea. Results for the UK indicate that all anticipated storage targets to achieve net-zero economy are achievable, requiring no more than 42 Gt of the storage resource base for the most ambitious target. Furthermore, the UK and the Norwegian North Sea may be able to serve as a regional CO2 storage hub. There are sufficient storage resources to support combined storage targets from the EU and the UK. The tools used here demonstrate a practical approach for regional stakeholders to monitor carbon storage progress towards future stated carbon abatements goals, as well as to evaluate future storage resource needs.

Zahasky, C., & Krevor, S. (2020). Global geologic carbon storage requirements of climate change mitigation scenarios. Energy & Environmental Science. https://doi.org/10.1039/D0EE00674B

How to cite: Zhang, Y., Krevor, S., and Jackson, C.: Geologic carbon storage resource requirements of climate change mitigation targets in Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10327, https://doi.org/10.5194/egusphere-egu21-10327, 2021.

EGU21-2975 | vPICO presentations | ERE4.1

Power-to-Gas-to-Power is a competitive excess energy subsurface storage technology

Natalie Nakaten, Thomas Kempka, and Michael Kühn

The underlying study addresses the ambitious German Federal Government’s objectives for the transition to a new energy era by proposing the implementation of a low-carbon energy system, improving the electricity grid as well as solar and wind power initiatives. Hereby, the “Power-to-Gas-to-Power” (PGP) approach combines the storage of excess energy from renewable power sources in the form of synthetic hydrocarbons, and their subsequent utilisation in a closed cycle to produce low-carbon electricity [1]. Based on the availability of two adjacent subsurface storage formations for CO2 and CH4 [2], hydrogen gained from excess solar and/or wind power is transformed into methane by means of CO2 captured on-site. When required, electricity is regained in a combined cycle plant by burning the CH4, with CO2 cycled in a closed loop.

In a show case study for the two German cities of Potsdam and Brandenburg, the PGP process chain was quantified to a total process efficiency of about 26%, exhibiting costs of 20 eurocent/kWh [2]. These previous assessments referring to energy production and storage technologies economics of the year 2012, have shown that PGP is generally economically competitive compared to conventional storage technologies [2]. Further results show that PGP can compete with global cost bandwidths of hydropower and compressed air storage as well as with upper limit COEs for solar thermal power and photovoltaic. However, PGP is not competitive compared to fossil fuel-based as well as onshore/offshore wind-based energy production [3]. However, cost trends related to energy production and storage technologies significantly correlate with fuel and commodity prices, CO2 emission charges as well as technology improvements that have been rapidly changing in the past few years. Thus, the purpose of the present study is to update the previously published PGP costs and elaborate a general overview on the current status of PGP on the global energy market.

[1] Kühn, M. (2013): System and method for ecologically generating and storing electricity. - Patent WO 2013156611 A1:

[2] Streibel, M., Nakaten, N. C., Kempka, T., Kühn, M. (2013): Analysis of an Integrated Carbon Cycle for Storage of renewables. - Energy Procedia, 40, pp. 202-211. DOI:

[3] Kühn, M., Nakaten, N., Kempka, T. (2020): Geological storage capacity for green excess energy readily available in Germany. - Advances in Geosciences, 54, 173-178. DOI:

How to cite: Nakaten, N., Kempka, T., and Kühn, M.: Power-to-Gas-to-Power is a competitive excess energy subsurface storage technology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2975, https://doi.org/10.5194/egusphere-egu21-2975, 2021.

EGU21-3496 | vPICO presentations | ERE4.1

Underground hydrogen storage in sedimentary and volcanic rock reservoirs: Foundational research and future challenges for New Zealand

Alan Bischoff, Ludmila Adam, David Dempsey, Andrew Nicol, Mac Beggs, Michael C. Rowe, Kate Bromfield, Matthew Stott, and Marlene Villeneuve

Novel technologies to store hydrogen in geological formations can substantially enhance New Zealand’s renewable energy market and help mitigate climate change impacts. New Zealand already supplies about 80% of its electricity demands from renewable sources, mostly geothermal, hydro and wind power. However, over 60% of the country’s net energy consumption still comes from fossil fuels. In New Zealand, extensive production and large-volume (>50,000,000 Nm3) storage of green hydrogen will be essential to buffer diurnal and seasonal shortage of hydro and wind power generation in a future energy mix dominated by renewable sources. Geological storage, technology in use since the 1970’s, is currently considered the best large-scale option for hydrogen storage globally.

Here we present preliminary results of an ongoing study into the feasibility of storing hydrogen in sedimentary and volcanic rocks across New Zealand. The country’s varied geology and diverse cultural communities provide a unique setting to evaluate the technical capacity, socio-environmental aspirations, and costs-benefits of hydrogen geo-storage for future domestic and export markets. We draw our investigation upon a substantial legacy dataset of petroleum exploration drillholes and seismic reflection surveys coupled with information from sedimentary and volcanic outcrops to determine the most suitable geological formations for hosting large-volumes of hydrogen nationwide. Four possible types of hydrogen geo-storage are considered: (i) construction of artificial rock caves, (ii) injection of hydrogen into sedimentary rocks and aquifers, (iii) utilisation of depleted natural oil and gas reservoirs and infrastructure; and (iv) hydrogen storage in highly porous and permeable volcanic rocks, the last of which would be a world first.

New Zealand has an extensive installed petroleum infrastructure, including 2,500 km of high-pressure gas pipelines and 17,960 km of gas distribution network to support the development of new hydrogen energy enterprises. Multiple depleted or depleting petroleum fields (e.g. Ahuroa, Kapuni and Maui) contain excellent reservoirs and efficient seal rocks confined in large (>25 km2) geological structures that offer scope for hydrogen storage. Porosity and permeability in commercial reservoirs vary from 5 to 25% and often up to several thousand millidarcys (mD), respectively, with high values of up to 9900 mD reported in sandstones of the Maui field. Studies in volcanic reservoirs on Banks Peninsula, Oamaru and offshore Taranaki Basin demonstrate that large sections of volcanoes (up to 1 km3) frequently have porosities of ca 50% and permeabilities above 100 mD, which may provide opportunities for storing hydrogen at relatively shallow (ca 100 m) depths.

Further technical assessment is ongoing to determine microbiological activity, chemical stability of rock targets, and geological modelling in hydrogen-rich reservoirs. This technical assessment will be complemented by community consultation to develop pathways for acceptance of hydrogen geo-storage in the country. Mātauranga Māori (native indigenous knowledge) has real potential to guide renewable energy investments towards a long-term vision that prioritises intergenerational well-being and prosperity for the wider New Zealand society. This convergence of thinking, integrating scientific knowledge, industry aspirations, and societal necessities will provide a novel approach for sustainable growth of the hydrogen industry in New Zealand and abroad.

How to cite: Bischoff, A., Adam, L., Dempsey, D., Nicol, A., Beggs, M., Rowe, M. C., Bromfield, K., Stott, M., and Villeneuve, M.: Underground hydrogen storage in sedimentary and volcanic rock reservoirs: Foundational research and future challenges for New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3496, https://doi.org/10.5194/egusphere-egu21-3496, 2021.

EGU21-13964 | vPICO presentations | ERE4.1

Mass Balance Threshold Matching of Geoelectric and Seismic Data – A case study from Ketzin

Wolfgang Weinzierl, Merlin Ganzer, Dennis Rippe, Stefan Lüth, and Cornelia Schmidt-Hattenberger

Seismic and geoelectric/electro-magnetic methods are used as complementary tools for the identification of fluid/gas effects in underground storage and production scenarios. Both methods generally have very different resolution. Seismic tends to be acquired by much more dense geometrical layouts and the geoelectric or electro-magnetic acquisition being a potential field method shows information integrated over spatial distances. These inherent scale and design dependent differences require spatial tuning in joint inversion approaches and careful matching in independent interpretations of both methods. We present results matching seismic and electrical resistivity tomography (ERT) results from two repeat surveys acquired during CO2 storage operations at the Ketzin pilot site in Germany. The approach is based on data acquired in 2009 and 2012, at different stages of total injected CO2 volume. Volumes of injected mass are obtained from the averaged acoustic impedance change (seismic) in the vicinity of the injection well and compared to volumes inferred from the ERT cross-well acquisition. The results are compared radially with increasing distances from the injection location. Seismically derived masses of injected CO2 are used as a benchmark for a threshold-driven workflow analyzing the electric resistivity model. The cross-well ERT results have been obtained in a quadrant of the seismic survey acquisitions. Assuming radial symmetry for the ERT makes it possible to compare individual mass balances in the near-vicinity of the injection well. Archie's equation is used to obtain saturations from the tomographic geoelectric models. The sensitivities of parameters relevant in determining the mass of injected CO2 is analyzed. Variations in saturation exponent n, baseline resistivity R0, and porosity Φ enable specifying applicable ranges of the parameters and determining the investigation radii compared to the seismic derived benchmark. This is done for individual threshold levels for saturations derived from the ERT field data. Seismically and ERT obtained masses match comparatively well and subtle variations of the sensitive parameters are capable in explaining differences for individual investigation volumes. Applicable investigation radii lie between 20-100 m. A 10% in- or decrease of the mean parameters is able to match the seismic derived mass in this range. Above a threshold of 10% for the saturations, the derived mass decreases more rapidly showing a larger deviation from the seismic derived mass. Both methods underestimate the total injected mass. This is not surprising as there are both fluid related processes and structural heterogeneities not accounted for in either. Results of surface-downhole measurements support the findings and show applicability of the developed approach. The threshold-based approach may support the monitoring concept of a CO2 storage site and provides a basis for quantitative evaluation of its containment, as investigated in the frame of the EU project SECURe.

 

How to cite: Weinzierl, W., Ganzer, M., Rippe, D., Lüth, S., and Schmidt-Hattenberger, C.: Mass Balance Threshold Matching of Geoelectric and Seismic Data – A case study from Ketzin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13964, https://doi.org/10.5194/egusphere-egu21-13964, 2021.

EGU21-14804 | vPICO presentations | ERE4.1

Optimal CSEM survey design for CO2 monitoring at Smeaheia offshore Norway

Peder Eliasson, Anouar Romdhane, Romina Gehrmann, Joonsang Park, and Hanbo Chen

Geophysical monitoring is essential for CO2 storage projects and mandatory Measurements, Monitoring, and Verification (MMV) plans. Various geophysical methods can be used to estimate, from measured data, selected properties (e.g. velocity, density, and resistivity) of the subsurface. Accurate knowledge of those properties in turn makes it possible to quantify important reservoir parameters such as CO2 saturation and pore pressure, giving the operator valuable information for predictable CO2 injection and storage.

A combination of seismic and non-seismic technologies is usually part of the CO2 monitoring plan throughout the project lifecycle (pre-injection, injection, and post-injection phases). The EM4CO2 project investigates whether marine Controlled Source Electro-Magnetics (CSEM) can be a cost-efficient complement to seismic in such monitoring plans. The main focus of the project is on demonstrating sufficient sensitivity of the technology and on further developing CSEM for time-lapse applications in areas with potentially interfering infrastructure. While improved data processing, imaging, and inversion techniques is often the subject of large research efforts, less attention is usually paid to developing better survey design strategies (rather relying on conventional methods). The work described here relates to the development and demonstration of new strategies for optimization of 4D survey design. Such optimization could decrease the large costs associated with acquisition of geophysical data (in this case CSEM), which could otherwise be a hurdle when proposing large-scale CO2 storage as a means to mitigate climate change.

Conceptually, survey design aims at selecting the data acquisition that optimally resolves the subsurface model parameters of interest while maintaining the cost as low as possible. In other words, it consists of finding the best trade-off between data value and data collection cost. In this work, the CSEM survey design strategy is based on the analysis of the eigenvalue spectrum of the data misfit Hessian. A Python notebook was implemented for interactive prototyping and testing of various optimization strategies. A few examples of survey design are given for a model of the Sleipner storage site, showing how well a given regular survey can be decimated without significant loss of information. The main part of the work is, however, focused on survey optimization for potential CO2 storage in the Smeaheia formation at about 1000 m depth below the sea surface, offshore Norway. This study shows how to determine the most valuable electric field components, most important frequencies, and source/receiver positions to use for reliable monitoring of a target region of choice. Initial results indicate that measuring the vertical component in addition to the horizontal electric field adds relevant information, and that lower frequencies (0.1-0.5 Hz) carry more information than higher (0.75-5 Hz) about the target depth. It is also clear that the method identifies sources and receivers distributed mainly above the target region as the most important.

How to cite: Eliasson, P., Romdhane, A., Gehrmann, R., Park, J., and Chen, H.: Optimal CSEM survey design for CO2 monitoring at Smeaheia offshore Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14804, https://doi.org/10.5194/egusphere-egu21-14804, 2021.

EGU21-8883 | vPICO presentations | ERE4.1

Site Selection Tool for Hydrogen Storage in Porous Media 

Eike Marie Thaysen, Sean McMahon, Gion J. Strobel, Ian B. Butler, Bryne Ngwenya, Niklas Heinemann, Mark Wilkinson, Aliakbar Hassanpouryouzband, Christopher I. McDermott, and Katriona Edlmann

Zero carbon energy generation from renewable sources can reduce climate change by mitigating carbon emissions. A major challenge of renewable energy generation is the imbalance between supply and demand. Subsurface hydrogen storage in porous media is suggested as a large-scale and economic means to overcome these energy imbalances. However, hydrogen is an electron donor for many subsurface microbial processes which may have important implications for hydrogen recovery, gas injectivity and corrosion.

We reviewed the state-of-the-art literature on the controls on the three major hydrogen-consuming processes in the subsurface: methanogenesis, homoacetogenesis, and sulphate reduction, as a basis to develop a hydrogen storage site selection tool. Sites with low temperature (<70°C), zero to moderate salinity (0-0.6 M) and close to neutral pH values provide the best growth conditions for most of the hydrogen-consuming methanogens, homoacetogens and sulphate reducers. Conversely, fewer strains are adapted to more extreme conditions (high temperature and pressure, increased salinity and acidic or alkaline pH), favouring hydrogen storage in these sites.

Testing our tool on 42 depleted gas and oil fields of the British and Norwegian North Sea and the Irish Sea showed that seven of the fields may be considered sterile with respect to hydrogen-consuming microorganisms due to either temperatures >122 °C or salinities >5 M NaCl. Only three fields can sustain all of the major hydrogen-consuming processes, due to either temperature, salinity or pressure constraints in the remaining fields. We calculated a potential microbial growth in the order of 1-17*107 cells ml-1 for these fields. The associated hydrogen consumption is negligible to small (<0.01-3.2 % of the stored hydrogen). Our results will advance a faster transition to a lower carbon energy supply by helping inform decisions about where hydrogen can be stored in the future.

How to cite: Thaysen, E. M., McMahon, S., Strobel, G. J., Butler, I. B., Ngwenya, B., Heinemann, N., Wilkinson, M., Hassanpouryouzband, A., McDermott, C. I., and Edlmann, K.: Site Selection Tool for Hydrogen Storage in Porous Media , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8883, https://doi.org/10.5194/egusphere-egu21-8883, 2021.

EGU21-16457 | vPICO presentations | ERE4.1

A method for simultaneous minimal-cost supply node location and network design in pipelined infrastructure.

Christropher Yeates, Cornelia Schmidt-Hattenberger, and David Bruhn

Designing low-cost infrastructure networks for transport of hydrogen represents a key step in the adoption and penetration of hydrogen technology in a low-carbon energy future.

For hydrogen distribution, network design amounts to creating pipeline systems in which supply is matched to demand through a transportation system that respects multiple constraints (technical, social, environmental) and minimizes cost. This can equate to recycling pre-existing pipelines or building new ones, but also involves the placement of carefully chosen supply nodes.

In a multi-level distribution network, supply nodes may assume many roles from large-capacity geological storage facilities, to local relay nodes addressing the end customers.

Finding minimum-cost pipeline network designs in which supply node locations are already chosen is itself a well-studied combinatorial optimization problem (Cayley’s formula predicts  possible spanning trees for  nodes) for which multiple heuristic and exact methods are known [1].

Allowing the supply node to take any position within the network renders the problem significantly more complex as the minimum-cost network topology (the specific connections to between nodes) will potentially change for each new supply node position.

We propose a heuristic algorithm that finds good solutions in a reasonable amount of time based on a back-and-forth between:

- Repositioning optimally the supply node, while maintaining the same connections to the supply node (reduces cost)

- Optimizing the network topology, assuming a fixed supply node position (also reduces cost)

The algorithm stops once no further cost reductions for the network design are found. The algorithm output is found to be sensitive to the initial guess of the supply node position, the initial guess of the connections to the supply node, and to the specific “path” of the back-and-forth taken to reach the given local minimum. As such, a good initial guess for a “housing polygon”, i.e. the nodes to which supply node is directly connected to, is crucial in finding the minimum-cost solution, and in the shortest time possible. We attempt to make this initial guess with a machine learning algorithm, with features describing the geometrical distribution of node capacity, as well as elementary network concepts.

Finally, an example is provided on a model hydrogen network comprised of typical elements and realistic cost-functions.

 

[1]: Brimberg J, Hansen P, Lin K, Mladenovi N, Breton M, Brimberg, J (2003) An oil pipeline design problem. Operations Research, 51(2):228–239. https://doi.org/10.1287/opre.51.2.228.12786

How to cite: Yeates, C., Schmidt-Hattenberger, C., and Bruhn, D.: A method for simultaneous minimal-cost supply node location and network design in pipelined infrastructure., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16457, https://doi.org/10.5194/egusphere-egu21-16457, 2021.

EGU21-8982 | vPICO presentations | ERE4.1

Coupled HM modeling assists in designing CO2 long-term periodic injection experiment (CO2LPIE) in Mont Terri rock laboratory 

Dario Sciandra, Víctor Vilarrasa, Iman Rahimzadeh Kivi, Roman Makhnenko, Christophe Nussbaum, and Dorothee Rebscher

We are performing a series of coupled hydro-mechanical (HM) simulations to model CO2 flow through Opalinus Clay at the Mont Terri rock laboratory in the CO2 Long-term Periodic Injection Experiment (CO2LPIE). CO2LPIE aims at inter-disciplinary investigations of the caprock sealing capacity in geologic CO2 storage in a highly monitored environment at the underground laboratory scale. Numerical modeling allows us to gain knowledge on the dynamic processes resulting from CO2 periodic injection and to assist the experimental design. The cyclic injection parameters (i.e., the period and the amplitude) have to be optimized for the field experiment and therefore different values are taken into account. Opalinus Clay is a claystone with nanoDarcy permeability that contains well developed bedding planes responsible for its anisotropic HM behavior. The hydraulic anisotropy is defined by a permeability parallel to the bedding planes being three times the one perpendicular to it. Additionally, the drained Young’s modulus is measured to be 1.7 GPa parallel and 2.1 GPa perpendicular to bedding. Excavation reports by swisstopo document a SSE-dip of 45° for the bedding planes at the experiment location. CO2 injection generates a mean overpressure of 1 MPa into the brine that propagates into the formation. The differential pressure between CO2 and formation water, i.e., capillary pressure, is lower than the entry pressure and thus, CO2 diffuses through the pores but does not advect in free phase. The liquid overpressure distribution is distorted by the hydraulic anisotropy, preferentially advancing along the bedding planes, as the associated permeability is higher than the one perpendicular to the bedding. The pore pressure buildup induces a poromechanical stress increase and an expansion of the rock that leads to a permeability enhancement of up to two orders of magnitude. The cyclic stimulation propagates trough the domain faster and with a lag time and an attenuation, both of which increase with distance from the source with, their values being dependent on permeability, porosity and stiffness of the rock. As a result of the model orthotropy, the attenuation and the lag time change with direction, i.e. they are higher in the direction perpendicular to the bedding and lower in the direction parallel to the bedding. Given the very low permeability of Opalinus Clay, the overpressure generated requires a long time to diffuse into the rock. Furthermore, the amplitude attenuation dissipates quite rapidly, so monitoring wells should be placed as close to the injection well as possible. The study of amplitude attenuation and time lag is necessary to determine how they can be utilized to evaluate the evolution of the HM properties as the rock is altered by the acidic nature of CO2-brine mixture Comparison between field data and numerical simulations will be a useful asset to fill the gap.

How to cite: Sciandra, D., Vilarrasa, V., Rahimzadeh Kivi, I., Makhnenko, R., Nussbaum, C., and Rebscher, D.: Coupled HM modeling assists in designing CO2 long-term periodic injection experiment (CO2LPIE) in Mont Terri rock laboratory , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8982, https://doi.org/10.5194/egusphere-egu21-8982, 2021.

More than 750 wildcat wells have been drilled in the Norwegian North Sea since 1966. Some of these wells could pose a risk for the environment, climate, and future H2 and CO2 storage projects by being preferred leakage paths for subsurface- and stored- gases (e.g., CH4, CO2 and/or H2). To ensure well integrity, these wells were secured by cement framing the well casing, and by building cement plugs at crucial positions in the well path before abandoning the well. However, in an early stage of exploration the geology of the subsurface was relatively uncertain, and the requirements for plug placing and how to abandon a well were not established and regulated. We analysed data relevant for the quality of a Plugging and Abandonment (P&A) work done on old exploration wells (1979 to 2003) from the Troll gas and oil field in the Norwegian North Sea. The data were extracted from public available well completion reports and the webpage of the Norwegian Petroleum Directorate. The dataset was analysed regarding their availability, plausibility and evaluated towards the present P&A regulations and geological knowledge for offshore Norway. Based on 12 criteria including reporting to the authorities, volumetric assessment of used cement quantities, position and length of the plugs in relation to reservoir- cap-rocks petrophysical conditions, and verification of the cementing job, a final P&A ranking of 31 exploration wells was established.

Parts of this data were used to build realistic numerical models of P&A'ed well to simulate electromagnetic responses using the finite element software COMSOL Multiphysics. Taking advantage of a dedicated implementation of low frequency ElectroMagnetics (EM), including effective formulations for thin electrical layers, it was possible to study the response of well components to external EM fields, both for the purpose of well detection and well monitoring. Results from the numerical models can be used as benchmark models in a realistic field scale well integrity monitoring approach.

In our presentation we will show results from the TOPHOLE project including realistic field distributions for different representative well configurations, examples of well detection and monitoring signals, and the ranking evaluation results.

Acknowledgments: This work is performed with support from the Research Council of Norway (TOPHOLE project Petromaks2-KPN 295132) and the NCCS Centre (NFR project number 257579/E20).

How to cite: Dupuy, B., Emmel, B., and Zonetti, S.: Evaluating the well integrity of old exploration wells as a risk factor for future storage projects – an example from the Troll field in the Norwegian North Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10856, https://doi.org/10.5194/egusphere-egu21-10856, 2021.

EGU21-8219 | vPICO presentations | ERE4.1

Assessing wells for reuse: a probabilistic approach to well integrity using a numerical model and Bayesian belief network

Logan Brunner, Bogdan Orlic, Al Moghadam, and Jan ter Heege

With increasing CO2 emissions from fossil fuels alongside the push for more sustainable energy systems, the subsurface as a valuable asset for various sustainable energy applications has gained interest. Two primary drawbacks for the use of assets and infrastructure in transition to sustainable energy are (1) the large costs associated with new subsurface infrastructure (e.g. wells, platforms and pipelines), and (2) the detailed integrity assessment of existing infrastructure required for reuse. The concept of reusing existing infrastructure is particularly attractive as it has the potential to facilitate cost-efficient access to the subsurface for sustainable energy applications. Wells are a crucial component for reuse since they generally have a long history of mechanical loads and exposure to formation fluids prior to reuse. A common threat to well integrity is the development of fractures in the cement surrounding the well, or microannuli, at the casing-cement or cement-formation interface that may promote upward migration of fluids. This migration is often difficult to assess with conventional logs but may enable fluid communication from the storage reservoir to the overburden. Such communication is a threat for safe and efficient subsurface energy or CO2 storage.

A methodology has been developed to model and assess the risk of well microannuli over the entire lifetime of a well (i.e. the drilling, completion, operation, abandonment, and post-abandonment phases). The basis of the assessment is a numerical model (DIANA finite element tools), in which a cross-section of the well, cement, and geology is modelled at a given depth. Deterministic parameters are incorporated to enable sensitivity analyses of results. Stochastic variables represent parameters that are uncertain but can be incorporated using a distribution of values, which are sampled using the Monte Carlo method. Probabilities of the microannulus aperture are analyzed using a Bayesian belief network approach. The results vary depending on the choice of values for the deterministic parameters, based on potential strategies of energy operators that can be modified to achieve a proper mix of risk-reduction and financial costs.

The methodology has been evaluated in the SECURe project, where it was applied to a Polish shale gas well and a (hypothetical) CO2 injection well in the offshore Netherlands, and in the REX-CO2 project, where it has been integrated into a tool designed to screen wells for suitability of reuse for CO2 storage. As the approach can handle different operations and fluids, its potential exceeds these use cases. Further application in subsurface energy projects can help in addressing well integrity issues and in advising and decision-making for potential reuse of wells.

This work is part of two projects, SECURe and REX-CO2, which have received funding from the European Union’s Horizon 2020 (grant agreement number 764531) and the ERA NET Cofund ACT (project number 299681), with financial contributions made from ADEME (FR); RVO (NL); Gassnova and RCN (NO); UEFISCDI (RO); BEIS, NERC, and EPSRC (UK); and US-DOE (USA). The contents of this publication reflect only the author’s view and do not necessarily reflect the opinion of the funding agencies.

How to cite: Brunner, L., Orlic, B., Moghadam, A., and ter Heege, J.: Assessing wells for reuse: a probabilistic approach to well integrity using a numerical model and Bayesian belief network, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8219, https://doi.org/10.5194/egusphere-egu21-8219, 2021.

EGU21-12401 | vPICO presentations | ERE4.1

Experimental study of cemented interfaces for applications in CO2 storage re-using depleted oil and gas reservoirs

Frédérique Rossillon, Vivien Esnault, and Eléonore Roguet

The European ERA-ACT REX-CO2 project aims to develop a tool to assess the compatibility of existing wells for CO2 sequestration. Indeed, the reuse of existing wells for storage in depleted reservoirs is an attractive medium-term solution for geological sequestration of CO2.

The mechanical integrity of the wells is a critical point in term of storage durability. A variety of flow paths that could lead to a migration of the stored CO2 to surrounding geological layers or the surface have been identified. Among those, operational feedback shows that a likely leakage route are along the interfaces of the well structure. These potential flow path can be generated by the debonding of the cement sheath from the steel casing or surrounding rocks. One ambition of REX-CO2 project is to ultimately predict the wells integrity as a function of the variations in undergone mechanical loadings. In order to reach this objective, it appears relevant to characterize the mechanical strength of these interfaces.

IFPEN work consists in carrying out mechanical tests on bimaterial specimens to study cement/steel or cement/rock interfaces in different configurations representative of downhole conditions. Two types of tests are performed allowing the characterization of the bonding in two different stress states: the pull-out test and the push-out test. Combined with simulations, these results can either be used directly or feed a damage interface models. The authors are currently running an extensive parametric study, to explore the impact of various downhole conditions, such as pressure or environment, and to CO2 exposure.

The presentation focuses on the mechanical testing methodology. The pull-out test is a tension test performed on a cylinder made of two materials. In this case, the stress pattern is obvious, the interface is loaded in tension. This test is difficult to carry out perfectly due to the weak and scattered behaviour in tension, and finding proper gluing solutions. The push-out test, commonly used in the literature, consists in pushing a plug (steel or rock) into a cement ring to measure the bonding resistance. Despite other push-out tests, a surrounding steel ring ensures the cement confinement and avoid radial cracks. FEM analysis shows stress pattern is more complex than a pure shear at the interface, as often assumed in the literature. An analysis of loading curves enables to understand the different damage stages of the interfaces.

How to cite: Rossillon, F., Esnault, V., and Roguet, E.: Experimental study of cemented interfaces for applications in CO2 storage re-using depleted oil and gas reservoirs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12401, https://doi.org/10.5194/egusphere-egu21-12401, 2021.

Countries in the world now are trying best to conserve energy and reduce emissions, at the meantime, efficient actions are taken to tackle with global warming. Emission reduction of main greenhouse gas CO2 can be achieved efficiently via CO2 geological storage, in terms of CO2 saline aquifer storage. The gas–liquid–solid interactions such as interfacial tension determines the injectability, sealing capacity and safety of this scheme. In order to better predict the storage capacity to evaluate the storage safety, this work aims at carrying out the numercial modelling work on the interfacial tension of CO2–water/brine binary system under the reservoir temperatures and pressures condition. 

A linear relationship between the increase in average interfacial tension and molality was observed and it is a function of the ionic type. Finally, modified empirical correlations based on experimental data in the literature, using only few regression coefficients with a relatively low error for most of the experimental data in the literature, were presented to estimate the CO2–water/brinebinary system interfacial tensions under wide range of temperatures, pressures, and the ionic strength.

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How to cite: Mutailipu, M. and Yao, Q.: Prediction of the interficial tension for CO2-Water/Brine binary system based on the linear fitting method, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-533, https://doi.org/10.5194/egusphere-egu21-533, 2021.

EGU21-7008 | vPICO presentations | ERE4.1

Experimental study on brine-CO2-rock interaction in carbonate formations of Tazhong-Uplift, Tarim Basin China

Kaisaerjiang Aihemaiti, Jianmei Cheng, Shiyi Wang, Ruirui Zhao, and Xiaoli Ma

Abstract: CO2 storage in saline aquifers is one of the most effective ways of geological carbon sequestration. In order to better understand brine-CO2-rock interaction in carbonate reservoirs, 4 series of autoclave experiments with the carbonate rock powder samples with injection of super critical CO2 have been performed. Two core samples were collected from the TC1well at the depth of 4030m (Lianglitage Formation) and 5100m (Qiulitage Formation), and another two samples from corresponding formation  and with varing mineral content were collected from the Yijianfang outcrop and Xiaoerbulake outcrop in Tazhong-Uplift, Tarim Basin, China. The experimental conditions simulate the environment of the reservoir around 4000m depth at the Tazhong Uplift with 25Mpa and 120 degree, where the brine water is CaCl2 type with TDS equal to 135g/l. The FESEM,EDS, XRD, ICP-OES analysis have been performed to examine the mineral chemical composition, morphology and water solution change. The results show that, in all cases after the injection of CO2, with CO2 dissolution, pH shows a decrease at the beginning days of the experiments and start to rise, becomes stable at the end of the experiment. Where as, with the dissolution of the minerals results in continuous increase in electrical conductivity. The SEM analysis demonstrates the dissolution of the calcite and dolomite resulted in a rough surface structure and the sharp edges of calcite and dolomite are dissolved. Also, it is able to observe the formations of new micropores and formation of secondary minerals such as ankerite. In the fluid analysis, Ca2+ is the dominant dissolved cation and originated from calcite and dolomite dissolution. The concentration of Ca2+will first increase sharply and then decreases, whereas concentration of Mg2+ will increase slowly, which means calcite dissolution take places faster than dolomite dissolution. Numerical modeling has been applied to validate the experimental observations with corrected reaction rate. These results can be used for numerical calculation of mineral trapping over long period. This study is helpful for implementation of carbon sequestration plan in Tarim Basin, China.

How to cite: Aihemaiti, K., Cheng, J., Wang, S., Zhao, R., and Ma, X.: Experimental study on brine-CO2-rock interaction in carbonate formations of Tazhong-Uplift, Tarim Basin China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7008, https://doi.org/10.5194/egusphere-egu21-7008, 2021.

EGU21-12191 | vPICO presentations | ERE4.1

Characterization of Fluid Connectivity in Reservoirs using Strontium Isotopes

Stéphane Polteau, Farhana Huq, Craig Smalley, Viktoriya Yarushina, Ingar Johansen, Christian Schöpke, Line Øvrebø, and Ebbe Hartz

Routine measurements of formation pressure while drilling reservoirs can indicate the presence of internal barriers to vertical fluid movement when there is a sudden shift in the pressure data. However, pinpointing the location of a barrier is often not possible since the density of pressure measurements is low and irregular. The aim of this contribution is to show how the Strontium isotopic system can help characterize the fluid connectivity and pinpoint the precise location of low permeability barriers in reservoir units and sedimentary sequences. As an example, we use a 25 m thick interval within the Middle Jurassic Hugin reservoir unit of the Langfjellet oil discovery on the Norwegian Continental Shelf. The location of the barrier is constrained by the upper and lower pressure measurements and could correspond to any of the several layers of silt, shale or coal layers in this interval. In this study, we collected every 2-4 m a total of 40 samples from a 110 m long cored section of a technical side-track well over the available. Each sample was prepared and analyzed using the SrRSA method (Strontium Residual Salt Analysis), which measures the 87Sr/86Sr ratio in salt residue that precipitated in the pore space after the core dried out. The 87Sr/86Sr is a natural tracer because the ratio is not affected by mass fractionation. The 87Sr/86Sr in rocks is mostly acquired by water-rock interactions during diagenesis and evolves through mixing and equilibration of different water bodies, unless low-permeability barriers prevent equilibration. Therefore, the SrRSA patterns observed in the well represent a 1D snapshot of the fluid dynamics at the time of oil filling, which is a frozen image of competing equilibrium vs disequilibrium conditions. The SrRSA data follow a smooth trend of content values at 0.713 and display a sudden jump to lighter 0.709 values near the top of the 25 m thick interval that suggests the presence of a potential barrier. The lithological core log shows that the SrRSA step change corresponds to a coal-shale unit, which is interpreted to represent the barrier. The SrRSA data further demonstrate the reservoir unit at Langfjellet does not contain any other barriers to fluid flow, since pressure equilibration could have masked a possible compartmentalization. This study shows that the SrRSA method is a powerful tool that should be routinely applied for the characterization of fluid connectivity of storage units.

How to cite: Polteau, S., Huq, F., Smalley, C., Yarushina, V., Johansen, I., Schöpke, C., Øvrebø, L., and Hartz, E.: Characterization of Fluid Connectivity in Reservoirs using Strontium Isotopes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12191, https://doi.org/10.5194/egusphere-egu21-12191, 2021.

EGU21-1485 | vPICO presentations | ERE4.1

Experiment and simulation of stress-dependent P-wave velocity anisotropy in sandstone

Haimeng Shen, Xiaying Li, and Qi Li

Velocity anisotropy is particularly important in field applications of seismic monitoring or exploration [1]. We investigate the stress-dependent P-wave velocity anisotropy of sandstones with triaxial experiments and PFC based numerical simulation [2-3]. The sandstone sample was taken from the lower Shaximiao formation, Sichuan Basin, China [4]. The evolution of anisotropy is discussed with the ellipse least-squares fitting method. The results show that the P-wave velocity is affected by both the bedding plane and loading conditions. As confining pressure increases, the anisotropy magnitude decreases for each sample. The direction of anisotropy is along with the direction of the bedding plane. Under deviator loading, the anisotropy is strengthened for the sample with bedding parallel to the maximum principal stress. The direction of anisotropy reversal occurs in the sample with bedding normal to the maximum principal stress. And the anisotropy magnitude of that sample is reduced firstly and then improved. The P-wave velocity anisotropy is originated from preferred mineral orientation and aligned cracks in these samples. The stress has little effect on the mineral orientation. The evolution of P-wave velocity anisotropy is related to closing and reopening of microcracks.

 

Keywords: Velocity anisotropy; Anisotropy reversal; Triaxial experiment; PFC2D; Sandstone

 

[1] Li, X., Lei, X. & Li, Q. 2018. Response of Velocity Anisotropy of Shale Under Isotropic and Anisotropic Stress Fields. Rock Mechanics and Rock Engineering, 51, 695-711, http://doi.org/10.1007/s00603-017-1356-2

[2] Li, X., Lei, X. & Li, Q. 2016. Injection-induced fracturing process in a tight sandstone under different saturation conditions. Environmental Earth Sciences, 75, 1466, http://doi.org/10.1007/s12665-016-6265-2

[3] Shen, H., Li, X., Li, Q. & Wang, H. 2020. A method to model the effect of pre-existing cracks on P-wave velocity in rocks. Journal of Rock Mechanics and Geotechnical Engineering, 12, 493-506, http://doi.org/10.1016/j.jrmge.2019.10.001

[4] Li, X., Lei, X., Li, Q. & Chen, D. 2021. Influence of bedding structure on stress-induced elastic wave anisotropy in tight sandstones. Journal of Rock Mechanics and Geotechnical Engineering, -, http://doi.org/10.1016/j.jrmge.2020.06.003

How to cite: Shen, H., Li, X., and Li, Q.: Experiment and simulation of stress-dependent P-wave velocity anisotropy in sandstone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1485, https://doi.org/10.5194/egusphere-egu21-1485, 2021.

EGU21-10495 | vPICO presentations | ERE4.1

Enhanced heavy oil recovery and CO2 storage in a reservoir with high-water-cut: laboratory to field

Xiang Zhou, Yongsheng Tan, and Qi Jiang

In this study, in order to enhance heavy oil recovery in the heavy oil reservoir with a high-water-cut after water flooding process, experimental and numerical simulation studies are conducted. In the experimental studies, firstly, the properties of the heavy oil-CO2 system were measured under different saturation pressures at the reservoir temperature. Secondly, to mimic the high-water-cut condition in the real reservoir, water flooding process was conducted for each core; then four long core experiments insist of one CO2 huff `n` puff process and three CO2 flooding processes were implemented. The CO2 huff `n` puff process is conducted to compare the production performance with that in the CO2 flooding process to optimize the method. Regarding the CO2 flooding process, different gas (pure CO2, flue gas) and different production categories (constant production pressure, pressure depletion) were applied to study the heavy oil production performance in the heavy oil reservoir with high-water-cut. The experimental results indicate that, the CO2 flooding coupling with pressure depletion process is the best choice to reduce the water-cut and enhance the heavy oil recovery, which is 41.84% of the original oil in place and the water-cut reduced to lower than 70%. In the numerical simulation studies, the WinProp module in CMG is applied to simulate the properties of the heavy oil-CO2 system, which is generated by recombining CO2 into heavy oil, and high agreement simulation results were obtained. Then the results of the optimized experiment were history matched using GEM module. Finally, the upscaling studied was conducted. The CO2 flooding processes are carried out in the studied reservoir to maximum the heavy oil recovery factor. Moreover, the CO2 storage ratio is studied using GEM model.

How to cite: Zhou, X., Tan, Y., and Jiang, Q.: Enhanced heavy oil recovery and CO2 storage in a reservoir with high-water-cut: laboratory to field, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10495, https://doi.org/10.5194/egusphere-egu21-10495, 2021.

EGU21-5148 | vPICO presentations | ERE4.1

Large-scale compressed air energy storage in porous media in a 100% renewable energy supply future

Firdovsi Gasanzade, Fahim Sadat, Ilja Tuschy, and Sebastian Bauer

Compressed air energy storage (CAES) in porous formations is one option to compensate the expected fluctuations in energy supply in future energy systems with a 100% share of renewable energy sources. Mechanical energy is stored as pressurized air in a subsurface porous formation using off-peak power, and released during peak demand using a turbine for power generation. Depending on share and type of renewable energy sources in the future, different storage capacities and storage power rates will have to be satisfied to compensate fluctuating nature of the renewable power supply. Therefore, this study investigates scenarios for subsurface compressed air energy storage using four potential future energy system development pathways. Because for CAES subsurface processes and power generation are strongly linked via reservoir pressure and flow rates, coupled power plant and geostorage model has to be developed and employed to evaluate potential operation conditions for such a storage technique.

In this study, a diabatic CAES is designed, with a three-stage compression and a two-stage expansion with heat recuperator in the power plant and a porous formation as a storage formation with 20 m thickness in an anticline trap structure at a depth between 700 and 1500 m. A withdrawal rate of 115 MW and a total stored energy of up to 348 GWh per year are derived from the future energy system scenarios. Scenario simulations are carried out by coupling the open-source thermal engineering TESPy code and the multiphase-multicomponent ECLIPSE flow simulator using highly fluctuating load profiles with a time resolution of one hour. In addition to the diabatic CAES, two adiabatic concepts are considered for the same geostorage configuration.

Results show that nine vertical storage wells are sufficient to deliver the target air mass flow rates required by the power plant during 98% of the year. Flow rate limitation occurs due to bottom hole pressure limits either during the injection or the withdrawal phases, depending on the specific load profile of the future energy systems, as well as the prior operation conditions. Thus, our scenario simulation shows that one porous media CAES site can cover all expected load profiles and balance the expected offsets between energy demand and energy supply up to the GWh scale. Balancing of the energy system at the national level can be achieved by up-scaling of the results obtained in this study.

How to cite: Gasanzade, F., Sadat, F., Tuschy, I., and Bauer, S.: Large-scale compressed air energy storage in porous media in a 100% renewable energy supply future, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5148, https://doi.org/10.5194/egusphere-egu21-5148, 2021.

The role of hydrogen as a potential renewable energy storage vector is essential for carbon emission reduction and a corresponding low-carbon renewable energy supply and demand in the future. The geological storage of hydrogen is central to a steady transition from carbon emitting fuels to renewable energy resources as an off-grid energy supply, supporting intermittencies from renewable technologies. The depletion of gas reservoirs (DGRs) creates potential for hydrogen storage, whilst porous aquifers (PAs) and salt caverns (SCs) also provide the necessary conditions for potential hydrogen storage plays. However, the containment of hydrogen is challenging, and leakage from store has adverse economic and environmental consequences. 

This project has examined and investigated risks associated with the components required for subsurface storage in three geological scenarios, and their relevant influences on the assessment of the long-term security of hydrogen in the subsurface. The construction of a database using a Features Events, Process (FEP) model comprising all concomitant aspects of hydrogen storage enabled the identification of key factors contributing to hydrogen leakage from geological stores. Information on the geological storage of hydrogen is sparse, hence the various risks associated with geological storage facilities were drawn from other subsurface operations (Nuclear Waste Storage and CO2 storage) to develop a generic FEP database. The final database contains a comprehensive overview of risks involved in a hydrogen storage operation and forms the basis of an expert elicitation.

The identified risks were then incorporated within an expert elicitation exercise to quantify and analyse risks in terms of the severity of leakage extent, the probability of their occurrence over time, and those of high impact. Discrepancies in expert opinion emphasised high uncertainty risks that may contribute to leakage across the three subsurface storage facilities. The assessment of risks across three scenarios enabled comparisons of the confidence in their security to be made. A total of 12 risks were highly ranked in impact and uncertainty across two or more geological scenarios and were put forward for enhanced prevention, operation and monitoring strategies. 

How to cite: Fuentes Tobin, G. E., Edlmann, K., and Heinemann, N.: Features, Events and Processes of geological hydrogen storage: Which pose highest risk for leakage?  A three-scenario analysis: Depleted Gas Fields, Porous Aquifers and Salt Caverns., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12754, https://doi.org/10.5194/egusphere-egu21-12754, 2021.

EGU21-16280 | vPICO presentations | ERE4.1

Nonthermal Plasma for Hydrogen Production 

Meisam Babaie, Ibrahim Bakoji, Rasool Erfani, and Amir Nourian

Methane (CH4) and carbon dioxide (CO2) and these greenhouse gases together represent 29 gigatons of emission per year, with a projection of 36 to 43 gigatons/year. At these levels in the atmosphere, these gases contribute to the global climate change. Innovative methods need to be developed that will decrease these emissions to zero. Plasma reforming of natural gas that converts CO2 and CH4 to hydrogen fuel can be an effective solution since it contributes towards reduction of two major greenhouse gases as well as producing clean hydrogen fuel. Plasma is an ionised gas consisting of a mixture of equal number of positively charged ions and negatively charged electrons produced by an electric field. Reforming with plasma is conducted using a dry reforming reaction, with plasma or catalyst and CH4 and CO2 are used to produce Syngas with other products such as hydrogen (H2). In this study, the applicability of non-thermal plasma for hydrogen production is discussed and the benefits and challenges are thoroughly investigated. The results of this work can help in developing the awareness of the industries and other relevant stakeholders towards the potential of plasma on hydrogen production and CO2 reduction.

How to cite: Babaie, M., Bakoji, I., Erfani, R., and Nourian, A.: Nonthermal Plasma for Hydrogen Production , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16280, https://doi.org/10.5194/egusphere-egu21-16280, 2021.

EGU21-10952 | vPICO presentations | ERE4.1

Assessing the feasibility of large-scale hydrogen storage in salt caverns on the UKCS using 3D seismic data

Hector Barnett, Mark T. Ireland, and Sanem Acikalin

The energy industry in the UK faces a challenge to decarbonize to support reaching net zero CO2 emissions by 2050. In nearly all scenarios emission reductions are characterized not only by energy demand reductions, but also the decarbonization of electricity and heating. The use of hydrogen as a replacement for natural gas is one proposed solution, where renewable hydrogen is either blended into the gas grid or used directly. To ensure continuity of supply large scale hydrogen storage will be needed to meet this demand.

Hydrogen has been stored in small volumes (<25GWh) in salt caverns at various locations onshore in the United Kingdom since 1959. These caverns store hydrogen for industrial usage. In order to meet the demand for energy related hydrogen storage an increasing number of new and potentially larger storage options will be needed. Engineering of larger salt caverns for a hydrogen energy system will require thick salt formations which are optimally located with respect to both the hydrogen production facility and the end use. The Permian and Triassic salts deposits of both the Southern North Sea and the East Irish Sea offer vast areas for potential cavern development. Previous studies have described the landscape of underground gas storage onshore and offshore the UK, but to date there have been few detailed geophysical and geological studies on the hydrogen storage potential offshore.

The identification of suitable storage sites requires an understanding of the subsurface geology including potential structural discontinuities which could compromise the integrity of storage sites and be pathways for leakage. This analysis of hydrogen storage sites will utilise extensive existing modern 3D seismic data and well data taken from the Southern North Sea. We describe the geological setting of the Permo-triassic salt in the SNS in relation to the potential to develop salt cavern storage and develop play risk assessment maps. These risk assessment maps form part of a play fairway analysis workflow in order to identify the optimal storage sites for hydrogen on the UCKS.

How to cite: Barnett, H., Ireland, M. T., and Acikalin, S.: Assessing the feasibility of large-scale hydrogen storage in salt caverns on the UKCS using 3D seismic data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10952, https://doi.org/10.5194/egusphere-egu21-10952, 2021.

EGU21-2655 | vPICO presentations | ERE4.1

Carbon isotopes of vegetation as proxy of natural or anthropogenic gas seeps

Wolfram Kloppmann, Frédérick Gal, Michaela Blessing, and Christine Fléhoc

There is evidence that the emission of 14C –free CO2 during volcanic emissions creates a bias for radiocarbon dating of volcanic events (Holdaway et al., 2018), showing that integration of “dead” carbon by vegetation can serve as indicator of geogenic gas emissions. We tested 14C activities and stable carbon isotope ratios of tree rings and herbal vegetation in the proximity of a natural gas seep in the French Subalpine chains where both methane (<90% in the main vent) and CO2 (<11%) are present (Gal et al., 2018). Wood samples were taken from two alder trees, at different distances and directions from the main gas vent. Grass leaves and roots (Carex sp.) were analysed for two spots with contrasting soil methane concentrations and fluxes within the zone of diffuse gas emanation around the main vent (Gal et al., 2019). Grass and wood samples show contrasting isotope compositions depending on their species, age, and position with respect to the gas seep, some with 14C activities significantly lower than present day values. This offers perspectives of using vegetation carbon isotopes as proxies for present and past gas emanations, including man-induced gas leaks, e.g. from gas storage or natural gas exploitation facilities.

This research was co-funded by the EU H2020 Programme (grant 764531 – SECURe “Subsurface Evaluation of Carbon Capture and Storage and Unconventional Risk”)

Gal F., Kloppmann W., Proust E., Humez P. (2018) Gas concentration and flow rate measurements as part of methane baseline assessment: Case of the Fontaine Ardente gas seep, Isère, France. Applied Geochemistry, 95, 158-171.

Gal F., Proust E., Kloppmann W. (2019) Towards a Better Knowledge of Natural Methane Releases in the French Alps: A Field Approach. Geofluids, 2019, 1-16.

Holdaway R. N., Duffy B., Kennedy B. (2018) Evidence for magmatic carbon bias in 14C dating of the Taupo and other major eruptions. Nature Communications, 9, 4110.

How to cite: Kloppmann, W., Gal, F., Blessing, M., and Fléhoc, C.: Carbon isotopes of vegetation as proxy of natural or anthropogenic gas seeps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2655, https://doi.org/10.5194/egusphere-egu21-2655, 2021.

CO2 geological storage (CGS) technology is currently one of the best choices for large-scale low-cost CO2 emission reduction in the world, and the primary issue of CO2 geological storage is the optimization of the selection of favorable areas for CO2 storage. In view of the insufficient research on the optimization of favorable areas for CO2 geological storage in the Majiagou Formation in the Ordos Basin, this study aims to determine the boundaries of the CO2 geological storage area in the Ordos Basin by studying the temperature and pressure conditions, reservoir conditions, structural conditions, caprock conditions , and the salinity conditions of the formation water using a large amount of geological, drilling, geophysical and experimental laboratory data. After the regional boundary of the CO2 geological sequestration is determined, it can be optimized and CO2 geological sequestration can be conducted in the areas that have favorable reservoir conditions, are relatively close to CO2 emission sources, have a high degree of exploration, have an appropriate formation depth and have a small impact on the development of other mineral resources. The results show that (1) the areas suitable for the geological storage of CO2 in the Ordos Basin are located in the distribution area of the Majiagou Formation in the Tianhuan Depression, except for the missing areas in the central paleo-uplift. The ares to the east of the Baiyanjing-Shajingzi fault, to the north of the northern margin of the Weibei uplift, to the west of the Yellow River fault, and to the south of the Yimeng uplift are suitable for CO2 geological storage. (2) Based on the three aspects of technology, safety, and economic feasibility, it was determined that the Wushenqi-Jingbian-Yan'an karst slope area (I1) is the best CO2 geological storage area, and the Yulin-Mizhi karst basin area (I2) is a favorable area for the geological storage of CO2 in the Ordos Basin.

 

How to cite: Lu, P., Jiao, Z., and Zhou, L.: Optimal Selection of Favorable Areas for CO2 Geological Storage in the Majiagou Formation in the Ordos Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15, https://doi.org/10.5194/egusphere-egu21-15, 2021.

EGU21-10063 | vPICO presentations | ERE4.1

Combining analytical and numerical modelling of gas flow in depleted natural gas fields to identify potential Underground Hydrogen Storage (UHS) sites in the Netherlands 

Joaquim Juez-Larre, Cintia Gonçalves Machado, Hamid Yousefi, and Remco Groenenberg

The Netherlands is seeking ways to integrate large amounts of renewable energy production capacity (wind/solar) into its energy system, in order to reduce CO2 emissions and decrease dependency on future energy imports. Currently the Netherlands uses underground gas storage (UGS) to provide flexibility to its natural gas system, and secure supply during the winter season. However, hydrogen is considered to be a potential candidate to substitute natural gas, because it is a versatile energy carrier that can be produced from renewable electricity and be used as a CO2-neutral fuel and feedstock. It can also be stored in large amounts underground. Storage of compressed hydrogen in salt caverns is a proven technology, with single-cavern storage capacities in the range of 10-100 million m3. Yet some studies on the future Dutch energy system suggest much larger volumes of hydrogen storage may be required (1 to 50 billion m3). This large storage capacity can only be practically achieved in depleted natural gas fields. UHS in gas fields is not yet a proven technology. Only some pilot projects have successfully injected small amounts of hydrogen in some available underground reservoirs. In order to make possible future development of UHS, screening methodologies are needed for the readily identification and characterization of potential underground candidates. In this study, we develop a methodology that allows assessing UHS performances of large portfolios of underground reservoirs. As a case study we use the entire portfolio of natural gas fields in the Netherlands, including three UGSs.

In a first stage of our study, we conducted a nodal analysis of the Inflow Performance Relationship (IPR) and the vertical flow performance (outflow) curves, in order to obtain a first order estimate of the potential UHS performance for each field (e.g. rates of injection/withdrawal, working/cushion gas volumes and ranges of working pressures). Results show that withdrawal performances of wells in an UHS can be 2-3 times higher than those in an UGS. High bottom-hole drawdowns and erosional velocities in the production tubing may however significantly restrict the potential flow of hydrogen. Furthermore, the working gas volume of an UHS may contain up to four times less energy than that of an UGS, if operated at the same ranges of working pressures. Secondly, we used Eclipse 300, and the geological Petrel model of some of the best candidates, to conduct a more detail analysis of their potential UHS performances and the controlling factors. For that we ran consecutive injection/withdrawal cycles at different timescales (daily-weekly-monthly), and distinct working pressure ranges and types of cushion gas (e.g. nitrogen/hydrogen). Results allow to determine the efficiency of the different operational strategies and the number of wells required to match the expected future demands of hydrogen in the Netherlands. They also show the degree of hydrogen mixing with the residual and cushion gas during each cycle. Therefore our analytical/numerical modelling approach provides a good methodology to quantify and rank potential UHS reservoir candidates, and a means to classify the potential storage capacity of the entire portfolio.

How to cite: Juez-Larre, J., Gonçalves Machado, C., Yousefi, H., and Groenenberg, R.: Combining analytical and numerical modelling of gas flow in depleted natural gas fields to identify potential Underground Hydrogen Storage (UHS) sites in the Netherlands , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10063, https://doi.org/10.5194/egusphere-egu21-10063, 2021.

EGU21-1990 | vPICO presentations | ERE4.1

A novel CO2 storage concept that reduces the leakage risk

Victor Vilarrasa and Francesco Parisio

Geologic carbon storage is needed to reach carbon neutrality and eventually achieve negative emissions. In the classical concept of storing CO2 in deep sedimentary aquifers, supercritical CO2 has a lower density than the resident brine. CO2 is therefore buoyant and the safety and effectiveness of the storage concept rely on the caprock sealing capacity to prevent CO2 leakage. To reduce the risk of CO2 leakage and widen the CO2 storage options, we propose an innovative concept that consists in injecting CO2 in reservoirs where the temperature and pressure of the resident brine are above the critical point ( 373.95 ºC and 22.064 MPa for pure water). At such conditions, which can be found at depths between 3 to 5 km in volcanic areas, CO2 is denser than the resident water and thus, sinks. The sinking tendency reduces the risk of CO2 leakage to the surface even in case of damaged or absent caprock. CO2 storage in supercritical reservoirs can potentially become an additional option to the existing storage concepts aimed at significantly reduce CO2 emissions. We estimate that every 100 wells drilled into supercritical reservoirs could store between 50 to 500 Mt/yr of CO2.

 

REFERENCES

Parisio, F. and Vilarrasa, V. (2020). Sinking CO2 in supercritical reservoirs. Geophysical Research Letters, e2020GL090456.

How to cite: Vilarrasa, V. and Parisio, F.: A novel CO2 storage concept that reduces the leakage risk, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1990, https://doi.org/10.5194/egusphere-egu21-1990, 2021.

EGU21-2478 | vPICO presentations | ERE4.1

A mechanistic interpretation of potential CO2 leakage through shaly caprocks

Iman Rahimzadeh Kivi, Victor Vilarrasa, and Roman Makhnenko

Global warming brought upon by anthropogenic CO2 emissions into the atmosphere is causing significant impacts on the Earth and represents one of the major concerns of the current century. To be controlled, it is widely accepted that huge amounts of CO2 at the gigatonne scale have to be captured and injected back into the underground in a process known as Carbon Capture and Storage (CCS). As CO2 is less dense than the in-situ brine, it tends to flow upward out of the storage reservoir by buoyancy and the injection overpressure. A laterally-extensive and thick non-fractured caprock possessing low permeability and high entry capillary pressure is commonly expected to keep CO2 within the host reservoir. However, the potential risks of CO2 leakage through the intact caprock need thorough assessment. This contribution brings together experimental observations and numerical simulations to inspect the sealing capacity of an intact shaly caprock and render an in-depth understanding of the governing flow mechanisms. Reproducing the subsurface conditions of CO2 intrusion and flow through the caprock, breakthrough experiments are conducted on Opalinus Clay as a representative caprock for CO2 storage. The adopted approach consists of injecting supercritical CO2 into the caprock sample lying between two permeable porous disks, all initially saturated with brine. Supplementary experiments are also performed to characterize the pore structure and hydromechanical properties of the specimen. The extracted properties are used to parameterize a two-phase flow model in deformable porous media and simulate the breakthrough experiment carried out on Opalinus Clay to make a mechanistic interpretation of the experimental observations. Simulation results reveal three concomitant CO2 flow mechanisms into and through the caprock: molecular diffusion, bulk volumetric advection, and transported CO2 dissolved in the advected brine. It is inferred that the high entry pressure and low effective permeability prevents free phase CO2 penetration deep into the caprock. The drainage path is followed by the imbibition of brine back into the pores from the downstream until recovering the initial state of being completely saturated with brine. While the contribution of brine advection to CO2 transport is found to be negligible, we find that CO2 flow through the caprock is mainly governed by molecular diffusion, whose effects on the potential leakage of CO2 during geological time scales have to be taken into account.

How to cite: Rahimzadeh Kivi, I., Vilarrasa, V., and Makhnenko, R.: A mechanistic interpretation of potential CO2 leakage through shaly caprocks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2478, https://doi.org/10.5194/egusphere-egu21-2478, 2021.

EGU21-9127 | vPICO presentations | ERE4.1

Compositional modelling of impure gas injection into saline aquifers with the MUFITS simulator

Andrey Afanasyev and Elena Vedeneeva

We present a recent extension of the MUFITS reservoir simulator for numerical modelling of multicomponent gas injection into saline aquifers. The extension is based on the compositional module of the simulator that implements a conventional cubic equation of state (EoS) for predicting phase equilibria of reservoir fluids [1]. Now, the module is supplemented with a new library of EoS coefficients for accurate modelling of CO2, N2, CH4, H2, O2, H2S, and other hydrocarbon components solubility in NaCl brine. In general, we follow the approach proposed by Søreide and Whitson [2] for modelling aqueous solutions, which involves a different and dependent on brine salinity binary interaction coefficients for aqueous and non-aqueous phases. However, we also use several published modifications to the EoS coefficients that were originally proposed in [2] to improve prediction of the mutual solubilities.

The extension is validated against 3-D benchmark studies of pure supercritical CO2 injection into saline aquifers. Also, we consider two more complicated injection scenarios to demonstrate potential applications of the new development. First, we simulate impure CO2 injection into a saline aquifer. We show that even a small amount of air (N2 and O2) in the injected gas results in a significantly more rapid spreading of the gas plume. Second, we consider a 3-D study of CO2 injection into subsurface natural gas storage aiming at the cushion gas substitution with supercritical CO2. The mechanical dispersion in the porous medium is accounted for an accurate modelling of CO2 and CH4 mixing. We simulate the propagation of CO2 in the storage by modelling several seasons of natural gas (CH4) injection and extraction.

The authors acknowledge funding from the Russian Science Foundation under grant # 19-71-10051.

References

1. Afanasyev A.A., Vedeneeva E.A. (2020) Investigation of the efficiency of gas and water Injection in an oil reservoir. Fluid Dyn. 55(5), 621-630.

2. Søreide I., Whitson C.H. (1992) Peng-Robinson predictions for hydrocarbons, CO2, N2, and H2S with pure water and NaCl brine. Fluid Phase Equil. 77, 217-240.

How to cite: Afanasyev, A. and Vedeneeva, E.: Compositional modelling of impure gas injection into saline aquifers with the MUFITS simulator, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9127, https://doi.org/10.5194/egusphere-egu21-9127, 2021.

EGU21-1656 | vPICO presentations | ERE4.1

Investigation of the effect of stress states on hydro-mechanical behaviors of reservoir rock under fluid injection

Qi Li, Miao He, Michael Kühn, Xiaying Li, and Liang Xu

Injecting fluid into the formation is an effective solution for improving the permeability and production of a target reservoir. The evaluation of economy and safety of injection process is a challenging issue faced in reservoir engineering [1-2]. As known, the relative magnitude and direction of the principal stresses significantly influence the hydro-mechanical behavior of reservoir rock during fluid injection. However, due to the limitations of current testing techniques, it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions, e.g. triaxial extension stress states [3]. To this end, a series of numerical simulations were carried out on reservoir rock to study the hydro-mechanical changes under different stress states during fluid injection. In this modelling, the saturated rock is first loaded to the target stress state under drainage conditions, and then the stress state is maintained and water is injected from the top end to simulate the reservoir injection process. Particular attention is paid to the difference in hydro-mechanical changes under triaxial compression and extension stresses. This includes the difference of the pore pressure propagation, mean effective stress, volumetric strain, and stress-induced permeability. The numerical results demonstrate that the differential stress will significantly affect the hydro-mechanical behavior of target rock, but the degree of influence is different under the two triaxial stress states. The hydro-mechanical changes caused by the triaxial compression stress states are generally greater than that of extension, but the difference decreases with increasing differential stress, indicating that the increase of the differential stress will weaken the impact of the stress state on the hydro-mechanical response. This study can deepen our understanding of the stress-induced hydro-mechanical coupling process in reservoir injection engineering.

Keywords: Reservoir injection; Subsurface flow; Hydro-mechanical coupling; Stress state; Triaxial experiment modelling

[1] Li, X., Lei, X. & Li, Q. 2016. Injection-induced fracturing process in a tight sandstone under different saturation conditions. Environmental Earth Sciences, 75, 1466, http://doi.org/10.1007/s12665-016-6265-2

[2] Yang, D., Li, Q. & Zhang, L. 2016. Propagation of pore pressure diffusion waves in saturated dual-porosity media (II). Journal of Applied Physics, 119, 154901, http://doi.org/10.1063/1.4946832

[3] Xu, L., Li, Q., Myers, M., Tan, Y., He, M., Umeobi, H.I. & Li, X. 2021. The effects of porosity and permeability changes on simulated supercritical CO2 migration front in tight glutenite under different effective confining pressures from 1.5 MPa to 21.5 MPa. Greenhouse Gases: Science and Technology, http://doi.org/10.1002/ghg.2043

How to cite: Li, Q., He, M., Kühn, M., Li, X., and Xu, L.: Investigation of the effect of stress states on hydro-mechanical behaviors of reservoir rock under fluid injection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1656, https://doi.org/10.5194/egusphere-egu21-1656, 2021.

EGU21-9894 | vPICO presentations | ERE4.1

Geochemistry of Geological Hydrogen Storage in Sandstone Reservoirs

Aliakbar Hassanpouryouzband, Katriona Edlmann, and Mark Wilkinson

To enable a fast transition of the global energy sector towards operation with 100% renewable and clean energy technology, the geological storage of hydrogen in depleted gas fields or salt caverns has been considered as a strong candidate for the future energy storage required for limiting global warming to well below 2 °C, as agreed under the Paris Agreement. As such, understanding the impact of injected hydrogen on the geochemical equilibrium in these storage reservoirs is critical. Here, using our bespoke high pressure/temperature batch reaction vessels we investigate the potential effects of hydrogen injection into 3 different sandstones reservoirs.  These experiments were conducted at reservoir temperature and at different injection pressures from 1 to 20 MPa with salinities from 0 to 10 weight% over different time periods from 1 to 8 weeks.  Our experiments reveal that there is no hydrogen-associated geochemical reaction for the selected sandstones. Although changing reservoir pressure slightly affected the mineral dissolution equilibria at ppm level for hydrogen injection scenarios, the fluctuations of mineral dissolution in water associated with pressure change have a negligible influence on the efficiency of geological hydrogen storage.  Therefore, based on the analysis of water chemistry before and after the mentioned experiments, we demonstrate that from geochemical point of view geological storage of hydrogen in these sandstone reservoirs is safe and we don’t expect any hydrogen loss due to geochemical reactions. 

How to cite: Hassanpouryouzband, A., Edlmann, K., and Wilkinson, M.: Geochemistry of Geological Hydrogen Storage in Sandstone Reservoirs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9894, https://doi.org/10.5194/egusphere-egu21-9894, 2021.

EGU21-7738 | vPICO presentations | ERE4.1

Compositional simulation of hydrogen storage in a depleted gas field

Jonathan Scafidi, Laurent Schirrer, Isabelle Vervoort, and Niklas Heinemann

UK natural gas demand is 2-4 times that of electricity and characterised by seasonal differences in demand of almost triple in the winter with larger spikes during extreme cold weather events. This makes any decarbonisation effort reliant on its ability to handle these large changes in demand. Conversion of the gas supply to hydrogen is the most promising solution. To facilitate this, large-scale underground storage will be required in the order of 150 TWh or 40 days’ worth of supply.

Subsurface gas storage in porous rocks requires a proportion of the gas to remain in the reservoir to maintain the pressure required for the minimum economic flow rate from the wells. This is called the cushion gas requirement. In the case of a hydrogen storage reservoir the use of a cheaper cushion gas, such as CO2 or N2, is the subject of much research.

We investigate the possibility of using natural gas within a partially depleted gas reservoir as cushion gas. We will present the results of a compositional simulation of seasonal hydrogen storage over a 20 year period in a closed reservoir. The study shows that natural gas has potential as a cushion gas, in this case achieving greater than 95% hydrogen recovery factors with minimal amounts of mixing in the reservoir. Use of natural gas as cushion gas also reduces the risk of water coning which can lead to loss of hydrogen.

Although these results are promising, the study highlights several key areas that need further investigation to improve the reliability of future simulations. These include defining relative permeability curves for hydrogen, refinement of how simulators handle viscosity equations, and a greater understanding of hydrogen well engineering. All of these factors will influence estimates of the hydrogen capacity of a porous rock reservoir.

How to cite: Scafidi, J., Schirrer, L., Vervoort, I., and Heinemann, N.: Compositional simulation of hydrogen storage in a depleted gas field, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7738, https://doi.org/10.5194/egusphere-egu21-7738, 2021.

EGU21-6762 | vPICO presentations | ERE4.1

Saturated carbon dioxide nanofluids enhanced oil recovery in carbonate reservoir cores using nuclear magnetic resonance

Yongsheng Tan, Qi Li, Liang Xu, Xiaoyan Zhang, and Tao Yu

The wettability, fingering effect and strong heterogeneity of carbonate reservoirs lead to low oil recovery. However, carbon dioxide (CO2) displacement is an effective method to improve oil recovery for carbonate reservoirs. Saturated CO2 nanofluids combines the advantages of CO2 and nanofluids, which can change the reservoir wettability and improve the sweep area to achieve the purpose of enhanced oil recovery (EOR), so it is a promising technique in petroleum industry. In this study, comparative experiments of CO2 flooding and saturated CO2 nanofluids flooding were carried out in carbonate reservoir cores. The nuclear magnetic resonance (NMR) instrument was used to clarify oil distribution during core flooding processes. For the CO2 displacement experiment, the results show that viscous fingering and channeling are obvious during CO2 flooding, the oil is mainly produced from the big pores, and the residual oil is trapped in the small pores. For the saturated CO2 nanofluids displacement experiment, the results show that saturated CO2 nanofluids inhibit CO2 channeling and fingering, the oil is produced from the big pores and small pores, the residual oil is still trapped in the small pores, but the NMR signal intensity of the residual oil is significantly reduced. The final oil recovery of saturated CO2 nanofluids displacement is higher than that of CO2 displacement. This study provides a significant reference for EOR in carbonate reservoirs. Meanwhile, it promotes the application of nanofluids in energy exploitation and CO2 utilization.

How to cite: Tan, Y., Li, Q., Xu, L., Zhang, X., and Yu, T.: Saturated carbon dioxide nanofluids enhanced oil recovery in carbonate reservoir cores using nuclear magnetic resonance, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6762, https://doi.org/10.5194/egusphere-egu21-6762, 2021.

Adsorptive gas transport (such as CO2) in subsurface through coal matrix alters the dimension of pores and cleats and results in reduction of coal formation permeability. We propose thermal-cracking could be a potential method to increase the coal-permeability. We tested a number of coal samples from Bansgara colliery, India and compared the permeability and strength of the air-dried vs. thermally-cracked samples. Samples were heated at 280°C for 36 hours and then quickly chilled to produce thermal-cracks mostly along the bedding planes, which were confirmed by microscopic study. We tested the mechanical strength keeping the bedding planes perpendicular (α=90°) and parallel (α=0°) to the loading directions.

The peak compressive strengths of air-dried samples from room to 15 MPa confinement were noted as 14-44 MPa and 12-37 MPa for α=90° and 0° conditions, respectively. The mechanical behavior of the thermally-cracked samples, interestingly, was not straight forward. The peak compressive strengths of thermally-cracked samples were comparable to those of air-dried samples when α=90°. Interestingly, when α=0°, the peak-strength dropped by 82% at room pressures and 67% at 15 MPa confining pressures with respect to the air-dried samples under similar conditions.  The stress strain profile of the deforming coal samples showed initial shallow slopes indicating pore closure, and then a steep slope in the elastic limit. Most of the samples were brittle and failed at the yield point. Few samples showed slight ductile signatures and plastic flow at higher confinements. Axial splitting was observed in samples at low confinements. At higher confinements, fracture pattern was more dominated by shear cracks as compared to tensile cracks. Our results also show that porosity of the samples increases by 30-35%. Gas permeability (N2 used as a probing gas) of the thermally cracked samples at 6.5 MPa confining pressure and 1 MPa pore pressures are 1.31 and 4 md for α=90° and 0° conditions, respectively. Permeability of air-dried samples at similar experimental conditions are 0.2 and 0.7 md for α=90° and 0° conditions, respectively.

We interpret that the loading sub-parallel thermal-cracks further opened and connected each-other during loading and therefore failed at lower stresses when α=0°. The interconnected pore and cleat network also resulted in permeability enhancement. Interlocking network of coal matrix resist the deformation of coal, and thermal cracks penetrate in coal matrix to reduce the entanglement of macerals in coal and lower its mechanical strength. In contrary, under α=90° loading conditions, the horizontal thermal cracks closed due to perpendicular load rather than opening further, and thus in those samples the strength reduction is less prominent. We conclude that thermal-cracking is a prospective method in enhancing the subsurface coal-permeability of deep-seated coal seams from micro to millidarcy. However, it must be ensured that the load imparted by the wellbore (injecting or recovery wells) on thermally cracked coal reservoir should act perpendicular to its bedding.

How to cite: Mukherjee, M., Sikdar, A., and Misra, S.: Compressive strength and permeability of thermally-cracked coals: implications for gas storage and transport in subsurface coal seams, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15482, https://doi.org/10.5194/egusphere-egu21-15482, 2021.

ERE4.3 – Towards a safe nuclear waste repository – assessment of barrier integrity, geoscientific, technological, societal and regulatory challenges and approaches

EGU21-16491 | vPICO presentations | ERE4.3

Multi-criteria site assessment process for candidate deep geological repository sites: Case study from the Czech Republic 

Lukas Vondrovic, Jaromir Augusta, Antonin Vokal, Katerina Konopacova, Eva Popelova, and Jozef Urik

The future deep geological repository for radioactive waste in the Czech Republic will be constructed in a suitable crystalline rock mass around 500 metres below the earth’s surface. The commencement of operation is planned for 2065. The current DGR development phase is devoted principally to the determination of the optimum disposal concept and the selection of the most suitable site. A total of nine potential sites have been assessed with the aim of reducing their number to four.

The data set subjected to assessment included site descriptions from the geological point of view (3D geological and hydrogeological model), and long-term site stability (seismotectonic, climate and erosion) and geomechanical data. A further assessed dataset included information on construction issues and on the evaluation of both environmental characteristics and the presence of groundwater resources. All the assessed characteristics were derived from surface-based exploration without the need for borehole drilling.

The key criteria reflected the three main areas of concern i.e. long-term and operational safety (including geological and hydrogeological indicators), technical feasibility and environmental impacts. The assessment of the sites was performed in two stages. The first stage involved the assessment of the probability of fulfilling the exclusion criteria (total 26), while the second stage involved the mutual comparison of the sites in terms of the defined key criteria (total of 13, divided into 38 indicators). The second stage involved the determination of weightings for the various criteria and indicators via the application of the SAATY method for the expert comparison of the significance of criteria. This method distinguished between relatively strongly weighted and less weighted criteria. The sites were graded with respect to the value estimation of the criteria; moreover, the grading of the sites considered various types of data.

A total of eight calculations were performed for five scenarios using various procedures for the estimation of the weightings and for data normalisation purposes. The first assessment stage indicated that all the sites fulfilled the DGR site assessment methodology requirements. The second stage, which comprised the assessment of the comparison of the site calculations (assessment grades) for each of the sites, was based on the levels of significance of the indicators and criteria and the resulting representative values for each site. The results of the subsequent comparison calculations indicated that the same four sites always occupied the first four positions with only minor variations in the order. The differences in the gradings of the four most suitable sites and the four relatively less suitable five sites ranged between 11% and 17.8% (between the fourth and fifth sites), which convincingly differentiated between the two groups of sites. One site was always in last position according to the calculations. In compliance with the assessment results, the four  sites were subsequently recommended to the Government of the Czech Republic for further follow-up research and analysis. Those sites that were not recommended for the next stage of research will continue to be considered as reserve (i.e. backup) sites.

How to cite: Vondrovic, L., Augusta, J., Vokal, A., Konopacova, K., Popelova, E., and Urik, J.: Multi-criteria site assessment process for candidate deep geological repository sites: Case study from the Czech Republic , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16491, https://doi.org/10.5194/egusphere-egu21-16491, 2021.

EGU21-5114 | vPICO presentations | ERE4.3

Deep Borehole Repository of HLW and SF - State of knowledge by SITEX.Network

Nadja Zeleznik, Muriel Rocher, Colin Wales, Frédéric Bernier, Doncho Karastanev, and Wilfried Pfingsten

Many countries develop geological disposal projects for high-level radioactive waste (HLW) and/or spent fuel (SF) when considered as waste. The most widely selected option is the deep geological repository (DGR) concept, a mined repository with galleries located underground in geological layers into which packaged waste would be placed; the sites for such DGR have been selected in Finland, France and Sweden, and a site selection process is on-going in several other countries, such as in the United Kingdom, Germany and Switzerland.

As an alternative concept to the DGR, the deep borehole repository (DBR) concept, where waste packages are placed into single boreholes, relies on a similar safety strategy: confining and isolating the waste from the biosphere and surface natural phenomena in order to respectively rely on the geological environment to ensure long term passive safety and reduce the risk of human intrusion. The concept of DBR was first considered in the 1950s, but was rejected until the 2000s as it was far beyond existing drilling capabilities among others, given the constraints for HLW and SF management.

New technical developments in the drilling field relaunched the interest of a safe management of HLW and SF based on DBR concept in several countries. Therefore, the SITEX.Network association developed an overview of the existing studies that have been published on the DBR concept with information on the concept itself, on deployment strategies and methods, on issues associated with requirements related to waste packages and borehole equipment, hydro-geology, disposal operation, backfilling and sealing, and finally on safety analyses. The main aim is to provide bibliographical overview providing the state of knowledge about the DBR concept, the technical solutions for its implementation or major obstacles evidenced as a basis to identify safety issues important to deal with in a Safety Case. This could be considered to identify for the future R&D as well. This paper discusses also the controversial issue of DBR trying to provide information from different viewpoints, like the design options, R&D programs required, societal concerns and regulatory needs.

How to cite: Zeleznik, N., Rocher, M., Wales, C., Bernier, F., Karastanev, D., and Pfingsten, W.: Deep Borehole Repository of HLW and SF - State of knowledge by SITEX.Network, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5114, https://doi.org/10.5194/egusphere-egu21-5114, 2021.

EGU21-12797 | vPICO presentations | ERE4.3

Uncertainty Chains in the Geological and Geotechnical Barriers of a HAW-disposal site

Volker Mintzlaff and Joachim Stahlmann

When projecting and planning a final high-level radioactive waste disposal site various uncertainties need to be addressed. A geological model is an abstraction of one possibility to interpret the exposed outcrops, drilling results and geophysical data. In numerical modelling the geological model is further simplified due to computational limitations. The behaviour of rocks is modelled with more or less complex constitutive models which are based upon laboratory experiments. Complex constitutive models have a huge range of input parameters, which rarely can be obtained completely by these experiments. The samples, which will be used in the laboratory experiments, are, as the data of the geological model, always a selection of drilling cores. For example, in a mechanical laboratory, harder rocks will be overrepresented in comparison to softer parts of the core.

Since the mentioned uncertainties are not avoidable many authors suggest that an open communication of these uncertainties can support the confidence of the public in the work of the professionals and as well as the projected development of the final disposal site. This contribution will present an overview of these uncertainties in the geological and geotechnical barriers of an final disposal site to discuss the relevance of these.

How to cite: Mintzlaff, V. and Stahlmann, J.: Uncertainty Chains in the Geological and Geotechnical Barriers of a HAW-disposal site, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12797, https://doi.org/10.5194/egusphere-egu21-12797, 2021.

EGU21-9429 | vPICO presentations | ERE4.3

Preliminary safety assessments in the high-level radioactive waste site selection procedure in Germany

Eva-Maria Hoyer, Christoph Behrens, Merle Bjorge, Julia Dannemann, Dennis Gawletta, Phillip Kreye, Thomas Lohser, Elco Luijendijk, Paulina Müller, Florian Panitz, Florian Schlüter, Tobias Wengorsch, and Wolfram Rühaak

The Federal Company for Radioactive Waste Disposal mbH (BGE mbH) is as Germans waste management organization responsible to implement the search for a site with the best possible safety for the disposal of high-level radioactive waste for at least one million years, following the amendments of the Repository Site Selection Act in 2017. The selection procedure is meant to be a participatory, transparent, learning and self-questioning process based on scientific expertise.

This contribution will provide an overview of the methodology of the forthcoming preliminary safety assessments as a major part of the next steps in the site selection procedure. This procedure overall consists of three phases with increasing level of detail for identification of the best site. The first phase consists of two steps. The objective of the first step was to determine sub-areas in the three considered host rocks, salt (halite), clay and crystalline rock, by applying legally defined exclusion criteria, minimum requirements and geoscientific weighing criteria. 90 sub-areas that cover approximately 54 % of the area of Germany were identified due to their general suitable geological conditions. The result was published in September 2020.

The second step of phase one is currently in progress and consists of representative preliminary safety assessments that aim to assess the safety of the repository system as well as its robustness. The requirements for the preliminary safety assessments in the site selection procedure are defined by a governmental directive released in October 2020. Representative preliminary safety assessments have to be performed for each sub-area and consist of the compilation of all geoscientific information relevant to the safety of a repository, the development of preliminary safety and repository concepts and the analysis of the repository system. In addition, a systematically identification and characterization of uncertainties has to be undertaken and the need for exploration, research and development must be determined. The application of the representative preliminary safety assessments as well as the following renewed application of geoscientific weighing criteria will lead to the identification of siting regions within the larger sub-areas of step one. These regions will be considered, first for surface-based geoscientific and geophysical exploration, including i.e. seismic exploration and drilling of boreholes. Subsequently the last phase of the site selection will proceed with subsurface exploration. Finally, all suitable sites will be proposed and the German government will decide the actual site. This process is expected to be finalized in 2031.

How to cite: Hoyer, E.-M., Behrens, C., Bjorge, M., Dannemann, J., Gawletta, D., Kreye, P., Lohser, T., Luijendijk, E., Müller, P., Panitz, F., Schlüter, F., Wengorsch, T., and Rühaak, W.: Preliminary safety assessments in the high-level radioactive waste site selection procedure in Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9429, https://doi.org/10.5194/egusphere-egu21-9429, 2021.

EGU21-15771 | vPICO presentations | ERE4.3

Significance of long-term climate evolution and associated impacts on the long-term safety of a high-level radioactive waste repository within the German siting process

Marc Wengler, Astrid Göbel, Eva-Maria Hoyer, Axel Liebscher, Sönke Reiche, Eike Völkner, and Wolfram Rühaak

According to the 'Act on the Organizational Restructuring in the Field of Radioactive Waste Disposal' the BGE was established in 2016. The amended 'Repository Site Selection Act' (StandAG) came into force in July 2017 and forms the base for the site selection by clearly defining the procedure. According to the StandAG the BGE implements the participative, science-based, transparent, self-questioning and learning procedure with the overarching aim to identify the site for a high-level radioactive waste (HLW) repository in a deep geological formation with best possible safety conditions for a period of one million years.

The German site selection procedure consists of three phases, of which Phase 1 is divided into two steps. Starting with a blanc map of Germany, the BGE completed Step 1 in September 2020 and identified 90 individual sub-areas that provide favorable geological conditions for the safe disposal of HLW in the legally considered host rocks; rock salt, clay and crystalline rock. Based on the results of Step 1, the on-going Step 2 will narrow down these sub-areas to siting regions for surface exploration within Phase 2 (§ 14 StandAG). Central to the siting process are representative (Phase 1), evolved (Phase 2) and comprehensive (Phase 3) preliminary safety assessments according to § 27 StandAG.

The ordinances on 'Safety Requirements' and 'Preliminary Safety Assessments' for the disposal of high-level radioactive waste from October 2020 regulate the implementation of the preliminary safety assessments within the different phases of the siting process. Section 2 of the 'Safety Requirements' ordinance provides requirements to evaluate the long-term safety of the repository system; amongst others, it states that all potential effects that may affect the long-term safety of the repository system need to be systematically identified, described and evaluated as “expected” or “divergent” evolutions. Additionally, the ordinance on 'Preliminary Safety Assessments' states in § 7, amongst others, that the geoscientific long-term prediction is a tool to identify and to evaluate geogenic processes and to infer “expected” and “divergent” evolutions from those. Hence, considering the time period of one million years for the safe disposal of the HLW and the legal requirements, it is essential to include long-term climate evolution in the German site selection process to evaluate the impact of various climate-related scenarios on the safety of the whole repository system.

To better understand and evaluate the influence of climate-related processes on the long-term safety of a HLW repository, climate-related research will be a part of the BGE research agenda. Potential research needs may address i) processes occurring on glacial – interglacial timescales (e.g. the inception of the next glaciation, formation and depth of permafrost, glacial troughs, sub-glacial channels, sea-level rise, orbital forcing) and their future evolutions, ii) effects on the host rocks and the barrier system(s) as well as iii) the uncertainties related to these effects but also to general climate models and predictions.

How to cite: Wengler, M., Göbel, A., Hoyer, E.-M., Liebscher, A., Reiche, S., Völkner, E., and Rühaak, W.: Significance of long-term climate evolution and associated impacts on the long-term safety of a high-level radioactive waste repository within the German siting process, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15771, https://doi.org/10.5194/egusphere-egu21-15771, 2021.

The political and social debate on nuclear energy in Germany has been characterized for many decades by a high potential for conflict and dissatisfaction. Especially the controversies surrounding the Gorleben salt dome gained international attention and changed the relationship between citizens and political decision-makers from the local to the national level. With the Repository Site Selection Act of 2013 (StandAG, first amendment in 2017) a new approach was chosen to implement a participative, inclusive and transparent search process for the best possible repository for high-level radioactive waste in Germany. In this context, a self-learning process was proclaimed, based on a white (unbiased) map, which should give citizens an active role. However, the first interim report of the Federal Company for Radioactive Waste Disposal and the publication of the colorful map, in which geologically suitable areas were identified on a large scale, already revealed a massive potential for conflict. Many citizens and activists who were already protesting against the Gorleben salt dome criticized in this early phase of the process, the lack of transparency and opportunities to have a say on the possible sitting regions.

To address this criticism, we want to provide an interactive map as an online platform that presents existing geographic data, that enables people to contribute spatially-located information (geological, on-surface), and thus a possibility for people to interact and participate regarding the possible siting regions. Therefore, we collect existing spatial data that is relevant to the ongoing process, such as possible siting regions (declared by the Federal Company for Radioactive Waste Disposal), nuclear power plants (active/inactive, research facilities, etc.), storage facilities (on-site, central, interim, etc.), historically relevant locations (places of protest, uranium enrichment & processing facilities, etc.) as well as basic data for orientation. We implement two possibilities for participatory interaction: (1) adding spatially-located notes that contain own experiences or local knowledge (e.g. reports, concerns, suggestions) and (2) initiating a platform for a spatially-located discussion. Against the background of transdisciplinary research, in an iterative process, we want to evaluate the participatory value of this application by consulting civic as well as scientific actors. We, therefore, employ focus groups with a transdisciplinary support group of citizens beforehand and surveys after using the application. For this panel we want to present our primary results from a first test with the aforementioned focus groups.

Aside from testing the suitability of such a mode of participation, we aim to analyze where problems emerge, and which information is necessary and/or might lead to conflict. Finally, we want to gain insight into how such modes of participation influence the quality of dialogue and how it contributes to the overall perception of a procedurally just process.

How to cite: Schwarz, L. and Bräuer, P.: Improving participation for the German search for a nuclear waste repository site: an interactive map as a transdisciplinary approach , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10969, https://doi.org/10.5194/egusphere-egu21-10969, 2021.

EGU21-13424 | vPICO presentations | ERE4.3

Deriving lumped parameters for DGR safety assessment by 3D transport model postprocessing

Milan Hokr and Jiří Landa

The safety assessment (SA) of the spent nuclear fuel repository is often based on lumped-parameter models (LPM) of radionuclide transport between the source term and the biosphere (under various terminology like a compartment model, or a channel model). It profits e.g. from computational efficiency when used with stochastic data. Useful property of LPM is intuitively clear influence of most of its parameters, in terms of “the larger/smaller the better”. On the other hand, some parameters are not clearly defined and their values depend on expert choice.

Gradual improvements of computing hardware and simulation software also allow using physically-based models on real geometry for SA application. Migration of radionuclides is simulated by means of groundwater flow and advective-dispersive transport with linear sorption on the input (hydro)geological configuration of site. Defining a LPM based on the 3D transport input data and results, it actually represents a model upscaling method and can keep the LPM advantages with avoided compromises of their input data definition.

As the LPM, we consider a generic 1D channel with analytical advection-diffusion-sorption solution, in particular implemented in GoldSim software as “Pipe” object. The 3D flow and transport are solved with Flow123d simulation code (open-source developed at author’s institute), but the presented principles are theoretically applicable to any finite-element or finite-difference code.

We derived a procedure of integral processing of 3D model velocity field and trajectories and the fictitious pulse or step input breakthrough curve between the repository and the output to the biosphere. Four tracers have been used at the same time: non-sorbing, less/more sorbing, and decaying. The relevance of estimation was verified by optimization of the LPM parameters to the best fit between the 3D model and the LPM for all kinds of tracers. The optimization decrease the fit criterion by a small factor, but graphically, all three curves (3D transport, postprocessed LPM, and optimized LPM) are similar.

The resulting data (path length, cross-section, flow rate, travel time, dilution factor, etc.) are obtained with little computing cost compared to the optimization. With a reasonable precision, they can serve for quick comparison of candidate sites, without explicitly running the 3D model or the lumped-parameter model with full source term temporal evolution. On the other hand, some of the parameters are questionable whether physical realistic, which is a consequence of possible model oversimplification. Therefore, other LPM configurations with more blocks representing the real conceptual path segments are evaluated – two serial, three serial and two serial couples in parallel. Due to more constraints, the breakthrough curve fit between LPM and 3D is little worse but with important advantage of physically realistic parameters.

The method was demonstrated on hydrogeological configuration of 9 anonymized (and with partly synthetic features) candidate sites in Czechia.

The project leading to this result has received funding from the EU’s Horizon 2020 programme under grant agreement No 847593. Computational resources were supplied by the project “e-Infrastruktura CZ” (e-INFRA LM2018140).

How to cite: Hokr, M. and Landa, J.: Deriving lumped parameters for DGR safety assessment by 3D transport model postprocessing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13424, https://doi.org/10.5194/egusphere-egu21-13424, 2021.

EGU21-1502 | vPICO presentations | ERE4.3

Does a stability constant decide on a repository permit?

Theresa Hennig and Michael Kühn

Safety of a nuclear waste repository is based to a large extent on the isolation of the radioactive waste within a suitable host rock. Clay rocks provide an option due to their very low hydraulic conductivity only allowing diffusive transport. Diffusion processes in clay formations are complex due to the diffuse double layers (DDL) enveloping the clay minerals to compensate their net surface charge and the associated different migration behaviour for cationic, anionic and neutral species. Therefore, determination of the speciation of an element in the porewater is essential to quantify migration lengths precisely. Safety assessments are based on numerical simulations to cover time periods of up to one million years and thus the predominant species of a radionuclide, dependent on the stability constants within the law of mass action, might be signififcant.

In the present study, we use uranium, one of the main components in spent fuel, as an example for the diffusion in the Swiss Opalinus Clay, a potential host rock for the storage of nuclear waste. In the geochemical system, uranium is mainly present as U(VI) in ternary uranyl complexes with calcium and carbonate, whereby speciation depends on the selected thermodynamic data (Hennig et al., 2020). For instance, the stability constants for the neutral uranyl complex Ca2UO2(CO3)3 differ slightly in literature. Depending on the selected one, either the neutral or the anionic complex CaUO2(CO3)32- is the predominant species in the system with an associated varying interaction with the DDL of the clay minerals. With our one-dimensional, multi-component diffusion models we quantified the effect of the selected stability constant on the diffusion length for the host rock scale.

The chemistry in the porewater of the three facies of the Opalinus Clay, shaly, sandy and carbonate-rich, plays a key role for the sorption processes (Hennig et al., 2020) as well as for the composition and thickness of the DDL and therewith the diffusive transport. Based on our results, we show, that the influence of the predominant uranium species on the migration lengths varies between the individual facies, but is overall negligible for the host rock scale. Consequently, a stability constant is not decisive for the required thickness of the host rock as geological barrier.

 

Hennig, T.; Stockmann, M.; Kühn, M. Simulation of diffusive uranium transport and sorption processes in the Opalinus Clay. Applied Geochemistry 2020, 123. doi:10.1016/j.apgeochem.2020.104777.

How to cite: Hennig, T. and Kühn, M.: Does a stability constant decide on a repository permit?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1502, https://doi.org/10.5194/egusphere-egu21-1502, 2021.

EGU21-11079 | vPICO presentations | ERE4.3

Impact of Surface Reactivity on the Simulation of Mineral Dissolution Rates

Jonas Schabernack and Cornelius Fischer

The kinetics of mineral dissolution plays a key role in many environmental and technical fields, e.g., weathering, building materials, as well as host rock characterization for potential nuclear waste repositories. Mineral dissolution rates are controlled by two parameters: (1) transport of dissolved species over and from the interface determined by advective fluid flow and diffusion (transport control) and (2) availability and distribution of reactive sites on the crystal surface (surface reactivity control). Reactive transport models (RTM) simulating species transport commonly calculate mineral dissolution by using rate laws [1]. However, the applied rate laws solely depend on species concentration in the fluid. While the effect of transport-controlled processes is addressed in current RTM approaches, the intrinsic variability of surface reactivity is neglected. Experimental studies under surface-controlled dissolution conditions have shown that surface reactivity is heterogeneously distributed over the surface [e.g., 2]. This heterogeneity in reactivity is largely caused by nanotopographical structures on the crystal surface, such as steps and etch pits. These structures are generated through defects in the crystal lattice. At these structures, the high density of reactive kink sites is leading to a local increase in surface reactivity observable through high dissolution rates.

In this study, we test whether the current rate calculation approach applied in RTMs is sufficient to reproduce experimentally observed rate heterogeneities. We apply a standard RTM approach combined with the measured surface topography of a calcite single crystal [2]. Calcite is an important mineral component in the sandy facies of the Opalinus clay formation, that is under investigation for nuclear waste storage. The modeled surface dissolution rate maps are compared to experimentally derived rate maps. Results show that the current RTM is not able to reproduce the measured rate heterogeneities on the calcite surface. To improve the predictive capabilities of RTMs over the large time scales required for the safety assessment of nuclear waste repositories, the surface reactivity that is intrinsic to the mineral needs to be implemented into future rate calculations. Investigating calcite surface reactivity in the context of dissolution can also yield information about other kinetic surface processes such as the adsorption of radionuclides during transport. We show the integration of surface reactivity into rate calculation by using a proxy parameter. The slope of the crystal surface at the nm scale is applied. We show that by adding a factor based on the slope to the rate law the RTM is able to approximate experimental rate maps. Other proxy parameters such as surface roughness could yield similar results as well. The implementation of surface reactivity proxy parameters will allow for a more precise prediction of host rock-fluid interaction over large time scales in RTMs, relevant for safety assessment of nuclear waste repositories.

[1] Agrawal, P., Raoof, A., Iliev, O. and Wolthers, M. (2020), Advances in Water Resources, 136, 103480. [2] Bibi, I., Arvidson, R.S., Fischer, C. and Lüttge, A. (2018), Minerals, 8, 256.

How to cite: Schabernack, J. and Fischer, C.: Impact of Surface Reactivity on the Simulation of Mineral Dissolution Rates, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11079, https://doi.org/10.5194/egusphere-egu21-11079, 2021.

EGU21-8552 | vPICO presentations | ERE4.3

In situ measurements at the Mont Terri rock laboratory to study argillaceous rocks

Dorothee Rebscher, Thies Beilecke, Stephan Costabel, Markus Furche, Jürgen Hesser, Tilo Kneuker, Stephan Schennen, Kristof Schuster, and Gesa Ziefle

Safe as well as sensible economic uses of the subsurface demand both the comprehensive knowledge of the present state of a system and the understanding of the relevant dynamical processes. In order to facilitate these requirements, adequate characterisation, sufficient monitoring, and conclusive experiments have to be performed. Following this directive, the German Federal Institute for Geosciences and Natural Resources (BGR) has developed, adapted, and successfully employed methods to prospect Opalinus Clay in the Swiss Mont Terri rock laboratory. These methods encompass geoscientific in situ characterisations as well as investigation techniques as part of long-term monitoring programmes from the complementing fields of e.g. micro-seismics, Electrical Resistivity Tomography, micro-structural petrography, geohydrology, and Nuclear Magnetic Resonance. With this expertise, BGR has contributed numerous experiments, which are embedded and coordinated in the long-standing and fruitful cooperation with the partners of the Mont Terri Consortium.

The knowledge gain, based on now almost 25 years of BGR's engagement in the Mont Terri Project, offers comparison and evaluation of different, complementing methods determining present values and their evolution in time of e.g. moisture, saturation, pressure, deformation, the characterisation of parameter variability, and localisation of heterogeneities. It provides information allowing for programme optimisation of in situ measuring methods concerning penetration, resolution, effort, time, or feasibility. Therefore, the research results can be used for decision-making to refine investigation endevours in regards to specific demands of a certain site or a particular scientific problem not only for Opalinus Clay but also other claystone formations, and in some cases even for non-argillaceous rocks.

How to cite: Rebscher, D., Beilecke, T., Costabel, S., Furche, M., Hesser, J., Kneuker, T., Schennen, S., Schuster, K., and Ziefle, G.: In situ measurements at the Mont Terri rock laboratory to study argillaceous rocks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8552, https://doi.org/10.5194/egusphere-egu21-8552, 2021.

EGU21-14456 | vPICO presentations | ERE4.3

Influence of rock environment on radionuclide migration 

Václava Havlová, Milan Zuna, Tomas Rosendorf, Eva Galeková, Filip Jankovský, and Eva Hofmanová

As the final barrier of the multi-barrier deep geological repository (DGR) for radioactive waste (RAW)  the rock environment fulfils the primary safety function by limiting the transport of radionuclides to the biosphere via the low hydraulic conductivity of the rock mass compared to other rock massifs (1). Moreover, the various properties and characteristics of the rock environment comprise important considerations with respect to the DGR safety assessment.

Samples of the various types of igneous and metamorphic rocks present in the Bohemian Massif were collected as part of the Research Support for the Safety Assessment of the DGR project (SURAO). The study of the rock materials also included that of the fracture fillings, the characteristics of which supplemented the input data set for the future DGR safety assessment. All the rock samples were subjected to both mineralogical (X-ray analysis) and petrological characterisation (2).

Fracture fillings (e.g. clay minerals, biotite, Fe oxyhydroxides, calcite) generally evince higher specific surface areas and cation exchange capacities than do the rocks themselves, i.e. properties that are able to significantly influence the sorption of radionuclides

The sorption experiments performed with radionuclides revealed differing degrees of sorption on the rock and fracture filling samples (e.g. 134Cs, 85Sr, U, Se). The initial experiments on the fracture filling materials determined that their presence can to significantly enhance the capture of radionuclides (e.g. 134Cs) during their migration towards the biosphere, and thus to enhance the safety function of the rock environment (2).

The diffusion characteristic values were determined experimentally using the through diffusion method (2). With respect to the diffusion characteristics (the effective diffusion coefficient De), although the samples were taken from different parts of the Czech Republic and from differing rock types, the effective diffusion coefficients were found to lie within a relatively narrow range: for 3H (4–10) · 10−13 m2 s−1, for 36Cl (1–10) · 10−13 m2 s−1 and for 125I (1–4) · 10−13 m2 s−1. Anionic exclusion was demonstrated for the metamorphic rock samples, which led to the determination of lower De values for 36Cl and 125I in comparison to  3H (2)

The experimental results were determined as part of the Research Support for the Safety Assessment of the Deep Geological Repository project, financed by SURAO (SO2014-061-01), and the EURAD WP FUTURE project.

How to cite: Havlová, V., Zuna, M., Rosendorf, T., Galeková, E., Jankovský, F., and Hofmanová, E.: Influence of rock environment on radionuclide migration , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14456, https://doi.org/10.5194/egusphere-egu21-14456, 2021.

EGU21-15894 | vPICO presentations | ERE4.3

Understanding dilatancy in rocksalt: a microphysical model of rocksalt at the grain-scale

Bart van Oosterhout, Chris Spiers, and Suzanne Hangx

The use of underground repositories excavated in low-permeability formations, such as rock salt, to store high-level, radioactive waste requires the analysis of its isolation properties. Underground excavation disturbs the original stress state of the rocksalt, resulting in a deviatoric stress distribution around the walls of excavated galleries and boreholes. At high deviatoric stresses and low confinement, dense rocksalt produces an increase in porosity and permeability. The extent of dilatancy in this disturbed zone, as well as the impact of dilatancy on the transport properties, are important for assessing the safety of radio-active waste disposal as well as the integrity of salt caverns and boreholes in the context of energy storage, brine cavern abandonment and gas well abandonment.  

The stress conditions at which dilatancy occurs have been measured experimentally, and are typically determined on the basis of macroscopic (sample-scale) measurements of volumetric strain and permeability, and/or acoustic velocity changes or emissions. However, the detailed mechanisms causing dilatancy at the grain-scale are poorly understood. We have developed a microphysical model for dilatancy in rocksalt, both under dry and wet conditions, including mechanisms such as slip and opening of grain boundaries. This model enables us to describe and predict the dilatancy behaviour of rocksalt based on physical, mechanical and chemical processes. The model is presently being independently verified through comparison with existing literature data, and new experiments.

How to cite: van Oosterhout, B., Spiers, C., and Hangx, S.: Understanding dilatancy in rocksalt: a microphysical model of rocksalt at the grain-scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15894, https://doi.org/10.5194/egusphere-egu21-15894, 2021.

EGU21-16149 | vPICO presentations | ERE4.3

Leaching behavior of cementitious material immobilizing Cs-containing B-10 enriched boric acid waste

Emanuel Nkotya, Mojtaba Rostamiparsa, Csaba Szabó, Zsuzsanna Szabó-Krausz, and Péter Völgyesi

Recently, boric acid enriched in B-10 has received attention over natural boric acid in nuclear industry, because the elevated content of B-10 is a prospective neutron absorber. Advantages connected to the use of B-10 enriched boric acid are the increased controllability of reactor core which results in use of reduced amount of boric acid and, subsequently, the reduction in the amount of the radioactive boric acid waste produced during reactor operation. In the other hand, consequent radioactive boric acid waste requires an adequate stabilization technology as it contains fission products of health concerns, importantly Cs-137. Cementation is one of the proven, commercially viable, durable, widely used, simple and flexible technology for immobilization of low-level radioactive wastes (Hyatt and Ojovan, 2019). General integrity and durability of the cementitious waste form containing boric acid is B-leachability dependent (Rostamiparsa et al, 2020). The B-10 enriched boric acid leaching is expected to control also the Cs-leaching. However, no study is found in which this is proven and the different geochemical behavior and phase distribution of the B and Cs might cause deviations. This calls for the investigation of the connection between B- and Cs-leaching behaviors in cementitious materials, in this case, especially focusing on B-10 enriched boric acid waste form. In this ongoing experimental work the B- and Cs-leaching behavior of cementitious materials are studied, which are made of Portland cement, boric acid enriched in B-10 isotope and CsCl. Boron- and Cs-leachability from the cementitious matrix are investigated in parallel by a standardized reference leaching test (ASTM, 2017). The tests are carried out by immersing the 28 days cured cement paste samples in deionized water in a glass bottle. Leachant renewal and solution sampling are done on a daily basis for the whole leaching test period of 11 days. Analysis of leached fractions are quantitatively measured by ICP-OES. Characterization of solid samples are conducted by XRD, SEM-EDX and Raman micro-spectroscopy methods. This is the first study to shed light on the connection between B-leaching and Cs-leaching in cementitious materials containing B-10 enriched boric acid.

Acknowledgements

Our special thanks goes to Környezettudományi Centrum, Eötvös Loránd University and the Prémium_2017-13 research grant.

References

ASTM (2017). Standard Test Method for Accelerated Leach Test for Diffusive Releases From        Solidified Waste and a Computer Program to Model Diffusive, Fractional Leaching from Cylindrical Waste Forms. ASTM Standard C1308-08(2017), West Conshohocken, PA.

Hyatt, N.C & Ojovan, M.I. (2019). Special Issue: Materials for Nuclear Waste Immobilization. Materials, 12(21), 3611.

Rostamiparsa, M., Szabó-Krausz, Z., Fábián, M., Falus, G., Szabó, C., & Völgyesi, P. (2020). Experimental assessment of interaction between boric acid enriched in boron-10 and cementitious matrix. In EGU General Assembly Conference Abstracts (p. 19441).

How to cite: Nkotya, E., Rostamiparsa, M., Szabó, C., Szabó-Krausz, Z., and Völgyesi, P.: Leaching behavior of cementitious material immobilizing Cs-containing B-10 enriched boric acid waste, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16149, https://doi.org/10.5194/egusphere-egu21-16149, 2021.

EGU21-2479 | vPICO presentations | ERE4.3

Influence of the filter properties in the diffusive transport of ions through a bentonite. Sensitivity analysis

Virginia Cabrera, Rubén López-Vizcaíno, Ángel Yustres, and Vicente Navarro

The deep geological repository concept for spent nuclear fuel considers many safety elements. Among them, compacted bentonite has been selected as the primary engineering barrier between the encapsulated radioactive waste and the host rock. Thermo-hydro-mechanical behaviour of this material has been studied in detail from an experimental and numerical point of view. Furthermore, the study of chemical behaviour has become very important, both for the evaluation of the transport of species through the clay matrix and for the evaluation of their coupling to other physico-chemical phenomena.

Generally, to conduct these types of studies, infiltration tests through compacted bentonite columns are carried out using an experimental setup composed of common parts: (i) porewater and infiltration water reservoirs, (ii) pumping devices and (iii) a confined sample of bentonite. The infiltration/output solutions are injected/extracted through filters positioned in the top/bottom of the sample. The results obtained in these tests are strongly influenced by the properties of these filters. For this reason, it is very important how the chemical species and the fluid are transported in the filters to correctly interpret the experimental observations. The study presented in this work is framed in this context, in which a numerical sensitivity analysis of the transport properties and size of the filters has been conducted. For this purpose, a reactive transport model for bentonites (assuming this material as a double porosity media) formulated by the authors and fully implemented in the multiphysics platform, COMSOL, has been used to simulate a cation exchange-infiltration test in MX-80 bentonite defined in the “Chemical session” of the Task Force on Engineered Barrier Systems (EBS) organised by SKB AB. The results obtained depend on the tortuosity, porosity and thickness of the filters. These parameters have been estimated for the correct interpretation of the selected test.

How to cite: Cabrera, V., López-Vizcaíno, R., Yustres, Á., and Navarro, V.: Influence of the filter properties in the diffusive transport of ions through a bentonite. Sensitivity analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2479, https://doi.org/10.5194/egusphere-egu21-2479, 2021.

EGU21-7588 | vPICO presentations | ERE4.3

THM analysIs of natural and engineered barriers for large excavations in deep nuclear waste repository

Matias Alonso, Jean Vaunat, Minh-Ngoc Vu, and Antonio Gens

Argillaceous rocks have great potential as possible geological host medium to store radioactive waste.  Andra is leading the design of a deep geological nuclear waste repository to be located in the Callovo-Oxfordian formation. In the framework of this project, excavations of large diameter galleries are contemplated to access and to store intermediate-level long-lived nuclear waste at repository main level. The closure of the repository will be realized by building sealing structures of expansive material.

The response of such structures is affected by several thermo-hydro-mechanical coupled processes taking place in the near and far field of the argillaceous formations. They include the formation of an excavation induced damaged zone around the galleries, the impact of the thermal load on host rock pressures and deformations, the long-term interaction with support concrete structural elements and the hydration and swelling of sealing materials. As a result, the study of their performance requires to perform simulation works of increasing complexity in terms of coupling equations, problem geometry and material behaviour. As well, challenging computational aspects, as the ones related to fractures creation and propagation, have to be considered for a representative analysis of the problem.

This work presents advanced large scale THM numerical models to provide keys about the response of the host rock around large diameter galleries during excavation and further thermal load as well as to analyse the performance of large diameter sealing structures. Particular features of the models include on one hand advanced constitutive laws to capture the development of the fractured zone around excavations, the behaviour of host rock/gallery support interfaces and the multi-scale response of bentonitic backfill. On the other hand, simulations consider geometries including constructive details of interest at decimetre scale within large discretization domain covering the whole formation stratigraphic column.

These challenging simulations provided qualitative and quantitative results on key aspects for natural and engineered barrier integrity, like extension of the damaged zone, impact of the thermal load and water pressure variations in the surrounding geological layers, duration of natural hydration phase, swelling pressure development and seals global stability.

How to cite: Alonso, M., Vaunat, J., Vu, M.-N., and Gens, A.: THM analysIs of natural and engineered barriers for large excavations in deep nuclear waste repository, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7588, https://doi.org/10.5194/egusphere-egu21-7588, 2021.

The Mont Terri rock laboratory is situated in a clay formation in the northwestern part of Switzerland and is the place of several research focused experiments. These experiments enable the study of relevant coupled effects in the Opalinus Clay formation, an important material in the context of radioactive waste management due to its possible use as geological barrier. Our study focuses on the cyclic deformation (CD-A) experiment, which aims at investigating the coupled hydro-mechanical (HM) behavior of the material, e.g. shrinkage, swelling, changes in permeability. These processes can affect the stability and integrity of the rock. The experiment encompasses seasonal variations such as natural cyclic humidity changes due to winter and summer and consists of two niches. While one niche is open to the influence of the surroundings and hence, subjected to the effects of the seasonal changes of air humidity, the other niche is kept under controlled, high humidity conditions. Long-term quasi-continuous as well as repeating measurements for parameters such as relative humidity, water content, temperature, electrical resistivity and deformation, e.g. tunnel wall convergence via laser scans, are carried out amongst others (start in October 2019). These monitoring data are used as input for calibration and validation of numerical models.

In this contribution we numerically model the HM coupled effects in the context of the CD-A experiment using a macroscopic poromechanical approach. The mathematical model consists of the mass balance of the solid and the liquid phases with displacements and pore pressure as independent variables. Furthermore, it considers unsaturated flow by the Richards approximation. The model is solved numerically with the finite element method using the open-source software OpenGeoSys (OGS 6). Based on a literature review on the material properties of the clay sandy facies and experimental data, a two-dimensional model has been setup stepwise considering (i) in-situ initial pore water pressures and stresses, (ii) the effect of excavation, (iii) the experimentally based seasonal climatic conditions in the niches and (iv) the effect of bedding-induced anisotropy on the HM coupled behavior. With this numerical investigation, we evaluate the temporal evolution of the unsaturated zone. The Nuclear Magnetic Resonance (NMR), Electric Resistivity Tomography (ERT) and Taupe measurements indicate the spatial and temporal evolution of the seasonal hydraulic effects near the niches within the first experimental year. A first comparative study indicates qualitative agreement between monitored ERT data and simulation results and offers paths for model improvement and extension such as in the context of shrinkage-induced cracking.

How to cite: Cajuhi, T., Ziefle, G., Maßmann, J., and Furche, M.: Numerical modeling of hydro-mechanical coupled effects in the cyclic deformation (CD-A) experiment: First results and comparison with observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4173, https://doi.org/10.5194/egusphere-egu21-4173, 2021.

EGU21-7401 | vPICO presentations | ERE4.3

Preliminary stochastic investigations of pore water induced loss of host rock integrity in radioactive waste disposal

Maximilian Bittens, Jobst Maßmann, and Jan Thiedau

Numerical studies on integrity of the geological barriers in heat generating radioactive waste disposal remain a challenging topic involving modelling of thermal, hydraulic and mechanical (THM) processes within complex geometries, as well as particularly long simulation time intervals . Due to this, unfeasible computational complexity emerges for many three-dimensional problems, resulting in the need of further model assumptions and simplification for many types of simulation. To make use of results of such simulations reliably as a tool in the decision-making process, uncertainties introduced by the modelling have to be addressed in the framework of safety assessment.

Consequently, the system describing partial differential equations are dependent on a set of parameters, each parameter possibly subject to uncertainty resulting from reduced knowledge or imprecise measurement. The treatment of uncertainties introduces additional dimensions into the physical system, resulting in a dramatic increase of computational complexity for each parameter considered uncertain.

For general applicability, the method chosen for uncertainty quantification should be problem-independent, i.e. an arbitrary set of stochastic input data is propagated through the physical system, while the output is again a freely selectable quantity of interest. To this end, sampling-based methods like Monte-Carlo methods and stochastic collocation seem to be favourable.

Since a full stochastic model is never computable, it is amenable to include only the most sensitive parameters into stochastic analyses, retaining all other parameters as deterministic, in order to spend available computational power efficiently. With aim of finding such a suitable set of stochastic parameters, preliminary studies of simplified two-dimensional models with less complex geometries and a less complex TH-process seem to be appropriate.

In this contribution, a simplified two-dimensional model of a radioactive waste disposal in clayey rock is proposed, as a starting point, and its results of the thermal induced increase in pore water pressure is compared with more sophisticated and established models for a set of deterministic input parameters. It will be demonstrated that the simplified two-dimensional model is suitable for first stochastic investigation of pore water induced tensile or shear failure.

Subsequently, the results of different stochastic simulations for this model are presented, giving rise to a better understanding of stochastic modelling as well as stochastic post-processing in discretized problems for computational safety assessment of radioactive waste disposal. In detail, sensitivity of the quantity of interest to changes in the input parameters can be studied and in addition, worst-case scenarios within the parameter interval can be found. Given known probability density functions for each input parameter, probability of occurrence of each scenario as well as expected values and variances can be calculated.

 

 

How to cite: Bittens, M., Maßmann, J., and Thiedau, J.: Preliminary stochastic investigations of pore water induced loss of host rock integrity in radioactive waste disposal, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7401, https://doi.org/10.5194/egusphere-egu21-7401, 2021.

EGU21-7823 | vPICO presentations | ERE4.3

Does a Staggered Scheme Pay Off on Large-scale Hydraulic-mechanical Simulations?

Dominik Kern, Fabien Magri, Victor Malkovsky, and Thomas Nagel

From previous studies it is evident that decoupled simulations lack the ability to capture certain coupled effects, such as the Noordbergum effect or the Mandel-Cryer effect in a hydraulic-mechanical context. Thus, for detailed simulations of geotechnical or geological system, coupled simulations are usually chosen. For example, thermal-hydraulic-mechanical (THM) coupled systems, and even chemical and biological couplings (THMCB), are considered in simulations used to assess barrier integrity over long time spans in the context of geological waste disposal.

This paper is restricted to coupled hydraulic-mechanical (HM) systems. A monolithic approach is both stable and accurate for strongly coupled systems. However, as site-scale models of geological disposal facilities are also large in spatial dimensions, it is worth to investigate how staggered methods may cut down the computational costs. The fixed-stress split appears to be a promising approach for staggered schemes in terms of stability, consistency, accuracy, and efficiency.

While adding another iteration level in comparison to monolithic schemes, staggered schemes allow for lower-order approximation spaces, whereas monolithic schemes require Taylor-Hood elements resulting in a larger number of degrees of freedom per element. Both coupling schemes are implemented in the the open-source finite-element (FE) software OpenGeoSys and used to simulate a large-scale model, which is oriented towards a real site in planning in Russia. Simulation results are compared in terms of accuracy, coupling effects and performance.

How to cite: Kern, D., Magri, F., Malkovsky, V., and Nagel, T.: Does a Staggered Scheme Pay Off on Large-scale Hydraulic-mechanical Simulations?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7823, https://doi.org/10.5194/egusphere-egu21-7823, 2021.

EGU21-13299 | vPICO presentations | ERE4.3

Hydrogeological simulation of sedimentary basin evolution during a glacial cycle

Christian Silbermann

Co-authors: Francesco Parisio, Thomas Nagel

Glaciation cycles affect the long-term evolution of geosystems by crustal deformation, ground freezing and thawing, as well as large-scale hydrogeological changes. In order to properly understand the present and future conditions of potential nuclear waste repository sites, we need to simulate the past history. 
For this, a sedimentary basin is considered here as a large-scale hydrogeological benchmark study. The long-term evolution during one glacial cycle is simulated using the open-source multi-field finite element code OpenGeoSys. The impact of the glacial loading (weight and induced shear) is taken into account using appropriate time-dependent stress boundary conditions. As a preliminary study, the hydro-mechanically coupled problem and the thermal problem are considered separately. For comparison with a previously published study by Bense et al. (2008), the entire displacement field is prescribed and the groundwater evolution (hydraulic problem) is regarded. Then, the displacement is only prescribed by means of boundary conditions. The impact of different constitutive assumptions on the deformation and hydraulic behavior is analyzed. The thermal problem is used to simulate the evolution of frost bodies in the subsurface beneath and ahead of the glacier.

V. F. Bense and M. A. Person. Transient hydrodynamics within intercratonic sedimentary basins during glacial cycles. Journal of Geophysical Research,
113(F4):F04005, 10 2008.

How to cite: Silbermann, C.: Hydrogeological simulation of sedimentary basin evolution during a glacial cycle, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13299, https://doi.org/10.5194/egusphere-egu21-13299, 2021.

EGU21-15604 | vPICO presentations | ERE4.3

Improved predictability of numerical flow models of fractured crystalline media: The effect of surface roughness.

Maria Alejandra Cardenas Rivera, Johannes Kulenkampff, Filip Jankovsky, and Vaclava Havlova

Transport and flow through fractured crystalline rocks is an important and often studied topic in the context of nuclear waste disposal, given that the heterogeneity of fluid transport constraints the efficiency of radionuclide sorption processes. In past years, several studies have provided numerical simulations of the flow rate that can be expected in different types of fractures. Such studies rely on the required length-scale and spatial resolution of geometrical data in order to conduct flow and transport modeling. The numerical results are validated against tracer data of break-through experiments, such as the recently available spatiotemporal tracer concentration analysis, obtained from positron emission tomography (PET) . In many cases, however, the results obtained from the numerical simulations differ greatly from the experimental observations. While some numerical models commonly operate under the cubic law assumption, which defines a fracture as two perfectly parallel smooth surfaces, more advanced simulations include the effect of fracture surface roughness. Such results suggest the need of an improved understanding of transport heterogeneities as a function of fracture surface roughness and topography. Moreover, a systematic evaluation provides insight into the model complexity required for reliable radionuclide transport and flow predictability in potential host rocks.

In this study, we focus on the numerical modeling of flow through a fracture while taking into account surface roughness of the fracture walls, and validating the results against tomographic methods. For this purpose, the structural parametrization of the fracture is carried out by performing the segmentation of micro-computed tomography (µCT) images obtained from Granite samples from the Mrákotín quarry  in the Czech Republic. Subsequently, interferometry measurements of identical fracture material are carried out in order to quantify the details in the surface topography at the nm to µm scale. Resulting data are combined with µCT data through statistical methods, which provide a more meaningful definition of the surface topography, and are compared with numerically generated surface roughness. Resulting numerical simulations are then validated against PET measurements. As a result from the outlined workflow and the quantitative comparison, we provide suggestions of general applicability of the required degree of complexity for surface geometry segmentation in flow simulations.

How to cite: Cardenas Rivera, M. A., Kulenkampff, J., Jankovsky, F., and Havlova, V.: Improved predictability of numerical flow models of fractured crystalline media: The effect of surface roughness., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15604, https://doi.org/10.5194/egusphere-egu21-15604, 2021.

EGU21-4157 | vPICO presentations | ERE4.3

Can microorganisms significantly influence cast iron corrosion in a DGR?

Nicole Matschiavelli, Vladyslav Sushko, Magdalena Dressler, Tom Neubert, Luise Kühn, Ariette Schierz, and Andrea Cherkouk

For the safe storage of high-level radioactive waste (HLW) in deep geological repositories (DGR), several metals could potentially act as canister material and are under investigation with respect to their properties under disposal-relevant conditions. An essential requirement for the selected metal(s) is the long-term stability which is mainly realized by the resistance to corrosion. The process of corrosion depends on the overall environment in the surrounding of the metal canister and which will change over time. Here, parameters like redox potential, pH, the presence of (pore-) water, the salinity and also the presence of metabolically active microorganisms are of relevance, among others. In order to analyze the influence of different pore waters and the natural microbial community of a Bavarian bentonite, which acts as geotechnical barrier and will be in direct contact to the canister, microcosm experiments were set up. These slurry experiments contained B25 bentonite, synthetic Opalinus Clay pore water or saline cap rock solution as well as copper- or cast iron plates in various combinations. During an incubation time of 400 days under anaerobic conditions at 37 °C, several bio-geochemical parameters (e.g. pH, redox potential and the concentration of minerals, sulfate, iron(II/III) and organic acids) were analyzed as well as the corrosion process and a potential microbial influence. The obtained results provide insights into the complex interplay between bentonite, pore water, metals and microorganisms. Different precipitates like carbonates, iron oxides and sulfides were identified on the cast iron surface, potentially accelerating or slowing down the corrosion process and, thus, affecting the long-term stability of the metal canister in a DGR.     

How to cite: Matschiavelli, N., Sushko, V., Dressler, M., Neubert, T., Kühn, L., Schierz, A., and Cherkouk, A.: Can microorganisms significantly influence cast iron corrosion in a DGR?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4157, https://doi.org/10.5194/egusphere-egu21-4157, 2021.

EGU21-9265 | vPICO presentations | ERE4.3

Microbiological research program in deep HRW repository «Yeniseisky»: plans and first results

Alexey Safonov, Elena Abramova, Nadezhda Popova, Grigory Artemiev, and Kirill Boldyrev

The concept of engineered geologic disposal has been developed for the safe long-term management of long-lived high-level radioactive waste (HRW) by many countries. Russian Federation evaluates the “Yeniseiskiy” Nizhnekansky granite-gneiss crystalline formation, in Krasnoyarsk region. To this date microbiological studies became an integral part of safety assessment in Russia like other countries.

A multi-barrier concept was used to create super-container (SC). SC contains a primary vitrified radioactive waste package, placed in the carbon steel casing, bentonite and aluminate concrete layers placed between the casing and inner IC surface. All selected barrier materials are potential areas for biogenic processes.

The talk presented a plan of experimental research of biogenic processes and first step results. Microbiological studies at the first stage are carried out in laboratory conditions, at the second stage they will be carried out under the conditions of URL and include:

- changes of host rock sorption and diffusion properties due to biofilms formation,

- assessment of the possibility biocolloidal particles formation and determination clay and ferruginous colloids stability during biogenic processes;

To date, the study of the phylogenetic and functional diversity of the microflora of the granite-gneiss massif, near-surface waters, and clay materials that will be used in disposal has been carried out. It has been established that microorganisms, isolated from samples, collected nearby the zone of the future repository are capable of participating in a number of undesirable processes, including steel corrosion acceleration, the formation of biogenic gases, and changes in the properties of clay materials. Our studies also show that microbial communities of clays are activated by hydrogen, which is a product of steel corrosion and water radiolysis. At the first stage, we found an increase in the corrosion of carbon steel in the presence of microorganisms sampled from the study area.

An acceleration of the corrosion rate of carbon steel (from 1.3 to 1.9 μm/year) was observed with an increase in temperature from 20 to 500С, the calculated value of the activation energy was 22 kJ/mol * K. Based on the data obtained, a kinetic model of carbon steel corrosion in the presence of microorganisms was created, including both the inclusion of the activation energy and the inhibition of corrosion by the formed corrosion products.

 

How to cite: Safonov, A., Abramova, E., Popova, N., Artemiev, G., and Boldyrev, K.: Microbiological research program in deep HRW repository «Yeniseisky»: plans and first results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9265, https://doi.org/10.5194/egusphere-egu21-9265, 2021.

EGU21-16492 | vPICO presentations | ERE4.3

Detection of living bacterial cells in clay - bentonite 

Veronika Hlavackova, Katerina Cerna, Lenka Kejzlarova, Deepa Bartak, Rojina Shestra, and Alena Sevcu

Bentonite is a swelling clay, consisting mainly of montmorillonire,  being planned to be used as a backfill material in the nuclear waste repository. It contains indigenous microbial populations that can negatively influence the long-term safety of the geological repository due to their metabolic activity (canister corrosion, illitization of bentonite, gas production, degradation of cementitious materials). However, reliable detection of microorganisms in clayish material is generally very difficult. Although the compactness of bentonite will undoubtedly limit the microbial activity, in the extremely long-time frame of repository lifetime this condition can fail. It is thus crucial to understand the potential of the naturally present microbial community in bentonite to compromise the safety of repository, if not limited by the compactness. Higher metabolic activity can be mainly expected at the interfaces or in the places with a lower density of bentonite.

Here we present an optimized cell extraction method enabling direct estimation of bacterial density and viability in bentonite. Indigenous bacterial cells were extracted from bentonite suspensions by an improved step-wise protocol and their viability was detected using live/dead staining and epifluorescence microscopy. We used dispersant (2.5 mM natrium pyrophosphate-based solution or 1% methanol) to partially disintegrate the bentonite and detach the vital and dead microbial cells from its surface. The dispersed material was subsequently stepwise centrifuged over two high-density media (sucrose and Histodenz) to remove most of the heavy bentonite particles while keeping the light bentonite particles and cells in the final extract. We were able to detect and enumerate the cells concentrated at the surface of the light bentonite particles, which served as a sieve to retain all free cells during centrifugation.    

Different extraction procedures were tested and their efficiency was estimated by comparing live/dead ratios of resulting extracts and was also proved by implementing both NGS and quantitative PCR. The results show that most of the microbial genera present in the original suspension are also present in extracts but as proved by Deseq2 analysis some genera tend to settle down with heavier bentonite particles during the first centrifugation step.

To conclude, we present a protocol for extraction and detection of metabolically active cells in clayish material – bentonite. The quality of the extraction procedure was estimated both by a combination of fluorescent microscopy and genetic methods. The protocol was successfully tested on different bentonite types showing general applicability of this approach for clay materials.

How to cite: Hlavackova, V., Cerna, K., Kejzlarova, L., Bartak, D., Shestra, R., and Sevcu, A.: Detection of living bacterial cells in clay - bentonite , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16492, https://doi.org/10.5194/egusphere-egu21-16492, 2021.

EGU21-14233 | vPICO presentations | ERE4.3

Stability of clay buffer systems in the conditions of deep geological disposal of radioactive waste in the presence of microorganisms

Elena Abramova, Alexey Safonov, Grigoriy Artemyev, Nadezhda Popova, and Kirill Boldyrev

Clay minerals are the main promising materials for engineering safety barriers in the disposal of radioactive waste in geological formations. Clays have high chemical stability, good sorption properties, and low diffusion coefficients. Bentonite clays combine the most optimal properties - high swelling pressure, low diffusion coefficients. At the moment, there is no unified international concept of the clay barrier density and its composition. Also, the parameters of the influence of biogenic processes on the properties of clay materials have not been correctly determined. It is planned to use of bentonite barrier between the metal container and the external environment in the design of the supercontainer for the new disposal of radioactive waste in the Nizhnekanskiy gneiss massif.

Within the studies of microbiological processes in the Yeniseisky disposal site, big attention will be paid to clay barriers as sources of biogenic elements in the system and microflora and organic and inorganic carbon.

Special attention will be paid to thermophilic microorganisms characterized by high growth rates and high levels of metabolic processes, which, along with the extreme impact of radioactive waste (temperature, gas release) on a site in the mountain range, can lead to the destruction of safety barriers.

Based on the data of phylogenetic analysis of the 16S rRNA gene sequences in clay materials, which are planned to be used as a barrier material, bacteria of the fermentative type of metabolism, capable of forming biogenic gases and organic acids, sulfate-reducing microflora, and a wide variety of microorganisms of the iron cycle were found. We investigating the processes under conditions corresponding to both the internal and external conditions of the clay barrier. As a result of our studies, in model experiments, the effect of microflora activation by radiolysis products, carbon steel corrosion products, hydrogen, and carbon dioxide was found. A thermophilic microbiota was found in samples with bentonite clays of the Khakass and Dinosaur deposits cultivated at temperatures of 50, 70, 90° C. High content of aluminum and silicon amorphous oxide phases was found in the liquid phase after cultivation, and an increase in bioleaching was observed with increasing temperature. Screening of biocidal additives was performed to suppress microbial activity, primarily sulfate reduction. The most effective, thermally stable biocide with prolonged action was polyhexamethylguanidine at a concentration of 0.5 wt. %.

How to cite: Abramova, E., Safonov, A., Artemyev, G., Popova, N., and Boldyrev, K.: Stability of clay buffer systems in the conditions of deep geological disposal of radioactive waste in the presence of microorganisms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14233, https://doi.org/10.5194/egusphere-egu21-14233, 2021.

ERE5.1 – Global Heritage Stone Resource: The sustainable way forward

EGU21-12485 | vPICO presentations | ERE5.1

Global Heritage Stones Resource: An IUGS designation

Gurmeet Kaur and Victor Cardenes

The initiative of designating the natural stones as Global Heritage Stones Resource by the IUGS is a novel one. The stakeholders are all those countries which record the stone built monuments of cultural significance. The stones used in the monuments with unique geological and architectural attributes and which have been used in the historical past with surviving and/or extinct quarries are being considered for designation of GHSRs. The European nations have been quick in identifying such stones and have proposed many significant stones for designation of GHSR in stark contrast to African, Asian and South American nations which are underrepresented on the world map in terms of designation of GHSR. The need of the hour is to promote the idea to all the nations to come up with the documentation of the stones used in the monuments, the state of preservation of historical quarries, the record and strategy for the upkeep of monuments and the historical quarries. The Project ‘The HERITAGE STONES RECOGNITION: A STEP FORWARD (HerSTONES)’ has been recently granted by IGCP-UNESCO to promote heritage Stones from emerging countries.

How to cite: Kaur, G. and Cardenes, V.: Global Heritage Stones Resource: An IUGS designation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12485, https://doi.org/10.5194/egusphere-egu21-12485, 2021.

EGU21-4536 | vPICO presentations | ERE5.1

The Heritage Stone of Nossa Senhora de Guadalupe Church, Mouçós, North of Portugal: Characterisation and Glyptography

David Freire-Lista, Bruno Campos, and Patricia Moreira da Costa

Granite is the most important building stone in the north of Portugal. The importance of the stones in this region is evidenced by the pre-Roman roots Mor (r), Mur (r) and Mour of place names such as Montemuro, Moreiras, Mouçós, and Mourelhe. These roots indicate the existence of building stones used since ancient times in these places.

The quarries of the main building stones of historical buildings were generally in the vicinity of the buildings. Formerly, stonemasons carved mason's marks on ashlars. The mason's marks are lapidary signs to indicate the work carried out by each one. The mason's marks are generally symbolised by the initial of the stonemason's name. They are often found on dressed stones in buildings and in other public structures.

Nossa Senhora de Guadalupe church of Mouçós (possibly 16th century) has typical characteristics from the late Romanesque. It is located in Vila Real (North of Portugal). It is made up of three volumes: a single nave, a lower rectangular apse, and a sacristy attached to the apse. The exterior of this church is preserved almost unaltered in its original state. Each of the granite ashlars that make up this church has a mason's mark in the center of its face.

The mason's marks of the church have been identified; all the ashlars with visible mason's marks have been mapped, and a glyptographic study has been carried out. This has made it possible to calculate the number of stonemasons that worked in the construction of the church and the number of ashlars that were transported in each carriage, and to determine the construction phases of the church.

Eight cubic samples have been cut to calculate the granite’s hydric properties (effective porosity, water absorption and bulk density) according to UNE-EN:1936. Ultrasound wave velocity was measured according to UNE-EN:14579. Furthermore, three thin sections have been made to characterise the granite petrographically under a polarisation microscope Leica DM-4500-P. A mosaic of photomicrographs has been made to evaluate the petrographic properties.

There are six main types of mason's marks in Nossa Senhora de Guadalupe Church. All quarrymen extracted the stones from the same quarry, or from nearby quarries. The mean effective porosity of the building granite is 3.2%±0.3, and the mean water absorption is 1.2%±0.1. Its mean bulk density is 2566 kg/m3±61.0 and its ultrasound P wave velocity is 2920 m/s±98.3.

The mason's marks are preserved because of the excellent petrographic and petrophysical properties of Mouçós granite. Further, Nossa Senhora de Guadalupe church was protected with lime plaster during the past centuries, and the plaster was not removed with the projection of abrasive particles.

The use of analytical techniques such as petrography, ultrasonic P wave velocity and the determination of hydric properties will guarantee the quality and durability of a sustainable restoration.

The historical quarries, forms of traditional stone extraction and uses of Mouçós granite constitute a heritage that must be safeguarded.

Acknowledgements: The Fundação para a Ciência e a Tecnologia (FCT) of Portugal. CEECIND/03568/2017.

How to cite: Freire-Lista, D., Campos, B., and Moreira da Costa, P.: The Heritage Stone of Nossa Senhora de Guadalupe Church, Mouçós, North of Portugal: Characterisation and Glyptography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4536, https://doi.org/10.5194/egusphere-egu21-4536, 2021.

Historical monuments represent an archive and a past full of information and emotions transmitted from our ancestors, to preserve this sacred and perilous heritage with universal value, it was necessary to study it and approach it meticulously as a living body that expressing by diseases or pathologies which must be well treated.

From one monument to another, the pathologies found change and differ following several criteria and conditions, in our work we will focus on the bio-calcarinite rock often used in the construction of historical monuments in the Rabat Sala Kenitra’s region because of its availability and its mechanical performances and also by focusing on the criterion of monument’s location opposite the agents of degradation (climate, urbanization, know-how, materials, direction, uses, marine aerosol, etc.) we will identify the various degradations of bio-calcarinites of the Borj Adoumoue monument (Tower of tears) located on the seafront of the city of Sala in Morocco and the Historic monument of Challah in the city of Rabat which was named shared heritage in 2012 and which knows currently a major urbanization project named Rabat capital of lights, the historic monument of Chellah overlooks the Bouregreg river.

And we will therefore compare the impact of the location of the monument on the latter and on the pathologies that manifest themselves on the biocalcarinite of this region.

How to cite: Belhaj, S. and Belhaj, O. E.: Identification and Comparison of Pathologies Encountered at the level of Bio Calcarinites used in the monuments of the city of Sala and Rabat in Morocco., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1408, https://doi.org/10.5194/egusphere-egu21-1408, 2021.

EGU21-8531 | vPICO presentations | ERE5.1

Global Heritage Stone Resource in Brazil

Eliane Aparecida Del Lama and Antônio Gilberto Costa

Since the establishment of the Heritage Stone Subcommission by the International Union of Geological Sciences (IUGS), in 2011, idealized with the purpose of designating stones of historical significance to compose the Global Heritage Stone Resource (GHSR), 22 of them have been designated. The nationalities of these GHSR are: 3 British, 1 Norwegian, 2 Belgian, 2 Swedish, 1 Slovenian, 3 Italian, 2 Portuguese, 3 Spanish, 1 Maltese, 1 Indian, 2 American and 1 Argentine. So far, no Brazilian stone has been designated as GHSR. We can observe in monuments and buildings in the Brazilian territory the following imported GHSR: Lioz Stone and Estremoz Marble from Portugal, Carrara Marble and Rosa Beta Granite from Italy and Larvikite from Norway. The use of stones from Portugal and Italy is related firstly to the Portuguese colonization and, later, to economic cycles, such as rubber and coffee, with Italian immigration being significant to the coffee cycle. The presence of Lioz is major, however, it is found almost exclusively in some Brazilian coastal capitals, such as Rio de Janeiro, Salvador and Belém. The churches of Salvador are richly decorated with numerous varieties of Lioz. In Belém, it is found in the Basilica of Nossa Senhora de Nazaré, among other churches, and in many tombstones in the Nossa Senhora da Soledade Cemetery. Estremoz Marble is found in commercial buildings and tombstones. In the city of São Paulo, lots of buildings have internal cladding and ornaments made in Carrara Marble, e.g. Municipal Theater, Palace of Justice, Metropolitan Cathedral and Obelisk Mausoleum for the Heroes of 32. In the city of Rio de Janeiro, the tomb of Orville Derby (founder of the Geological Survey of Brazil) at São João Batista Cemetery, among others, is decorated with Carrara Marble, which can also be seen in tomb art of Salvador, Belo Horizonte, Curitiba and São Paulo. Rosa Beta Granite can be seen at Monument to Bartolomeu de Gusmão in the city of Santos, costal area of São Paulo State. The use of Larvikite is contemporary. This stone is mainly present in tombstones, for example, at the Consolação Cemetery in São Paulo, but it also decorates the façades of several commercial buildings, both in capitals and several Brazilian cities. In Brazil, several types of Brazilian stones are found in monuments and religious or administrative buildings. These stones, which have been used since Colonial Brazil, are characteristic of certain regions, such as Augen Gneiss in Rio de Janeiro, Itaquera Granite in São Paulo, beachrock in northeastern Brazil, quartzites and steatite in Minas Gerais, among others. Some of them constitute UNESCO World Heritage Sites, and due to their historical importance to our heritage, these stones may be indicated as GHSR in the future.

How to cite: Del Lama, E. A. and Costa, A. G.: Global Heritage Stone Resource in Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8531, https://doi.org/10.5194/egusphere-egu21-8531, 2021.

EGU21-2022 | vPICO presentations | ERE5.1

Decay detection in an ancient column with combined close-range photogrammetry (CRP) and ultrasonic tomography.

Giuseppe Casula, Silvana Fais, Francesco Cuccuru, Maria Giovanna Bianchi, Paola Ligas, and Alessandro Sitzia

The diagnosis of the conservation state of monumental structures from constraints to the spatial distribution of their physical properties on shallow and inner materials represents one of the key objectives in the application of non-invasive techniques. In situ, CRP and 3D ultrasonic tomography can provide an effective coverage of stone materials in space and time. The intrinsic characteristics of the materials that make up a monumental structure and affect the two properties (i.e., reflectivity, longitudinal velocity) through the above methods substantially differ. Consequently, the content of their information is mainly complementary rather than redundant.

In this study we present the integrated application of different non-destructive techniques i.e., Close Range Photogrammetry (CRP), and low frequency (24 KHz) ultrasonic tomography complemented by petrographycal analysis based essentially on Optical Microscopy (OM). This integrated methodology has been applied to a Carrara marble column of the Basilica of San Saturnino, in Byzantine-Proto-Romanesque style, which is part of the Paleo Christian complex of the V-VI century. This complex also includes the adjacent Christian necropolis in the square of San Cosimo in the city of Cagliari, Sardinia, Italy. The column under study is made of bare material dating back probably to the first century A.D., it was subjected to various traumas due to disassembly and transport to the site, including damage caused by the close blast of a WWII fragmentation bomb.

High resolution 3D modelling of the studied artifact was computed starting from the integration of proximal sensing techniques such as CRP based on Structure from Motion (SfM), with which information about the geometrical anomalies and reflectivity of the investigated marble column surface was obtained. On the other hand, the inner parts of the studied body were successfully inspected in a non-invasive way by computing the velocity pattern of the ultrasonic signal through the investigated materials using 3D ultrasonic tomography. This technique gives information on the elastic properties of the material related with mechanical properties and a number of factors, such as presence of fractures, voids, and flaws. Extracting information on such factors from the elastic wave velocity using 3D tomography provides a non-invasive approach to analyse the property changes of the inner material of the ancient column. The integrated application of in situ CRP and ultrasonic techniques provides a full 3D high resolution model of the investigated artifact. This model enhanced by the knowledge of the petrographic characteristics of the materials, improves the diagnostic process and affords reliable information on the state of conservation of the materials used in the construction processes of the studied monumental structure. The integrated use of the non-destructive techniques described above also provides suitable data for a possible restoration and future preservation.

 

Acknowledgments: This work was partially supported by FIR (Fondi integrativi per la Ricerca) funded by the University of Cagliari (Italy). The authors would also like to thank the Ministero dei Beni e delle Attività Culturali. Polo Museale della Sardegna and Arch. Alessandro Sitzia for their kind permission to work on the San Saturnino Basilica.

How to cite: Casula, G., Fais, S., Cuccuru, F., Bianchi, M. G., Ligas, P., and Sitzia, A.: Decay detection in an ancient column with combined close-range photogrammetry (CRP) and ultrasonic tomography., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2022, https://doi.org/10.5194/egusphere-egu21-2022, 2021.

EGU21-9394 | vPICO presentations | ERE5.1

Rajnagar Marble: a prominent heritage stone from Rajasthan, India

Sanchit Garg, Pradeep Agarwal, Pushpendra Ranawat, Parminder Kaur, Amritpaul Singh, Jaspreet Saini, Kireet Acharya, Manoj Pandit, and Gurmeet Kaur

Rajnagar Marble, occurring around Rajnagar and Kankroli towns in Rajsamand district of south-central Rajasthan make up the largest marble deposits in India. Rajnagar Marble belongs to late Paleoproterozoic Aravalli Supergroup.  It is mostly white, coarse-grained and compact dolomitic marble. Mining is currently being carried out at several, small to medium-sized, open quarries using both conventional and mechanized operations. Although the Rajnagar Marble has been extensively used in archaeological monuments for centuries, it received recognition since the construction of spectacularly carved embankment (Nau-Chowky) of the Lake Rajsamand built during the period 1662-1676 CE. Its use has been recorded in the 8th century Eklingji Temple and numerous other temples in Udaipur and vicinity. Besides temples, embankments, step-well constructions, Rajnagar Marble was preferred for carving of idols of various Hindu deities, including the famous 12th century Palasma 7-horse drawn chariot Sun idol with nine planets revolving around it. But use of this Dev-Patthar (God's Stone), was avoided for flooring and private dwellings of humans in keeping with the Hindu mythological beliefs. Hence for the residential buildings, Rajnagar Marble was popularly used as a unique ground-in-hand-mill-and-sieved-through-muslin-sieve marble powder-lime paste (~100-micron size) to give the walls, pillars, lanterns, or even floors the "marble-finish". An intangible heritage process typical and unique of the erstwhile Rajputana.  Most palaces and havelies of Mewar area, including the five palaces of Udaipur namely, the City Palace Complex, Jagniwas (now the Taj Lake Palace Hotel), Jag Mandir, Lakshmi Vilas Palace and the Sajjangarh (Monsoon Palace) were all built partly in Rajnagar Marble stone, but mostly with marble powder-lime paste finish on lime-sand-quartzite masonry works.  Numerous architectural sites such as Moti Mahal, embankments of Fateh Sagar Lake and Rajsamand Lake, Eklingji Temple, Jagdish Temple, Saheliyon-ki-Badi, cenotaphs of the Royal family members at Ayad (1620 CE onwards) were built of Rajnagar Marble.

The low water absorption, high bulk density and high compressive, shearing and tensile strength of the Rajnagar Marble, and its ‘blockability’ made it technically suitable for monuments that have sustained for five centuries or more, with no signs of weathering and discoloration. The Rajnagar Marble entered the global market in the later 20th century with its export to various countries including the Middle East and Japan. At present, it is extensively used in building and handicraft industry and is also famous for contemporary artworks. In light of these variety of applications of the Rajnagar Marble, we propose ‘Rajnagar Marble’ for the designation of ‘Global Heritage Stone Resource’.

How to cite: Garg, S., Agarwal, P., Ranawat, P., Kaur, P., Singh, A., Saini, J., Acharya, K., Pandit, M., and Kaur, G.: Rajnagar Marble: a prominent heritage stone from Rajasthan, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9394, https://doi.org/10.5194/egusphere-egu21-9394, 2021.

EGU21-11107 | vPICO presentations | ERE5.1

Red Ereño and Cantera Gorria: Natural and Cultural Geoheritage (Basque Country, Spain)

Laura Damas Mollá, Arantza Aranburu, Uriarte Jesus Ángel, Ane Zabaleta, Tomás Morales, and Iñaki Antigüedad

Construction and ornamental stones are important elements of cultural heritage and identity and shape the urban landscape of the territories (Pereira & Cárdenes Van den Eynde, 2019). These stones and their quarries are a part of geoheritage that is gaining interest in the tourism industry (Mateos et al., 2011). Red Ereño is an urgonian limestone (Lower Cretaceous) with abundant rudist fossil shells, which white colours highlight on an intense red micritic matrix. This stone is exploited since Roman times in the north of the Iberian Peninsula (Basque Country, Spain). This lithology is found in many buildings, both heritage and common. Its uniqueness has contributed to its expansion worldwide and, it can be found in such emblematic places as the Colon Theatre in Buenos Aires (Argentina) or St Peter´s basilica in the Vatican (Italy) (Damas Mollá et al., 2021).

The main quarry related to Red Ereño is called Cantera Gorria (meaning Red Quarry) and is located inside the Urdaibai Biosphere Reserve (x: 529,659.29 m; y: 4,800,839.60 m; z: 15 m). It is included in the Geosites Inventory of the Basque Country (LIG nº 15), and is part of the historical heritage of the Biscay province. The last concessionaire of the quarry was Marmolería Bilbaína and it ceased its activity in 1968. At present the quarry is abandoned.  Nevertheless, on its exploitation fronts outstanding geologic features are recognised: stratigraphic (bioconstructions, facies changes), petrologic (diagenesis, mineralisations), tectonic (succession verticality, faults) or geomorphologic (karst). All of them make Cantera Gorria a point of reference for both research and teaching activities. Additionally, it is important to underline the richness related to the mining heritage itself. Numerous buildings from the mining activity are still preserved. Also noteworthy are the signs engraved on the rock showing the progress of exploitation in various stages, from manual to the use of helical steel wire.

In the case of Red Ereño and Cantera Gorria the symbiosis between geoheritage and cultural heritage is significant. This symbiosis, together with all the above mentioned characteristics of the quarry makes Cantera Gorria an interesting space for dissemination of geoheritage as well as for tourism (Damas Mollá, 2011).

References

  • Damas Mollá, L. (2011): Las Calizas rojas de Ereño: facies, paleoambiente, mineralización y diagénesis. Patrimonio geológico-histórico de Bizkaia. PhD Thesis, University of the Basque Country.
  • Damas Mollá L., Uriarte J.A., Zabaleta A., Aranburu A., García Garmilla F., Sagarna M, Bodego A., Clemente J.A., Morales T. & Antigüedad I. (2021). Red Ereño: an ornamental and construction limestone of international significance from Basque Country (northern Spain). Geoheritage 13:2. https://doi.org/10.1007/s12371-020-00529-5
  • Mateos R.M, Durán, J.R & Robledo P.A. (2011). Marès Quarries on the Majorcan Coast (Spain) as Geological Heritage Sites. Geoheritage 3: 41-54. http://doi.org/10.1007/sl12371-010-0026-5
  • Pereira D. & Cárdenes Van den Eynde V. (2019). Heritage Stones and Geoheritage. Geoheritage 11: 1-2. http://doi.org/10.1007/s12371-019-00350-9

How to cite: Damas Mollá, L., Aranburu, A., Jesus Ángel, U., Zabaleta, A., Morales, T., and Antigüedad, I.: Red Ereño and Cantera Gorria: Natural and Cultural Geoheritage (Basque Country, Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11107, https://doi.org/10.5194/egusphere-egu21-11107, 2021.

EGU21-9638 | vPICO presentations | ERE5.1

New sustainable mortars for stone restoration in the context of climate change

Jose Diaz-Basteris

Restoration mortars are a designated group of products made to repair damaged masonry. They must be compatible with the former support of stones and bricks, and protect original materials from environmental agents; aesthetical and historic aspects must not be neglected. 

To improve the ecological footprint of the restoration mortars while keeping their efficiency, we have tested several combinations of lime with aggregates and additives. Recycled and natural materials were used as additives such as pinecone resin, semi-milled cones of pine, milled glass waste, brick production residue.

For research purposes different physical properties have been measured in prepared mortars: porosity, density, capillarity absorption, moisture absorption, water vapour permeability. We have also tested the mechanical properties and the P and S waves velocities (from which dynamic Young's modulus and Poisson’s ratio were inferred). The durability of mortars has been estimated by salt crystallization and frost/thaw cycles.

The life cycle analysis (LCA) of such mortars allows us to understand the carbon footprint of each manufacturing process. Considering this we selected the raw materials, from an environmental and commercial point of view, to produce mortars fulfilling sustainability requirements. As a result, the developed mortars are compatible with aged stones, minimize environmental impact, and use minimum natural resources.

 Twenty mortar formulations with three different types of limes (NHL5, NHL3.5, CL90) and two different aggregates (siliceous and calcareous) have been studied using the LCA. Currently, five new formulations are being selected to be tested on Euville limestone. Adhesive strength (James Bond test), and physical properties will be measured on these mortars. 

How to cite: Diaz-Basteris, J.: New sustainable mortars for stone restoration in the context of climate change, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9638, https://doi.org/10.5194/egusphere-egu21-9638, 2021.

EGU21-12534 | vPICO presentations | ERE5.1

The Crevoladossola marble (Piedmont, northern Italy): nine commercial varieties in just one quarry!

Alessandro Cavallo and Giovanna Antonella Dino

The Ossola valley (central Alps, northern Italy) is well known to produce a wide range of dimension stones: granites, gneisses, marbles and soapstones. The calcitic Candoglia marble is well-known because it was used in the cathedral of Milan, whereas the dolomitic Crevoladossola marble is widely spread and appreciated on the market. This work focusses on the varieties of the latter, the Crevoladossola marble: it pertains to the Mesozoic metasedimentary cover that tectonically separates the Monte Leone and Antigorio nappes (lower Penninic Units), with a quite steep structural setting and multiphase folding. The location of the quarry (Lorgino di Crevoladossola) is the same of the historic Pavia quarry of the «Fabbriceria del Duomo di Pavia», at the beginning of the 16th century. At present time there is only one active quarry which produces nine commerciali varieties: among these, Palissandro Bluette, Palissandro Blu Nuvolato, Palissandro Classico and Palissandro Oniciato are the most common ones. The quarry front is terraced and the extraction technology only uses diamond wire technology; the large extracted blocks are then selected based on their dimension, textural and chromatic features. The Crevoladossola marble (dolomite content 75 – 90% wt.)  has fine grain size and variable colour and texture due to the different amount of phlogopite (10 – 25% wt.) which defines the foliation plane, characterized by abundant isoclinal folds; there are also smaller amounts of quartz, anorthite, chlorite, tremolite, and rare disseminated sulphides. The presence of tremolite initially created doubts about the possible presence of asbestiform phases, however in-depth SEM-EDS analytical investigations excluded the presence of fibers, showing only cleavage fragments or prismatic - acicular crystals. With respect to the Candoglia and Ornavasso marbles, the Crevoladossola marble has markedly anisotropic physical and mechanical properties. In the Archaeological Museum of Milano possibly there is the first evidence of the use of this type of marble, represented by a sculpture of a Roman person (T. Labieno). Since 13th and 14th centuries this material was widely utilized in the local architecture of Domodossola, Baceno and Montecrestese, whereas its use was scarce in Lombardy: the main representative buildings are Arco della Pace in Milano with eight monolithic marble columns (10 m height) and the Duomo in Pavia (since 14th century). The marble is now used for internal facing, furnishings and valuable objects: in 1995 a block of Palissandro Classico was worked to produce the significant sculpture «Uovo della Pace» for UNICEF. The overall good quality of the rock mass and a rational exploitation make this quarry an exemplary model of dimension stone extraction; at the present time, efforts are also being made to exploit production waste, from crushed stone up to sawing sludge.

How to cite: Cavallo, A. and Dino, G. A.: The Crevoladossola marble (Piedmont, northern Italy): nine commercial varieties in just one quarry!, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12534, https://doi.org/10.5194/egusphere-egu21-12534, 2021.

EGU21-13576 | vPICO presentations | ERE5.1

Valentia Slate, Co. Kerry, Ireland: a Global Heritage Stone Resource proposal

Patrick Wyse Jackson, Louise Caulfield, Aidan Forde, Iseult Conlon, Peter Cox, and George Sevastopulo
Valentia Slate from the southwest of Ireland, is herein proposed as a Global Heritage Stone Resource. This Middle Devonian (Givetian) purple to pale green-colouredfine-grained siltstone comprises the Valentia Slate Formation, part of the Old Red Sandstone which extensively crops out in southern Ireland.  The unitwhich developed as an alluvial fan, has a thickness of over 3000m and shows a well developed cleavage and low metamorphic grade imposed during the Variscan which produced its slaty fabric. Although quarried from small surface openings from the late eighteenth century, the commercial value of certain horizons of the Valentia Slate Formation was first recognised by the local landowner The Knight of Kerry who commenced its extraction at Dohilla in 1816 for use as roofing slates.  The operation was expanded from the 1820s by the Hibernian Mining Company and later by the Valentia Slab Company and its successorthe Valentia Slate Companywhich continued to quarry the stone until the late 1870s. Initally stone was extracted from surface workings but since 1840 it has been exclusively obtained from underground workings. From the 1880s the quarry went into decline due to competition from Wales and extraction ceased altogether in 1911 following a large rockfall at the opening to the quarry.  It was revived in the 1980s and recent investment has resulted in being able to provide this quality stone to widespread markets. Although not easily split into thin slates Valentia Slate was first used locally for roofing and general building. Howeveras it could be cut into slabs of a variety of thicknesses and lenghts of up to 3m it was more readily adoptedboth nationally and internationallyfor use in buildings for window cills, steps, domestic fittings in bathrooms and kitchens, and paving both externally and internally as in the Houses of Parliament in London, the Paris Opera House, and for flagging in a number of British railway termini.  The stone was susceptible to and held sharp carving, and it it was also fabricated into headstones, memorials, garden furniture, and shelving. Stone was even exported in the 1870s to Brazil for use as railway sleepers. Craftsmen also fabricated lamps and birdhouses from the material and its most celebrated use was for billiard and snooker tables, a number of which were highly decorative having been enamelled.  During the height of production over 500 men were employed quarrying and working Valentia Slate. The first tramway in an Irish quarry was installed in about 1816 and was used to transport stone and sawn slabs from the quarry to Knightstownsome 4km awaywhere it was further fabricated if required in a dedicated stoneyard prior to exportation from the adjacent slate quay.  Today extraction continues and the stone is used for a variety of restoration, decorative and construction purposes. The longevity of its extraction, its versatility of use, and the extent of the exportation of the Valentia Slate makes it worthy to be proposed as a Global Heritage Stone Resource.

How to cite: Wyse Jackson, P., Caulfield, L., Forde, A., Conlon, I., Cox, P., and Sevastopulo, G.: Valentia Slate, Co. Kerry, Ireland: a Global Heritage Stone Resource proposal, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13576, https://doi.org/10.5194/egusphere-egu21-13576, 2021.

EGU21-13615 | vPICO presentations | ERE5.1

Mapping Lioz limestone in monuments at Rio de Janeiro, Brazil

Amanda Mozer, Nuria Castro, Kátia Mansur, and Roberto Carlos Ribeiro

Lioz limestone is a well-known Portuguese natural stone, recognised as Global Heritage Stone Resource (GHSR) by the International Union of Geological Sciences (IUGS). This microcrystalline Cretaceous limestone was broadly used in churches and monuments, especially in Lisbon, where it is exploited. It exhibits four varieties of colours: ivory (Lioz), beige (Chainnette), dark pink (Encarnadão), yellow (Amarelo de Negrais), and also many fossils of Rudists, Gastropods and Thalassinoides. This rock was brought to Brazil as ballast in vessels, to stabilise them, and to bring a Portuguese symbol to the "new land". It was mostly used in historical buildings in coastal cities (Belém, Recife, Salvador, São Luis, and Rio de Janeiro) from the 16th to the 20th century, though it can be found in many other of Brazil. The stone that shines in Lisbon, the Royal Stone from Portugal, keeps in Brazilian monuments the memory of the strong relationship between Portugal and Brazil, along this country's history, first as an overseas colony and later as the seat of the United Reign of Brazil, Portugal and the Algarves. The history engraved in these monuments guards that memory, being essential to study the processes of degradation that these rocks suffer. In the central region of Rio de Janeiro, known as “Old Rio”, many heritage buildings present Lioz limestone, usually together with local gneisses, in their construction and ornamentation: in floors, altars in churches, walls, columns and others. Some examples are the Royal Portuguese Cabinet of Reading, the Church of Our Lady of the Candelaria, the Bank of Brazil Cultural Center, the Imperial Palace, the Saint Francis of Paola Church, the Saint Luzia Church, the Master Valentim Fountain, the Holy Cross of the Military Church, the Saint Joseph Church, the Riachuelo Teather, and the Gustavo Capanema Palace. The last one is a symbol of the modernism in Brazil. Some of these buildings are in routes of urban geotourism as a form to disseminate science. These places are relevant in many aspects, such as cultural, historical, architectural, geological and educational. Rio de Janeiro is a coastal city with an average temperature of 23,2ºC, rainfall of 1,278mm per year and relative humidity of 78%. Lioz limestone's alteration gets more accentuated in these conditions, and the deterioration can be even more intense. Another point to observe is that many of these buildings are in high traffic areas, and the pollution emitted by the vehicles is highly prejudicial because of the cycles of dry and wet deposition. The Lioz limestone presents low porosity; however, problems as black crusts and biological colonisation are common and can lead to severe forms of degradation, and the monuments' mischaracterisation. This work aims to elaborate an inventory of the monuments constructed and ornamented with Lioz limestone and the observed decay patterns of this stone in Rio de Janeiro. The inventory and the study of the mechanisms and extension of their degradation over time are crucial for their effective conservation for future generations.

How to cite: Mozer, A., Castro, N., Mansur, K., and Ribeiro, R. C.: Mapping Lioz limestone in monuments at Rio de Janeiro, Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13615, https://doi.org/10.5194/egusphere-egu21-13615, 2021.

EGU21-1129 | vPICO presentations | ERE5.1

The map of the Global Heritage Stones: a resource in development

Victor Cardenes Van den Eynde and Gurmeet Kaur

In 2008, during the 33rd IGC in Oslo, a working group on natural stones and heritage built in stone was created. In 2012, the working group was accepted as an IUGS Task Group and in 2016 the network was upgraded to Subcommission: the IUGS Heritage Stones Subcommission (HSS). Since then, HSS has worked on the designation of 22 stones as Global Heritage Stone Resource (GHSR), a figure that distinguishes and protects extraordinary stones that have been used to construct some of the most important monuments and historic buildings, some even designated as UNESCO World Heritage. GHSR is a geological standard approved by the IUGS Executive Committee. The Subcommission continues working on the study, nomination and designation of more GHSR, following a strict and transparent protocol that guarantees that the designated stones are perfectly identified and documented. This process is performed under the review of experts in stone heritage and dimension stone. The results on the heritage stones have been published in different journals, special issues of scientific journals and books. The present work displays the 22 stones designated as GHSRs up to now, showing their locations on the world map, exhibiting the rock specimens, together with a list of the publications considered for the designation of these as GHSRS by the Heritage Stones Subcommission. The map will continuously be updated, plotting the new designated GHSRs as and when approved by the IUGS-EC.

How to cite: Cardenes Van den Eynde, V. and Kaur, G.: The map of the Global Heritage Stones: a resource in development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1129, https://doi.org/10.5194/egusphere-egu21-1129, 2021.

ERE5.3 – Sustainability as a challenge to face and a goal to reach: interdisciplinary approach to support raw materials and energy supply

EGU21-6629 | vPICO presentations | ERE5.3

A concept for sustainable and digitalized hydropower going beyond the sustainable hydropower sustainability tool

Eduard Doujak, Marko Hočevar, Elena Pummer, Vittorio Di Federico, and David Finger

The EU energy policy has the ambitious objective to become the first carbon-neutral continent in the world. In order to achieve this objective hydropower will have to play an essential role as energy source and energy storage in pump storage facilities. Hydropower is a clean, low carbon, and cost-efficient energy source that can be exploited sustainably if an adequate management system is implemented. Nevertheless, in the past, hydropower operations have led to conflicting interests over water usage, impacts on aquatic flora and fauna, and significant socio-economic implications. In order to avoid and mitigate possible negative consequences of hydropower plants the Hydropower Sustainability Assessment Protocol (HSAP, https://www.hydrosustainability.org/) provides a helpful tool to minimize related impacts. In this presentation we will delineate how the 26 topics of the HSAP could be complemented in order to provide a fully digitalized sustainability framework for hydropower. In particular, we will outline innovative solutions for the most challenging topics of sustainable hydropower plants, including i) energy supply securing with a high share of renewable energies ii) climate change impacts on water resources and hydropower production, ii) altered flow and changed turbidity dynamics in rivers, iii) long-term downstream effects on river beds and groundwater exchange, iv) degradation of river ecology, v) socio-economic impacts on local stakeholders, vi) adequate assessment of the water-energy-food nexus, vii) near real time digitalisation framework to streamline information. Through the digitalization of the HSAP a standardized and transparent flow of information will be guaranteed. Within the presented digitalized framework, all data will be processed to standardize, harmonize and synthesize results and information from all working tasks into a data lake. We may apply this framework to demonstration hydropower plants of different types to improve their sustainability, efficiency and management.

How to cite: Doujak, E., Hočevar, M., Pummer, E., Di Federico, V., and Finger, D.: A concept for sustainable and digitalized hydropower going beyond the sustainable hydropower sustainability tool, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6629, https://doi.org/10.5194/egusphere-egu21-6629, 2021.

EGU21-3168 | vPICO presentations | ERE5.3

Setting the problem of energy production forecasting for small hydropower plants in the Target Model era

Korina Konstantina Drakaki, Georgia-Konstantina Sakki, Ioannis Tsoukalas, Panagiotis Kossieris, and Andreas Efstratiadis

The highly-competitive electricity market over EU and the challenges induced by the so-called “Target Model”, introduce significant uncertainties to day-ahead trades involving renewable energy, since most of these sources are driven by non-controllable weather processes (wind, solar, hydro). Here, we explore the case of small hydropower plants that have negligible storage capacity, and thus their production is just a nonlinear transformation of inflows. We discuss different forecasting approaches, which take advantage of  alternative sources of information, depending on data availability. Among others, we investigate whether is it preferable to employ day-ahead predictions based on past energy production data per se, or use these data in order to retrieve past inflows, which allows for introducing hydrological knowledge within predictions. Overall objective is to move beyond the standard, yet risky, point forecasting methods, providing a single expected value of hydropower production, thus quantifying the overall uncertainty of each forecasting method. Power forecasts are evaluated in terms of economic efficiency, accounting for the impacts of over- and under-estimations in the real-world electricity market.

How to cite: Drakaki, K. K., Sakki, G.-K., Tsoukalas, I., Kossieris, P., and Efstratiadis, A.: Setting the problem of energy production forecasting for small hydropower plants in the Target Model era, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3168, https://doi.org/10.5194/egusphere-egu21-3168, 2021.

EGU21-10919 | vPICO presentations | ERE5.3

The HYPOS project as a support to the hydroelectric sector

Erica Matta, Mariano Bresciani, Claudia Giardino, Marina Amadori, Thomas Heege, Karin Schenk, Kim Knauer, Alena Bartosovar, Ilias Pechlivanidis, Marcelo Leite Ribeiro, Marina Launay, José Pedro Matos, Declan Kelleher, Nils Rüther, and Kordula Valerie Anne Schwarzwälder

The EC HYPOS (HYdro-POwer-Suite) project (https://hypos-project.eu/) has the main goal of assessing the environmental impact of existing and future hydropower systems. The project will provide a suite of data analysis applications which integrates Earth Observation (EO) technologies and hydrological modelling. These include an online Decision Support Tool (DST) for investment planning and monitoring, as well as a subscription portal combining satellite data over time, current measurements and detailed estimates for present and near future assessments. A dedicated analysis on the “blue footprint” (i.e. the amount of water used to produce a service) of reservoirs is included for addressing sustainable monitoring solutions. Such analysis comprises the evaluation of the climate change effects on reservoirs management and hydropower production. For instance, extreme weather events like short-term heavy precipitations are connected with flooding and transport of large amounts of sediments in dammed reservoirs, with critical consequences for their management. Similarly, global warming can heat the surface of water bodies and induce higher evaporation rates, thus decreasing the amount of water available for energy production.  

In this study we present the first products from HYPOS project. These products are representative of what can be generated within the DST using elaboration techniques of EO data. Gridded products of water quality parameters (e.g. water turbidity, Chlorophyll-a concentration, suspended sediments concentration) are generated for the test sites of the project, which are small dammed reservoirs located in Switzerland, France, Albania and Georgia. These products are obtained using the Modular Inversion and Processing System (MIP), a sensor independent image processing chain based on radiative transfer models, which works in a multi-layer system, solving the light transfer in the atmosphere, at the water surface and inside the waterbody.

For the assessment of the “blue footprint” of a reservoir, the water loss due to evaporation is computed by applying a consolidated mass transfer evaporation method to EO data. The resulting evaporation rates are first compared with the outputs of semi-automatic evapotranspiration EO-based models (e.g. SEBAL), and then with the estimates ​​obtained from two different numerical models: a hydrological model (E-Hype) and a 3D hydrodynamic model (Delft3D). The key parameters influencing water evaporation rates, their behavior and the issues related to each approach are analyzed. The first comparison results are made for lake Garda, where a complete set of data is available for the production of evaporation maps.

How to cite: Matta, E., Bresciani, M., Giardino, C., Amadori, M., Heege, T., Schenk, K., Knauer, K., Bartosovar, A., Pechlivanidis, I., Ribeiro, M. L., Launay, M., Matos, J. P., Kelleher, D., Rüther, N., and Schwarzwälder, K. V. A.: The HYPOS project as a support to the hydroelectric sector, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10919, https://doi.org/10.5194/egusphere-egu21-10919, 2021.

EGU21-6929 | vPICO presentations | ERE5.3

Assessing the impact of climate change on Southeast Asia’s hydropower availability

Thanh Duc Dang, Jia Yi Ng, and Stefano Galelli

Southeast Asia’s electricity supply largely depends on the hydropower resources of the Mekong, Chao Phraya, Irrawaddy, and Salween River Basins. Uncertain precipitation patterns, rising temperature, and other climate-driven changes are exposing these resources to unprecedented risks, prompting decision makers to re-evaluate existing reservoir management strategies through climate change risk assessments. These assessments are important in shaping the operators’ response to hydro-climatic variability and are necessary to ensure energy security in the region. In this study, we developed high-resolution, semi-distributed hydrological models to examine the potential changes of hydropower availability under projected future climate scenarios in the four largest river basins in South East Asia. Specifically, we relied on a novel variant of the Variable Infiltration Capacity (VIC) model that integrates reservoir operations into the routing scheme, warranting a more accurate representation of cascade reservoir systems. Climate change impacts were derived from the outputs of five Global Circulation Models (GCMs) forced by two Shared Socioeconomic Pathways (SSPs 2.6 and 8.5) emission scenarios in the Coupled Model Intercomparison Project Phase 6 (CMIP6). We find that hydropower generation would be altered significantly in all scenarios in terms of temporal variability and magnitude due to the changes in duration and magnitude of the summer monsoon. Our findings further stress the importance of exploring how the impact of climate change on hydropower availability propagates through water-energy systems and call for adaptive reservoir operation strategies.

How to cite: Dang, T. D., Ng, J. Y., and Galelli, S.: Assessing the impact of climate change on Southeast Asia’s hydropower availability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6929, https://doi.org/10.5194/egusphere-egu21-6929, 2021.

Reservoir sedimentation has a prominent impact on the hydropower performance in the future and is a growing concern for hydropower stakeholders. Sedimentation caused by soil erosion is influenced by various parameters. Reservoir sedimentation is one of the most challenging problems that affect hydroelectric production since it overall causes a reduction of the reservoir capacity that overcomes the annual increase in storage volume and implies a dangerous net loss of energy. The first part of this study examined various Italian reservoirs (50 dams) to determine sedimentation rates and storage capacity loss based on available bathymetric surveys. All the reservoirs studied here have reached an average age of 74 years as of 2019, with the highest loss of capacity observed at 90% and the highest annual sediment yield of 2471 m3/km2/year. Out of all the reservoirs studied, 25% of them already have reached their half-life as of 2019. The second part of this study extended the work to the specific case study of the Ceppo Morelli hydropower plant. The study was carried out to analyse the water-sediment interaction, future sediment load and prioritizing of critical soil erosion areas using the Soil and Water Assessment Tool (SWAT). The distinguishing feature of this work lies in the possibility to exploit remote sensing data (i.e. actual/potential evapotranspiration) to successfully calibrate hydrological models in scarce data regions. Simulation results indicated that the discharge and sediment load entering Ceppo Morelli reservoir will decline and the rate of reduction of latter is higher than that of former for all the future climate scenarios implemented. This analysis will provide a starting point for management and prioritization of adaptation and remediation policies for addressing the issue of reservoir sedimentation. These results are part of the RELAID project funded through PRIN-Italy. The aim of this project is to integrate updated knowledge on hydrologic, hydraulics, and sedimentation processes to address the water and flood risk management of impounded Italian rivers through a holistic paradigm.

Keywords: reservoir sedimentation; hydropower; hydrological modeling; RELAID; Italy

How to cite: Patro, E. R. and Michele, C. D.: Assessment of Reservoir Storage Capacity Loss and Investigating the Effects of Climate Variability on Reservoir Sedimentation in Italy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2651, https://doi.org/10.5194/egusphere-egu21-2651, 2021.

EGU21-16429 | vPICO presentations | ERE5.3

Emerging mitigation measures and strategies are needed for riverine ecology to ensure sustainable hydropeaking production in Norway 

Jo Halvard Halleraker, Mahmoud S. R. Kenawi, Jan Henning L’Abée - Lund, Anders G. Finstad, and Knut Alfredsen

Riverine biodiversity is threatened with severe degradation from multiple pressures worldwide. One of the key pressures in European rivers are hydromorphological alterations. Rehabilitation of river habitats is accordingly high on the political agenda at the start of UN decade of ecological restoration (2021-2030).

Water storage for hydropower production (HP) has severe impacts on aquatic ecology in Norway, with more than 3000 water bodies designated as heavily modified due to hydropower. Norway is the largest hydropower producer in Europe with a huge amount of high head storage schemes. Ca 86 TWh of this is storage hydropower, which constitutes more than 50% of the total in Europe. This makes Norway a potentially significant supplier of hydropeaking services. Flexible hydropower operations are crucial for EUs Green Deal in balancing electricity from renewable intermittent power generation such as wind and solar. 

Many Norwegian HP licenses were issued before modern environmental requirements evolved. Few are re-licensed with emerging strategies to mitigate hydropeaking. Still, there seems to be a common understanding of relevant mitigation strategies emerging between many large hydropower producers. For example, flow ramping from hydropower tailrace water with direct outlet into fjords or other lake reservoirs may be less environmentally harmful than outlet into riverine habitat.In this study, we have assessed the Norwegian hydropower portfolio of more than 1600 HP facilities constructing a national database focusing on the knowledge base for assessing potential downstream hydropower ecological impacts. The ecological severity of such flow ramping and the restoration/mitigation potential, may depend on;

 

About 51 % of the HPs (ca 80TWh) have tailrace into shorter rivers (<1 km) or directly into fjords or lake/reservoirs. Many of the largest HPs are in this category (e.g 50 HP> 500 MW). Close to 800 HP might have downstream impacts on rivers (> 0.5 km; about 49 % of all HP, in total of ca 56 TWh). Probably > 3 000 km of regulated rivers in Norway therefor might need more ecosystem-based mode of HP operation. Flow ramping analysis:  Ecosystem-based HP operational rules are established in a selection of sustainably managed Norwegian rivers, still with significant baseload production (0.35-0.76 - TWh annual prod). However, eco-friendly mode of operation seems to be rare as our analysis indicate that flow ramping with potential ecological degradation seems widespread in many rivers. Surprisingly, even in many with operational ramping restriction as required mitigation.Our database may be further improved and updated (with e.g. more flow ramping data and biological indicators) and serve as a basis for a national hydropeaking strategy, and hence make more of the Norwegian hydropower portfolio in line with the EUs sustainability taxonomy.

How to cite: Halleraker, J. H., Kenawi, M. S. R., L’Abée - Lund, J. H., G. Finstad, A., and Alfredsen, K.: Emerging mitigation measures and strategies are needed for riverine ecology to ensure sustainable hydropeaking production in Norway , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16429, https://doi.org/10.5194/egusphere-egu21-16429, 2021.

EGU21-14452 | vPICO presentations | ERE5.3

Quanitification of sustainable hydropower potential in the Upper Indus basin

Sanita Dhaubanjar, Arthur F. Lutz, David Gernaat, Santosh Nepal, Saurav Pradhananga, Sonu Khanal, Arun Bhakta Shrestha, and Walter Immerzeel

Considering the lack of a comprehensive assessement of hydropower potential in the Upper Indus basin, we developed and implemented a systematic framework to explore four different classes of hydropower potential. Our framework uses high-resolution discharge generated by a coupled cryosphere-hydrology model as the bio-physical boundary conditions to estimate theoretical potential. Thereafter, diverse context-specific constraints are implemented stepwise to estimate the technical, economic and sustainable hydropower potential. The successive classes of hydropower potential integrate considerations for various water demands under the water-energy-food nexus, multiple geo-hazard risks, climate change, environmental protection, and socio-economic preferences. We demonstrate that the nearly two thousand Terawatt-hour of theoretical potential available annualy in the upper Indus can be misleading because a majority of this is technically and economically not viable. Even smaller potential remains if we account for the various sustainability constraints that vary spatially. Our concept of the sustainable hydropower potential enables decision makers to look beyond the energy sector when selecting hydropower projects for development to achieveenergy security under the Sustainable Development Goal 7 (SDG7).The generated portfolio of sustainable hydropower projects is superior to the current portfolio based on outdated studies because our method looks beyond theoretical possibilities and excludes projects that conflict with management objectives under other SDGs. The spatial maps with potential and the cost curves for hydropower production provide a science-based knowledge base for hydropower development in the Indus basin. Our method could similarly be adapted to inform hydropower development in other basins across the globe.

How to cite: Dhaubanjar, S., F. Lutz, A., Gernaat, D., Nepal, S., Pradhananga, S., Khanal, S., Bhakta Shrestha, A., and Immerzeel, W.: Quanitification of sustainable hydropower potential in the Upper Indus basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14452, https://doi.org/10.5194/egusphere-egu21-14452, 2021.

EGU21-3781 | vPICO presentations | ERE5.3

In-stream turbines for sustainable hydropower development in the Amazon river basin

Suyog Chaudhari, Erik Brown, Raul Quispe-Abad, Emilio Moran, Norbert Mueller, and Yadu Pokhrel

Given the ongoing and planned hydropower development projects in the Amazon River basin, appalling losses in biodiversity, river ecology and river connectivity are inevitable. These hydropower projects are proposed to be built in exceptionally endemic sites, setting records in environmental losses by impeding fish movement, altering flood pulse, causing large-scale deforestation, and increasing greenhouse gas emissions. With the burgeoning energy demand combined with the aforementioned negative impacts of conventional hydropower technology, there is an imminent need to re-think the design of hydropower to avoid the potentially catastrophic consequences of large dams. It is certain that the Amazon will undergo some major hydrological changes in the near future because of the compounded effects of climate change and proposed dams, if built with the conventional hydropower technology. In this study, we present a transformative hydropower outlook that integrates low-head hydropower technology (e.g., in-stream turbines) and multiple environmental aspects, such as river ecology and protected areas. We employ a high resolution (~2km) continental scale hydrological model called LEAF-Hydro-Flood (LHF) to assess the in-stream hydropower potential in the Amazon River basin. We particularly focus on quantifying the potential and feasibility of employing instream turbines in the Amazon instead of building large dams. We show that a significant portion of the total energy planned to be generated from conventional hydropower in the Brazilian Amazon could be harnessed using in-stream turbines that utilize kinetic energy of water without requiring storage. Further, we also find that implementing in-stream turbines as an alternative to large storage-based dams could prove economically feasible, since most of the environmental and social costs associated with dams are eliminated. Our results open multiple pathways to achieve sustainable hydropower development in the Amazon to meet the ever-increasing energy demands while minimizing hydrological, social, and ecological impacts. It also provides important insight for sustainable hydropower development in other global regions. The results presented are based on a manuscript under revision for Nature Sustainability.

How to cite: Chaudhari, S., Brown, E., Quispe-Abad, R., Moran, E., Mueller, N., and Pokhrel, Y.: In-stream turbines for sustainable hydropower development in the Amazon river basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3781, https://doi.org/10.5194/egusphere-egu21-3781, 2021.

EGU21-10030 | vPICO presentations | ERE5.3

Experimental and CFD Simulation Studies on the Flow Approaching a Type-A Piano Key Weir

Subhojit Kadia, Binit Kumar, Elena Pummer, Nils Ruther, and Zulfequar Ahmad

Many dams around the world are ageing and require upgradation in terms of spillway capacity and other safety aspects. In recent times, challenges faced due to global warming, climate change and cloudburst events have grown not just in numbers but also in extremity. Consequently, several dams and diversion structures are being modified to cope up with the floods resulting from such events. Piano key weir (PKW) has effectively been used in many dam upgradation projects, especially in France and Vietnam, to enhance the discharge capacity of the existing ogee-crested weirs or labyrinth weirs. It has also been used in a diversion scheme in India (Sawra Kuddu). The flow field around a PKW is spatially varied, complex and three-dimensional in nature. The previous researches on PKWs were predominantly focused on the effect of different parameters on its discharging capacity and limited studies are available on the flow field, sediment movement and scouring at PKWs. Considering these gaps, this study was initiated to understand the flow pattern near PKW and its effect on the sediment transport over PKW. Presented here is the experimental work carried out at IIT Roorkee, India on a Type-A PKW flume model with two discharge values, the CFD simulations of those two flow conditions and a comparison between the results. The time-averaged velocity values were measured at different locations in the front of inlet and outlet keys (upto a distance of 0.1 m from the bed level) using a 3D Acoustic Doppler Velocimeter. The simulations were performed in Ansys (academic 19.1) CFX solver using finite volume method, standard k-ε turbulent model, (where k denotes the turbulent kinetic energy and ε is the rate of dissipation of k) and multiphase (volume of fluid) modelling. The experimental results showed an increase in the depth-averaged longitudinal flow velocity towards the inlet, but a decrease in that towards the outlet. A significant rise in the upward velocity (in the outer flow region) towards both the keys was observed experimentally and numerically. Both the approaches also indicated a significant increase in the lateral velocity near the inlet, especially in the inner flow region. CFD simulations clearly showed decelerating and accelerating flow zones in front of the outlet and inlet keys, respectively, and also revealed an accelerating flow over the inlet. However, the velocity profile inside the inlet key could not be measured experimentally, possibly due to flow unsteadiness, high turbulence and flow separation, and it demands further research. The CFD results generally underestimated the velocity values for the measured 0.1 m depth of flow and the mean absolute error values for the resultant velocity were 18.32% and 15.52% for the two discharges, respectively. The rise in the approaching flow velocity components towards the inlet and the sloping key enhance the opportunity of sediment passage over a PKW in comparison to other weirs. Extending this work, the study on the flow field near two-cycles and three-cycles PKW models is undergoing.

How to cite: Kadia, S., Kumar, B., Pummer, E., Ruther, N., and Ahmad, Z.: Experimental and CFD Simulation Studies on the Flow Approaching a Type-A Piano Key Weir, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10030, https://doi.org/10.5194/egusphere-egu21-10030, 2021.

EGU21-8352 | vPICO presentations | ERE5.3

Vision of the mine of the future

Gorazd Žibret

Average mined ore grades are constantly decreasing and easily accessible high-grade mineral deposits have already been mined out. Together with the ever-increasing demand for raw materials, a sustainable supply is becoming very challenging for the mining industry. Ores are being exploited in very large operations and in more and more extreme environments. The presence of high temperatures, poisonous gasses or other harmful substances, water, geotechnical instabilities, etc., limits the possibilities for humans to work in such environments, and increases the costs of mining. New paradigm of ore prospection and extraction is needed, and the use of robotics and automation provides a potential solution.

The mid-term vision of mines of the future is that humans would not need to be present at the extraction sites anymore. Mining machinery will become remotely controlled or semi-automated. This would significantly reduce the costs of mining operations and eliminate the risks associated with humans working in life-threating environments. The main challenges are related to sensing of the surroundings and the presentation of such data in a virtual reality model, the machine-human-machine and machine-machine communication, positioning, energy supply and similar. This technology can transform the mining industry in a similar way as the development of construction machines transformed the construction sector in the last century.

In the long-term vision the mines will be completely automated. Mining machines will be able to sense its environment, allowing them to make decisions autonomously. They will also be able to self-assemble, repair, and perhaps even produce their own copies underground. Robots of the mines of the future will be specialised in a similar way workers are specialised today. Ore processing will be accompanied by an autonomous ore processing system at the site of extraction, which will enable the delivery of concentrate or even ingots to the surface and leave the waste material underground. With such systems highly selective low-environmental impact mining of many currently uneconomical ore bodies could become feasible and would allow mining in ultra-deep environments which are today far beyond our reach. With such mining system, mining of extra-terrestrial bodies could also become a reality, and could even put an end to mining on Earth altogether. Many challenges need to be addressed, including energy supply, locomotion, communications, environmental awareness, big data handling and processing, automated decision-making systems, new rock-cutting technologies, ore transport systems, machine and software maintenance and adaptation, etc.

Humanity is already taking first steps towards this vision. Several international projects have been funded on the topic of sensing, using remotely controlled machines or autonomous robots to perform dangerous exploration or mining tasks: iVAMOS!, UNEXMIN, ROBOMINERS, AutoFlyMap, ROBUST, RODEO,  BADGER, Real-Time Mining, MINERAL EYE and others (funded by the Horizon2020), BlueHarvesting, FIREM-II, HoloMine, UNDROMEDA and others (funded or co-funded by the EIT RawMaterials), or several industrially-funded projects such as Longwall automation mining, A3R, MSRBOTS, ARIDuA, and many others. Many companies which develop robots or other automatic equipment for mines are also emerging, including Unexmin Georobotics, EXPLORA, Equipois, Sandvik, Superdroid Robots, National Robotics Engineering Center, BROKK and others.

How to cite: Žibret, G.: Vision of the mine of the future, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8352, https://doi.org/10.5194/egusphere-egu21-8352, 2021.

EGU21-6606 | vPICO presentations | ERE5.3

Making a mine invisible: the coming challenge for geoscientists for sourcing critical raw materials

Vitor Correia, Julian Hilton, Hari Tulsidas, Michael Neumann, and Balazs Bodo

Converging technologies in robotics, miniaturisation, and cost-efficient drilling are already being used by European researchers to create a robot-miner prototype[1] for small and difficult to access mineral deposits. This will certainly trigger more research and innovation in scalability, resilience, reconfigurability, collective behaviour and operation of the robot(s) in harsh environments, alongside ore metallurgy and processing close-loop systems. The combination of these technologies and the robotisation of underground mining enables the creation of invisible mines. Invisible mines have the potential to reduce the environmental impacts of mines and their footprint while increasing the social acceptance of mining.

A recent United Nations[2] paper emphasises the need of innovation as a critical pathway to achieving the objectives in the 2030 Agenda for Sustainable Development and makes an urgent call for new business models in the mining industry. One of the principles it advocates is ‘comprehensive extraction’, also called ‘comprehensive and integrated resource recovery’. This new paradigm rests on the key assumption that a mine site should be disturbed only once, in the process recovering useful materials in an optimised integrated flowsheet and future-proofing any resources that are not of immediate interest rather than discarding them as wastes. The implementation of ‘comprehensive and integrated resource recovery’ can be pulled by the combination of current progress in three areas: a) research and innovation; b) investment activities; and c) skills, education and knowledge. All three, alone or in combination, have a role to play in developing invisible mines. 

Despite efforts to reduce the environmental impacts of mines and their footprint, and to increase the social acceptance of the activity, a conventional economic rationale underpins economic feasibility studies. Under that logic, many minerals are either not extracted or are considered ‘waste’ an end-up being discarded. Advances in mining and ore processing methods designed to maximise robotic mining will create a fundamental shift in traditional business models since the extraction and maximisation of the value of all extracted materials increases the number of interactions in downstream industries. This will change traditional feasibility assessments, calling for the development of intelligent business models, capable of delivering sophisticated, comprehensive analysis, integrating a range of different value streams.

The unfolding of invisible mines combined with intelligent business models will shift skills and competencies of the mining workforce towards more complex cognitive categories with increased requirements in digital literacy, alongside a holistic understanding of the value chains that are using mining outputs and enhanced expertise on communication and stakeholder engagement. This entails the urgent alignment of education and training contents and the continuous review and update of the international sectoral qualifications framework for the raw materials sector[3].


[1] Robominers H2020 project. See https://cordis.europa.eu/project/rcn/223247/factsheet/en

[2] Hilton et al. (2018). Transforming our world’s natural resources: A step change for the United Nations Framework Classification for Resources? https://www.unece.org/fileadmin/DAM/energy/se/pp/unfc_egrm/egrc9_apr2018/ece.energy.ge.3.2018.7_e.pdf

[3] Intermin H2020 project. See https://interminproject.org/

How to cite: Correia, V., Hilton, J., Tulsidas, H., Neumann, M., and Bodo, B.: Making a mine invisible: the coming challenge for geoscientists for sourcing critical raw materials, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6606, https://doi.org/10.5194/egusphere-egu21-6606, 2021.

EGU21-12675 | vPICO presentations | ERE5.3

Raw materials (CRM/SRM) supply from waste recycling and landfill mining: interdisciplinary approach to exploit resources from extractive waste facilities

Giovanna Antonella Dino, Alessandro Cavallo, and Claudia Chiappino

The acceleration in deployment of the key low carbon technologies in the wind, solar, and energy storage areas has real implications for the commodities market, not only rare earths, such as indium and neodymium. Aluminum, copper, silver, bauxite, iron, lead, and others all stand to potentially benefit from a strong shift to low carbon technologies. It would be reasonable to expect that all low carbon energy systems are more likely than not to be more metal intensive than high-carbon systems. All literature examining material and metals implications for supplying clean technologies agree that building these technologies will result in considerably more material-intensive demand than would traditional fossil fuel mechanisms. At present the minerals/materials considered “critical” (Critical Raw Materials – CRM) for EU economy are mainly constituted by rare earth metals, base and precious metals. The supply of CRM is highly connected to international politics and global market conditions; most of them are exploited in countries other than EU ones, causing high economic dependence from non-EU countries.

RM and CRM are principally extracted from natural resources, urban and industrial landfill sites, and extractive waste facilities. To evaluate the potentially exploitable quantity and typologies of RM/CRM and secondary raw materials (SRM), standardized protocols, including waste characterization and waste volume potentially exploitable are needed. Further to this, and together with environmental and human health aspects, the economic and societal aspects need to be integrated and therefore common cost benefit analysis (CBA) and life cycle assessment (LCA) methodologies should be also used. A more sustainable and integrated approach in the management of extractive industry at large, also thanks to proper Guidelines, is needed to boost the waste recycling. Some tools, as the sustainable finance, can be applied to encourage industries to be more responsible.

Fundamental is the interaction within Research Centers, Academies, Industries and Public Administrations in researching innovative and newer solutions for waste recycling (in terms of new technologies and products) and in guaranteeing the application at a wider scale of the products, objects of patents and already tested, not already present in the global market. In many cases, the possibility to re-use SRM from mining waste is invalidate from landscape constraints or bans on protected areas; to move these limits, it’s necessary working harmonically with Public Administrations and Mining Companies in order to show them the results of materials recovered in terms of LCA, if compared to mining.  The typical objection from “stakeholders” is to consider the removing operations too much invasive on territory, but this belief could be debunked with a correct, agreed approach of the project; good solutions of environmental recovery should be found after exploitation, also to solve safety and pollution problems and return the site in better condition. For these reasons, we consider to give priority to the case-histories which represent a real or potential risk (for production, of stability, hydrogeological, chemical, etc.), but in perspective mostly a precious resource.

The present research investigates the chance to guarantee a more sustainable mining in selected Italian case studies.

How to cite: Dino, G. A., Cavallo, A., and Chiappino, C.: Raw materials (CRM/SRM) supply from waste recycling and landfill mining: interdisciplinary approach to exploit resources from extractive waste facilities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12675, https://doi.org/10.5194/egusphere-egu21-12675, 2021.

EGU21-9385 | vPICO presentations | ERE5.3

Valorisation of mine and quarry waste in production of sustainable cements 

Sabina Dolenec, Katarina Šter, Klemen Teran, Andrej Ipavec, Maruša Borštnar, Lea Žibret, Bence Kószó, Snežana Nenadović, Nikolina Stamatovska Aluloska, Ildiko Merta, Richard Laucournet, and Gorazd Žibret

Various industrial residues that are either landfilled or currently have a low recycling rate could represent important secondary mineral resource potential for the construction sector. An ever-increasing construction sector causes increased demand for cement-based materials and consequently implies in increase of CO2 emission. Belite-sulfoaluminate cements are potentially an alternative cementitious binder to ordinary Portland cements, due to the lower embodied energy and reduced CO2 emissions compared to OPC clinkers. Its production also allows the substitution of natural raw materials with secondary ones. In the frame of RIS-ALiCE project, funded by the EIT RawMaterials, various industrial and mine residues in Eastern-Southeastern Europe are being mapped. In addition, as a matchmaking tool between the waste holders/producers and potential end-users the registry of secondary mineral raw materials has been developed. In this study, mine and quarry residues have been valorised in order to evaluate their suitability for production of innovative and sustainable low CO2-mineral binders. Residues from three mine sites (mine spoils from two Pb-Zn mines from Slovenia and Serbia and brown coal open pit mine from Slovenia) and two quarry sites (limestone quarries from Slovenia) were considered. Samples were characterized with respect to their chemical, mineralogical, physical and radiological properties. Furhermore, to assess the usability of particular residue in cement production, cement clinkers with belite, calcium sulfoaluminate and ferrite as main phases were synthesised, incorporating certain amounts of mine and quarry waste replacing primary raw materials. Main and trace elements as well as REE of residues were determined by X-ray fluorescence spectroscopy and ICP optical emission spectrophotometry. Mineralogical composition of residues as well as sythesised clinkers was determined by X-ray powder difraction and Rietveled method. Content of radionuclides (40K, 226Ra, and 232Th) was determined by gamma spectroscopy. Depending on the chemical composition of the residues, lower or higher amounts were allowed to be incorporated in the raw mixture for clinker production with targeted phase composition. Potential barriers in the cement production and environmental impact are also discussed. Developed registry with the data valuable for both, waste providers as waste users in Eastern-Southeastern Europe region, can be later-on upscaled also to other regions of Europe. It will provide the data on the available and appropriate secondary resources for cement production which will contrbute to the implementation of sustainable management of raw materials and circular economy.

Keywords: mine waste, quarry waste, cement, valorisation.

How to cite: Dolenec, S., Šter, K., Teran, K., Ipavec, A., Borštnar, M., Žibret, L., Kószó, B., Nenadović, S., Stamatovska Aluloska, N., Merta, I., Laucournet, R., and Žibret, G.: Valorisation of mine and quarry waste in production of sustainable cements , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9385, https://doi.org/10.5194/egusphere-egu21-9385, 2021.

EGU21-7589 | vPICO presentations | ERE5.3

Spatial distribution of the ophiolite-hosted Co–Ni–As-rich hydrothermal mineralization in the Punta Corna Mining complex, Lanzo Valleys, Northern Italy

Giovanni Grieco, Marilena Moroni, Micol Bussolesi, Alessandro Cavallo, and Simone Orizio

Cobalt is a transition metal with a trace element abundance in the Earth’s crust (26.6 ppm). It forms mainly sulfides like carrollite, siegenite and linneite and enters the cobaltite-gersdorffite solid solution and di-tri-arsenides safflorite, rammelsbergite and skutterudite while erythrite and asbolane are secondary Co phases. Cobalt is a Critical Raw Material for the EU, strategically important due to its use in the industry (batteries, superalloys, catalysts etc.).

Italy hosts several Co-bearing hydrothermal deposits, which were variably exploited in the past. In this work we focus on the Co-Fe-Ni hydrothermal veins emplaced within the metabasites of the Lanzo Valleys ophiolite complex in the western sector of the Alpine belt. The vein system is collectively called “Punta Corna mining complex”, and was exploited for Fe, Ag and later Co in the past (Castelli et al., 2011, Moroni et al., 2019).

A detailed field survey of the past cobalt mining works was carried out in summer 2019, followed by sampling, mostly inside mining tunnels and from waste dumps in order to increase data about this poorly known vein system.  Preliminary data comprise transmitted and reflected light study in thin section, XRD and EMPA analyses of selected samples.

Four deposition stages have been recognized in the samples, in agreement with preliminary results in Moroni et al. (2019), with Co enrichment occurring during the third stage. Detected Co phases are skutterudite, safflorite and secondary erythrite. Other common metallic minerals are löllingite, tetrahedrite, chalcopyrite, with Fe carbonate, quartz and baryte as gangue minerals.

In situ sampling allowed for the first time to map distribution of parageneses related to the different stages. Stage I, characterized by the deposition of siderite and ankerite, was detected in the western sector of Punta Corna. Stage II, characterized by baryte deposition, was not detected in any sample, but it was possible to observe baryte associated to siderite on the field in the western sector of Punta Corna. Stage III, characterized by Co-Fe-Ni arsenides, is developed mainly in the ore bodies of Punta Corna but extends also both to the West and to the East. Stage IV, characterized by base metal sulfides, covers the same area of stage III, with the exception of Speranza Mine, to the East of Punta Corna, where it was not detected. These studies are aimed to to evaluate the full extent of the ore system and better characterize the style of the mineralization.

References:

Moroni M., Rossetti P., Naitza S., Magnani L., Ruggieri G., Aquino A., Tartarotti P., Franklin A., Ferrari E., Castelli D., Oggiano G., Secchi F. (2019). Factors Controlling Hydrothermal Nickel and Cobalt Mineralization—Some Suggestions from Historical Ore Deposits in Italy. Minerals 2019, 9, 429.

Castelli, D., Giorza, A., Rossetti, P., Piana, F., Clerico, F. Le mineralizzazioni a siderite e arseniuri di cobalto-ferro-nichel del vallone di Arnàs (Usseglio, valli di Lanzo). In: Rossi M., Gattiglia A. (Eds.), Terre rosse, pietre verdi e blu cobalto. Miniere a Usseglio. Prima raccolta di studi. Museo Civico Alpino “Arnaldo Tazzetti”, Usseglio 2011, 14-21.

How to cite: Grieco, G., Moroni, M., Bussolesi, M., Cavallo, A., and Orizio, S.: Spatial distribution of the ophiolite-hosted Co–Ni–As-rich hydrothermal mineralization in the Punta Corna Mining complex, Lanzo Valleys, Northern Italy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7589, https://doi.org/10.5194/egusphere-egu21-7589, 2021.

EGU21-14821 | vPICO presentations | ERE5.3

Blast vibration reduction

Bernd Trabi, Florian Bleibinhaus, and Cornelia Tauchner

Blasting operations in quarries are accompanied by ground vibrations which can endanger buildings nearby. A production blast is made of several holes with a small distance to each other, which are blasted with a time delay, for the purpose of production and to reduce the ground vibrations. These production blasts produce a specific radiation pattern. It would be favorable to focus the ground vibrations to a less sensitive direction or area. We want to be able to predict the ground vibrations for a realistic inhomogeneous case at an area around the iron ore mine at mount Erzberg in Austria. Therefore a numerical forward modeling on a 3D model of the iron ore mine and its surrounding area was performed with a 3D elastic code with topography. The 3D model itself is the result of a tomographic travel time inversion. One problem is that the spectral response of a single blast is unknown and therefore we had to find a transfer function which transfers the numeric spectral response to the observed spectral response. After applying the transfer function the amplitude spectra of the numerical solution show a good match to the amplitude spectra of the observed production blasts. In this study, we investigate, if a reduction of ground vibrations can be achieved by blasting simultaneously two arrays with optimized time delays. To achieve that optimized time delays we developed a global search algorithm, based on Markov chain Monte Carlo method which finds potential blast configurations, with minimum impact to critical locations near the quarry. This study is part of the EU-funded project SLIM (Sustainable Low Impact Mining, www.slim-project.eu).

How to cite: Trabi, B., Bleibinhaus, F., and Tauchner, C.: Blast vibration reduction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14821, https://doi.org/10.5194/egusphere-egu21-14821, 2021.

EGU21-16018 | vPICO presentations | ERE5.3

Seismic radiation patterns of mine blasts

Florian Bleibinhaus and Bernd Trabi

Seismic vibrations induced by mine blasting are often a nuisance to residents and may even threaten the integrity of sensitive structure in the vicinity of mines. In this study we investigate the potential to reduce such vibrations through the interference with a second blast sequence. Assuming perfectly repeatable source wavelets and an acoustic, homogeneous model, we predict the radiation patterns of blast sequences with the Fourier shift theorem as a function of azimuth and incidence, and we benchmark those predictions with observations from a seismic array deployed at the iron ore mine Mt Erzberg, Austria. We then use our model to optimize the delay times of blast sequences with an inverse algorithm geared towards minimizing the predicted vibrations in certain target zones. Due to its symmetry, a single row of blasts has no azimuthal reduction potential. A second, quasi-simultaneous mine blast can, however, reduce blast-induced vibrations by up to 20% according to our model. In this study, we discuss the principles and the potential of this approach to vibration reduction. In a second study, we will present applied results obtained with a fully elastic model.

How to cite: Bleibinhaus, F. and Trabi, B.: Seismic radiation patterns of mine blasts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16018, https://doi.org/10.5194/egusphere-egu21-16018, 2021.

EGU21-10825 | vPICO presentations | ERE5.3

From hazardous asbestos containing wastes (ACW) to new secondary raw material through a new sustainable inertization process: a multimethodological mineralogical study

Narcisa Mihaela Marian, Giovanna Giorgetti, Claudia Magrini, Giancarlo Capitani, Lucia Galimberti, Alessandro Cavallo, Riccardo Salvini, Vanneschi Claudio, and Cecilia Viti

 Nowadays, asbestos-containing wastes (ACW) still represent an important environmental problem and a severe health hazard due to the well know pulmonary diseases derived from asbestos fibres inhalation. Except for a very few cases, ACW are currently confined in controlled landfills, giving rise to increasingly high amounts of still hazardous wastes. A promising alternative to landfill confinement is represented by ACW inertization, but the high cost of the inertization processes so far proposed by the scientific community have hampered the creation of actually operative plants. In this paper, we explore the possibility to use an innovative process that ensures the obtainment of asbestos-free inert material in an exceptionally short processing time, thus greatly reducing cost-related problems. The efficacy of the inertization process has been verified through accurate mineralogical investigations on both chrysotile and crocidolite de-activated fibres, through X-ray diffraction, scanning and transmission electron microscopy. Overall mineralogical, microstructural and granulometric characteristics of the inert bulk material suggest that it could be successfully re-used as a secondary raw material in ceramic industries. This innovative inertization procedure could therefore provide an effective and economically sustainable solution for ACW management.

How to cite: Marian, N. M., Giorgetti, G., Magrini, C., Capitani, G., Galimberti, L., Cavallo, A., Salvini, R., Claudio, V., and Viti, C.: From hazardous asbestos containing wastes (ACW) to new secondary raw material through a new sustainable inertization process: a multimethodological mineralogical study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10825, https://doi.org/10.5194/egusphere-egu21-10825, 2021.

EGU21-14169 | vPICO presentations | ERE5.3

Insight into municipal solid waste fly ash (MSWFA) heavy metals speciation by selective extractions and geochemical modelling

Davide Bernasconi, Caterina Caviglia, Enrico Destefanis, Linda Pastero, Costanza Bonadiman, Alessandro Pavese, Angelo Agostino, and Renato Boero

Nowadays municipal solid waste incineration (MSWI) has become a widespread and consolidated technology for MSW treatment all over the world. Indeed, it allows to reach up to 90% of waste volume reduction, while also producing energy. However, the incineration process has some drawbacks, one of which is the production of different residues that must be disposed of. Specifically, particular attention must be paid to fly ash (FA), which generally represents one of the most dangerous residues. FA is collected by the flue gas purification system and counts for around the 5% w/w of total incinerated waste. MSWI FA is regulated as a hazardous waste, mainly due to high concentrations of heavy metals (Pb, Cr, Zn, Cd) and soluble salts (chlorides and sulfates). Moreover, the average size of FA particles can be as low as 50-20 µm, thus determining a high surface area, which can increase toxic elements release into the environment. Therefore, many preliminary physicochemical stabilization treatments have been proposed over the years for their possible reuse as construction materials (e.g. water washing, thermal treatment, etc..). However, a detailed characterization of the residue in terms of heavy metals speciation is often overlooked. Indeed, this represents necessary information in order to understand and control the residue behavior in a reuse scenario and to design stabilization treatments as effective as possible.

In this work the analysis of heavy metals distribution and speciation of Turin MSW FA has been conducted, by combining both experimental treatments and geochemical modelling. In particular, a 4-step sequential extraction method has allowed to evaluate how heavy metals are distributed among four fractions with different physicochemical properties and, then, to deduct preliminary considerations about their leaching availability. In addition, pH-dependant leaching tests coupled by geochemical modelling using Virtual MINTEQ software has provided a more detailed insight into heavy metals speciation, by proposing possible phases which are often not detected by bulk analytical techniques. Finally, a general assessment of the hazardousness of Turin FA is discussed.

How to cite: Bernasconi, D., Caviglia, C., Destefanis, E., Pastero, L., Bonadiman, C., Pavese, A., Agostino, A., and Boero, R.: Insight into municipal solid waste fly ash (MSWFA) heavy metals speciation by selective extractions and geochemical modelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14169, https://doi.org/10.5194/egusphere-egu21-14169, 2021.

EGU21-14543 | vPICO presentations | ERE5.3

MSWI fly ash particle size chemical and mineralogical characterization, before and after leaching tests, aimed to reuse. 

Enrico Destefanis, Caterina Caviglia, Angelo Agostino, Davide Bernasconi, Linda Pastero, Costanza Bonadiman, and Alessandro Pavese

Municipal solid waste incinerator (MSWI) fly ash can represent a sustainable source of construction materials, but it needs to be treated in order to remove dangerous substances as chlorides, sulfates, and heavy metals. The concentration of salts and heavy metals in fly ash usually exceeds the law threshold and so they are considered a hazardous waste, unsuitable for reuse in concrete and civil engineering applications.In this work, a complete characterization of fly ash coming from a northern Italy thermovalorization plant was investigated, both on the solid and leachates composition, focused on the particle size, by X-Ray fluorescence and X-Ray diffraction on the solid matrices and ICP-MS analysis on the leachates.Using mechanical sieving on several subsamples of fly ash, six different particle size were separated and analyzed, and compared to the bulk fly ash composition.The most abundant elements are represented by Ca, Cl, S, and Si; trace elements and heavy metals are mainly represented by Zn, Fe, Al, Pb. The XRF and ICP-MS analysis show a general increasing trend, as the particle size decrease, of Na, K, Cl, S, as well as Cr, Cd, Cu, Pb, Sb, Zn, Ba, both on solid and leachates composition; on the contrary Ca and Si decrease.After leaching Cl and K decrease consistently, while it can be observed an increase of all the other elements, due to the weight loss attributable mainly to the leaching of Na-K chlorides, that is confirmed also by the X-Ray diffraction analysis.

How to cite: Destefanis, E., Caviglia, C., Agostino, A., Bernasconi, D., Pastero, L., Bonadiman, C., and Pavese, A.: MSWI fly ash particle size chemical and mineralogical characterization, before and after leaching tests, aimed to reuse. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14543, https://doi.org/10.5194/egusphere-egu21-14543, 2021.

EGU21-12038 | vPICO presentations | ERE5.3

Sustainability in georesources management: the importance of an updated school system to face the new challenges connected to mining activities

Manuela Lasagna, Giovanna Antonella Dino, Susanna Mancini, and Domenico Antonio De Luca

In recent decades, the environmental aspects connected to georesources management have come to the forefront. Topics such as “Sustainability”, “Responsibility”, “Eco-compatibility” are more and more important and the path towards an environmental and social sustainability of the "wise" use of georesources, leads to a "rethink" of "our" way of producing and consuming in an intergenerational perspective, also through a deeper understanding of the ethical value of the close link between socio-economic and natural systems.

The acquisition of the awareness about the necessity to move towards a more sustainable society needs a deep change of human attitude, which should involve institutions, industries and individuals. Itis fundamental to involve developed and developing countries in this new approach. A change in human attitudes starts with a proper training and education for all the subjects involved in georesource management, and in particular for students. Indeed, education for sustainable development is a strategic objective for the present and for the future of global development (UNECE, 2009). Education at all levels is the basis of the training of people able to live in current affairs with critical and conscious thinking and with a sense of legality in continuous construction (UNECE, 2011).

An example based on improving capacity building for the sustainable use of georesources is SUGERE (Sustainable Sustainability and Wise Use of Geological Resources) project, whose main objectives are the international standardization of university training and teaching activities concerning Earth Sciences and Mining Engineering, and the promotion of a more responsible and sustainable use of georesources. Thanks to SUGERE project, a strong research and training networks between European and non-European universities interested in mining issues have been set up.

SUGERE project aims to strengthen the role of the investigated discipline (earth sciences and mining engineering), to develop updated strategies for the sustainable management of natural resources, and to implement new collaboration thanks to an international network focused on local and social economic development in the geological/mining context. It has been elaborated a prototype proposal involving three representative African countries (Capo Verde, Angola and Mozambique) that can be replicated in other countries (African and not African). The key issue is the concept of Local Economic Development (LED) in the context of Mining/Geology combined with Environmental and Social Economic aspects.

The main objective is to graduate persons that are able to oppose the "Resource Curse"   that strikes countries that underperform economically, despite benefitting from valuable natural resources. Furthermore, it is expected to bring new ideas back to the European Partners. Main output of the project is the implementation of five degrees covering the three levels (BSc, MSc and PhD) whose common denominator LED is new in Geology/Mining.

The culture of sustainability and the deepening of skills in the field of geomining form the basis for the development of critical thinking, which is necessary for the resolution of local problems, for the acquisition of ethical values and technical skills that underpin sustainable development.

How to cite: Lasagna, M., Dino, G. A., Mancini, S., and De Luca, D. A.: Sustainability in georesources management: the importance of an updated school system to face the new challenges connected to mining activities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12038, https://doi.org/10.5194/egusphere-egu21-12038, 2021.

ERE5.4 – Mineral exploration for the XXI Century

EGU21-1368 | vPICO presentations | ERE5.4 | Highlight

UNEXUP, a robotic exploration technology for underground flooded mines

Márcio Pinto, Norbert Zajzon, Balazs Bodo, Luís Lopes, Stephen Henley, José Almeida, Jussi Aaltonen, Claudio Rossi, and Gorazd Zibret

UNEXUP is an EIT RawMaterials supported project (Project Number 19160) with the aim to improve and commercialize the robot-based technology developed in the H2020 UNEXMIN project (2016-2019). In UNEXMIN three underwater robot prototypes (UX-1 a,b,c) were built with geoscientific and navigational instruments capable of collecting valuable geological, mineralogical and spatial information from flooded mines without causing harm to the environment, risk to human lives, or high dewatering costs. This technology was tested in five different field trials and proved to be an efficient exploration method to sustainably evaluate the potential for mineral resources in these mines. For example, scanning sonars and structured light systems can map the environment even with near-zero visibility, the visible light cameras allow the identification of structural and geological features, the gamma-ray counter helps to identify minerals with natural radiation, and the pH, EC and water sampler allow the characterization of the waters in these sites.

In UNEXUP (2020-2022) the objective is to further improve this robot-based technology, test it in real-life environments, and commercialize it as an exploration service. The UNEXUP technology will comprise two new robots, which will add to the three UX-1s that were developed in UNEXMIN. These new robots consider the feedback and requirements from potential customers (e.g., mining companies and Geological Surveys) and other stakeholders of the predecessor project.

The first robot, UX-1Neo, is an upscaled version of UX-1, with the same dimensions and functionalities. This robot was built to address the limitations and malfunctions found in the previous line of robots, and it has software improvements that allow reduction of the number of operators, with faster mission setup time, and more efficient data collection and processing. With hardware improvements, it is a lighter, modular robot with better thruster control, an additional camera, and easily swappable batteries. The second robot, UX-2, to be built in 2021, will be a more complex unit with increased modularity, higher TRL, and greater operational depth. The modularity of both robots allow the sharing of some geoscientific instruments that are being developed, such as multispectral camera, water sampling unit, water chemistry measurement, and fluxgate magnetometer. In addition, there will be a rock sampling unit supported by a robotic arm, which will be developed exclusively for UX-2.

The robots will demonstrate their capabilities under real-life environments during the project. A real service-to-client approach is being carried out, and commercial missions have already been scheduled for the UX-1Neo in 2021. Some examples include a 3D inspection of a water well, geoscientific survey of a flooded salt mine, as well as other survey missions under discussion in Europe and worldwide.

Both robots are equipped with navigational and geoscientific instruments to address surveying requirements in flooded mines. However, there is a range of other applications for this technology, including: inspection of water wells and reservoirs, cultural heritage sites, cave exploration, environmental risk evaluation, and many other underwater structures that can benefit from this technology.

How to cite: Pinto, M., Zajzon, N., Bodo, B., Lopes, L., Henley, S., Almeida, J., Aaltonen, J., Rossi, C., and Zibret, G.: UNEXUP, a robotic exploration technology for underground flooded mines, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1368, https://doi.org/10.5194/egusphere-egu21-1368, 2021.

EGU21-11144 | vPICO presentations | ERE5.4

Towards robots with geologist eyes? Computer vision and Deep Learning approaches to field samples analysis

Antoine Bouziat, Sylvain Desroziers, Abdoulaye Koroko, Antoine Lechevallier, Mathieu Feraille, Jean-Claude Lecomte, and Renaud Divies

Automation and robotics raise growing interests in the mining industry. If not already a reality, it is no more science fiction to imagine autonomous robots routinely participating in the exploration and extraction of mineral raw materials in the near future. Among the various scientific and technical issues to be addressed towards this objective, this study focuses on the automation of real-time characterisation of rock images captured on the field, either to discriminate rock types and mineral species or to detect small elements such as mineral grains or metallic nuggets. To do so, we investigate the potential of methods from the Computer Vision community, a subfield of Artificial Intelligence dedicated to image processing. In particular, we aim at assessing the potential of Deep Learning approaches and convolutional neuronal networks (CNN) for the analysis of field samples pictures, highlighting key challenges before an industrial use in operational contexts.

In a first initiative, we appraise Deep Learning methods to classify photographs of macroscopic rock samples between 12 lithological families. Using the architecture of reference CNN and a collection of 2700 images, we achieve a prediction accuracy above 90% for new pictures of good photographic quality. Nonetheless we then seek to improve the robustness of the method for on-the-fly field photographs. To do so, we train an additional CNN to automatically separate the rock sample from the background, with a detection algorithm. We also introduce a more sophisticated classification method combining a set of several CNN with a decision tree. The CNN are specifically trained to recognise petrological features such as textures, structures or mineral species, while the decision tree mimics the naturalist methodology for lithological identification.

In a second initiative, we evaluate Deep Learning techniques to spot and delimitate specific elements in finer-scale images. We use a data set of carbonate thin sections with various species of microfossils. The data comes from a sedimentology study but analogies can be drawn with igneous geology use cases. We train four state-of-the-art Deep Learning methods for object detection with a limited data set of 15 annotated images. The results on 130 other thin section images are then qualitatively assessed by expert geologists, and precisions and inference times quantitatively measured. The four models show good capabilities in detecting and categorising the microfossils. However differences in accuracy and performance are underlined, leading to recommendations for comparable projects in a mining context.

Altogether, this study illustrates the power of Computer Vision and Deep Learning approaches to automate rock image analysis. However, to make the most of these technologies in mining activities, stimulating research opportunities lies in adapting the algorithms to the geological use cases, embedding as much geological knowledge as possible in the statistical models, and mitigating the number of training data to be manually interpreted beforehand.   

How to cite: Bouziat, A., Desroziers, S., Koroko, A., Lechevallier, A., Feraille, M., Lecomte, J.-C., and Divies, R.: Towards robots with geologist eyes? Computer vision and Deep Learning approaches to field samples analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11144, https://doi.org/10.5194/egusphere-egu21-11144, 2021.

EGU21-15760 | vPICO presentations | ERE5.4

3D photogrammetry of flooded mines and caves with the UX-1 series underwater exploration robots – The UNEXUP Project

Richárd Zoltán Papp, Krisztián Szentpéteri, Gergely Balázs, Boglárka Anna Topa, and Norbert Zajzon

The UNEXUP project, funded under EIT Raw Materials, is a direct continuation of the Horizon 2020 UNEXMIN project. The aim of the project is to improve the original design of the UX-1 series robot prototypes (UX-1 a, b, c) built in the UNEXMIN project (2016-2019). Originally the effort was made to develop and test an innovative exploration technology for underground flooded mines cannot be obtained without high costs, or risks to human lives, in any other ways, and during the continuation, the main goal is to create market-ready robots and commercialize the technology.

The UX-1 series robots contain several different geoscientific instruments; a multispectral camera module, UV camera, gamma counter, water sampler, pH - EC measuring unit, fluxgate magnetometer and sub-bottom sonar. These instruments provide valid information about the water chemistry, the mineralogical and geological features of the explored mine during a dive. However, the use of this data requires the most accurate positioning and navigation possible, which robots also reveal to us using various tools: different short and long-range sonars and a so-called Structured Light Sensor (SLS) which provide a very detailed 3D point cloud. These complex and challenging navigational solutions are required to collect meaningful geospatial information for accessing not only safety conditions of the mines but, the primary focus the future economic potential of these mines if any. The occurrence and the orientation of mineralized rocks and structures (veins, faults, fractures, bedding) are imperative to understand for a successful new exploration program or reopening an old mine. The 3D underwater photogrammetry technique is of one the best currently available technologies that can provide such information for exploration companies.

The original UX-1 series robots have 5 built-in RGB cameras connected with simultaneously triggered light sources which also collect visual information from the underwater corridors. These images and videos can be used for photogrammetry. With the help of this technology, a 3D map can be built independently from the other navigational sensors. The difference of this technology is that a visual image is accompanied by the 3D surface thus geological information can be seen and directly collected from such surfaces (more like a digital compass). Photogrammetry 3D surfaces are somewhat tighter, but contain larger amounts of data, i.e. denser point cloud compared to other sensors results. For this reason, it may be viable to restrict such surveys to geologically important and or more informative sites i.e. where 3D orientation of geological structures can be easily seen than measured. Furthermore, photogrammetry surveys require a slightly different way of navigation i.e. constant drifting along walls, hemispherical scanning of AOI, that is planned to be automated in future robotic missions. This technology was tested with the UX-1 series robots in a flooded underground mine shafts (Ecton) and underwater cave (Molnar Janos Cave) and resulted in good geological details in selected areas. In future upgrades of the photogrammetry system, we plan to improve the camera specification (geometry, field of view) and navigational requirements to obtain more continuous sections and semi- or fully- automated acquisitions. 

How to cite: Papp, R. Z., Szentpéteri, K., Balázs, G., Topa, B. A., and Zajzon, N.: 3D photogrammetry of flooded mines and caves with the UX-1 series underwater exploration robots – The UNEXUP Project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15760, https://doi.org/10.5194/egusphere-egu21-15760, 2021.

EGU21-2364 | vPICO presentations | ERE5.4

Petalite alteration products from the Bajoca pegmatite (Central Portugal): a multiapproach for lithium exploration

Joana Cardoso-Fernandes, Filipa Dias, Alexandre Lima, Maria Anjos Ribeiro, Mônica Perrotta, Encarnación Roda-Robles, and Ana Cláudia Teodoro

Key hydrothermal or supergene alteration minerals are crucial in the remote detection of several mineral deposit types using satellite images. Hydrothermal metasomatic alteration of spodumene and petalite can form eucryptite, albite, K-feldspar and/or micas, and cookeite in more acidic conditions [1, 2]. Moreover, either hydrothermal or supergene alteration of petalite and spodumene lead to the formation of clay minerals like kaolinite, halloysite, pink montmorillonite, and greenish illite-montmorillonite aggregates [1, 3, 4].

This study aims at describing for the first time the petalite alteration products from the Bajoca pegmatite (Central Portugal, Fregeneda-Almendra pegmatite field). Field campaigns allowed to identify white to greenish alteration products with increasing alteration degree respectively, but often with a pseudomorphic character preserving the petalite shape and cleavage. Despite being exploited for more than two decades, hitherto such green clayey assemblage was not described. This alteration was not observed at the surface and is restricted to a sector in the base of the open-pit, with intense fracturing.

A multidisciplinary study was employed to characterize the alteration products through optical microscopy, XRD, SEM-EDS, and reflectance spectroscopy (350-2500 nm). Petrographic studies show that petalite alteration started along the cleavage, fractures, and crystal borders. Fine white mica and pale brown clays were observed in fractures. Compositional data and spectra obtained with SEM-EDS are compatible with white mica and montmorillonite. Eucryptite was also identified. More heavily altered samples show a complete pseudomorph replacement of petalite, widening of the cleavage and quartz precipitation, the formation of cookeite in close association with white mica, and pseudospherulitic illite filling voids. Locally, a later sericitization is observed superimposed on the previous alteration. The clay agglomerates analyzed with XRD consisted of quartz, illite, montmorillonite/nontronite association with occasional muscovite, albite, kaolinite, and orthoclase. The reflectance spectra show the presence of montmorillonite (ubiquitous), illite and/or white mica, and kaolinite (in two samples).

The results seem to indicate at least two stages of petalite alteration: one consistent with the formation of kaolinite in acidic conditions, and another in an alkaline environment that favored illite-montmorillonite [1]. Intense fracturing associated with a known fault-zone was key for fluid circulation. Further investigations are needed to establish the succession of the alteration stages and their relationship with the late-magmatic hydrothermal alteration of petalite to form albite, orthoclase, and eucryptite. Nonetheless, these findings will help to improve satellite detection of lithium-minerals.

Acknowledgment

The work was financial supported by FCT with the ERA-MIN/0001/2017–LIGHTS project, the UIDB/04683/2020–ICT project, and through Ph.D. Thesis, ref. SFRH/BD/136108/2018 and 2020.05534.BD (ESF, NORTE2020).

1. London, D. and D.M. Burt, Chemical models for lithium aluminosilicate stabilities in pegmatites and granites. American Mineralogist, 1982. 67(5-6): p. 494-509.

2. Charoy, B., F. Noronha, and A. Lima, Spodumene-petalite-eucryptite: mutual relationships and pattern of alteration in Li-rich aplite-pegmatite dykes from northern Portugal. The Canadian Mineralogist, 2001. 39(3): p. 729-746.

3. Quensel, P., Minerals of the Varuträsk Pegmatite. Geologiska Föreningen i Stockholm Förhandlingar, 1937. 59(2): p. 150-156.

4. Quensel, P., Minerals of the Varuträsk Pegmatite. Geologiska Föreningen i Stockholm Förhandlingar, 1938. 60(2): p. 201-215.

How to cite: Cardoso-Fernandes, J., Dias, F., Lima, A., Anjos Ribeiro, M., Perrotta, M., Roda-Robles, E., and Teodoro, A. C.: Petalite alteration products from the Bajoca pegmatite (Central Portugal): a multiapproach for lithium exploration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2364, https://doi.org/10.5194/egusphere-egu21-2364, 2021.

EGU21-3442 | vPICO presentations | ERE5.4

Subsurface seismic imaging with a hammer drilling source at an exploration drilling test center in Örebro, Sweden 

Monika Ivandic, Ayse Kaslilar, and Christopher Juhlin

Seismic imaging while drilling technology offers possibilities of imaging ahead of the drill-bit, which could be useful for determining when to go from hammer drilling to core drilling. Moreover, seismic images of the surrounding rock can improve geological models which could be then used to guide drilling programs.

A seismic imaging while drilling field test was carried out in August 2020 at the I-EDDA Test Center next to the Epiroc factory in Örebro, which is an outcome of the EIT Raw Materials funded project “Innovative Exploration Drilling and Data Acquisition (I-EDDA)”. The purpose of the test presented here was to determine if the signals from hammer drilling can be used for seismic imaging around the drill-bit. The I-EDDA test site has been extensively investigated with geophysical investigations, geological mapping and diamond core drilling, and it therefore represents an ideal location to perform the proposed feasibility study.

The data were recorded along a west-east oriented line consisting of 45 active 1C vertical geophones with a spacing of about 2 m and the rig located approximately in the middle of the profile. A reference signal, which is usually recorded by the pilot sensor fixed to the top of the drill string to be used to convert geophone recordings to impulsive-like seismic data, was not available. The passive recordings on the surface were thus correlated with the trace from the geophone closest to the rig.

After data pre-processing and cross-correlation, the shot-gathers were vertically stacked over the length of a drill pipe to achieve further signal improvement. A comparison with the results of a modelling study shows certain agreement. However, it has to be noted that the velocity model obtained from earlier studies and used to generate the synthetic data set here is rather a simple one and the noise level in the real data set is still significant, in spite of careful processing. Besides the strong contamination by the rig noise, more typical for data with smaller offsets, the mono-frequency waveform footprints present in the cross-correlograms, which have been observed in similar experiments where a trace from the nearest geophone was used to approximate the bit signal, could also play a role. The recent results from the active seismic studies conducted at the site have not detected any clear reflections within the bedrock, which further hinders the quality assessment of the seismic signal.

 

 

This work was partly supported by VINNOVA with the project 2019-04832 titled Integrated Smart Test environment for the mining industry - SMIG. We gratefully acknowledge this financial support.

How to cite: Ivandic, M., Kaslilar, A., and Juhlin, C.: Subsurface seismic imaging with a hammer drilling source at an exploration drilling test center in Örebro, Sweden , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3442, https://doi.org/10.5194/egusphere-egu21-3442, 2021.

EGU21-3473 | vPICO presentations | ERE5.4

Mercury vapour haloes in near-surface air above ore deposits and faults on Vancouver Island, British Columbia, Canada

Alexei S. Rukhlov, Luke Ootes, Adrian S. Hickin, and Nikolay R. Mashyanov

Volatile geogenic components, such as CO2, He, Rn, and Hg0, form haloes in soil gas and near-surface air directly above mineral deposits. This contrasts with lithochemical, hydrochemical, and biochemical dispersion haloes that can be laterally displaced or obscured by transported overburden. Mercury vapour surveys have been used in exploration, because Hg occurs in most types of enogenic ore deposit types and is highly mobile. Low background concentrations in the atmosphere (1.2 to 1.5 ng/m3) enable detecting even weak Hg emissions directly above buried ore deposits. In this study, we measured Hg vapour in air 1-50 cm above ground at 15 sites on Vancouver Island, British Columbia, Canada. To evaluate the effectiveness of the method across a range of settings, these sites include different types of known mineralized zones, barren rocks, and faults, both buried and exposed. The direct and continuous analysis via a portable RA-915M mercury analyzer reveals Hg vapour concentrations ranging from 0.5 to 54.4 ng/m3. The highest Hg concentration was observed above tailings at the Bentley Au occurrence, possibly due to the amalgamation technique used for fine gold extraction between late 1800s and early 1900s. Prominent Hg vapour haloes mark shear-hosted Cu-Ag-Au sulphides at Mount Skirt (13.4x background Hg), epithermal Au-Ag-Cu at Mount Washington (8.9x background Hg), and sediment-covered polymetallic volcanogenic massive sulphides at the Lara-Coronation occurrence (4.2 to 6.6x background Hg). Basalt-hosted Cu-Ag-Au sulphide zones at the Sunro past producer are marked by weak Hg vapour anomalies relative to local background. Faults, including the Leech River fault, which was active in the Quaternary, are also marked by weak Hg vapour anomalies. The study confirms that, although the Hg level is influenced by weather, the real-time Hg vapour measurement of near-surface air can instantly delineate mineralized zones and fault structures that are buried under overburden 10s of m thick. In contrast to soil gas sampling, this simple and rapid technique can be applied to mineral exploration and geological mapping under overburden above any type of surface, including outcrops, talus, bogs, water bodies, snow, and permafrost.

How to cite: Rukhlov, A. S., Ootes, L., Hickin, A. S., and Mashyanov, N. R.: Mercury vapour haloes in near-surface air above ore deposits and faults on Vancouver Island, British Columbia, Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3473, https://doi.org/10.5194/egusphere-egu21-3473, 2021.

EGU21-5091 | vPICO presentations | ERE5.4

Remote sensing characterization of transitional to alkaline igneous rocks and their potential mineralizations using ASTER data: the Moroccan Central High Atlas case study

Youssef Ahechach, Muhammad Ouabid, Otmane Raji, Jean-Louis Bodinier, Khalid Amrouch, Houssa Ouali, and Abderrahmane Soulaimani

Alkaline complexes are an important target for geological exploration, with both scientific and economic interests. They are host to different types of mineral deposits, such as Rare Earths, igneous phosphates, -and K-rich minerals and rocks. In Morocco, the Central High-Atlas (CHA) hosts several transitional to alkaline complexes ranging from Upper Jurassic to Eocene and showing almost all the differentiation terms of transitional to alkaline suites. These alkaline complexes are however poorly explored and their potential in terms of mineral resources is still elusive.

The aim of this research is to use Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to discriminate different transitional to alkaline rock lithologies and their associated mineralizations. For that purpose, series of band ratios proven to be sensitive to the silica, mafic, felsic and carbonate contents of transitional to alkaline rocks were applied. Our results show that the major Upper Jurassic magmatic intrusions of Moroccan CHA, such as Anemzi, Inouzane, Tassent, and Tasraft, hold distinct igneous facies, mainly composed of Mafic to felsic rocks. Field and petrographic observations have confirmed the ASTER results and highlighted that these rocks are formed of gabbro to syenite. The later are associated with significant feldspar concentrations, but also host apatite, garnet, and magnetite vein-type ores. Thereafter, field- and petrographic-based data were used as training data to perform a supervised classification allowing to refine the geological mapping of the studied alkaline intrusions.

How to cite: Ahechach, Y., Ouabid, M., Raji, O., Bodinier, J.-L., Amrouch, K., Ouali, H., and Soulaimani, A.: Remote sensing characterization of transitional to alkaline igneous rocks and their potential mineralizations using ASTER data: the Moroccan Central High Atlas case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5091, https://doi.org/10.5194/egusphere-egu21-5091, 2021.

EGU21-5174 | vPICO presentations | ERE5.4 | Highlight

Snow as environmentally low-impact sampling media for mineral exploration - a case study from Northern Finland

Solveig Pospiech, Anne Taivalkoski, Yann Lahaye, Pertti Sarala, Janne Kinnunen, and Maarit Middleton

Modern mineral exploration is required to be conducted in a sustainable, environmentally friendly and socially acceptable way. Especially for the geochemical exploration on ecologically sensitive areas this poses a challenge because any heavy machinery or invasive methods might cause long-lasting damage to nature. One way of reducing the impact of mineral exploration on the environment during the early stages of exploration is to use surface sampling media, such as upper soil horizons, water, plants and, on high latitudes, also snow. Of these options, snow has several advantages: Sampling and analysing snow is fast and low in costs, it has no impact on the environment, and in wintertime it is ubiquitous and available independent of the ecosystem.
In the “New Exploration Technologies (NEXT)” project*, snow samples were collected in March-April 2019 to evaluate the usage of snow as a sampling material for mineral exploration. The test site was the Rajapalot Au-Co prospect in northern Finland, located 60 km west from Rovaniemi and operated by Mawson Oy. A stratified random sampling strategy was applied to place the sampling stations on the test site. The sampling comprised 94 snow samples and 12 field replicates. The samples were analysed at the GTK Research laboratory using a Nu AttoM single collector inductively coupled plasma mass spectrometry (SC-ICPMS) which returned analytical results for 52 elements at the ppt level. After applying quality control to the data, the elements Ba, Ca, Cd, Cr, Cs, Ga, Li, Mg, Rb, Sr, Tl and V showed good quality and were used in the final data analysis.
Geochemical data of drill cores were used to train a model to predict bedrock geochemistry based on the 12 available element concentrations of snow analysis. Prior to statistical methods, all geochemical data was transformed to log-ratio scores in order to ensure that results are independent of the selection of elements and to avoid spurious correlations (compositional data approach). Results show that snow data provide reasonable predictions of bedrock geochemistry for elements such as Ca, Cr, Li and Mg, but also for elements not used in snow data, such as Mn and Na. This suggests that snow can serve as a lithogeochemical mapping tool for potential geological domains. For the ore related elements Au, Ag, Co, and U the model provided predictions with higher uncertainty. Yet, the pattern of the predicted values of ore related elements show that snow can also be used to delineate prospective areas for continuing exploration with more sensitive methods.
*) This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 776804.

How to cite: Pospiech, S., Taivalkoski, A., Lahaye, Y., Sarala, P., Kinnunen, J., and Middleton, M.: Snow as environmentally low-impact sampling media for mineral exploration - a case study from Northern Finland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5174, https://doi.org/10.5194/egusphere-egu21-5174, 2021.

EGU21-7257 | vPICO presentations | ERE5.4

The role of fault intersection in fluid flow patterns and the formation of world-class unconformity-related uranium deposits, Athabasca Basin, North Canada 

Khalifa Eldursi, Luc Scholtes, Marianne Conin, Fabrice Golfier, Julien Mercadier, Patrick Ledru, Pauline Collon, and Rémy Chemillac

The epigenetic uranium deposits in the eastern part of the Athabasca Basin are classified as unconformity-related ore deposits. Their explicit spatial association to reactivated basement faults is observed within the regional structural NNE trend Wollaston-Mudjatik transition zone, marked by elongated dravite, illite, and chlorite alteration zones. Accordingly, geochemical studies have advocated a circulation and focalization of large amount of one or more fluids to carry and precipitate aqueous chemical materials. At the deposit-scale, the uranium deposits are found mainly at the intersection between two or more fault sets, and described as elongated-like bodies varying in orientation from E-W to NNE direction along the regional transitional zone. Furthermore, some orebodies show a change of orientation and dip of their structures. Thus, what is the hydro-mechanical response of reactivated and inherited fault architecture (e.g., intersection zone) under different stress states (e.g., reverse, strike-slip, and normal faulting regime), and its potential contribution to the shape and orientation of orebodies at deposit scale?

Using hydro-mechanical numerical modeling, this project demonstrates the role that fault intersections play in controlling mineralized fluids by examining the various fluid flow patterns observed when reactivated intersected faults are under various stress states. Numerical modeling is performed using 3-Dimensional Distinct Element Code (3DEC). The numerical models are subdivided into two categories: 1) simplified 3-D models of two intersecting faults, 2) 3-D complex models of fault network at different deposits sites (e.g., the Cigar Lake deposit). While the first simple models attempt to evaluate the effects of intersection angle, burial depth, fluid pressure, basin permeability and stress states on the fluid flow patterns; the second models investigate the stress state under which certain orebodies may have formed.

Our preliminary results from simplified models show that at defined intersection angles, the fluid flow deviates from the main fault toward the secondary fault at their intersection point. The deviation in fluid flow is referred to the value of intersection angle at which the shear stress varies along the secondary fault, leading to the opening of secondary fault. Additionally, the burial depth does not affect the flow along the basement faults, whereas, the overlying highly permeable basin reduces the horizontal flow along the basement faults toward the intersection zone, and reorients a part of the flow toward the basin.  In the complex models (the Cigar Lake model), considering a compressional regime, the E-W fault set is reactivated once the maximum stress is oriented N40W to N65W, which is in agreement with field observations.

How to cite: Eldursi, K., Scholtes, L., Conin, M., Golfier, F., Mercadier, J., Ledru, P., Collon, P., and Chemillac, R.: The role of fault intersection in fluid flow patterns and the formation of world-class unconformity-related uranium deposits, Athabasca Basin, North Canada , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7257, https://doi.org/10.5194/egusphere-egu21-7257, 2021.

EGU21-10046 | vPICO presentations | ERE5.4

Digitization of the multi-compositional Storkwitz carbonatite diatreme (Delitzsch Complex, Germany)

Sascha Schmidt, Hripsime Gevorgyan, Ilja Kogan, and Manuel Lapp

 

The Storkwitz diatreme is a multiphase composite body within the Late Cretaceous Delitzsch Complex in north-western Saxony, Germany. The lithology of the Delitzsch Complex varies from rauhaugite and fenite aureole to ultramafic and alkaline lamprophyric intrusions (dykes, sills and pipe-shaped bodies) accompanied by the formation of diatremes of variable composition (Krüger et al., 2013; Röllig et al., 1990). The final stages are represented by beforsite and alvikite dykes (Röllig et al., 1990). The multi-component nature of the Storkwitz diatreme can be attributed to the formation of polymict breccias and numerous injections of compositionally varied carbonatites (Gevorgyan et al., 2020; Seifert et al., 2000).  

The entire area was extensively explored through an intensive drilling campaign by the SDAG Wismut between 1972 and 1989, due to a locally increased REE content. For a better understanding of the development of the diatreme, detailed petrographical observations and new imaging methods on extensive drill core material were applied. The combination of microscopic images and high-resolution 2D-images allows to create 3D-models of drill core sections via photogrammetry. Identifying the components (xenoliths and intraclasts) and analyzing the pattern of their distribution in the 3D-models of drill cores will enable obtaining textural information of the minerals within the rocks.

Further investigations using Hyperspectral Imaging (HIS) for chemical information, to be carried out in cooperation with the Institute for Mine Surveying and Geodesy, TU Bergakademie Freiberg, combined with mineralogical information and 3D-models, will provide new insights into the shape and geometry of the diatreme body.

 

References

Gevorgyan, H., Schmidt, S., Kogan, I., Lapp, M., 2020. EGU2020-10678.

Krüger, J.C., Romer, R.L., Kämpf, H., 2013. Chemical Geology, 353, 140-150.

Röllig, G., Viehweg, M., Reuter, N., 1990. Zeitschrift für Angewandte Geologie, 36, 49-54.

Seifert, W., Kämpf, H., Wasternack, J., 2000. Lithos, 53, 81-100.

How to cite: Schmidt, S., Gevorgyan, H., Kogan, I., and Lapp, M.: Digitization of the multi-compositional Storkwitz carbonatite diatreme (Delitzsch Complex, Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10046, https://doi.org/10.5194/egusphere-egu21-10046, 2021.

EGU21-10191 | vPICO presentations | ERE5.4

Mineral exploration in the glaciated terrain using upper soil horizon geochemistry and compositional statistical data analysis

Pertti Sarala, Solveig Pospiech, Maarit Middleton, Anne Taivalkoski, Helena Hulkki, and Janne Kinnunen

Vulnerable nature in northernmost Europe requires development of new, environmentally friendly sampling and analyses techniques for mineral exploration. Those areas are typically covered by transported glaciogenic sediments where the glacial till is most dominant. To offer an alternative for conventional basal till and bedrock sampling with heavy machines, the use of different surface geochemical sampling media and techniques which are quick and cost-effective have been actively applied during the last decade. Particularly, the development of selective and weak leach techniques for the upper soil (Ah and B) horizons’ geochemistry has been intensive, but the reliability needs to be improved and testing is required in different glaciogenic environments.

In this research, carried out under the project New Exploration Technologies (NEXT), funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 776804, we used stratified random sampling strategy for choosing sampling locations and developed novel compositional statistical data analysis for the interpretation of geochemical data obtained by surface geochemical techniques. The test area is located in the Rajapalot area, Ylitornio, northern Finland, where an active project is carried out by Mawson Oy for Au-Co exploration. The thickness of till cover varies from some metres to 5 m and the glacial morphology is composed of the ribbed moraine ridges with peatlands in between. A sampling network for the Ah and B horizon samples was comprised of 89 routine samples and 10 field replicates acquired of mineral Podsol-type soils. The chemical analyses methods used were Ultratrace 1:1:1 Aqua Regia leach and 0.1 M sodium pyrophosphate leach for the Ah horizon samples, and Ionic leach and Super Trace Aqua Regia leach methods for the B horizon samples. The laboratory analyses were supported by the portable X-Ray Fluorescence (pXRF) analyses done directly in the field. The statistical analysis was based on log-ratio transformations of the geochemical compositions to avoid spurious results. In addition, the response ratios were calculated to measure the degree of enrichment in each element per sample.

The preliminary results of the soil geochemistry show a significant response to many elements (e.g. Au, Co, Cu, Mo, Sc, Te and W) with known mineralized bedrock targets observed in the drill core data. Elemental distribution is also reflecting the lithological variations of the rock units in the bedrock. Based on the results, it is obvious that a) there is good or moderate correlation for several elements between the surface geochemical data and underlying bedrock, and b) soil analysis method using certain soil sampling procedure and selective extraction is an effective, environmentally friendly geochemical exploration technique in the glaciated terrains.

How to cite: Sarala, P., Pospiech, S., Middleton, M., Taivalkoski, A., Hulkki, H., and Kinnunen, J.: Mineral exploration in the glaciated terrain using upper soil horizon geochemistry and compositional statistical data analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10191, https://doi.org/10.5194/egusphere-egu21-10191, 2021.

Rapid technological improvements made in in-situ analysis techniques, including LA-ICPMS, have transformed the field of analytical geochemistry. This has a far-reaching impact for different petrogenetic and ore-genetic studies where minute major and trace element compositional changes between different mineral zones within a single crystal can now be demarcated. Minerals such as garnet although robust are quite sensitive to the changing P-T and fluid conditions during their formation. These minerals have become powerful tools to characterize mineralization types. Previously, Meinert (1992) has used in-situ major element EPMA analysis results to classify different skarn deposit based on the end-member composition of hydrothermal garnets. Alternatively, Tian et al. (2019) used the garnet trace element composition for the similar purpose. However, these discrimination plots/ classification schemes show major overlap in different skarn deposits, such as Fe, Cu, Zn, and Au. The present study is an attempt to use machine learning approach on available garnet data to found a more potent classification scheme for skarn deposits, thus reaffirming garnet as a faithful indicator for hydrothermal ore deposits. We have meticulously collected major and trace element data of Ca-rich garnets, associated with different skarn deposits worldwide from 40 publications. This collected data is then used to train a model for fingerprinting the skarn deposits. Stratified random sampling method has been used on the dataset with 80% of the samples as test set and the rest 20 % as training dataset. We have used K-nearest neighbour (KNN), Support Vector Machine (SVM) and Random Forest algorithms on the data by using Python as a platform. These ML classification algorithm performs better than the earlier existing models available for classification of ore types based on garnet composition in skarn system. Factor importance is calculated that shows which elements play a pivotal role in classification of the ore type. Our results depict that multiple garnet forming elements taken together can reliably be used to discriminate between different ore formation settings.

How to cite: Ghosh, U. and Chakraborty, T.: Classification of different skarn deposits based on the compositional variability of associated grandite garnets: a data science and Machine Learning approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10537, https://doi.org/10.5194/egusphere-egu21-10537, 2021.

EGU21-10571 | vPICO presentations | ERE5.4

Unravelling the origin of placer gold: A case study on the largest Roman gold mining sector of NW Spain (Jamuz, León)

Javier Fernández-Lozano, José María Esbrí, Ignacio Garrido, Rosa María Carrasco, Javier Pedraza, Antonio Bernardo-Sánchez, and Pablo Higueras

NW Iberia hosts a substantial number of mineral resources. Among them, gold (Au) acquired particular relevance since Antiquity, representing one of the largest Roman Au mining provinces in Europe. While primary deposits associated with orogenic Au have been widely studied in the past years, the Plio-Quaternary Raña Au-bearing placer deposits of the western Duero Basin have received little attention. Besides, the different morphology of Au particles suggests complex processes that may have been responsible for the secondary formation of colloidal particles and Au growth grains from complex geochemical soil interactions and biological activity. In this context, exploring the mechanism by means these secondary deposits developed may contribute to understanding the source of Au (extrinsic or intrinsic factors that rule in within Raña deposits) and the formation of potential mineral exploration sectors. This paper outlines the geochemical analysis of a Cenozoic Raña-like deposit in the Jamuz valley (León), where the source of Au and the main characteristics are established. The correlation matrix showed notable relationships between Au, Fe, Na, K, Ca, Pb and As, among the most important. High values in Fe and As provides direct evidence of Au precipitation. Likewise, a non-linear correlation was found between Au-Na, and Au-Ca, suggesting a direct link to soil formation processes. Finally, the presence of apparent differences in grain roundness and the particles' characteristics ranging from monomineral angular Au to polymineral rounded-shaped particles points towards a complex process affecting the Raña deposits. The ubiquitous rubefaction and top-bottom leaching activity produced during rainwater percolation aided by the extreme drainage affecting this conglomeratic formation have often been argued to be responsible for the transformation of mineral phases in soils. The presence of secondary silicification processes and pH drop due to biological reactions (i.e., presence of P) may have been a triggering mechanism for digestion and reprecipitation of Au colloids in these sediments. Our results have outstanding implications on the mechanisms that may determine the Au enrichment of certain levels within the Raña deposits of the western Duero Basin.

This work was funded by the wine company “Fuentes del Silencio”.

How to cite: Fernández-Lozano, J., Esbrí, J. M., Garrido, I., Carrasco, R. M., Pedraza, J., Bernardo-Sánchez, A., and Higueras, P.: Unravelling the origin of placer gold: A case study on the largest Roman gold mining sector of NW Spain (Jamuz, León), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10571, https://doi.org/10.5194/egusphere-egu21-10571, 2021.

EGU21-12115 | vPICO presentations | ERE5.4 | Highlight

A new mining life for non-feasible mineral deposits?

Balazs Bodo, Luis Lopes, Claudio Rossi, Giorgia Stasi, Christian Burlet, Stephen Henley, Vitor Correia, Tobias Pinkse, Alicja Kot-Niewiadomska, Jussi Aaltonen, Nikolaus Sifferlinger, Nelson Cristo, Éva Hartai, Gorazd Zibret, Janos Horvath, and Asko Ristolainen

ROBOMINERS is developing an innovative approach for the exploitation of currently non-feasible mineral deposits. The approach entails the use of a robot-miner - a bio-inspired reconfigurable robot with a modular nature - in a new mining setting where the activities are nearly invisible and where mining presents less socio-environmental constraints, thus contributing to a more safe and sustainable supply of mineral raw materials.

The main aim is to design and develop a robotic prototype that is able to perform mining related tasks in settings including both abandoned, currently flooded mines not accessible anymore for conventional mining techniques; or places that have formerly been explored, but whose exploitation was considered as uneconomic due to the small-size of deposits, or their difficulty to access.

ROBOMINERS’ innovative approach combines the creation of a new mining ecosystem with novel ideas from other sectors, particularly robotics. At this point, work has been done to understand the best methods for the robotminer’s development in 1) biological inspiration, 2) perception and localisation tools, 3) behaviour, navigation and control, 4) actuation methods, 5) modularity, 6)autonomy and resilience, and 7) the selective mining ability. All these aspects combined aim to provide the robotminer XXI Century tools for mineral exploration and exploitation of (currently) unfeasible deposits.

At the same time, for the vision of a new vision of a mining ecosystem, work is involving studies on 1) developing computer models and simulations, 2) data management and visualisation, 3) rock-mechanical and geotechnical characterisation studies, 4) analysing ground/rock support methods, bulk transportation methods, backfilling types and methods, and 5) sketching relevant upstream and downstream mining industry analogues for the ROBOMINERS concept.  

After design and development, based on the previously mentioned studies, the robot-miner is set to be tested at targeted areas representatives which include abandoned and/or operating mines, small but high-grade mineral deposits, unexplored/explored non-economic occurrences and ultra depth, not  easily accessible environments. Possible candidates for testing purposes include mines in the regions of Cornwall (UK), mines in the Kupferschiefer Formation (e.g. Poland) or coal mines in Belgium.

When compared to usual mining methods the ROBOMINERS approach shows: 1) no presence of people in the mine, 2) less mining waste produced, 3) less mining infrastructure, 4) less investment, 5) possibility to explore currently uneconomic resources and 6) new underground small-sized mines, practically “invisible”. Altogether, ROBOMINERS can contribute to solve some of the main issues that make mining’s social license to operate so difficult to get in Europe: land-use, environmental limitations, and socio-economic aspects.

How to cite: Bodo, B., Lopes, L., Rossi, C., Stasi, G., Burlet, C., Henley, S., Correia, V., Pinkse, T., Kot-Niewiadomska, A., Aaltonen, J., Sifferlinger, N., Cristo, N., Hartai, É., Zibret, G., Horvath, J., and Ristolainen, A.: A new mining life for non-feasible mineral deposits?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12115, https://doi.org/10.5194/egusphere-egu21-12115, 2021.

EGU21-13152 | vPICO presentations | ERE5.4

High-frequency ambient noise surface wave tomography at the Marathon PGE-Cu deposit (Ontario, Canada)

Daniela Teodor, Charles Beard, Laura Alejandra Pinzon-Rincon, Aurélien Mordret, François Lavoué, Sophie Beaupretre, Pierre Boué, and Florent Brenguier

Ambient noise surface wave tomography (ANSWT) is an environmentally friendly and cost-effective technique for subsurface imaging. In this study, we used natural (low-frequency) and anthropogenic (high-frequency) noise sources to map the velocity structure of the Marathon Cu-PGE deposit (Ontario, Canada) to a depth of 1 km. The Marathon deposit is a circular (ø = 25 km) alkaline intrusion comprising gabbros at the rim and an overlying series of syenites in the centre. Cu-PGE mineralisation is hosted by gabbros close to the inward-dipping footwall of the intrusion. The country rocks are Archaean volcanic breccias that are seismically slower than the gabbros, and similar in velocity to the syenites. We used ANSWT to image the footwall contact that controls the location of the mineralisation.

An array of 1024 vertical-component receivers were deployed for 30 days to record ambient noise required for surface wave analysis. Two overlapping grids were used: a 200 m x 6040 m dense array with node spacing of 50 m, and a 2500 m x 4000 m sparse array with node spacing of 150 m.  The signal was down-sampled to 50 Hz, divided into segments of 30 minutes, cross-correlated and stacked. Surface wave analysis was conducted over the dense array and the sparse array data. We considered the fundamental mode of Rayleigh wave propagation for our frequency-wavenumber (F-K) analysis and focused on the phase velocity variation in the high-frequency ambient noise signal (up to 22 Hz). We reconstructed the shallow structure with progressively increased resolution using surface wave dispersion curves extracted from receiver arrays divided into segments of variable lengths. Several average dispersion curves were computed from individual dispersion curves belonging to different seismic lines. Each average dispersion curve was inverted to obtain S-wave velocity models using an McMC transdimensional Bayesian approach.

The tomographic images reveal a shallow high-velocity anomaly, which we interpret as being related to the gabbro intrusion that hosts the mineralization. The large-wavelength structures in the S-wave velocity models are relatively consistent with the geological structures inferred from surface mapping and drill core data. These results show that the ANSWT, focused on the high-frequency signal provided by anthropogenic noise sources, is an efficient technique for imaging “shallow" (1 km depth) geological structures in a mineral exploration context. 

How to cite: Teodor, D., Beard, C., Pinzon-Rincon, L. A., Mordret, A., Lavoué, F., Beaupretre, S., Boué, P., and Brenguier, F.: High-frequency ambient noise surface wave tomography at the Marathon PGE-Cu deposit (Ontario, Canada), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13152, https://doi.org/10.5194/egusphere-egu21-13152, 2021.

EGU21-13241 | vPICO presentations | ERE5.4

Vectors to ore in replacive VMS deposits of the northern Iberian Pyrite Belt: the case study of Aguas Teñidas deposit

Guillem Gisbert, Fernando Tornos, Emma Losantos, and Juan Manuel Pons

Volcanogenic Massive Sulphide (VMS) deposits represent a major source of base, precious and other metals of economic and industrial importance. The Iberian Pyrite Belt (IPB) is an outstanding VMS district located in the SW Iberian Peninsula. It is arguably the largest known accumulation of sulphides on the Earth’s crust, and represents the main mining area in Spain and one of the main zones of base metal production in Europe. As in other mining areas, progressive exhaustion of the most shallow and easily accessible deposits is leading to increasingly complex exploration. In this context, the combined study of the mineral systems and the development of new exploration strategies and technologies based on geophysical methods and vectors to ore play a vital role.

Vectors to ore have the potential to detect the nearby presence of an ore deposit, and to provide information on its likely location or characteristics. But work on vectors to ore in IPB is far from systematic or complete. Previous works have focused on the study of the larger exhalative shale-hosted deposits of the southern IPB or the giant Rio Tinto deposit, but little attention has been paid to the predominantly volcanic rock hosted replacive deposits of the northern IPB, which, although generally smaller in size compared to southern deposits, typically present higher base metal concentrations.

In this work we have performed a detailed study of the main vectors to ore currently used in the exploration of VMS systems on a representative volcanic rock hosted replacive VMS deposit located in the northern IPB, the Aguas Teñidas deposit. These have included: mineralized unit identification based on whole rock geochemistry, study of the characteristics and behaviour of whole rock geochemical anomalies around the ore (e.g. alteration-related compositional changes, characteristics and extent of geochemical halos around the deposit), with definition of mineralization-related indicative elements threshold values, application of portable XRF analysis to the detection of the previous vectors, and characterization of major elements trends in mineral chemistry (muscovite, chlorite, carbonate) within and away from the mineralized system.

Data presented in this work are not only applicable to VMS exploration in the IPB, but on a broader scale they will also contribute to improve our general understating of vectors to ore in replacive-type VMS deposits.

The authors thank MATSA for providing information and access to drill-cores from Aguas Teñidas deposit. This research has been conducted within the NEXT (New Exploration Technologies) project and has received funding by the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 776804.

How to cite: Gisbert, G., Tornos, F., Losantos, E., and Pons, J. M.: Vectors to ore in replacive VMS deposits of the northern Iberian Pyrite Belt: the case study of Aguas Teñidas deposit, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13241, https://doi.org/10.5194/egusphere-egu21-13241, 2021.

EGU21-14771 | vPICO presentations | ERE5.4

Probabilistic Machine Learning for improved Decision-making with 3-D Geological Models

Florian Wellmann, Miguel de la Varga, Nilgün Güdük, Jan von Harten, Fabian Stamm, Zhouji Liang, and s.Mohammad Moulaeifard

Geological models, as 3-D representations of subsurface structures and property distributions, are used in many economic, scientific, and societal decision processes. These models are built on prior assumptions and imperfect information, and they often result from an integration of geological and geophysical data types with varying quality. These aspects result in uncertainties about the predicted subsurface structures and property distributions, which will affect the subsequent decision process.

We discuss approaches to evaluate uncertainties in geological models and to integrate geological and geophysical information in combined workflows. A first step is the consideration of uncertainties in prior model parameters on the basis of uncertainty propagation (forward uncertainty quantification). When applied to structural geological models with discrete classes, these methods result in a class probability for each point in space, often represented in tessellated grid cells. These results can then be visualized or forwarded to process simulations. Another option is to add risk functions for subsequent decision analyses. In recent work, these geological uncertainty fields have also been used as an input to subsequent geophysical inversions.

A logical extension to these existing approaches is the integration of geological forward operators into inverse frameworks, to enable a full flow of inference for a wider range of relevant parameters. We investigate here specifically the use of probabilistic machine learning tools in combination with geological and geophysical modeling. Challenges exist due to the hierarchical nature of the probabilistic models, but modern sampling strategies allow for efficient sampling in these complex settings. We showcase the application with examples combining geological modeling and geophysical potential field measurements in an integrated model for improved decision making.

How to cite: Wellmann, F., de la Varga, M., Güdük, N., von Harten, J., Stamm, F., Liang, Z., and Moulaeifard, s. M.: Probabilistic Machine Learning for improved Decision-making with 3-D Geological Models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14771, https://doi.org/10.5194/egusphere-egu21-14771, 2021.

EGU21-15817 | vPICO presentations | ERE5.4

Classifying Copper-Molybdenum-Gold Porphyry Deposit Alteration using Magnetic and Spectral data

Oliver Dixon, William McCarthy, Nasser Madani, Michael Petronis, Steve McRobbie, and Jonathan Cloutier

Copper is one of the most important critical metal resources needed to achieve carbon neutrality with a projected increase in demand of >300% over the next half century from electronics and renewables.  Porphyry deposits account for most of the global copper production, but the discovery of new reserves is ever more challenging. Machine learning presents an opportunity to cross reference new and traditionally under-utilised data sets with a view to developing quantitative predictive models of hydrothermal alteration zones to guide new, ambitious exploration programs.

The aim of this study is to demonstrate a new alteration classification scheme driven by quantitative magnetic and spectral data to feed a machine learning algorithm. The benefits of an alteration model based on quantitative data rather than subjective observations by geologists, are that there is no bias in the data collected, the arising model is quantifiable and therefore easy to model and the process be fully automated. Ultimately, this approach aids more detailed exploration and mine modelling, in turn, reducing the extraction process carbon footprint and more effectively identifying new deposits.

Presented here are magnetic susceptibility and shortwave infrared (SWIR) data collected from the KazMinerals plc. owned Aktogay Cu-Mo giant porphyry deposit, eastern Kazakhstan, which has a throughput of 30Mtpa of ore. These data are cross referenced using a newly developed machine learning algorithm. Generated autonomously, our results reveal twelve statistically and geologically significant clusters that define a new alteration classification for porphyry style mineralisation. Results are entirely non-subjective, reproducible, quantitative and modellable.

Importantly, magnetic susceptibility measurements improve the algorithm’s ability to identify clusters by between 29-36%; enhancing the sophistication of the included magnetic data promises to yield substantially better statistical results. Magnetic remanence data are therefore being complied on representative samples from each of the twelve identified clusters, including hysteresis, isothermal remanent magnetisation (IRM) acquisition, FORC measurements, natural remanent magnetisation (NRM) and anhysteretic remanent magnetisation (ARM). Through collaboration with industry partners, we aim to develop an automated means of collecting these magnetic remanence data to accompany the machine learning algorithm.

How to cite: Dixon, O., McCarthy, W., Madani, N., Petronis, M., McRobbie, S., and Cloutier, J.: Classifying Copper-Molybdenum-Gold Porphyry Deposit Alteration using Magnetic and Spectral data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15817, https://doi.org/10.5194/egusphere-egu21-15817, 2021.

EGU21-15874 | vPICO presentations | ERE5.4

Hybrid mineral predictive mapping with self-organizing maps and a multilayer perceptron applied to tin deposits in the Erzgebirge, Germany

Andreas Brosig, Andreas Barth, Peggy Hielscher, Claus Legler, Stefan Schäfer, Peter Bock, and Andreas Knobloch

Self-organizing maps (SOM) are a useful tool to analyze and interpret gridded datasets like potential field or stream sediment geochemistry data. The data are transformed from geographic space to SOM space where they can be clustered according to overall similarity. By transforming the clusters back to geographic space, geological interpretation of the clusters is facilitated. We present the application of a multilayer perceptron (MLP) in SOM space to produce mineral predictive maps. The reduced number of grid cells in SOM space greatly enhances the performance of the MLP and the tolerance to noise in the input data, compared to an application of the MLP to the original data. The method is applied to tin skarn deposits in the German part of the Erzgebirge. The training and validation data required for the MLP are compiled from mining and exploration records. The input data for the SOM are reprocessed gravimetric, magnetic, stream sediment geochemistry, geologic and tectonic data sets. Potentially ore-controlling spatial relationships, such as the distance to different types of partly covered granite intrusions, are derived from a regional scale 3D geological model. The resulting mineral prediction map allows the definition of exploration zones for detailed studies.

The paper has been compiled in the frame of "NEXT - New EXploration Technologies" project. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 776804.

How to cite: Brosig, A., Barth, A., Hielscher, P., Legler, C., Schäfer, S., Bock, P., and Knobloch, A.: Hybrid mineral predictive mapping with self-organizing maps and a multilayer perceptron applied to tin deposits in the Erzgebirge, Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15874, https://doi.org/10.5194/egusphere-egu21-15874, 2021.

Gadag schist belt, India is known for sulphide-gold mineralization. In the study area mineralization is controlled structurally and lithologically. In this context, Airborne Visible-Infrared Imaging Spectrometer - Next Generation (AVIRIS-NG) Visible Near InfraRed (VNIR) - Shortwave Infrared (SWIR) bands were utilized to derive alteration zones and structures present in the study area. Lithological boundaries have also been updated using AVIRIS-NG VNIR-SWIR bands derived images enhancement products i.e. Minimum Noise Fraction (MNF) and False Colour Composite (FCC). Further, image spectra of alteration zones (Hydrous mineral etc.) derived from AVIRIS-NG calibrated VNIR-SWIR bands were compared with the standard corresponding reference library spectra (USGS, JPL spectral library). These image spectra have been utilized to demarcate the alteration zones using the Matched Filtering spectral mapping method. Structures were demarcated using high pass (HP) filtered image and FCC images. Low pass (LP) filter image and along with MNF & FCC image composite were utilized to update the lithological boundaries in the study area.

Ground gravity data has also been processed to derive the subsurface evidences relevant to the deposit in the present study area. Subsurface structures which are responsible for the transportation of mineral rich fluid in the near subsurface are delineated using the gravity data derived products. Apart from this, basement depths are also derived from the gravity data which are being utilized for the validation as well as to further precise the locations of mineral deposits.  These subsurface structures (gravity data), lithology, lineament density and alteration zones are very important evidential layers which have been integrated using fuzzy logic integration techniques to identify potential zones of gold-sulphide mineralization in the present study area. The prospective zones are validated using the secondary data and basement depth derived from the gravity data.

For similar kind of gold-sulphide mineralization, AVIRIS-NG data and Gravity data can be used to derive the important evidential layers in any part of the world. There are only few studies where such integration approach has been utilized to explore new potential zones of gold sulphide mineralization. 

Keywords: AVIRIS-NG, VNIR-SWIR, alteration, MNF, FCC, Gravity, Basement Depth

How to cite: Rani, K.: Mineral Prospectivity Modeling using AVIRIS-NG VNIR-SWIR data and Gravity data for Gold-Sulphide mineralization in parts of GADAG schist belt, Karnataka, India , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15900, https://doi.org/10.5194/egusphere-egu21-15900, 2021.

EGU21-15929 | vPICO presentations | ERE5.4

Geological mapping of carbonatites and related ores from the Oulad Dlim massif (Dakhla Province, Morocco) using remote sensing, portable X-ray fluorescence, and mineralogical data

cheikh elwali Malainine, Otmane Raji, Muhammad Ouabid, Abdou Khouakhi, Jean-Louis Bodinier, Fleurice Parat, and Hicham El Messbahi

During the last decades, carbonatites and associated rocks have received increased interest from mining companies and the scientific community. They represent a classic source of a variety of critical elements required by certain emerging technologies and industries such as niobium, rare earth elements (REE), and phosphorus. Morocco like many other countries have several Alkaline igneous complexes, however, their potential in terms of REE-P-rich carbonatites is poorly explored and needs to be investigated. This study is an attempt to develop an advanced exploration tool for the detection and mapping of these rocks using remote sensing.  Preliminary investigations were focused on the Oulad Dlim massif at the western Reguibat Shield (Southeast of Dakhla province) where several carbonatite structures were reported, including Gleibat Lafhouda, Twihinate, Lamlaga, Lahjayra. Advanced Spaceborne Thermal and Reflection Radiometer (ASTER) data were used to: (i) identify and map carbonatites and associated rocks liable to contain REE-P mineralization, (ii) investigate their spectral features, and produce predictive maps. Several image processing techniques, have been performed including band ratio, color composite image, principal component analysis and minimum noise fraction. The combination of these techniques appears to more effectively detect carbonatites and associated rocks. The effectiveness of this approach was verified using field investigation, in-situ geochemical analysis with portable X-ray fluorescence, and petrography. The field data were used to train classifiers to better delineate the spatial distribution of the different lithological facies. The results are generally consistent with available geological maps indicating that this approach can be satisfactorily applied in the early stages of geological exploration.

How to cite: Malainine, C. E., Raji, O., Ouabid, M., Khouakhi, A., Bodinier, J.-L., Parat, F., and El Messbahi, H.: Geological mapping of carbonatites and related ores from the Oulad Dlim massif (Dakhla Province, Morocco) using remote sensing, portable X-ray fluorescence, and mineralogical data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15929, https://doi.org/10.5194/egusphere-egu21-15929, 2021.

ERE5.6 – Antimony and associated elements: from mineralisation to the environment.

EGU21-144 | vPICO presentations | ERE5.6

The Sb-Au-district Brandholz/Goldkronach (Fichtelgebirge, Germany): mineralogical indications for the evolution of hydrothermal Sb-mineralization.

Björn Fritzke, Thomas Seifert, Elmar Linhardt, and Christin Kehrer

The Brandholz/Goldkronach district is situated in the southeastern part of Germany in the Bavarian Fichtelgebirge. Previous literature of the mineralogy of the district is rather descriptive and modern geochemical analysis are entirely missing. In this contribution, we combine petrography, bulk rock-geochemical analysis, SEM-MLA as well as EPMA to infer on precipitation mechanism and ore-forming processes. The quartz-polymetallic-sulfide veins are hosted in Ordovician shists, called “Phycodenschiefer”, which were intruded by upper Devonian meta-basalts. Antimony-sulfides are the main ore mineralization inside of the quartz-veins, accompanied by minor auriferous arsenopyrite and pyrite. Petrographic observations suggest a precipitation of an early stibnite phase (stage I). Sb-Pb-sulfides/sulfosalts (stage II) precipitated in fractures and fissures of stage I stibnite with a slightly change to Pb-rich Sb-phases. The antimony-mineralization event evolved from stibnite (Sb2S3), over fülöppite (Pb3Sb8S15), zinkenite (Pb9Sb22S42), plagionite (Pb5Sb8S17) to boulangerite (Pb5Sb4S11). Chemical analyses corroborate the petrographic observations and indicate a change in the hydrothermal environment from a Sb- to Sb-Pb dominated system with a distinct geochemical change from Pb-free to Pb-containing Sb-phases. A characterization of the precipitation sequence can be used to improve the understanding of the hydrothermal evolution of the whole Sb-Au-ore system in Goldkronach.

How to cite: Fritzke, B., Seifert, T., Linhardt, E., and Kehrer, C.: The Sb-Au-district Brandholz/Goldkronach (Fichtelgebirge, Germany): mineralogical indications for the evolution of hydrothermal Sb-mineralization., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-144, https://doi.org/10.5194/egusphere-egu21-144, 2021.

EGU21-4054 | vPICO presentations | ERE5.6

The genesis of gold in Sb-As and Sb-Au ore veins, new constraints from the study of the La Bellière and La Lucette districts (Armorican Massif, France)

Florent Cheval-Garabédian, Eric Marcoux, Jérôme Gouin, Maxime Picault, and Michel Faure

Shear zones hosted antimony (Sb) quartz vein-type deposits are the most important sources of Sb worldwide. They have been recognized and mined since the Antiquity in the European Variscan belt, and particularly in the French Variscan Massifs, as the Armorican Massif. Among this type of deposit two subtypes are identified, i) the Sb and gold (Au) quartz vein-type (Sb-Au) as the La Lucette deposit located in the North Armorican Domain, and ii) the Sb-As quartz vein-type as those from the la Bellière district in the Ligerian domain.

The recent advances in the understanding of the Sb mineralizations in the European Variscan Belt are typically focused on the Sb ore-genesis and its regional implications, ignoring its potential valuable co-products as gold. In this study, detailed textural-mineralogical investigations coupled with geochemical analyses in rock-samples with in-situ EPMA and LA-ICPMS ore-minerals trace element analyses, were carried out for the first time in the Late-Variscan mineralizations from the La Bellière Sb-As occurrences, and the La Lucette Sb-Au deposit, to ascertain the distribution and amount of Au in the ore-minerals and provide new data on ore deposition conditions.

In the La Bellière Sb-As occurrences, no visible gold has been observed, but low-grade gold, ranging between 0.2 to 1 g/t Au, are correlated with high-grade As in rock sample. In the La Lucette Sb-Au deposit, historical assays have shown high-grade gold with an average at 40 g/t Au. EPMA and LA-ICP-MS analyses have demonstrated that gold is already present during the early time of the mineralization as invisible gold, trapped in the lattice of the Sb-rich arsenopyrites, with an average grade of 70 ppm Au in La Bellière, and at higher average grade of 223 ppm Au for La Lucette. For both type of mineralization, the early invisible gold is concentrated preferentially in the borders of the arsenopyrite crystals, and is correlated with an increase of the As content, and a decrease of the Sb and Fe. We argue that gold could be added in the arsenopyrite by substitution with the Fe and Sb at high temperature > 300 °C.

Visible gold corresponds to the economic gold ore of the Sb-Au mineralizations. In the La Lucette ore, it is emplaced in the late stages, as discrete electrum grains spatially associated with the arsenopyrites, as native gold inclusions within the stibnite, and associated with rare aurostibite. Remobilization processes of the gold-bearing arsenopyrite at lower temperature, coupled with a minor initial enrichment of the Sb-bearing ore-fluid might be responsible of the late high-grade gold ore, and the visible expression of this element. In the absence of such remobilization process with late ore-fluid-enrichment, only low-grade gold is present, under the form of invisible gold in auriferous-arsenopyrites.

The presence of a valuable gold co-product, also present in the Sb-As mineralizations, unknown until now in the French Variscan Massifs, will improve its economic attractivity. Gold potential in the huge French Sb-districts as the Vendée or the Brioude-Massiac districts must be reassessed.

How to cite: Cheval-Garabédian, F., Marcoux, E., Gouin, J., Picault, M., and Faure, M.: The genesis of gold in Sb-As and Sb-Au ore veins, new constraints from the study of the La Bellière and La Lucette districts (Armorican Massif, France), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4054, https://doi.org/10.5194/egusphere-egu21-4054, 2021.

EGU21-12122 | vPICO presentations | ERE5.6

Mafic magma as metal source for Sb-W-Hg mineralisation? A case study of the early Carboniferous mafic magmatic event from the French Armorican Variscan belt

Anthony Pochon, Giada Iacono-Marziano, Saskia Erdmann, Eric Gloaguen, and Johann Tuduri

A possible genetic link between Sb-W-Hg mineralisation (vein-type and stratabound) and mafic magmatism has been proposed for the Variscan belt during the early Carboniferous, but this hypothesis remains to be rigorously assessed. The metal enrichment of the fluids producing Variscan Sb-W-Hg deposits may be ascribed to (i) crystallization of metal-rich primary mafic magma, and/or (ii) exsolution of metal-rich magmatic fluids and their local concentration, and/or (iii) an efficient hydrothermal leaching of surroundings sedimentary rocks by fluid release due to contact metamorphism. The aim of this project is thus to estimate the contribution of mafic magmas as the metal source of Sb-W-Hg deposits. Our case study focuses on the Saint-Jean-du-Doigt gabbro from the Variscan Armorican belt, Brittany, France. We have characterized the Sb-, W-, and Hg-carrier minerals (e.g. Fe-Ti oxides) and volatile-bearing minerals (e.g. apatite) to quantify the metal content and volatile inventory during purely magmatic and magmatic-hydrothermal processes. Abundant primary amphibole and biotite, and the presence of pegmatoids indicate that the melt was likely to be enriched in volatile. An alteration gradient is observed from the base of the intrusion towards its roof. Moreover, high temperature replacement mineral reactions (e.g. saussuritization) mainly occur in the upper part of the intrusion, suggesting that magmatic fluids were accumulated toward the top of the intrusion. Cathodoluminescence and apatite compositions are taken to record the magmatic-hydrothermal transition and hydrothermal alteration. Apatite ranges in composition between fluorapatite and fluor-hydroxyapatite, but the latter is largely more frequent. A high volatile content of the silicate melt is suggested by the high proportion of negative-shaped fluid inclusions into ilmenite (up to 15 % crystal volume), which hint at a primary magmatic origin. SEM, EPMA and LA-ICP-MS investigations show that magmatic fluid inclusions contain significant amounts of Sb and W. Our results highlight that metals (i.e. Sb, W) were partly partitioned into the fluid phase during magma crystallization and degassing. In addition, trace element content of ilmenite also records metal enrichment from the base to the intrusion roof, probably due to magma degassing and deuteric/metasomatic processes. We therefore propose that mafic magmatism is a potential metal source of the early Carboniferous Sb-W-Hg mineralization event and should be considered as possible sources for other Sb-W-Hg province worldwide. This work was funded by the ANR (ANR-19-MIN2-0002) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project (https://aureole.brgm.fr).

How to cite: Pochon, A., Iacono-Marziano, G., Erdmann, S., Gloaguen, E., and Tuduri, J.: Mafic magma as metal source for Sb-W-Hg mineralisation? A case study of the early Carboniferous mafic magmatic event from the French Armorican Variscan belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12122, https://doi.org/10.5194/egusphere-egu21-12122, 2021.

EGU21-12365 | vPICO presentations | ERE5.6

Sb, As and W contents of magmas: insights from geochemical databases

Valentin Mollé, Giada Iacono-Marziano, Eric Gloaguen, Johann Tuduri, Anthony Pochon, and Héctor Campos

Magmatic heat sources allow hydrothermal fluids to transport and deposit various types of metals and metalloids. For instance, antimony (Sb) is frequently spatially associated with mafic intrusions, and may be associated with various amounts of other elements, such as Hg, As, W, Au and Ag. However, source-sink relationships in those settings remain poorly constrained. Whether mafic magmas contribute fluids, metals and metalloids to hydrothermal systems at the origin of Sb mineralisation remains uncertain. Spatial and chronological correlations between Sb ore deposits and mafic magmatism have been acknowledged in Variscan settings (i.e. the Armorican Massif and the Central Iberian Zone), but no causal processes have been established yet (Pochon et al., 2019).

We herein investigated the Sb, As and W contents of magmatic rocks available in the literature, to assess mafic magmas as a potential source for metals and metalloids. The GEOROC database covers most of the rock types occurring in a TAS diagram (n = 7215, whole rock), whereas the Jenner and O’Neill (2012) database focuses on MORBs (n = 601, glass).

Sb, As and W are highly covariant, suggesting a common behaviour during magmatic processes. Sb, As and W concentrations in oceanic magmatic rocks increase with increasing K2O content. This increase is up to two orders of magnitude in mafic compositions, and one order of magnitude through intermediate and differentiated compositions. Differentiated alkaline magmas therefore generally yield higher Sb, As and W concentrations. Variations in Sb, As and W with major and trace elements composition suggest a major role of mantle source processes, and a minor contribution from fractional crystallisation. In particular, Sb, As and W contents in mafic compositions show a good correlation with the La/Sm ratio, and an absence of correlation with the 87Sr/86Sr and the 143Nd/144Nd isotopic ratios, suggesting a crucial control of partial melting processes.

Continental magmatic rocks show a strong Sb, As and W variability, with values up to 3 orders of magnitude higher than oceanic rocks, suggesting the occurrence of crustal contamination. Post-magmatic alteration does not seem to have any effect on Sb, As and W concentrations.

We finally investigate mafic rocks spatially and temporally associated with Sb-Hg ± As-W-Au-Ag ore deposits, and discuss the possible processes at the origin of their enrichment.

 

GEOROC, 2020. Geochemical rock database. , accessed: 02/10/2020.

Jenner F. E., O’Neill H. St. C., 2012. Analysis of 60 elements in 616 ocean floor basaltic glasses: TECHNICAL BRIEF. Geochemistry, Geophysics, Geosystems 13 (2), 11 p.

Pochon A., Branquet Y., Gloaguen E., Ruffet G., Poujol M., Boulvais P., Gumiaux C., Cagnard F., Baele J.-M., Kéré I., Gapais D., 2019. A Sb ± Au mineralizing peak at 360 Ma in the Variscan belt. BSGFEarth Sciences Bulletin 190 (4), 12 p.

How to cite: Mollé, V., Iacono-Marziano, G., Gloaguen, E., Tuduri, J., Pochon, A., and Campos, H.: Sb, As and W contents of magmas: insights from geochemical databases, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12365, https://doi.org/10.5194/egusphere-egu21-12365, 2021.

EGU21-12390 | vPICO presentations | ERE5.6

Unravelling the relationship between mafic magmatism and Sb mineralization through dolerite geochemistry (Central Iberian Zone, Spain)

Héctor Ricardo Campos Rodríguez, Eric Gloaguen, Anthony Pochon, Pablo Higueras, Saturnino Lorenzo, José María Esbri, Valentin Mollé, and Giada Iacono-Marziano

This work presents the preliminary results of geochemistry of mafic intrusions (diabase dykes) and their relationship with antimony mineralization in the Central-Iberian Zone (Variscan Belt). Two different areas were studied, the Almadén (Al) and the San Antonio (SA) areas.

Both macroscopic and microscopic observations show that mafic dykes are mainly composed by clinopyroxene, plagioclase, Fe-Ti oxides and to a lesser extent of calcite and sulphides (pyrite, chalcopyrite and pyrrhotite). These samples are altered presenting chlorite and epidote as alteration minerals. Pyroxene is sometimes altered to amphibole.

Whole rock geochemistry analyses from 20 samples show a difference between SA and Al dolerites. The first fall into the classical basalt field whereas the second fall into the alkali basalt field according to the Zr/TiO2 vs Nb/Y diagram. The tectonic setting for the SA samples coincides with the volcanic arc setting whereas the samples from Al fall into the within plate magmatism. 

Primitive mantle normalized diagrams display high negative anomalies in Rb, K, with small negative anomalies in Nb and Ta for both SA and Al. High positive anomalies for both areas in Cs, Pb (especially for SA) and Li accompanied by small positive anomalies in P and Ti can be observed. Dolerites from Al are more enriched in Ba, Th, U, Nb, Ba, La, Ce, Sr, P, Nd, Sn, Zr, Hf than SA. All samples are depleted in HREE and enriched in LREE. Anomalies in Rb, Nb, Ta and Li may be related with crustal contamination. Pb anomalies could be associated with assimilation of country rocks, especially marine sediments, this anomaly is also related to subduction processes. Positive P and Ti anomalies of some samples is due to the apatite and ilmenite enrichment respectively. Negative anomalies in K could be associated with presence of phlogopite in the source. Rare Earth Elements contents are compatible with the presence of garnet in the source and low degree of partial melting, this is consistent with the correlation between La/Sm vs Gd/Yb and La/Sm vs Rb. Trace element ratios such as Th/La (0,10 for SA) and (0,09 for Al) suggest an enriched mantle source.

Some of these mafic intrusions were collected near antimony mineralization whereas the other are located at distance but in the same swarm of mafic dykes. A spatial and genetic link between Sb mineralization and mafic magmatism has been proposed in other parts of the Variscan Belt, especially in the Armorican Massif.

The source of these Sb mineralization could be related to an enriched mantle with crustal contamination. The geochemical link between mafic magmatism and Sb mineralization and their source in the Central Iberian Zone is still a matter of study.

Acknowledgments

This work was funded by the ANR (ANR-19-MIN2-0002-01), the AEI (MICIU/AEI/REF.: PCI2019-103779) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project, as well as by Project SBPLY/17/180501/000273, Consejería de Educación, Regional Government of Castilla-La Mancha, Spain.

How to cite: Campos Rodríguez, H. R., Gloaguen, E., Pochon, A., Higueras, P., Lorenzo, S., Esbri, J. M., Mollé, V., and Iacono-Marziano, G.: Unravelling the relationship between mafic magmatism and Sb mineralization through dolerite geochemistry (Central Iberian Zone, Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12390, https://doi.org/10.5194/egusphere-egu21-12390, 2021.

EGU21-13154 | vPICO presentations | ERE5.6

Origin and significance of the antimony mineralisation associated to mafic intrusions in the Iberian Zone and the Central Armorican Domain

Eric Gloaguen, Héctor Campos, Anthony Pochon, Pablo León Higueras, Saturnino Lorenzo, José-María Esbrí, Giada Iacono-Marziano, and Alexandre Lima

In the Central Iberian Zone (CIZ) and its French counterpart, the Central Armorican Domain (CAD), widespread swarms of mafic dykes with various ages and compositions are known. Indeed, numerous mafic events are recognized in the late Neoproterozoic, in the Cambrian to the Ordovician, in the Ordovician to the Devonian, at the Devonian-Carboniferous boundary, in the Permian and in the Jurassic. Such a succession of mantle partial melting events, localised or generalized, may have strong consequences (i) on the composition and the homogeneity of the mantle below both the CIZ and CAD, and (ii) on the transfert of metals in the overlying crust. Moreover, the mantle below these domains must have been modified also by the subduction of large to small oceanic crusts from the Iapetus, the Rheic, the Galicia-Moldanubian and the Paleo-tethys. Although the occurrences of paleo-subductions below the CIZ and CAD remain discussed, the southern border of the CIZ, the Ossa-Morena Zone (OMZ), is considered as a suture zone resulting from a subduction followed by a collision between 390 and 360 Ma (D1), according to the 2 opposite structural vergences at the CIZ/OMZ boundary, as well as the location of a NE-dipping slab imaged by seismic profiles. In the Armorican massif, the end of subduction is also dated at 360 Ma and associated to a north-directed subduction. The trace of this subduction below the CAD is visible in the tomographic dataset. Interestingly, these two domains (CIZ and CAD) contain the largest number of Palaeozoic antimony deposits, antimony being a volatile element. In these domains, the large clustering of antimony deposits and occurrences is observed within a ca 100km wide bands along their southern parts. In the two domains, the antimony deposits are frequently spatially associated with diabase dykes. Diabase dykes and associated antimony mineralisation have been dated at 360 Ma in the CAD but remain temporally unconstrained in the CIZ. Nevertheless, since these dykes are strongly affected by the Variscan deformation a minimum age of 350 Ma is inferred. Both, the peculiar composition of these diabase dykes, relatively enriched in Cs, Li, Pb and relatively depleted in K and Rb, the spatial association with antimony at the end of a 360Ma subduction, suggest a link between antimony and a ca 360Ma mafic magmatism which could result from the partial melting of a subduction-related metasomatized mantle.

This work was funded by the ANR (ANR-19-MIN2-0002), the AEI (MICIU/AEI/REF.: PCI2019-103779), the FCT (ERA-MIN/0005/2018) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project (https://aureole.brgm.fr).

How to cite: Gloaguen, E., Campos, H., Pochon, A., León Higueras, P., Lorenzo, S., Esbrí, J.-M., Iacono-Marziano, G., and Lima, A.: Origin and significance of the antimony mineralisation associated to mafic intrusions in the Iberian Zone and the Central Armorican Domain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13154, https://doi.org/10.5194/egusphere-egu21-13154, 2021.

EGU21-2425 | vPICO presentations | ERE5.6

Antimony-Gold mineralization in Rates (Northern Portugal)

Alexandre Lima, Rui Frutuoso, Sara Leal, André Vieira, and Maria Ribeiro

In the Dúrico-Beirão mining district several paragenetic associations have been described in gold mineralizations, including Sb-Au. The objective of this research was the study of the Sb-Au mineralization in the Rates area, from field reconnaissance of the mineralized structures by soil sampling to the petrographic and mineralogical study of the parageneses associated with this gold mineralization, mined by the Romans.

The portable XRF was used to measure Sb and As in farms and forest soils. The observed Au-Sb-As anomalies in the Rates area must be linked to Lagoa Negra mine by the same north-western trend fault. Historical mining works have been identified both in Lagoa Negra and in Rates, where rock-chip sampling returned results up to 30 g/t Au from the Rates prospect.

Some rock samples from Rates were studied by geochemical and petrographic analyses and were analysed in detail by scanning electron microscopy. The results indicate that the paragenetic association in Rates is Sb-Au, with stibnite as primary Sb sulfide mineral, valentinite as alteration mineral, and gold in native and granular form.

Acknowledgment

The work was financial supported within the compass of the ERA-MIN/0005/2018—AUREOLE project, FEDER through operation POCI-01-0145-FEDER-007690 funded by the Programa Operacional Competitividade Internacionalização—COMPETE2020 and by National Funds through FCT within the ICT (reference UIDB/04683/2020).

How to cite: Lima, A., Frutuoso, R., Leal, S., Vieira, A., and Ribeiro, M.: Antimony-Gold mineralization in Rates (Northern Portugal), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2425, https://doi.org/10.5194/egusphere-egu21-2425, 2021.

EGU21-3039 | vPICO presentations | ERE5.6

Antimony deposit exploration of antimony by pXRF measurements: example from the Vendean Antimony District (France) 

Jérémie Melleton, Bruno Lemière, Pascal Auger, Virginie Derycke, Eric Gloaguen, and Loïc Bouat

Competitiveness of mineral exploration for companies is based on reducing costs and capital intensity, improving dynamics and shortening delays between target testing and feasibility analysis. As the use of in situ analyses increases, pXRF (portable X-ray fluorescence) represents a good perspective for a fast and reliable low-footprint exploration approach. This study was carried out as part of the European EIT Raw Materials project UpDeep, which aimed at the demonstration of the applicability of modern geochemical methods for the discovery of new critical metals ore deposits.

We revisited a historic Vendean Sb district, located in western France and southeast of Brittany. First mining activities on antimony ore deposits took place during the 18th century at La Ramée, followed at the beginning of the 19th century, by the discovery of a rich vein at Rochetrejoux, which led to new activities until 1925. The French Geological Survey (BRGM) conducted large-scale survey during the 1970-1980s by stream-sediment followed by soil sampling focusing on sediment anomalies, which led to discovery of around 20 new prospects distributed on a 50x20 km area, in particular at Les Brouzils, La Télachère and La Copechagnière. Mining operations started again until the mid-1990s at Les Brouzils mine. The area is characterized by extensive agricultural practices.

The geological framework of the area is Variscan metamorphic rocks (gneiss and amphibolites) and slightly metamorphised sedimentary rocks, locally crosscut by dolerite dykes. Variscan thrust and shear-zones generated a network of conjugated tension fractures, controlling Sb mineralisations emplacement. The Les Brouzils ore deposits consists of a principal lode system dipping at 70°  and extending over at least 800 m horizontally and recognized up to 100 m vertically. The principal characteristic of this ore deposit is the presence of large blades of stibnite. Berthierite, pyrite and arsenopyrite complete the paragenesis. In the La Télachère prospects, trenches and drill holes on the two principal anomalies determined the presence of a quartz lode system with associated stibnite. Paragenesis comprises stibnite, arsenopyrite, galena, sphalerite, berthierite, chalcopyrite, tetrahedrite, pyrrhotite and gold in a quartz gangue. At La Copechanière, known deposits correspond to subvertical quartz NW-SE veins with stibnite, with thickness of 0.2 – 0.3 m. All the area is partially covered by plateaux silts and gravels of mixed allochtonous (eolian) and autochtonous origin. Thickness of the plateau loess can be comprised in the range 0.5 – 2 m.

For this study, we performed shallow-soil sampling (Ah and B horizons) along profiles across known veins to capture the endogenic geochemical anomaly signals. Despite an expected bias with laboratory analyses, pXRF measurements effectively located the Sb veins, with Sb and associated pathfinder elements (As, Mn) patterns, especially when using the pXRF multi-element capabilities enhanced by compositional data processing methods. Similar geochemical patterns obtained for both studied horizons suggest that application of on-site approach to humic horizon can increase efficiency of the survey and decrease its impacts.   

How to cite: Melleton, J., Lemière, B., Auger, P., Derycke, V., Gloaguen, E., and Bouat, L.: Antimony deposit exploration of antimony by pXRF measurements: example from the Vendean Antimony District (France) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3039, https://doi.org/10.5194/egusphere-egu21-3039, 2021.

EGU21-4850 | vPICO presentations | ERE5.6

Regional soil geochemistry for Sb and Hg in Guadalmez and Almadén synclines, South-Central Spain

Sofía Rivera Jurado, Saturnino Lorenzo, Carmelo Monsuy Minang Eyang, José María Esbrí Víctor, Eric Gloaguen, and Pablo Higueras

The geochemical similarities between Hg and Sb (along with W and As), have produced ore deposits in which both elements are present. In the present work we investigate the relationships between the Sb deposits of the Guadalmez synclinal and the Hg deposits of the Almadén synclinal, separated only 8 kilometres. To accomplish this porpoise a regular sampling grid was used, locating samples in each square (4 km2) according to lithologic criteria. In total, 116 soil samples have been taken at two depths using an Ejkelkamp sampler. The samples have been taken in an area of around 100 m2 around the set point at different depths, sample A at 2-15 cm and sample B at 15-30 cm. Each sample represents a composite sample of 3 subsamples taken at different but close locations, randomly chosen. The preparation of the samples has included drying at room temperature to avoid Hg losses, as well as its disaggregation and homogenization, prior to obtaining an aliquot of 100 grams that was ground in agate mortar until obtaining a grain size of less than 100 microns. The geochemical characterization of the samples included the analysis by energy dispersion X-ray fluorescence (EDXRF) to obtain the concentrations of major and trace elements. Total Hg data has obtained by means of Atomic Absorption Spectrometry using a Lumex equipment with a pyrolysis attachment. The distribution of Sb and Hg contents in the two synclines studied has not shown appreciable similarities. The highest concentrations of Sb have been found in the Guadalmez syncline, where the known mines of La Balanzona and Accesos are located. A particularly anomalous zone has been located in the southeaster zone of the Guadalmez synclinal, in the Ordovician age materials. Elevated Sb contents have also been found in the Almadén syncline, especially in the western zone without an observable predominance by lithology using a 4 km² grid size that could be less sensitive to scarces lithologies (e.g dykes). The Hg distribution, on the other hand, offers its maximum contents, as expected, in the Almadén syncline, particularly at the southeast part. Some anomalous Hg values have been found in Devonian materials of Guadalmez syncline. Concentrations of Cr and Ni are clearly related with the volcanic rocks of Almadén syncline, as well as with the presence of diabase intrusions in the Guadalmez syncline. Considering the age, a higher variability is observed in Hg contents than in Sb, especially in Devonian materials. Sb contents show little variability in general, but this is appreciable in the Ordovician materials of the Gualdamez syncline.

This work was funded by the ANR (ANR-19-MIN2-0002-01), the AEI (MICIU/AEI/REF.: PCI2019-103779) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project, as well as by Project SBPLY/17/180501/000273, Consejería de Educación, Regional Government of Castilla-La Mancha, Spain.

How to cite: Rivera Jurado, S., Lorenzo, S., Minang Eyang, C. M., Esbrí Víctor, J. M., Gloaguen, E., and Higueras, P.: Regional soil geochemistry for Sb and Hg in Guadalmez and Almadén synclines, South-Central Spain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4850, https://doi.org/10.5194/egusphere-egu21-4850, 2021.

EGU21-7339 | vPICO presentations | ERE5.6

Machine learning models for Hg prospecting in the Almadén mining district

Julio Alberto López-Gómez, Daniel Carrasco Pardo, Pablo Higueras, Jose María Esbrí, and Saturnino Lorenzo

Traditionally, prospectivity models were designed using approaches mainly based on expert judgement. These models have been widely applied and they are also known as knowledge-driven prospectivity models (see Harris et al. (2015)). Currently, artificial intelligence approaches, especially machine learning models, are being applied to build prospectivity models since they have been proven to be successful in many other domains (see Sun et al., 2019 and Guerra Prado et al., 2020). They are also known as data-driven prospectivity models. Machine learning models allow to learn from data repositories in order to extract and detect relationships from the data to predict new instances.

In this work, a geological dataset was collected by a team of expert geologists. The data collected includes the geographical coordinates as well as several geological features of points belonged to seventy-seven different mercury deposits in the Almadén mining district. The resulting dataset is composed by a total of 24798 points and 24 attributes for each point. In particular, we have collected geological and mining-related data regarding the Almadén mercury (Hg) mining district; these data include the location of the several Hg mineralizations, including their typology, size, mineralogy, and stratigraphic position, as well as other information associated to the metallogenetic model set up by Hernández et al. (1999).

Later, few machine learning models are built to select the one which offers the best results. The aim of this work is twofold: on the one hand, it is intended to build a machine learning model capable of, given the geological features of a data point, to determine the mercury deposit to which it belongs. On the other hand, the aim is to build a machine learning model capable of, given the geological features of a data point, to identify the kind of deposit to which it belongs. The experiments conducted in this work have been properly designed, validating the results obtained using statistical techniques.

Finally, the models built in this work will allow to generate mercury prospectivity maps. The final aim of this process is to get and train a system able to perform antimony prospection in the nearby Guadalmez syncline.

This work was funded by the ANR (ANR-19-MIN2-0002-01), the AEI (MICIU/AEI/REF.: PCI2019-103779) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project.

References

Guerra Prado E.M.; de Souza Filho C.R.; Carranza E.M.; Motta J.G. (2020). Modeling of Cu-Au prospectivity in the Carajás mineral province (Brasil) through machine learning: Dealing with embalanced training data.

Harris, J.R.; Grunsky, E.; Corrigan, D. (2015). Data- and knowledge-driven mineral prospectivity maps for Canda’s North.

Hernández, A.; Jébrak, M.; Higueras, P.; Oyarzun, R.; Morata, D.; Munhá, J. (1999). The Almadén mercury mining district, Spain. Mineralium Deposita, 34: 539-548.

Sun, T.; Chen, F.; Zhong, L.; Liu, W.; Wang, Y. (2019). GIS-based mineral prospectivity mapping using machine learning methods: A case study from Tongling ore district, eastern China.

How to cite: López-Gómez, J. A., Carrasco Pardo, D., Higueras, P., Esbrí, J. M., and Lorenzo, S.: Machine learning models for Hg prospecting in the Almadén mining district, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7339, https://doi.org/10.5194/egusphere-egu21-7339, 2021.

EGU21-9939 | vPICO presentations | ERE5.6

AI oriented prospectivity mapping to study relationships between Sb mineralization and geological framework

Alex Vella, Charles Gumiaux, Guillaume Bertrand, Bruno Tourlière, Eric Gloaguen, and Stanislas Sizaret

Prospectivity mapping aims at producing favorability maps, outlining areas with the highest likelihood to host mineralization. This process can be done using data-driven approaches, based on statistical and spatial analyses on geological features and known mineral occurences. Besides, such approach contributes to better understand metallogenic processes by highlighting specific and systematic associations between deposits and geological features (structures, lithologies, contacts, geophysical anomalies, etc).

As part of the AUREOLE project, prospectivity maps of Sb throughout the West European Variscan Range are being produced using CBA (“Cell-Based Associations”). CBA is a prospectivity tool developped for mineral prospectivity mapping by the French Geological Survey (BRGM). This method divide at first space into a regular cells grid. Inside each cell, the associations of geological factors, such as lithological, structural, geophysical or geochemical features, are grouped together and define the geological framework in the vicinity of the given cell. This project aims at developing and improving this method by the addition of new machine learning methods and statistical and spatial analysis tools for the automated classification and the calculation of favorability score.

Application of this approach to the Ibero-Armorican Arc, relying heavily on Artificial Intelligence to process the data, will highlight statistical relationships between the Sb deposits and their surrounding geological framework. Computations will be performed at multiple scales and in different areas trough the Arc, in order to observe the influence of scale in the consistency of the results and to bring out general laws from local specificities in the metallogenic models. Results from this almost purely data-driven approach will be compared to the metallogenical models traditionnaly proposed for Sb deposits in the studied areas. We infer this new multiscale and multidomains study  would improve our understanding of the genetic processes resulting in  Sb deposits through the Variscan Range and give new metallotects or specify the common ones, to be used for mineral exploration purpose.

This Phd work is funded by the ERA-MIN2 AUREOLE project (ANR-19-MIN2-0002, https://aureole.brgm.fr).

Keywords: Antimony, Prospective Mapping, Machine Learning, Data-Driven.

How to cite: Vella, A., Gumiaux, C., Bertrand, G., Tourlière, B., Gloaguen, E., and Sizaret, S.: AI oriented prospectivity mapping to study relationships between Sb mineralization and geological framework, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9939, https://doi.org/10.5194/egusphere-egu21-9939, 2021.

Over the last few decades, the construction industry has become interested in materials that are durable, environmentally friendly and easily recyclable. This interest is due to the advantages these materials offer, among others local availability, low carbon footprint, energy efficiency and indoor comfort. The objective of this work is to study the properties of plasters prepared from a mixture of two types of gypsum. We were interested in the evolution of thermal conductivity, mechanical resistance and setting time as a function of the percentage of addition.

Two types of gypsum were studied, the first one belongs to the Safi basin and the second one comes from the High Atlas of Marrakech.

The characterization of the gypsums was necessary to determine its physical and geotechnical properties, its mineralogy, its thermal behavior and its microscopic structure. Several analyses were developed such as density measurement by pycnometer, X-ray diffraction, infrared spectroscopy and scanning electron microscopy.

We have made samples, of standardized dimensions, of mixtures based on both types of plaster. The water/gypsum mass ratio was set at 0.75.

The results revealed that the properties of gypsum as well as the percentage of addition affect the mechanical and thermal properties and the setting time of the composite material. The addition of the High Atlas gypsum of Marrakech allowed improving the material in terms of thermal insulation. The results of the other tests will be communicated later.

How to cite: baba, I., Ibnoussina, M., Witam, O., and Saadi, L.: Thermal and mechanical characterization of a new material based on two gypsums from different localities : High Atlas of Marrakech and Safi Basin, Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11102, https://doi.org/10.5194/egusphere-egu21-11102, 2021.

EGU21-12933 | vPICO presentations | ERE5.6

Preliminary petrographic study of dolerites related to Sb-Au mineralizations: example of Ribeiro da Serra mine (Dúrico-Beirão mining district, NW Portugal) 

Rui Frutuoso, Maria dos Anjos Ribeiro, Alexandre Lima, and Helena Sant'Ovaia

In the Dúrico-Beirão mining district, several occurrences of Sb-Au are known, which were exploited since the Roman occupation in Iberia until mid-last century. This region is located in the Central Iberian Zone of the Iberian Massif, part of the Ibero-Armorican Arc. The country rocks in the area consist of folded metasedimentary rocks from Cambrian to Carboniferous surrounded by syn- to post-orogenic Variscan granites. The Ribeiro da Serra Sb-Au mine, intensively exploited in the 19th century, occurs west of the western limb of the Valongo Anticline, a major ante-Stephanian structure with NW-SE trend. This Sb-Au deposit consist mainly of stibnite-bearing quartz veins hosted by slates, quartzites and conglomerates of the Schist-Greywacke Complex in a possible spatial relationship with dolerite dykes. These mafic dykes are emplaced in sub-parallel shear zones to the sinistral Douro Shear Zone and their presence may suggest the existence of mafic/ultramafic bodies at depth, which contributed to the occurrence of Sb-Au deposits.

This study aims to describe the dolerite dykes present through the region (petrographic composition, weathering, distribution, and dimension) considering a possible contribution for the Sb-Au occurrence. Dolerites are greyish-green colored and are intensely weathered. The samples surface shows a few millimeters of brownish supergenic alteration. The petrographic study highlighted an intense chloritization and saussuritization of plagioclase, whose tabular form and twinning are still preserved. The primary igneous texture is better preserved than the primary mineralogy. The texture is ophitic to sub-ophitic although the interstitial mass of the pyroxene is totally altered.  Chlorites occur as fresh, green-colored patches, sometimes with radiated fibrous textures. Frequent polycrystalline quartz lenses and veins occur, also as consequence of the hydrothermal/metamorphic alteration. The opaques, not yet identified, occur in a great modal percentage, and are frequently associated with titanite. They do not seem to have a special concentration related to quartz veins and lenses. Apatite is a frequent accessory phase and appears to be preferentially associated with opaque minerals.

The knowledge of the petrographic characteristics of these dolerite dykes, associated with geochemical data, can be a great contribution to the understanding of the distribution of Sb mineralization and corroborate the hypothesis of non-outcropping mafic/ultramafic bodies.

 

Acknowledgment

The work was financial supported within the compass of the ERA-MIN/0005/2018—AUREOLE project, FEDER through operation POCI-01-0145-FEDER-007690 funded by the Programa Operacional Competitividade Internacionalização—COMPETE2020 and by National Funds through FCT within the ICT (reference UIDB/04683/2020).

How to cite: Frutuoso, R., Ribeiro, M. D. A., Lima, A., and Sant'Ovaia, H.: Preliminary petrographic study of dolerites related to Sb-Au mineralizations: example of Ribeiro da Serra mine (Dúrico-Beirão mining district, NW Portugal) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12933, https://doi.org/10.5194/egusphere-egu21-12933, 2021.

EGU21-43 | vPICO presentations | ERE5.6

Antimony leaching from mine waste and soil at a stibnite mine in North-Vietnam

Valérie Cappuyns, Axelle Van Campen, and Jillian Helser

While the impact of Sb mining is documented in literature from China, Australia, and Europe, little information is available concerning the environmental impact of Sb mining in Vietnam. This paper presents the results of an exploratory study of mine waste and soil samples from the Mau Due mine (North Vietnam). Besides the chemical and mineralogical composition of soils, waste rock and slag samples, water-soluble and exchangeable/reversibly adsorbed Sb species were also determined, as well as the pH dependent release of Sb. Stibnite and pyrite were found in slag and waste rock samples, with total Sb concentrations in the range of 191–15,699 mg/kg. Soils were characterized by Sb concentrations in the range of 47–95 mg/kg. 
The leaching test show that, when mine waste stored on the Mau Due mining site comes into contact with water, up to 1.7% of its total Sb content is leached. However, because of the high Sb content of some of the waste materials, high dissolved Sb concentrations are found in the leachates. Some of the investigated samples are listed by the EU as absolutely hazardous waste, because of the leaching potential of Sb. Especially in the rainy season, leaching of Sb from the mine waste and slags can contribute to the dispersion of Sb. An increased release of Sb was observed from pH 7.5 to 12.8. Modelling also indicated that the dissolution of stibnite and reprecipitation as Sb(OH)3 is not the only factor that explains Sb solubility. Desorption reactions and the incorporation of Sb in other mineral phases are most likely also important factors determining the retention and release of Sb from the waste materials and slags.
The waste heaps consist of fine-grained material, that can be prone to wind erosion in the dry season. Therefore, measures to prevent the further dispersion of Sb and other potentially hazardous elements, both via leaching and wind erosion, should be put in place. In order to establish regulations for environmental protection, it is necessary to raise governmental and public awareness. The high concentrations of Sb imply an important potential hazard for soils, water bodies, and the food chain, for which appropriate measures are necessary.

 

Reference

Cappuyns, V., Van Campen, A., Helser, J.  (2020). Antimony leaching from soils and mine waste from the Mau Due antimony mine, North-Vietnam. Journal Of Geochemical Exploration, 220, Art.No. 106663, 1-13. doi: 10.1016/j.gexplo.2020.106663 

How to cite: Cappuyns, V., Van Campen, A., and Helser, J.: Antimony leaching from mine waste and soil at a stibnite mine in North-Vietnam, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-43, https://doi.org/10.5194/egusphere-egu21-43, 2021.

EGU21-2781 | vPICO presentations | ERE5.6

Mobility of antimony in samples from diverse environmental compartments of Sb mines in Spain: leaching experiments in oxidizing and reducing conditions

Fabienne Battaglia-Brunet, Hugues Thouin, José Maria Esbri Victor, Eva Maria Garcia Noguero, Saturnino Lorenzo, Pablo Leon Higueras Higueras, and Eric Gloaguen

Antimony (Sb) is a valuable element, exploited for diverse applications including flame retardants, munitions, batteries, glasses, and industry for diodes. However Sb is also a toxic metalloid, often associated with other harmful elements (arsenic, lead, mercury…) in mining sites. The biogeochemical behavior of Sb remains poorly documented, and data must be acquired in order to elaborate solid environmental studies related with Sb mining. Here, the mobility of Sb from solid phases present in former mining sites was assessed through leaching experiments performed in oxidizing or reducing conditions. Five Sb mines located in South-Central Spain were considered: La Nazarena, Accesos, Balanzona, Pilar, and Susana mines. Rock samples were analysed by X-ray diffraction, confirming that the main Sb carrier was stibnite (Sb2S3), present in all mines. Surface soils and mine wastes were sampled, together with sediments when ponds or galleries were present. The total Sb concentrations of 18 samples varied from 28 to 221 000 mg kg-1. However, stibnite was only detected in a soil sample from Balanzona mine and tetrahedrite ((Cu,Fe)12Sb4S13)in a sediment from the Balanzona mine. The most common Sb secondary minerals were bindheimite (Pb2Sb2O6O), senarmontite (Sb2O3), valentinite (Sb2O3) and stenhuggarite (CaFeSb(AsO3)2O). These materials were incubated in slurries at 10 % solids, at 25°C under agitation, either in presence of air or under N2/H2 atmosphere. Sb was generally more mobile in oxidizing conditions; however, for 2 samples, mobility was higher in reducing conditions. The highest Sb concentrations in water were in the range 20 to 30 mg L-1. The final percentage of solubilized Sb exceeded 1 % (between 1 and 12 %) for 10 samples. For one sediment sampled in Balanzola mine, final Sb concentrations were close to 20 mg L-1 in oxidizing conditions and 10 mg L-1 in reducing conditions. Acidification was observed with several samples; however, Sb release was not systematically related with the evolution of pH. The mobility of Sb during leaching might be driven by diverse mechanisms: release of sorbed Sb, abiotic or biotic dissolution of Sb-bearing minerals, including oxidation of Sb sulfides in aerobic conditions, or reductive dissolution of Sb-bearing iron or manganese oxides, and finally release of soluble thio-Sb complexes in anaerobic conditions. Supporting the occurrence of these last mechanisms, final analyses indicated solubilization of Fe and Mn and traces of dissolved sulfide in reducing conditions. Our results, that showed a higher mobility of Sb in oxidizing conditions, are globally consistent with previous works indicating a higher occurrence of the oxidized form of Sb, i.e. SbV, in water streams impacted by mining sites. However, we also observed that non negligible release of Sb can be linked to mechanisms occurring in reducing conditions. Perspectives of this work include the elucidation of the biological processes, directly or indirectly involved in Sb release or immobilisation, in order to better predict the evolution of environmental quality on mining sites and propose remediation strategies.

This work was funded by the ANR (ANR-19-MIN2-0002-01), the AEI (MICIU/AEI/REF.: PCI2019-103779) and author’s institutions in the framework of the ERA-MIN2 AUREOLE project.

How to cite: Battaglia-Brunet, F., Thouin, H., Esbri Victor, J. M., Garcia Noguero, E. M., Lorenzo, S., Higueras Higueras, P. L., and Gloaguen, E.: Mobility of antimony in samples from diverse environmental compartments of Sb mines in Spain: leaching experiments in oxidizing and reducing conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2781, https://doi.org/10.5194/egusphere-egu21-2781, 2021.

EGU21-12353 | vPICO presentations | ERE5.6

Antimony and arsenic speciation in the major waste dump of the abandoned Lojane Sb-As-Cr mine, North Macedonia

Tamara Đorđević, Stefan Uiblein, Uwe Kolitsch, Peter Nagl, Miriam Unterreiner, Goran Tasev, and Todor Serafimovski

We present the results of mineralogical and geochemical investigations of the solid waste dump material from the abandoned Lojane mine in the northern part of North Macedonia. The geologically unusual Lojane deposit was mined for Sb (stibnite), As (realgar) and Cr (chromite) until 1979. Its waste dumps and tailings were left without any proper rehabilitation. Hence, it represents an extensive source of antimony and arsenic pollution.

In April 2018 we took samples from the major waste dump near Vaksince village. This 70 m long and 20 m wide, relatively ore-rich dump lies parallel to the creek bed of the immediately adjacent Suva creek (NW-SE). In 2017 a Turkish exploration company had dug a ~1.6 m deep trench along the middle of the elongate dump. The samples were taken along this trench using a hand-drill tool (ca. 20 cm deep) and laterally along the exposed profiles.

X-ray fluorescence (XRF) spectroscopy analyses showed that the mean concentrations of Sb and As are 9950 ppm and 32004 ppm, respectively, but can locally rise to extreme values of 24 g/kg for Sb and 200 g/kg for As. Besides Sb and As, very high amounts of Ni (up to 4672 ppm) and Cr (up to 5136 ppm) have been measured.

A combination of powder X-ray diffraction, Raman spectroscopy and SEM-EDS analyses (of polished aliquots) showed that the main primary source of antimony is stibnite with up to 2 at.% of As, while the main primary sources of arsenic are realgar, gersdorffite (up to 9 at.% of Sb) and As-rich pyrite (up to. 10 at.% of As). Additionally, minor amounts of Sb and As (up to 1.5 at.%) were detected in violarite (Fe2+Ni3+2S4) and greigite (Fe2+Fe3+2S4). Secondary phases of Sb and As are associated with amorphous iron oxyhydroxides (with up to 2 at.% Sb and up to 11 at.% As) and finely crystalline, porous and chemically inhomogeneous Ca-Fe-Sb-As-oxides/hydroxides belonging to the roméite group, with up to 7 at.% of As. Occasionally, dissolved Sb and As reprecipitated as senarmontite/valentinite, Sb2O3, scorodite, FeAsO4∙H2O (up to 2 at.% of Sb), annabergite, Ni3(AsO4)2∙8H2O, hörnesite, Mg3(AsO4)2∙8H2O, and arseniosiderite, Ca2Fe3(AsO4)3O2∙3H2O. These observations are in good agreement with our prior study focussing on the secondary mineralogy of this and other dumps (Kolitsch et al., 2018).

Further phases confirmed, in approximate order of decreasing abundance are: dolomite, serpentine group-minerals, magnesite, gypsum, quartz, talc, vermiculite, clay minerals, micas (muscovite, phlogopite, annite), plagioclase (albite, anorthite), calcite, siderite, chromite, magnesiochromite, spinel, magnetite, vaesite, clinochlore, tremolite, diopside, fluorapatite, rutile, zircon, monazite-(Ce), hydroxylapatite(?), hydroniumjarosite, chamosite, hematite, manganese oxyhydroxides, bornite, chalcopyrite, cobaltite, galena and baryte.

Financial support of the Austrian Science Fund (FWF) (P 30900-N28) is gratefully acknowledged.

 

Kolitsch, U., Đorđević, T., Tasev, G., Serafimovski, T., Boev, I., Boev, B. (2018): Supergene mineralogy of the Lojane Sb-As-Cr deposit, Republic of Macedonia: Tracing the mobilization of toxic metals. Geol. Maced., 32, 95-117.

How to cite: Đorđević, T., Uiblein, S., Kolitsch, U., Nagl, P., Unterreiner, M., Tasev, G., and Serafimovski, T.: Antimony and arsenic speciation in the major waste dump of the abandoned Lojane Sb-As-Cr mine, North Macedonia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12353, https://doi.org/10.5194/egusphere-egu21-12353, 2021.

EGU21-13392 | vPICO presentations | ERE5.6

The fate of Sb(V) in the Sb-polluted old mine area of Su Suergiu (SE-Sardinia, Italy): the role of secondary mopungite [NaSb(OH)6]

Elisabetta Dore, Dario Fancello, Daniela Medas, Nicola Rigonat, Stefano Naitza, and Giovanni De Giudici

Antimony (Sb) is widely present in the environment as a consequence of both natural processes and human activities. Extremely high Sb concentrations can be found in present and past mine areas and in their surroundings, representing a serious environmental and toxicological threat.

The abandoned Sb mine of Su Suergiu (Sarrabus-Gerrei mining district, SE Sardinia, Italy), has been exploited from 1880 to 1980; the mined ore was dominated by stibnite (Sb2S3), which was processed in the smelter adjacent to the mine. After the closure of the complex, mining and metallurgical residues were dumped without intervention to mitigate their environmental impact. Waters draining Su Suergiu have high Sb concentration (up to 103 - 104 µgL-1) and the contamination extends several km downstream reaching the Flumendosa River, the main river of south-eastern Sardinia, used in agriculture and domestic consumption.

The mineralogy of outcropping rocks, mine wastes and foundry slags from the mine area was investigated by X-Ray Powder Diffraction (XRPD) and Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM-EDS) to understand the oxidation pathways and the role of secondary Sb-bearing minerals on Sb dispersion.

At Su Suergiu, the foundry slag heaps are the main contamination sources. Indeed, the residues of metallurgical processes, consisting of metallic Sb (Sb0) and Sb2O3 (valentinite/sénarmontite) together with carbonates and NaAl-silicate hydrate, are exposed to surface environment and subjected to oxidation and weathering processes. The oxidation of Sb0 and Sb3+ phases leads to the formation of Sb5+ that, at the slightly alkaline and oxidizing conditions of surface water draining the Su Suergiu area, is present in solution as dissolved Sb(OH)6.

The local geochemical conditions of waters circulating within the foundry slag heaps, affected by the carbonates and Si-Na-Al phases, promote the precipitation of a rare secondary Sb mineral, namely mopungite NaSb(OH)6. On the slag fragments, mopungite occurs as euhedral crystals (about 100 µm), alteration crusts and micro-aggregates filling the fractures; the different occurrences are likely due to the local availability of Na and water circulation.

Results indicate that mopungite is the last forming mineral in the oxidation paths of Sb phases and derives by a dissolution-precipitation process. Due to its relatively high solubility, mopungite act as a temporary sink, whose effectiveness is conditioned by the hydrological regime and the water physicochemical conditions (T, pH, Eh, etc.).

At Su Suergiu foundry slag heaps the Sb mobility is mainly controlled by mopungite, whereas the role of Fe-bearing compounds, recognized as the main Sb binders in the most part of polluted sites worldwide, is here negligible.

 

The authors acknowledge CESA (E58C16000080003) from RAS and RAS/FBS (F72F16003080002) grants, FP7 ERANETMED2 72094 SUPREME, the Grant of Excellence Departments, MIUR (ARTICOLO 1, COMMI 314 – 337 LEGGE 232/2016), and the CeSAR (Centro Servizi d'Ateneo per la Ricerca) of the University of Cagliari, Italy, for SEM analysis. This work has been supported by the POR FESR Sardegna 2014-2020 (project cluster Top-Down: TESTARE)

How to cite: Dore, E., Fancello, D., Medas, D., Rigonat, N., Naitza, S., and De Giudici, G.: The fate of Sb(V) in the Sb-polluted old mine area of Su Suergiu (SE-Sardinia, Italy): the role of secondary mopungite [NaSb(OH)6], EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13392, https://doi.org/10.5194/egusphere-egu21-13392, 2021.

EGU21-15753 | vPICO presentations | ERE5.6

Antimony and arsenic distribution and impacts at a derelict antimony mine in Scotland 

Lenka Mbadugha, Duncan Cowper, Sapar Dossanov, and Graeme Paton

Mining activities are acknowledged to introduce contaminants into localised environments and cause wider spread diffuse pollution. The concentration, distribution and fate of arsenic (As) and antimony (Sb) were studied at the former metalliferous Louisa Mine at Glendinning, Scotland. The associated deposit is one of very few able to produce Sb in the UK and was mined for three brief periods between 1793 and 1922.  

The remnants of the mine consist of the ore processing area and two spoils. Soils withing these zones as well as around the mine were sampled and complemented by water samples from the adjacent stream, the Glennshanna Burn. All samples were subsequently analysed to map the distribution of contamination and identify pollution sources. The maximum concentrations of As and Sb, 15490 and 1504.2 mg kg−1 respectively, were determined in soils associated with the ore processing area and spoil heaps. Anthropogenic activities also redistributed As and Sb within these mine zones and altered their relative ratios. The fractions of dissolved As and Sb in soils were < 1 and < 5% of total soil content, respectively, confirming findings of previous studies that As and Sb are relatively immobile. Yet, the concentrations of As and Sb released by soils exceeded regulatory limits.

Concentrations of As and Sb in surface water in the immediate vicinity of the mine were impacted by a gully discharge, but rapidly diluted. While the concentrations affected by the run-off waters did not exceed EU environmental standards for freshwater, the concentrations of As and Sb sharply increased to 11.43 ± 3.43 and 9.28 ± 0.59 μg l−1, respectively, approximately 100 m downstream of the mine site. The unaltered As to Sb ratios in water samples suggested a geogenic source of contamination.

While there is a justifiable concern about the soil pollution caused by the historic mining in the studied area, the Glenshanna Burn is affected more by indigenous geochemical processes than the derelict mine.

How to cite: Mbadugha, L., Cowper, D., Dossanov, S., and Paton, G.: Antimony and arsenic distribution and impacts at a derelict antimony mine in Scotland , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15753, https://doi.org/10.5194/egusphere-egu21-15753, 2021.

ERE5.7 – Towards an environmentally sustainable transformation of tailings and mine waste: circular economy and future vision

EGU21-3257 | vPICO presentations | ERE5.7

Mineralogical Characterization, Resource Estimation and 3D Modeling of Sulfidic Tailings at the Neves Corvo Mine: An On-going Assessment 

Alexandra Escobar, Jorge Relvas, Alvaro Pinto, and Mafalda Oliveira

Neves Corvo is an underground high-grade Cu-(Sn)-Zn mine, currently producing copper, zinc and lead concentrates. Copper production started in 1989, followed by tin production, between 1990 and 2001, and zinc / lead production started in 2006. The operation is owned by SOMINCOR, a subsidiary of Lundin Mining, with a maximum capacity of 2.6Mtpy for the copper processing plant and 1.0Mtpy (ongoing expansion to 5.6Mtpy) for the zinc processing plant.

The Neves Corvo VMS deposit is located in the Portuguese part of the world-class Iberian Pyrite Belt (IPB) and is composed of seven orebodies. The Neves, Corvo, Zambujal and Lombador orebodies are currently in production, whereas the Semblana and Monte Branco orebodies are relatively recent discoveries still under development and evaluation, and the Graça orebody has been already fully mined.

From 2010 till end of 2019, the mine has accumulated 7.3Mt of waste rock and 17Mt of thickened tailings. These mining residues are stored in Cerro do Lobo Tailings Management Facility (Cerro do Lobo TMF), which completes a volume of 47Mt since the beginning of the operation in 1989 (30Mt are slurry tailings).

The deposition method changed in 2010 from slurry subaquatic deposition to sub-aerial thickened tailings stack (vertical expansion) in co-deposition with potentially acid-generating (PAG) waste rock. The thickened tailings have an average of 63% solids. X-ray fluorescence analysis have shown copper and zinc grades variation in the waste rock between 0.3 and 0.9%, and 0.4% and 1.1%, respectively, and concentrations up to 0.3% and 0.4% of copper and zinc, respectively, in the tailings.

Mineralogically, the tailings consist mainly in pyrite, sphalerite, chalcopyrite, +/- arsenopyrite, +/- tetrahedrite-tennantite, gangue minerals such as quartz, phyllosilicates, carbonates and some oxides, and have a non-uniform particle size distribution ranging between 1 and 100 µm. The waste rock fraction is millimetric to centimetric in size, and is formed by the local host rocks, which include acid volcanic rocks, schists and graywackes, all of them containing variably significant disseminated sulfides, largely dominated by pyrite.

On-going research is being undertaken aiming to build a geometallurgical model for the Neves Corvo mine, ground on a huge database on the chemical and mineralogical composition, and particle size distribution of the mine tailings, coupled with (and calibrated by) new analytical and automated data acquired in a large set of carefully selected representative samples, in order to assess the potential recovery of base metals and their by-products out of these potentially valuable mine residues. The model construction and consequent resource estimation will be based on the daily monitoring of the tailings deposition at the disposal units, over the past 10 years (i.e., since the subaerial deposition has started at Neves Corvo), in terms of volume/tonnage, chemical and mineralogical compositions and physical characterization of the material.

This study is part of the work package 1 (WP1) of ETN–SULTAN project (H2020) - European Training Network for the remediation and reprocessing of sulfidic mining waste sites. Publication supported by FCT- Project UID/GEO/50019/2019 - Instituto Dom Luiz.

How to cite: Escobar, A., Relvas, J., Pinto, A., and Oliveira, M.: Mineralogical Characterization, Resource Estimation and 3D Modeling of Sulfidic Tailings at the Neves Corvo Mine: An On-going Assessment , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3257, https://doi.org/10.5194/egusphere-egu21-3257, 2021.

EGU21-9454 | vPICO presentations | ERE5.7

Mineralogical characterisation and deportment studies of different mine waste material from a historic tailings pond in Plombières, East Belgium.

Srećko Bevandić, Philippe Muchez, Rosie Blannin, Kai Bachmann, Max Frenzel, Alexandra Gomez Escobar, Álvaro Pinto, and Jorge M. R. S. Relvas

Recent studies on historic mine waste (e.g. tailings, waste rock, metallurgical waste) indicate the recycling potential of the material for metal extraction. Historic mine wastes have been shown to be of more interest than modern mine wastes, due to the lower efficiency of ore processing in the past. Although the knowledge of processing has significantly improved, there are still some areas in the processing sector that could be improved. Most previous studies have focused on the bulk analysis of mine wastes, without a detailed analysis of important characteristics, such as mineral texture, associations, liberation and locking. Recent studies focus on detailed mineralogical analysis, in order to more accurately assess the availability of the metals within the potential material for metal extraction. The present study investigates the geochemical and mineralogical characteristics of different mine and metallurgical waste material from a tailings pond in Plombières (East Belgium). The tailings pond covers a minimum surface area of 8000 m2, comprising 4 main types of material.  Ore microscopy, X-ray fluorescence (XRF), quantitative X-ray powder diffraction (XRD), scanning electron microscope (SEM) based Mineral Liberation Analysis (MLA) and electron microprobe (EPMA) were used to identify and characterise Pb and Zn phases within the material. XRF analysis shows that the mine wastes dominantly consist of SiO2, Al2O3 and Fe2O3, while the content of Zn and Pb varies from 51 ppm to 24 wt % and 10 ppm to 10.1 wt %, respectively. The mineralogy of the mine waste is characterised by quartz, amorphous phases and phyllosilicates, with minor amounts of Fe-oxide, Pb- and Zn-bearing minerals. Based on the processing of the ore, the amorphous phase is present as pyrometallurgical slag.  Mineral- to element- conversion shows a lack of Pb and Zn content. MLA and EPMA analysis confirm that the missing Pb is distributed between Pb- droplets within the slags and in the amorphous structure of the slags. Additionally, the analyses reveal that zinc is also dominantly located within the slags.

How to cite: Bevandić, S., Muchez, P., Blannin, R., Bachmann, K., Frenzel, M., Gomez Escobar, A., Pinto, Á., and M. R. S. Relvas, J.: Mineralogical characterisation and deportment studies of different mine waste material from a historic tailings pond in Plombières, East Belgium., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9454, https://doi.org/10.5194/egusphere-egu21-9454, 2021.

EGU21-2992 | vPICO presentations | ERE5.7

A novel approach for the geospatial modelling and resource assessment of tailings storage facilities

Rosie Blannin, Max Frenzel, and Jens Gutzmer

Tailings are the fine-grained residues of ore processing operations, typically stored in dedicated tailings storage facilities (TSFs). Despite being viewed as ‘waste’ materials, tailings can contain significant amounts of valuable metals which were not recovered by original processing techniques or were previously not of economic interest. Re-processing of tailings deposits for the recovery of remaining metals has the additional benefits of mitigation of environmental hazards posed by the TSFs, such as Acid Mine Drainage (AMD). The estimation of mineral resources requires the construction of accurate and reproducible geospatial models. However, the sedimentary-style deposition and subsequent weathering of tailings results in a complex internal structure which is challenging to model, with a laterally and vertically heterogeneous distribution of the minerals comprising the residues. The present study investigates a novel approach for the geospatial modelling of a TSF case study. The surface of the tailings deposit was densely sampled in order to assess the intrinsic horizontal variability. Drill core samples were taken from a depth of 1-3 m, on a 30 m grid and nested grids of 15 m and 7.5 m, with additional random and twin holes. The entire depth of the TSF was sampled in 2 m intervals with a total of 10 drill holes to assess vertical variability. All drill core samples were analysed with x-ray fluorescence spectrometry and inductively coupled plasma mass spectrometry. The compositional data was log-ratio-transformed and variography and subsequent ordinary kriging and co-kriging were performed on the surface samples. The variogram models obtained for the surface samples were then applied for kriging of the deeper layers. Historical photographs of the surface of the TSF were used to improve estimates with co-kriging for the corresponding layers. The entire data set will be used to determine the most efficient sampling approach for the resource estimation of TSFs.

How to cite: Blannin, R., Frenzel, M., and Gutzmer, J.: A novel approach for the geospatial modelling and resource assessment of tailings storage facilities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2992, https://doi.org/10.5194/egusphere-egu21-2992, 2021.

EGU21-4776 | vPICO presentations | ERE5.7

Environmental assessment of sulfidic mine waste and its integration into green construction materials

Jillian Helser and Valérie Cappuyns

Proper management and storage of mine waste (e.g., tailings and waste rock) is one of the main issues that mining industries face. Additionally, there is already an uncountable amount of existent historical mine waste, which may, even centuries later, still be leaching contaminants into the environment. One solution to minimize the risks associated with the waste, with also potential economic benefits, is through the valorization of the waste. This can be done by first recovering valuable metals and removing hazardous contaminants. Then, the remaining residue can be valorized into green construction materials, such as geopolymers, ceramics or cement.  For some mine waste materials, such as those with only trace levels of metals, that are not economically viable to extract, the “waste” can be reused directly without this additional cleaning step. In the present study, mine waste originating from 3 different sites, both operational and historical mines, was characterized and assessed in comparison with the cleaned mine waste (i.e., cleaned by bioleaching or ion flotation methods) and with different types of green construction materials containing (cleaned and uncleaned) mine waste. Particular emphasis was given to the study of the mobilization of metal(loid)s from the mine waste and green construction materials (i.e., ceramics, geopolymers and cement) under different conditions, through a series of leaching tests (i.e., EN 12457-2, US EPA’s Toxicity Characteristic Leaching Procedure, and a pH-dependent leaching test). The standardized leaching tests were applied to either mimic neutral conditions in nature, conditions in a landfill (end of life), or a worst-case scenario (i.e., in extremely acidic or alkaline pH).

Mineralogical (X-ray diffraction) and chemical (X-ray fluorescence) characterizations of the original mine waste samples revealed high levels of Pb, Zn, and As in most samples. Additionally, the samples consisted mostly of quartz, micas, clay minerals and/or feldspars. Some samples also contained pyrite (FeS2), a key mineral that generates acid mine drainage. Based on the leaching studies, some geopolymers, ceramics, and cement efficiently immobilized certain metals (such as Pb and Zn). Also, longer curing durations of the geopolymers in most cases improved the immobilization of metal(loid)s. Overall, the leaching studies revealed that the concentrations of mine waste incorporated in the construction materials, as well as the pH of those materials, were the main factors influencing the mobility of metal(loid)s. Additionally, for ceramics, the temperature at which the test pieces were fired, also played a major role. Through this detailed characterization, the environmental impacts were assessed from the mine waste to the downstream products, determining which valorization methods are the most viable to close the circular economy loop.

How to cite: Helser, J. and Cappuyns, V.: Environmental assessment of sulfidic mine waste and its integration into green construction materials, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4776, https://doi.org/10.5194/egusphere-egu21-4776, 2021.

EGU21-7639 | vPICO presentations | ERE5.7

Turning mine waste into a ceramic resource: Plombières mine tailing case

Francisco Veiga Simão, Hilde Chambart, Laure Vandemeulebroeke, Peter Nielsen, and Valérie Cappuyns

Mining and quarrying waste is considered the second largest waste stream in Europe. According to Eurostat, in 2018, this extractive waste accounted for over a quarter of all the EU-27 waste output (26.2%). The accumulation of this type of waste in tailing dams or waste rock piles, with no end-use, can pose as a significant environmental and health hazard as well as a resource loss. Sulphidic mine waste processing residues (tailings) pose a large challenge, as their content in hazardous metalloids and sulphates tend to become more chemically available, leading to the generation of acid mine drainage. Apart from the hazardous metalloids and sulphates, these mine tailings contain valuable base, precious and critical metals which can be used in different technological applications. Moreover, silicates and clay minerals are amongst the most common and abundant minerals in sulphidic mine tailings, which indicates that after pre-treatment, if necessary, they can be used in different ceramic building applications (e.g. roof tiles and blocks) for an increasing world’s population.

Plombières Zn-Pb inactive mine (Eastern Belgium), was exploiting an ore deposit between 1844-1882 and after closure of the mine, imported ores were smelted at the Plombières site until 1922. The dumped material from the mining operations consist of mainly mine waste and metallurgical waste, such as tailings and slags, from the processing plants. The goal of the present study is to evaluate the potential use of (uncleaned) Plombières tailing material in 3 different ceramic products (roof tiles, blocks and pavers), with different compositions and firing temperatures, taking into account production parameters, product quality and environmental compliance in Flanders (Belgium).

After a detailed physical, mineralogical, chemical, thermal and environmental characterisation of the Plombières mine tailing material, as well as of the replaced raw materials, one company-specific blend has been modified on a lab scale for each ceramic product, by partly or totally replacing some primary raw materials (mainly clay and sand) by 5%, 10% and 20% of Plombières fine tailing material. The shaping, drying and firing behaviour of lab test pieces was assessed and compared to the standard, as well as the required technical, aesthetical and chemical properties of each ceramic product. Furthermore, environmental compliance tests (column leaching test) were performed on the fired test pieces of all the ceramic products. The column leaching test is performed considering a 2nd life scenario where shaped building products are demolished and can be recycled as granulates (non-shaped building products).

How to cite: Veiga Simão, F., Chambart, H., Vandemeulebroeke, L., Nielsen, P., and Cappuyns, V.: Turning mine waste into a ceramic resource: Plombières mine tailing case, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7639, https://doi.org/10.5194/egusphere-egu21-7639, 2021.

EGU21-8895 | vPICO presentations | ERE5.7

Opportunities related to Moroccan mine wastes valorisation

Yassine Taha, Rachid Hakkou, and Mostafa Benzaazoua

Large amounts of solid wastes are produced by the mining industry. These wastes are often considered as problematic materials as they can lead to harmful impacts on the surrounding environment and the society. However, it was proved by many studies that most of mine wastes are inert but sometimes mixed with problematic components such as sulfidic minerals and hazardous metals and metalloids. Reprocessing and retreatment of mine wastes is a key sustainable solution to remove the sources of pollution and to recover the remaining high value products. Many studies around the world have demonstrated the big interest in recovering the residual metals and the use of mine wastes in other applications such as the construction sector.

 

In this study, a special accent will be given to the current management practices of mine wastes in Morocco as well as the possible opportunities related to the reuse of mine wastes coming from different mining activities. Three main materials categories are targeted: phosphate waste rocks and tailings, coal waste rocks and zinc tailings. The goal is to suggest more sustainable management methods and to explore new future opportunities related to the re-use and reprocessing of these wastes. Some possible high value-added products from these types of wastes are suggested based on their characteristics, location and volume. Construction aggregates, ceramics, bricks, cement, glass, acid mine drainage control, and road-base construction are among the possible explored channels.

How to cite: Taha, Y., Hakkou, R., and Benzaazoua, M.: Opportunities related to Moroccan mine wastes valorisation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8895, https://doi.org/10.5194/egusphere-egu21-8895, 2021.

EGU21-3050 | vPICO presentations | ERE5.7

Flocculation as an Alternative to Increase the Recovery of Ultrafine Particles of Pyrite in Flotation of Tailings

Ana Luiza Coelho Braga de Carvalho, Feliciana Ludovici, Henrikki Liimatainen, André Carlos Silva, and Daniel Goldmann

Nowadays, flotation is the most commonly used method for mineral concentration. However, conventional flotation circuits are not suitable for ultrafine particles, and this is a challenge for the concentration of finely disseminated minerals. Moreover, tailing contain a considerable amount of very fine particles which can include valuable and hazardous minerals that have the potential to be recovered. Concern about ultrafine particles has increased as they are present in a wide variety of mineral pulps and can contain valuable minerals that have been lost to the tailings. Several alternatives have been proposed to improve the recovery of ultrafine particles in flotation, for example, decreasing the size of the air bubbles, column flotation, selective agglomeration of particles, etc. Among all, selective polymeric flocculation represents a promising option. The current study focuses on the use of polymeric flocculation to increasing the size of pyrite particles aiming to improve its recovery in the flotation of sulfidic tailings. Flocculation was performed with pyrite particles presenting P80 < 4 mm, in aqueous medium and alkaline conditions. Two polyacrylamides and a new nanocellulose-based chemical were used as flocculants. Microflotation tests were performed, without the addition of collector, to evaluate the formation of flocs through the reduction of the mechanical entrainment of pyrite after being submitted to flocculation.

How to cite: Coelho Braga de Carvalho, A. L., Ludovici, F., Liimatainen, H., Silva, A. C., and Goldmann, D.: Flocculation as an Alternative to Increase the Recovery of Ultrafine Particles of Pyrite in Flotation of Tailings, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3050, https://doi.org/10.5194/egusphere-egu21-3050, 2021.

EGU21-3298 | vPICO presentations | ERE5.7

Low-Energy Desalination Technologies for Treating Mining Effluents 

Georgios Kolliopoulos

As our societies evolved and the quality of primary resources deteriorated, water use in process circuits has led to the generation of ever-increasing volumes of contaminated effluents. Despite the efforts for water recycling in process circuits, desalination technologies fail to treat solutions of high salinity, due to their focus on dilute solutions, such as seawater. The lack of energy efficient effluent desalination technologies leaves vast volumes of aqueous residues sitting in tailings ponds. This practice often allows oxygen to dissolve in water and oxidize certain elements, which leads to the generation of acid in a sequence of events known as acid mine drainage. Uncontrolled discharges resulting from such mining wastes have detrimental effects on the nearby water quality and aquatic ecosystems as well as on the health of the people of the local communities. In this work, we report on novel freeze desalination processes that can recover clean water from such industrial effluents in the form of ice at significantly lower energy compared to state-of-the-art desalination processes. Therefore, the developed technologies promise to economically and efficiently reduce the water-consumption related environmental footprint of the processing industry, the risks and liabilities associated with tailings ponds, as well as to secure access to safe clean water for nearby communities.

How to cite: Kolliopoulos, G.: Low-Energy Desalination Technologies for Treating Mining Effluents , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3298, https://doi.org/10.5194/egusphere-egu21-3298, 2021.

EGU21-12048 | vPICO presentations | ERE5.7

Combining bioleaching and brine-leaching in metal leaching processes: alternative to conventional

Tamara Azevedo Schueler and Daniel Goldmann

The recovery of valuable metals such as copper (Cu), zinc (Zn) and lead (Pb) from mine tailings has gained attention in recent years, mainly for the environmental risk of tailings storage facilities and the demand of such elements in different industrial sectors. Many sulphide tailings deposits are spread worldwide, and some of them belong to active mines, which produce tons of material per year. Leaching is a well-known technology for metal extraction. However, two aspects must be considered: the dissolution of metals involves the use of fresh water and, the tailings contain low metal concentrations and high impurities. As a result, leaching is too expensive due to energy input in water purification and high acid consumption. The use of salt water in mineral extraction processes is becoming more attractive in the mining sectors over the years, especially in regions where fresh water is scarce. The presence of salt water in metal leaching has demonstrated a great capacity to increase metal extraction from ore, for example, by increasing the surface and porosity of copper containing minerals. This phenomenon plays an important role in metal leaching. The formation of a passive layer on the surface of the mineral in oxidizing conditions is a strong barrier in the extraction of the target metal. Conditions that overcome this obstacle are of utmost importance for the mining industry. Furthermore, a combination of conventional leaching systems with biological methods (bioleaching) is shown to be a good strategy in tailings leaching. Bioleaching has been applied to the treatment of poor ores and tailings, since acidophilic bacteria can oxidize Fe2+ with the regeneration of Fe3+ ions, together with the reduction of sulphur species to sulfuric acid, leading to the extraction of metals. Moreover, it is considered a more environmentally friendly technology than traditional extraction methods, as it occurs naturally, more economical and results in significantly less pollution. Therefore, some studies have been applying biological leaching as a pre-treatment for chemical leaching of mining tailings. The aim of this work is to present and discuss possibilities to conventional metal extraction processes, combining the two strategies of bioleaching and brine-leaching.

How to cite: Azevedo Schueler, T. and Goldmann, D.: Combining bioleaching and brine-leaching in metal leaching processes: alternative to conventional, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12048, https://doi.org/10.5194/egusphere-egu21-12048, 2021.

EGU21-12333 | vPICO presentations | ERE5.7

Functionalized nanocelluloses as bio-based chemicals in froth flotation

Feliciana Ludovici, Ana Luiza C.B. de Carvalho, Robert Hartmann, and Henrikki Liimatainen

Froth flotation is the most common process in the mining industry for the beneficiation of complex sulfide ores. For this purpose, thiol collectors (mostly xanthates) are typically used as flotation chemicals because of their efficacy. However, concerns for their effect on human health and negative impact on the environment increasingly urge for alternative candidates. Consequently, there are great ecological and economical interests to develop novel green chemicals from renewable resources to overcome the inherent environmental and health problems associated with traditional petroleum-derived mining chemicals. Cellulose, which is the most abundant natural polymer resource, represents a green alternative raw material to develop sustainable chemicals that could replace currently used synthetic additives. In the present work, we introduce a novel environmentally friendly and industrially feasible process to produce selective froth flotation chemicals. Therefore, the pulp fibers were disintegrated to cellulose nanoparticles and further functionalized with a silylation reaction in aqueous conditions. Two different functional groups were incorporated into the cellulose nanoparticles and subsequently investigated, namely a thiol-functional moiety, which has an affinity towards pyrite ore surfaces, or an amine-functional moiety, which has an affinity towards silica surfaces. Microflotation tests were carried out in a Hallimond tube to study the flotability of pure pyrite or quartz as a function of pH value, collector concentration, flotation time, and gas flow rate using the novel green nanoparticles, and their results were compared with commercial xanthate and amine chemicals.

 

Keywords: cellulose nanoparticles, deep-eutectic solvent, silylation, ore beneficiation, froth flotation.

How to cite: Ludovici, F., C.B. de Carvalho, A. L., Hartmann, R., and Liimatainen, H.: Functionalized nanocelluloses as bio-based chemicals in froth flotation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12333, https://doi.org/10.5194/egusphere-egu21-12333, 2021.

EGU21-10617 | vPICO presentations | ERE5.7

Sustainable Development Goal Conflicts in Re-Mining of Tailings

Philipp Büttner, Jens Gutzmer, Jonathan Engelhardt, and Mirko Martin

The Davidschacht tailings storage facility (TSF), operated from 1944 to 1964, represents one of the largest tailings dams in the historic Freiberg mining district. It contains a volume of 760,000 m³ of sulfidic flotation tailings, residues of former base metal and silver ore beneficiation. The tailings material still contains elevated concentrations of valuable elements such as zinc (0.4 wt.% on average), lead (0.2 wt.%) and copper (0.05 wt.%) as well as indium (10 ppm). The material has thus become the focus of efforts to enable eventual re-mining and recovery of valuable metals. However, such efforts have to take into account a number of important interests of the public. The first of these is the fact that the unrehabilitated tailings pose a significant risk to the environment. Cd (44 ppm on average) and As (0.6 wt.%) concentrations are particularly high – and have a marked influence on the adjacent water bodies, such as the Freiberg Mulde river. Curbing this influence has been the subject of multiple remediation studies, but pressure to act has risen recently due to increasing regulatory demands on the quality of surface water (EU Water Framework Directive of 2000). This is, in principle, very much in favor of re-mining the tailings in an effort to remove also hazardous components. Counteracting this reclamation scenario is the fact that the TSF is part of the UNESCO World Heritage Site “Erzgebirge / Krusne Hory” that was awarded in 2019. Another restriction pertains to the highly protected status of individual species (esp. sand lizard) settling on the TSF surface. This constellation obviously provides ample space for discussion as to how to deal with the tailings material contained in the Davidschacht TSF in future. Different sustainable development goals (SDG) have to be weighed against each other in order to find a holistic and sustainable. Airlift reactor-based bioleaching has been considered as an opportunity to maximize the sustainability of re-mining activities on the Davidschacht TSF. This innovative approach – and its circumstantial limitations – are documented in this contribution.

How to cite: Büttner, P., Gutzmer, J., Engelhardt, J., and Martin, M.: Sustainable Development Goal Conflicts in Re-Mining of Tailings, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10617, https://doi.org/10.5194/egusphere-egu21-10617, 2021.

EGU21-4734 | vPICO presentations | ERE5.7

Challenges in the sampling and characterisation of mining residues for CRMs recovery

Adriana Guatame-Garcia, Mike Buxton, Sara Kasmaee, Francesco Tinti, Rachel Horta Arduin, Aina Mas Fons, Francoise Bodenan, and Joachim Schick

The recent Circular Economy Action Plan for Europe1 considers mine waste a secondary source of minerals. These deposits contain potentially economic concentrations of Critical Raw Materials (CRMs), such as Al, Li, Co and REE, which are strategic for the global economy and energy transition. However, there are significant knowledge and technological gaps that hinder their successful recovery. The INCO-Piles 2020 project2 is currently working on the recapitulation, establishment and development of innovative technologies for the sustainable extraction of CRMs from the residuals of mining activities, focusing on Regional Innovation Scheme (RIS) strategic areas. The project includes the definition of potential applications, best practices, and the promotion of technology transfer through round tables that count with international experts' participation.

The first Round Table, a hybrid event held in December 2020 with 73 experts from 23 countries, addressed the challenges in recovering CRMs from tailings. The discussions were based on three topics: (1) challenges in sampling and characterisation from mining residue, (2) extraction and processing challenges, and (3) economic and environmental challenges. Regarding the first topic, one of the most significant issues is the inherent heterogeneity of mine waste deposits, which is a product of the mine processing and deposition methods, and the post-depositional weathering reactions. The lack of historical data, particularly for old deposits, hampers the understanding of such processes. A second challenge concerns the specific type of information required for assessing the CRMs potential. Representative geochemical and mineralogical data must be collected and interpreted at different scales (i.e., from individual minerals to tens of meters tall waste rock piles and tailings). The collection of representative samples faces issues related to the accessibility to the mine waste sites, the coverage and the sample contamination (i.e., material mixing) related to sample recovery methods. The scalability can be addressed by a combination of laboratory analyses, in-the-field surveys and remote sensing techniques. Current innovations in the combination of modern analytical instruments for geochemistry and mineralogy (e.g., pXRF, LIBS and portable infrared spectrometers) and the implementation of machine learning and artificial intelligence techniques will contribute to closing the knowledge and technology gaps.

Lastly, the discussions included the potential hazards faced during the characterisation and re-intervention of old-sites. Well-known mine wastes issues related to human health, environment and license to operate that can hinder a characterisation campaign must be properly considered before the commencement of a CRMs recovery project. The participants also identified transversal challenges for the three discussion topics, such as the need for regulation and professionals with an appropriate background.

All the insights discussed during this First Round Table will serve as a baseline for defining the best practices for characterisation and sampling of CRMs in mine wastes and contributing to increasing the sustainability in the supply of mineral resources and improving old mining sites' environmental quality.    


1 EU Circular Economy Action Plan https://ec.europa.eu/environment/circular-economy/

2 INCO-Piles is a two-year project funded by EIT RawMaterials. More information: https://site.unibo.it/inco-piles-2020/en

How to cite: Guatame-Garcia, A., Buxton, M., Kasmaee, S., Tinti, F., Horta Arduin, R., Mas Fons, A., Bodenan, F., and Schick, J.: Challenges in the sampling and characterisation of mining residues for CRMs recovery, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4734, https://doi.org/10.5194/egusphere-egu21-4734, 2021.

EGU21-7764 | vPICO presentations | ERE5.7 | Highlight

Mine waste reuse and reprocessing: an important step for the implementation of the circular economy in Europe

Françoise Bodénan, Yannick Ménard, and Patrick d'Hugues

Whereas there are growing needs for mineral resources (metals for the energy and digital transitions
and construction materials), the mining industry must produce them from poorer, more
heterogeneous and more complex deposits. Therefore, volumes of mine waste produced (including
tailings) are also increasing and add up to waste from mining legacy. For example in Europe (x27): 732
Mtons of extractive waste are generated per year and more than 1.2 Btons of legacy waste are stored
all over the European territory. The localisation (and potential hazards) are well known and covered
by the inventories carried out in EU countries under the Mining Waste Directive.
At the same time, Europe is implementing the circular economy approach and put a lot of emphasis
on the resource efficiency concept. In this context, reprocessing operation to recover both metals and
mineral fraction is studied with the objective of combing waste management (reducing final waste
storage and long-term impact) and material production from secondary resources.
Numerous industrial experiences of reprocessing of mine waste and tailings exist all over the world to
recover metals such as copper, gold or critical raw materials - CRM They concern mainly active mine
where both primary and secondary resources are considered in profitable operations; for example in
Chile, South Africa, Australia. Mineral fraction recovery is often not considered which still leaves the
industry with a high volume of residual minerals to store and manage.
In addition, legacy mining waste are potentially available for reprocessing. In this case, numerous
mining liabilities issues need to be managed. Some of the European legacy mining waste have residual
valuable metals that could be recovered but some of them have very low metal contents. In Europe,
classical rehabilitation operations – usually at the charge of member states and local authorities – is
the priority and concern the reduction of instabilities and impacts to the environment including heap
remodelling, covering and water management with long-term treatment. Completing this risk
management approach by a circular economy one is a very active R&D subject in EU27.
This presentation will give an overview of EU research projects which tackled the legacy mining waste
challenge from inventory to process development. Several process flowsheets to recover metals were
designed and tested on several case studies with CRM – REE, Co, W, Sb, etc. Initiatives to reuse mineral
fraction are also underway and should be ready for commercialisation in the coming years.
Resources efficiency concept and the circular economy implementation starts on mining sites. In order
to facilitate the implementation of this approach, the technical solutions will need to be included in
innovative global initiatives covering also legal (liability management), environmental (Life Cycle
Analysis approaches) and social (acceptance) questions.

How to cite: Bodénan, F., Ménard, Y., and d'Hugues, P.: Mine waste reuse and reprocessing: an important step for the implementation of the circular economy in Europe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7764, https://doi.org/10.5194/egusphere-egu21-7764, 2021.

EGU21-4027 | vPICO presentations | ERE5.7

Legacy deposits: can a small-scale mining paradigm contribute to the re-processing mining wastes to supply critical raw materials?

Jérôme Bodin, Guillaume Bertrand, and Patrick D'Hugues

In line with the perspective of the Raw Material Initiative launched in 2008 by the European Commission to ensure access to and supply of critical raw materials in Europe, the H2020-funded IMPaCT project (Grant no. 730411) aims to develop a Switch-On Switch-Off (SO-SO) concept as an emergence of a new modern small-scale mining paradigm. Its ultimate goal is to increase the viability of many critical metals hosted in small primary deposits, particularly in Europe, by developing a modularized mobile plant (MMP) concept that can economically operate different type of ores in different types of geological and geographical contexts.

In addition, the project addresses the prospect of applying the SO-SO concept and the small-scale mining paradigm with regard to the reprocessing of mineral wastes in Europe. A dataset of legacy deposits of interest for the SO-SO concept was drawn from the ProMine Anthropogenic Concentration (AC) database (built during the European FP7 ProMine project) used as the data source and by applying a sequential-rating as a methodology to rank records and to highlight potential targets.

Apart from national mining wastes registries, the ProMine AC database remains so far the most exhaustive and reliable attempt at a consolidated pan-European database regarding mining wastes. Despite data shortcoming in the ProMine AC database, this study proposes potential targets of mineral wastes for the SO-SO concept in Europe and provides with preliminary information on location, type of waste, commodities content, tonnage and their potential.

To put into perspective the application of the SO-SO concept and the small-scale mining paradigm in regards with mineral wastes reprocessing, this study also proposes generic flowsheets to address specific potential targets identified among the records from the ProMine AC database and based on the preliminary information available. However, the relevancy and completeness of these information still require a case-by-case assessment. As a result, this methodology falls into a scoping approach that could be applied ahead of (pre)feasibility studies.

Combining the re-exploitation of a primary ore deposit along with the reprocessing of its wastes inherited from previous mining and ore processing activities is of great interest in seeking social acceptance. Eventually, in such perspective, a cross survey of the potential of both primary deposits, using the ProMine Mineral Deposits (MD) database, and secondary deposits, using the ProMine AC database, therefore appears as a relevant scoping strategy ahead of implementing small-scale mining.

How to cite: Bodin, J., Bertrand, G., and D'Hugues, P.: Legacy deposits: can a small-scale mining paradigm contribute to the re-processing mining wastes to supply critical raw materials?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4027, https://doi.org/10.5194/egusphere-egu21-4027, 2021.

ERE6.1 – Induced/triggered seismicity in geo-energy applications: monitoring, modeling, mitigation, and forecasting

EGU21-4740 | vPICO presentations | ERE6.1

Numerical Analysis of the Induced Seismicity Triggered by Hydraulic Fracturing in the Duvernay Formation in Alberta, CA

Dima Yassine, Alissar Yehya, and Elsa Maalouf

In the past decades, induced seismicity has become a major concern due to its correlation with oil and gas production and wastewater disposal. Unlike the induced seismicity observed in the United States that is associated with massive saltwater disposal, the induced seismicity observed in the Duvernay formation, a shale target in Alberta, Western Canada, is associated with hydraulic fracturing operations. In this work, we explore the possible mechanisms and the hydro-geological factors responsible for the seismic events that occurred between 2014 and 2015 in the Duvernay formation. By a two-dimensional finite element poroelastic model, using COMSOL Multiphysics, we couple fluid flow and solid deformation to estimate the change in the Coulomb Failure Stress (CFS) along two critically stressed faults existing near the hydraulic fracturing operations. One fault (Fault 1) is 1.01 km away from the location of hydraulic fractures while the second fault (Fault 2) is 0.425 km below the location of hydraulic fractures. The variations of the CFS along the two pre-existing faults are analyzed and compared to the seismic events obtained from the observational data in the Duvernay formation from December 2014 to March 2015 (Bao & Eaton, 2016). Our results show that most of the seismic events correlate spatially and temporally with positive CFS values that imply a risk of failure. During the early stages of hydraulic fracturing, the triggering failure mechanism of “Fault 1” is the increase in the shear stress on portions of the fault that are under extension and that of “Fault 2” is the pore pressure diffusion. Moreover, the distance between the centers of the two faults must range between 1.5 km and 2 km for the CFS results to agree with the observed seismic events. Under this condition, the shallower sections of “Fault 1” are under compression and show a stabilizing behavior (i.e., negative CFS) that is confirmed by the lack of seismic events from observational data, and the deeper sections of “Fault 1” are under extension and show a destabilizing behavior (i.e., positive CFS), which correlates with the measured seismic events. If the distance between “Fault 1” and “Fault 2” is less than 1.5 km, the shallower section of “Fault 1” would be destabilized by the effect of pore pressure, which does not agree with the observed seismic data. Moreover, if the distance between “Fault 1” and “Fault 2” is greater than 2 km, “Fault 1” would be entirely stabilized. Hence, the position of the faults with respect to the location of the hydraulic fracturing operations played an important role in the induced earthquakes triggering mechanisms and in the spatiotemporal distribution of the seismic events.

How to cite: Yassine, D., Yehya, A., and Maalouf, E.: Numerical Analysis of the Induced Seismicity Triggered by Hydraulic Fracturing in the Duvernay Formation in Alberta, CA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4740, https://doi.org/10.5194/egusphere-egu21-4740, 2021.

EGU21-2437 | vPICO presentations | ERE6.1

Dominant strike-slip faulting and near-constant stress drop of induced earthquakes in the Kiskatinaw area, northeastern British Columbia, Canada

Marco Pascal Roth, Kilian B Kemna, Rebecca M Harrington, and Yajing Liu

An increasing number of hydraulic fracturing (HF) operations in­ low-permeable tight shales in the Kiskatinaw area, northeastern British Columbia, have been associated with M3+ earthquakes in the last decade, including a ML 4.5 on 11/30/2018 near Dawson Creek. Here, we use a catalog of 8285 events ranging from magnitude ML -0.5 to 4.5 between July 2017 and July 2020 to investigate their source parameters. We identify event families using waveform cross-correlation and event temporal correlation, and estimate the focal mechanism solutions (FMS) of the highest-magnitude event within each family using the probabilistic earthquake source inversion framework Grond. We also estimate FMS for events with a magnitude larger than ML 2.5 that do not belong to a family (independent events). We compile a FMS catalog using the robustly constrained solutions for the largest events, and associate all smaller earthquakes with a cross-correlation coefficient (CCC) > 0.8 with the corresponding FMS. In addition, we estimate seismic moment and static stress drop values using spectral fitting methods on both single spectra and spectral ratios, and investigate their scaling relations.

 

In total, we constrain 65 FMS, of which 53 are clustered events, and the remaining 12 are independent events. An additional 4255 events have a CCC > 0.8 with one of the constrained FMS and are listed accordingly in the catalog. Of the total 4320 FMS, 93% are strike-slip events with one nodal plane at low angles to SH, 3% are dominantly strike-slip with thrust-faulting components, and the remaining 4% have a dominantly thrust-faulting mechanisms perpendicular to SH. The thrust-style events comprise the relatively larger magnitudes contained in the catalog, and may indicate slip on pre-existing faults. Most strike-slip events are part of an event family with multiple matching waveforms, while most thrust-faulting events are isolated with a low number of matching waveforms.

 

We fit the spectral corner frequency of 2360 P-phases and 1981 S-phases using single spectra estimates, and 1031 P-phases and 919 S-phases using the spectral ratios. While results from spectral ratios suggest a roughly constant stress drop of ~1 MPa for all magnitudes, the constant stress drop trend from single spectrum fitting breaks down at magnitudes smaller ~ ML 2.0, as has commonly been observed for events recorded by surface stations. We do not observe significant dependence of stress-drop values with the faulting style, nor with event depth.

How to cite: Roth, M. P., Kemna, K. B., Harrington, R. M., and Liu, Y.: Dominant strike-slip faulting and near-constant stress drop of induced earthquakes in the Kiskatinaw area, northeastern British Columbia, Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2437, https://doi.org/10.5194/egusphere-egu21-2437, 2021.

EGU21-5244 | vPICO presentations | ERE6.1

The relevance of small-magnitude earthquakes in detailing the spatiotemporal correlation between hydraulic fracturing related injection and seismicity

Kilian B. Kemna, Marco P. Roth, Ricarda M. Wache, Rebecca M. Harrington, and Yajing Liu

Over the last decade, low-permeability tight shale formations in the Western Canada Sedimentary Basin (WCSB) have been extensively developed using hydraulic fracturing (HF) techniques for oil- and gas exploration. In the meantime, an increasing number of M3+ earthquakes (e.g., ML 4.5 11/30/2018 near Dawson Creek, and an Mw 4.6 08/17/2016 near Ft. St. John) has been associated with HF operations. By increasing the seismicity in areas of low historical seismicity, the relationship between operational parameters and the rate of fault activation needs to be fully understood to avoid economic losses due to operation shutdowns or damages caused by ground shaking.

As earthquakes follow a well-known power-law magnitude-frequency relation, standard earthquake catalogs are typically dominated by microearthquakes in quantity. However, they usually still miss a large number of earthquakes due to insufficient station coverage and/or limited duration of observation. The latter could also lead to an inadequate time window for detecting larger earthquakes, which results in uncertainties of the power-law relation parameters for a particular area.

Here, we enhance a local seismic catalog derived from a dense seismic network in the Kiskatinaw (Montney Formation) area in British Columbia, Canada, using a multi-station matched filter technique. The existing automated STA/LTA catalog > 8000 earthquakes contains earthquakes from July 2017 - July 2020 with manually revised phase arrivals from up to 25 broad-band stations, ranging between ML -0.6 to 4.5. Using all the ~8000 events from the initial catalog as templates, we detected > 40,000 additional earthquakes, lowering the magnitude of completeness Mc from ~1.3 to ~0.2. We observe a b-value of approximately 1, and the majority of events occurred between 1.0 - 3.0 km depth, where injection depths range from 1.5 - 2.5 km.  

In addition to the previously observed clustering of earthquakes around specific HF wells, we also observe ~8000 earthquakes with no apparent spatial (up to 5 km) or temporal (within two weeks of the reported HF stimulation) connection to HF operations. We estimate the contribution of the uncorrelated events to background seismicity rates. Furthermore, we detect earthquakes with templates related to HF operations, with spatial, but lacking temporal correlation to HF stimulation. Spatially correlated earthquakes with a no temporal correlation could highlight either areas with delayed induced seismicity (if following well stimulation) or areas with previous background seismicity (if preceding it). We will also show the correlation between background seismicity rates and cumulative injection rates and volumes of all wells within the study area.

How to cite: Kemna, K. B., Roth, M. P., Wache, R. M., Harrington, R. M., and Liu, Y.: The relevance of small-magnitude earthquakes in detailing the spatiotemporal correlation between hydraulic fracturing related injection and seismicity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5244, https://doi.org/10.5194/egusphere-egu21-5244, 2021.

EGU21-14795 | vPICO presentations | ERE6.1

Testing hypotheses of stress drop variations with hydraulic fracturing induced seismicity in the Horn River basin

Adam Klinger, Joanna Holmgren, and Max Werner

Source parameters can help constrain the causes and mechanics of induced earthquakes. In particular, systematic variations of stress drops of fluid-injection induced seismicity have been interpreted in terms of the role of fluids, differences between tectonic and induced events, and self-similarity. The empirical basis for the variations, however, remains controversial. Here, we test three hypotheses about stress drops with observations of seismicity induced by hydraulic fracturing in the Horn River basin (Canada). First, stress drop is self-similar and independent of magnitude. Second, stress drop increases with distance from the point of fluid injection, which might be expected if in-situ effective stresses increase away from the point of fluid injection. Third, stress drops estimated with empirical Green’s functions (EGFs) are systematically larger than those estimated from direct fits to source models, which is expected if seismic waves attenuate in a frequency-dependent manner or experience site effects.

We probe the hypotheses with a large microseismic dataset collected during hydraulic fracturing operations in the Horn River shale gas play in British Columbia. 90,000+ seismic events were recorded by three borehole geophone arrays with a moment magnitude range of -3 < M< 0.5. To calculate corner frequencies, we assume small, co-located seismic events can be approximated as EGFs, which effectively remove propagation and site effects from a larger target event. We target 34 Mw > 0 events and search for EGFs over a 100 m radius for each event, choosing only those EGFs that satisfy multiple quality criteria. This study builds on previous work that estimated stress drops from direct fitting of standard Brune source models and found systematic high frequency resonances recorded by the geophones.

Of the 34 target events, we retrieve corner frequency and stress drop estimates for 22 events to test the three hypotheses. We observe that stress drop appears relatively constant over M, but the magnitude range (0 < M< 0.5) is currently too limited to draw strong conclusions. Second, stress drop appears to decrease, rather than increase, with distance from the point of injection (with a moderate Pearson’s correlation co-efficient of -0.5 ± 0.2); this could be caused by a direct hydraulic connection causing a reduction of in-situ effective normal stresses distal to the point of injection. Third, we observe no systematic difference between stress drops from direct source fits and EGF-based estimates, although stress drop uncertainties are large compared to standard earthquake source studies because of limited azimuthal coverage and high-frequency instrument resonances. These initial results do not support the systematic variations of stress drop for fluid-injection induced seismicity that have been observed in other datasets.

How to cite: Klinger, A., Holmgren, J., and Werner, M.: Testing hypotheses of stress drop variations with hydraulic fracturing induced seismicity in the Horn River basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14795, https://doi.org/10.5194/egusphere-egu21-14795, 2021.

EGU21-13438 | vPICO presentations | ERE6.1

Analysis of non-double-couple source mechanisms in an area of induced seismicity, West Texas (USA).

Savvaidis Alexandros and Roselli Pamela

In the scope to investigate the possible interactions between injected fluids, subsurface geology, stress field and triggering earthquakes, we investigate seismic source parameters related to the seismicity in West Texas (USA). The analysis of seismic moment tensor is an excellent tool to understand earthquake source process kinematics; moreover, changes in the fluid volume during faulting leads to existence of non-double-couple (NDC) components (Frohlich, 1994; Julian et al., 1998; Miller et al., 1998). The NDC percentage in the source constitutes the sum of absolute ISO and CLVD components so that %NDC= % ISO + %CLVD and %ISO+%CLVD+%DC=100%. It is currently known that the presence of NDC implies more complex sources (mixed shear-tensile earthquakes) correlated to fluid injections, geothermal systems and volcano-seismology where induced and triggered seismicity is observed.

With this hypothesis, we analyze the micro-earthquakes (M <2 .7) recorded by the Texas Seismological Network (TexNet) and a temporary network constituted by 40 seismic stations (equipped by either broadband or 3 component geophones). Our study area is characterized by Northwest-Southeast faults that follow the local stress/field (SHmax) and the geological characteristic of the shallow basin structure of the study area. After a selection based on signal-to-noise ratio, we filter (1-50 Hz) the seismograms and estimate P-wave pulse polarities and the first P-wave ground displacement pulse in time domain. Then, we perform the full moment tensor analysis by using hybridMT technique (Andersen, 2001; Kwiatek et al., 2016) with a detailed 1D velocity model. The key parameter is the polarity/area of the first P-wave ground displacement pulse in time domain. Uncertainties of estimated moment tensors are expressed by normalized root-mean-square (RMS errors) between theoretical and estimated amplitudes (Vavricuk et al., 2014). We also evaluate the quality of the seismic moment tensors by bootstrap and resampling. In our preliminary results we obtain NDC percentage (in terms of %ISO and %CLVD components), Mw, seismic moment, P, T and B axes orientation for each source inverted.

How to cite: Alexandros, S. and Pamela, R.: Analysis of non-double-couple source mechanisms in an area of induced seismicity, West Texas (USA)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13438, https://doi.org/10.5194/egusphere-egu21-13438, 2021.

EGU21-1076 | vPICO presentations | ERE6.1

Deciphering the source parameters and genesis of the 2017, Mw 4 Montesano earthquake close to the Val d’Agri Oilfield (Italy)

José Ángel López-Comino, Thomas Braun, Torsten Dahm, Simone Cesca, and Stefania Danesi

On October 27th, 2017, a Mw 4 earthquake occurred close to the municipality of Montesano sulla Marcellana, less than 10 km external to the concession of the largest European on-shore hydrocarbon reservoir - the Val d’Agri oilfield (Southern Italy). Being a weak event located outside the extended monitoring domain of the industrial concession, the relevance of this earthquake and possible links with the hydrocarbon exploitation were not deepened. The study of weak to moderate earthquakes can improve the characterization of the potentially destructive seismic hazard of this particular area, already struck by M>6.5 episodes in the past. Taking advantage of a wide coverage of seismic stations deployed in the VA region, we analyze the source parameters of this Mw 4 earthquake applying advanced seismological techniques to estimate the uncertainties derived from the moment tensor inversion and identify plausible directivity effects. The moment tensor is dominated by a NW-SE oriented normal faulting with a centroid depth of 14 km. A single ML 2.1 aftershock was recorded and used as empirical Green function to calculate the apparent source time function for the mainshock. Apparent durations (in the range 0.11 - 0.21 s, obtained from S-waves) define an azimuthal pattern which reveals an asymmetric bilateral rupture with the 70% of the rupture propagation in the N310°W direction, suggesting a rupture plane dipping to the SW. Our results conclude that the Montesano earthquake activated a deeper fault segment associated to the Eastern Agri Fault System close to the basement. The relative low trigger potential below 10% based on depletion-induced stress changes discards an induced or triggered event due to the long-term hydrocarbon extraction in the Val d’Agri oilfield, and it rather suggests a natural cause due to the local tectonic stress.

How to cite: López-Comino, J. Á., Braun, T., Dahm, T., Cesca, S., and Danesi, S.: Deciphering the source parameters and genesis of the 2017, Mw 4 Montesano earthquake close to the Val d’Agri Oilfield (Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1076, https://doi.org/10.5194/egusphere-egu21-1076, 2021.

The United Downs enhanced geothermal system in Cornwall, UK, has induced several microseismic events since flow testing began in August 2020, targeting a granitic intrusion at 5 km depth. As of January 2021, two events exceeding local magnitudes (ML) 1.5 have occurred, highlighting the associated seismic hazard and providing initial data for a preliminary assessment of the region’s ground motion response. However, with only one national seismic station publicly available within 90 km of the site, public data are scarce. In an effort to involve the surrounding communities in the geothermal project, United Downs provided Raspberry Shake 1D or 4D (one vertical geophone, with 4D containing an additional three accelerometers) seismographs to nearby schools, increasing the number of publicly available seismic stations to ten within 15 km of the site. In this study, we assess the ground motions recorded by the Raspberry Shake stations and evaluate their utility for probing ground motions models (GMMs) and the effects of the local geology.

171 earthquakes between ML -1.3 to 1.7 originating at United Downs have been recorded to date, with 37 events above ML 0.0. Unfortunately, the accelerometer components of the Raspberry Shake instruments contained too high background noise levels to be useable, leaving only the vertical geophone component to be analysed for each of the instruments. We find that while the peak ground velocity (PGV) values are in line with those predicted from the Douglas et al. (2013) geothermal GMM, the area experiences higher peak ground acceleration (PGA) than expected. We also find that the observed PGVs and PGAs match the region’s geological features, consisting of a combination of igneous intrusions and sedimentary sandstones and mudstones. For sparse national seismic networks, Raspberry Shake stations can provide a quick initial evaluation of seismic events and their ground motions before industry releases private data for more detailed analyses.

How to cite: Holmgren, J. and Werner, M.: Raspberry Shakes provide initial ground motion assessment of the geothermally induced seismicity at United Downs in Cornwall, UK, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14448, https://doi.org/10.5194/egusphere-egu21-14448, 2021.

EGU21-7124 | vPICO presentations | ERE6.1

Evaluation of 2 years seismic monitoring for geothermal development in Vienna, Austria 

Maria-Theresia Apoloner, Fee-Alexandra Rodler, and Wolfgang Lenhardt

Possible geothermal water resources in the eastern part of Vienna could ideally provide hundreds of thousands of Viennese households with environmentally friendly heat and hot water. Currently, the potential of low-lying hot water resources in this area is being explored geologically and geophysically within the scope of the multi-disciplinary project GeoTief Explore 3D.

For the development of geothermal projects, studies of historical seismicity and monitoring of current seismicity are basic requirements. Therefore, we deployed a seismic network consisting of four stations in the area of interest in 2019. After 2 years of recording, we search the data for previously undetected small magnitude local earthquakes. Also we evaluate the local background noise and its variability with time. Based on these results, we estimate site-specific detection thresholds within in the project area.

How to cite: Apoloner, M.-T., Rodler, F.-A., and Lenhardt, W.: Evaluation of 2 years seismic monitoring for geothermal development in Vienna, Austria , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7124, https://doi.org/10.5194/egusphere-egu21-7124, 2021.

EGU21-12774 | vPICO presentations | ERE6.1

Wave propagation simulation on a 3D model of the Ruhr district for locations of seismic monitoring.

Gabriela de los Angeles Gonzalez de Lucio, Claudia Finger, and Erik Saenger

The Ruhr district meets the necessary elements to carry out geothermal projects due to its geothermal potential and demand, as it is a densely populated industrial area. Currently, there are projects for direct use, whereas projects for electricity generation are planned. The latter, due to greater depths, reservoir enhancement techniques are required in some cases. This may increase the associated seismic risk which should be elaborated in detail.

With available data, a three-dimensional geological and structural model was created. The shallower parts have been widely studied and documented by mining activity in the Ruhr region during the last century.  Below a depth of 1 km, data are scarce, and uncertainties increase. The full elastic wavefield emitted by a realistic seismic source has been simulated using a finite differences scheme and the derived geological model. The elastic properties were estimated with well data. The source has common characteristics of real seismic events in the area.

The wave propagation simulations let us analyze the seismic response with different sources and velocities models. Three cases are considered, two seismic events with distinct depths based on real events. The third case is based on the proposed location of a deep geothermal project.

Especially for the case with the deeper source, the areas with relatively high amplitudes of displacement correlated with structural features of the model. Applying the imaging condition of maximum energy density allows us to define zones with a potentially increased seismic risk that should be monitored more closely.

How to cite: Gonzalez de Lucio, G. D. L. A., Finger, C., and Saenger, E.: Wave propagation simulation on a 3D model of the Ruhr district for locations of seismic monitoring., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12774, https://doi.org/10.5194/egusphere-egu21-12774, 2021.

EGU21-8374 | vPICO presentations | ERE6.1

Induced and triggered seismicity from Nov 2019 to Dec 2020 below the city of Strasbourg, France

Jean Schmittbuhl, Olivier Lengline, Sophie Lambotte, Marc Grunberg, Cécile Doubre, Jérôme Vergne, François Cornet, and Frédéric Masson

Since Nov 2019, a series of seismic of events were felt by the population of the city of Strasbourg, France. The first main event (Ml3.0) on Nov 12, 2019 was part of a seismic swarm that has been initiated a few days before, lasted four month and was located by the BCSF-RéNaSS (EOST) in the northwestern part of the town (Robertsau area) at a depth of 5 km. Its location in the vicinity of the deep geothermal wells (GEOVEN), the temporal correlation with the injection activity on site, the similarity of the depth between the bottom of the wells and the hypocenter of the event, the lack of local seismicity before the event occurrence, the known geological structures including crustal faults in the area, all strongly support the possible triggering of the events by the deep geothermal activities despite the relatively large distance (4-5km). Template matching has been applied and allowed for a significant improvement of the detections. Double-difference relocations evidenced a complex fault zone in the swarm area that extends over 800m. Focal mechanisms of the two main events are consistent with the known orientation of the fault zone. The regional stress field in combination with the fault orientation and a Coulomb failure criterion, shows that the swarm location is in an unstable domain if the cohesion of the fault is weak, particularly sensitive to stress perturbations. Since Oct 2020, hydraulic tests were initiated and a second cluster of seismic events with more felt earthquakes developed closer to the geothermal wells. It includes the largest event (Ml3.6) that was induced on Dec 4, 2020 and caused the definitive arrest of the project. A preliminary analysis shows that most of the largest events happened along the same fault zone as in Nov 2019 but very close to the injection well, where a significant over-pressure has been maintained over time.

This presentation is dedicated to the memory of Prof. François Cornet.

How to cite: Schmittbuhl, J., Lengline, O., Lambotte, S., Grunberg, M., Doubre, C., Vergne, J., Cornet, F., and Masson, F.: Induced and triggered seismicity from Nov 2019 to Dec 2020 below the city of Strasbourg, France, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8374, https://doi.org/10.5194/egusphere-egu21-8374, 2021.

The research site of Soultz-sous-Forêts (Alsace, France) was a pioneer pilot geothermal site in Europe. In this study, we use the available data from 2000 and 2003 hydraulic stimulation tests to analyze the seismicity evolution. We apply the ETAS (Epidemic-Type Aftershock Sequence) model to extract the background seismicity rate during the two stimulation periods.

For the 2003 sequence, to retrieve the nonstationary seismicity component, we use a moving window of 400 events for the whole catalog. The evolution of the background seismicity rate μ is successfully retrieved with an evolution in two peaks coherent with the wellhead pressure evolution, while the triggering parameter Κ is stable. At the end of the stimulation μ decrease significantly. Then we look at the evolution of ETAS parameter by selecting five clusters of seismicity. The evolution of μ for each cluster is in agreement with a propagation of the pressure away from the well with the cluster closer to the well showing one early peak only, the middle clusters showing two peaks and the far cluster showing a later peak. All clusters show a decrease of μ at the end of stimulation.

For the 2000 sequence, the background seismicity rate is less well constrained but it stays globally constant during the stimulation with some decrease after its end. We see no clear peak in μ as was present during 2003 and K is relatively low. However, μ also decreases at the end of the stimulation. The selection of clusters does not change this global behavior and all clusters present grossly the same characteristics.

Our results are in agreement with the different characteristics observed by several authors (e.g. Calo and Dorbath, 2013; Dorbath et al, 2009) between these two stimulations. On one hand, the 2003 stimulation consists in an activation of several existing structures that yields a seismicity well explained by the ETAS model with a combined effect of Coulomb stress transfer and perturbation induced by the stimulation (e.g. pore pressure variation).  The evolution in space is also coherent with the finding of Calo and Dorbath (2013) that the injected water goes far from the well avoiding increase in effective stress near the well. In this case, background seismicity rate can be related to the measured pressure. On the other hand, the 2000 stimulation developed a 3D reservoir with the creation of a fresh shear zone (Cornet et al, 2015) and so the direct effects of the stimulation are dominants. However, no clear relation between the background seismicity rate and the operational parameters can be observed. At the end of stimulation, we observe a decrease of background rate corresponding to a progressive return to a natural background rate, similar to what is observed in other settings (Oklahoma, Rousse).

How to cite: Maury, J. and Aochi, H.: Comparison of the seismicity evolution during the 2000 and 2003 stimulations at Soultz-sous-Forêts., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8864, https://doi.org/10.5194/egusphere-egu21-8864, 2021.

EGU21-7206 | vPICO presentations | ERE6.1

Characterisation of seismic events using time-reverse imaging 

Claudia Finger and Erik H. Saenger

In addition to stable and accurate hypocenters of seismic events, the characterisation of events is crucial for the investigation of seismicity in the context of geothermal reservoirs, CO2-sequestration and other geotechnical applications. Since the origin and nature of the seismicity in such cases is still under investigation, tools should rely on as few a priori assumptions about the sources as possible. Here, an approach is presented to determine the time-dependent moment tensor and origin time in addition to commonly derived hypocenter locations of seismic events using time-reverse imaging (TRI). The full six component moment tensor is derived and may be used to display for example focal mechanisms. The workflow consists of determining the location of potential sources, discriminating artificial and true source locations and obtaining the time-dependent moment tensors by recording the stress components at the derived source locations. Since TRI does not rely on the identification of seismic phases but on the simulation of the time-reversed wavefield through an adequate velocity model, no assumptions about the source location or the type of source mechanism is made. TRI is less affected by low signal-to-noise ratios and is thus promising for noisier sites and quasi-simultaneous events. However, a sufficient number of seismic stations are needed to accurately sample the wavefield spatially. The proposed workflow is demonstrated by locating and characterising microseismic events in the geothermal field of Los Humeros, Mexico. Although higher levels of noise are present and only a one-dimensional velocity model is available at this time, selected events could be located and characterised.

How to cite: Finger, C. and Saenger, E. H.: Characterisation of seismic events using time-reverse imaging , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7206, https://doi.org/10.5194/egusphere-egu21-7206, 2021.

EGU21-2631 | vPICO presentations | ERE6.1

3D and 4D seismic imaging of the Nesjavellir geothermal field, Iceland

Ortensia Amoroso, Ferdinando Napolitano, Vincenzo Convertito, Raffaella De Matteis, Thorbjörg Ágústsdóttir, Gylfi Páll Hersir, Vala Hjörleifsdóttir, and Paolo Capuano

EGU21-12217 | vPICO presentations | ERE6.1

Seismicity associated with 2018 and 2020 hydraulic stimulations at EGS in Helsinki, Finland, shows limited earthquake interaction: Implication for seismic hazard assessment

Grzegorz Kwiatek, Maria Leonhardt, Patricia Martínez-Garzón, Matti Pentti, Marco Bohnhoff, and Georg Dresen

In this study we investigate the statistical spatio-temporal characteristics induced seismicity associated with two stimulation campaigns performed in 2018 and 2020 in a 6.1 km deep geothermal well near Helsinki, Finland as part of the St1 Deep Heat project. We aim to find out whether the seismic activity is passively responding to injection operations, or whether we observe signatures of significant stress transfer and strong interactions between events. The former suggests stable relaxation of seismic energy proportional to hydraulic energy input, while the latter includes stress transfer as an additional source of stress perturbation, hence implying larger seismic hazard.

The selected catalogs from 2018 and 2020 stimulation contained in total 60,814 and 4,368 seismic events, respectively, recorded during and after stimulation campaigns and above the local magnitude of M -1.5. The analyzed parameters include magnitude-frequency b-value, correlation integral (c-value), fractal dimension (D-value), interevent time statistics, magnitude correlation, interevent time ratio and generalized spatio-temporal distance between earthquakes. The initial observations suggest significant time-invariance of the magnitude-frequency b-value, and increased D and c-values only at high injection rates, the latter also guiding the rate of seismicity. The seismicity covering the stimulation period neither provide signatures of magnitude correlations, nor temporal clustering or anticlustering. The interevent time statistics are generally characterized with Gamma distribution (close to Poissonian distribution), and the generalized spatio-temporal distance suggest very limited triggering (90% of the catalog was classified as background seismicity). The observable parameters suggest the seismicity passively respond to hydraulic energy input rate with little to no time delay, and the total seismic moment is proportional to total hydraulic energy input. The performed study provides the base for implementation of time-dependent probabilistic seismic hazard assessment for the site.

How to cite: Kwiatek, G., Leonhardt, M., Martínez-Garzón, P., Pentti, M., Bohnhoff, M., and Dresen, G.: Seismicity associated with 2018 and 2020 hydraulic stimulations at EGS in Helsinki, Finland, shows limited earthquake interaction: Implication for seismic hazard assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12217, https://doi.org/10.5194/egusphere-egu21-12217, 2021.

EGU21-12888 | vPICO presentations | ERE6.1

Array based analysis of induced earthquake characteristics using beamforming and back-projection methods in Helsinki, Finland

Bo Li, Alice-Agnes Gabriel, Annukka Rintamäki, and Gregor Hillers

The evolution and characteristics of induced seismicity in geothermal stimulations can shed light on water pathways and fracture network development. However, these seismic sources are usually difficult to characterize due to their small magnitudes and the low signal-to-noise ratio (SNR) of observational recordings. Heterogeneous and ill-constrained 3D subsurface structure further restricts the local-scale application of array based methods, such as the back-projection method. The 2018 st1 Deep Heat geothermal stimulation experiment in Espoo, Finland, induced thousands of seismic events in the 5-6 km depth range with magnitudes smaller or equal to ML 1.8 (Hillers, et al., 2020). The competent bedrock and absence of a dissipating sedimentary layer results in high SNR seismograms collected by three 4-station arrays, three 25-station arrays and tens of standalone stations located within 5 km distance around the wellhead. These high-quality data facilitate the application of multi-array beamforming and the back-projection methods, to image small-magnitude induced seismicity sources and characterize their properties at reservoir scales.

The beamforming results demonstrate array, frequency and phase (P or S) dependent slowness biases of catalog locations, which are obtained using standard location procedures with manually picked P- and S-wave arrivals. This indicates multi-scale heterogeneity in the study region. Specifically, we find that the back azimuth of the slowness at each array points to inconsistent locations and leads to poorly constrained epicenters. We show that the systematic slowness variability can be reduced and multi-array location estimates can be greatly improved by calibration using well-constrained catalog events.  

To perform the back-projection, we select unclustered stations from narrow epicentral distance ranges to avoid unfavorably large variations in the duration of the body phases, and we set the azimuth gap threshold to less than 40 degrees. The locations determined by the back-projection are close to the catalog locations, with the majority of them within 150 m, suggesting a successful application of the back-projection technique using local stations to study small events. We repeatedly observe  “swimming” artifacts (Ishii et al., 2007; Walker and Shearer, 2009), i.e. the back-projection locations migrate in a certain direction with time. This is typically attributed to array-source directivity effects in teleseismic applications, but in our case the stations are well-distributed around the source. We next use numerical wave propagation simulations, with receivers homogeneously azimuthal distributed at constant epicentral distance to a point-source. We apply the back-projection using synthetic seismograms. The results confirm the consistent appearance of “swimming” patterns and the apparent migration direction which changes in dependence on the focal mechanism of the point source. We conclude that the back-projection method may provide useful proxies for source mechanisms to help track and link the evolving fracture network.

How to cite: Li, B., Gabriel, A.-A., Rintamäki, A., and Hillers, G.: Array based analysis of induced earthquake characteristics using beamforming and back-projection methods in Helsinki, Finland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12888, https://doi.org/10.5194/egusphere-egu21-12888, 2021.

Enhanced Geothermal Systems apply the pressurized fluid injection to fracture impermeable rocks to form pathways in which water circulates. The cold water under high pressure is pumped into the hot subsoil, where it heats up and returns to the surface. However, the induced fractures may coalesce into unwanted paths that allow the fluids to reach pre-existing faults, triggering major seismic events.

This work investigates the relationship between injection and a degree of disordering of sources, ZZ, at Cooper Basin geothermal field in Australia, following the methodology developed and applied to study The Geysers geothermal field case (Lasocki & Orlecka-Sikora, 2020). The parameter ZZ quantifies the potential of seismicity to build pathways for fluid migration. It is the average distance between the seismic events in the eight-dimensional parameter space consisting of three hypocentral coordinates, T- and P-axis plunges, T-axis trend, and polar and azimuthal angles in the spherical system of coordinates beginning at the open hole of an injection well. A decrease of ZZ indicates an increasing hazard of forming far-reaching migration pathways. In The Geysers case, ZZ turned out to be highly correlated with the injection rate.

Here we focus on the case of Habanero 4 well stimulation from 17 - November 30, 2012 (data access, see: IS EPOS, 2020). We processed 489 seismic events with known focal mechanisms. The events moment magnitude varies between 0.8 and 3.1.  

Our analysis shows that ZZ is significantly correlated with both the injection rate and the wellhead pressure. The higher the injection rate / the wellhead pressure was, the less probable was the creation of undesired fluid migration pathways. The Cooper Basin’s and The Geyser’s reservoir rocks are vastly different, the former – granite, the latter – greywacke sandstone, likewise the stimulation techniques applied in these two reservoirs. However, in both cases, ZZ was positively correlated with injection rate; thus, the potential to build unwanted paths for fluids was negatively correlated. These results suggest that such correlation may be a global feature of rock fracturing caused by pressurized fluid injections.

This work has been supported by S4CE (Science for Clean Energy) project, funded from the European Union’s Horizon 2020 - Framework Programme, under grant agreement No 764810 and by PRIN-MATISSE (20177EPPN2) project funded by Italian Ministry of Education and Research.

 

References:

IS EPOS (2020), Episode: COOPER BASIN, https://tcs.ah-epos.eu/#episode:COOPER_BASIN, doi:10.25171/InstGeoph_PAS_ISEPOS-2020-001

Lasocki, S., & Orlecka-Sikora, B. (2020). High injection rates counteract formation of far-reaching fluid migration pathways at The Geysers geothermal field. Geophysical Research Letters, 47, e2019GL086212. https://doi.org/10.1029/2019GL086212

How to cite: Battimelli, E., Lasocki, S., and Capuano, P.: High injection rates decrease the probability of creating undesired, far-reaching fluid migration pathways at Cooper Basin geothermal field, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4902, https://doi.org/10.5194/egusphere-egu21-4902, 2021.

EGU21-5138 | vPICO presentations | ERE6.1

Stochastic modelling of injection-induced seismicity in the Cooper Basin enhanced geothermal system

Georgios Michas and Filippos Vallianatos

Fluid-injections under high pressures into deep “hot” rock formations are routinely performed during the development of Enhanced Geothermal Systems (EGS). Such fluid-injections, which aim to enhance the permeability in the targeted rock formation, can induce intense microseismicity and in some cases even larger magnitude earthquakes. A characteristic of injection-induced seismicity is its spatial migration with time, which is considered indicative of pore-pressure diffusion and the geometry of the stimulated volume in which permeability is enhanced. Understanding the details of earthquake migration during stimulation operations is particularly important for the design of EGS, the management of operations, as well as for the mitigation of hazardous induced earthquakes. Herein, we develop a stochastic model to map the spatiotemporal evolution of injection-induced seismicity. The model is based on the well-established Continuous Time Random Walk (CTRW) theory that has widely been applied in nonlinear transport phenomena in complex heterogeneous media. Within this context, we describe the spatiotemporal evolution of injection-induced seismicity with an appropriate master equation and the time-fractional diffusion equation. Application of the model to two stimulation experiments in the Cooper Basin (Australia) EGS shows that induced seismicity migrates slowly with time away from the injection points according to a subdiffusive process, with waiting times between the successive earthquakes drawn from a broad probability density function with asymptotic power-law behavior. Moreover, we show that the solution of the time-fractional diffusion equation adequately describes the propagation of induced seismicity in time and space, showing a peak of earthquake concentration close to the injection point and a stretched exponential decay for the concentration of distant events. The results demonstrate that the CTRW model can efficiently describe nonlinear diffusion of injection-induced seismicity during stimulation operations in EGS.       

Acknowledgements

The research project was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “2nd Call for H.F.R.I. Research Projects to support Post-Doctoral Researchers” (Project Number: 00256).

How to cite: Michas, G. and Vallianatos, F.: Stochastic modelling of injection-induced seismicity in the Cooper Basin enhanced geothermal system, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5138, https://doi.org/10.5194/egusphere-egu21-5138, 2021.

EGU21-6912 | vPICO presentations | ERE6.1

A numerical study of the mechanism of injection-induced and triggered seismicity at the Pohang Enhanced Geothermal Systems project, South Korea

Kwang-Il Kim, Hwajung Yoo, Seheok Park, Juhyi Yim, Linmao Xie, Ki-Bok Min, and Jonny Rutqvist

Hydraulic stimulation for the creation of an Enhanced Geothermal System (EGS) reservoir could potentially reactivate a nearby fault and result in man-made earthquakes. In November 15, 2017, an Mw 5.5 earthquake, the second largest after the initiation of the South Korean national instrumental monitoring system, occurred near an EGS project in Pohang, South Korea. The earthquake occurred on a previously unmapped fault, that is here denoted the Mw 5.5 Fault. A number of previous studies to model the hydraulic stimulation in the Pohang EGS project have been carried out to identify the mechanism of seismic events. Those previous studies focused on coupled hydro-mechanical processes without the consideration of pre-existing fractures and thermal effects. This study presents an investigation of the mechanisms of induced and triggered seismicity in the Pohang EGS project through three-dimensional coupled thermo-hydro-mechanical numerical simulations. Fractures intersecting the open-hole sections of two deep boreholes, PX-1 and PX-2, clearly indicated by field observations are modeled along with the Mw 5.5 Fault. Models of stress-dependent permeability models are calibrated based on the numerical reproduction of the pressure-time evolution during the field hydraulic stimulations. The Coulomb failure stress change at the Mw 5.5 Fault is calculated to quantify the impact of five hydraulic stimulations. In the case of PX-2 stimulations, the pore pressure buildup results in a volumetric expansion of the reservoir and thereby the perturbation of stresses is transferred to the Mw 5.5 Fault. The volumetric contraction of the reservoir by the temperature reduction could slightly perturb the stress distribution at the Mw 5.5 Fault. In the case of PX-1 stimulations, shear slip of the PX-1 fracture is explicitly modeled. The modeling shows that transfer of the shear stress drop by the shear slip stabilizes the Mw 5.5 Fault, which is consistent with the field observation that the seismicity was not induced at the Mw 5.5 Fault by the PX-1 stimulations. The cooling-induced thermal stress additionally reduces the effective normal stress of PX-1 fracture. Thus, some additional shear slip of the PX-1 fracture is induced by the thermal effect. However, the modeling shows that for both PX-1 and PX-2 stimulations, thermally-induced stress perturbations are very small compared to pressure-induced stress perturbations.

How to cite: Kim, K.-I., Yoo, H., Park, S., Yim, J., Xie, L., Min, K.-B., and Rutqvist, J.: A numerical study of the mechanism of injection-induced and triggered seismicity at the Pohang Enhanced Geothermal Systems project, South Korea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6912, https://doi.org/10.5194/egusphere-egu21-6912, 2021.

EGU21-14518 | vPICO presentations | ERE6.1

Deep geothermal-induced seismicity: controlling factors and hazard mitigation measures

Francesca De Santis, Emmanuelle Klein, and Alain Thoraval

As many industrial activities impacting the underground, deep geothermal projects can be associated with the occurrence of induced seismic events. This seismicity is sometimes a direct consequence of stimulation operations needed to enhance the permeability of geothermal reservoirs, but, in other cases, it can also occur in different phases of geothermal projects, as during wells shut-in, after injection operations, or during the production phase, which generally implies lower flow rates and injection pressures. The intensity of this seismicity, in terms of magnitudes of seismic events, can be extremely variable, from microseismic events (M < 2), not felt at the surface, to large earthquakes (M > 5) that pose a serious risk to neighboring populations and may lead to the abandon of geothermal projects. In this context, it is of paramount importance to: i) better characterize and understand the interactions between natural and anthropogenic factors which may lead to geothermal-induced seismicity and ii) evaluate currently applied approaches to handle and minimize associated risks.

The objective of this work is to establish a state of the art about deep geothermal-induced seismicity, by describing factors that have a bearing on the generation of seismic events, as well as by discussing existing means to handle their occurrence. Based on a worldwide review of geothermal projects, we created a large database describing each selected case study in terms of geological properties and tectonic setting, operational parameters and type of geothermal systems, as well as spatio-temporal characteristics of the observed induced seismicity. Collected data are analyzed in order to better understand possible cause-effect relationships between induced seismicity and geothermal operations with the aim of identifying the most important preexisting and anthropogenic factors, as well as their interactions, which may have a key role on the occurrence of seismic activity.       

How to cite: De Santis, F., Klein, E., and Thoraval, A.: Deep geothermal-induced seismicity: controlling factors and hazard mitigation measures, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14518, https://doi.org/10.5194/egusphere-egu21-14518, 2021.

EGU21-7475 | vPICO presentations | ERE6.1

Estimation of earthquakes location errors distribution for LUMINEOS local seismic network in Poland. 

Jakub Kokowski and Łukasz Rudziński

Estimation of hypocenter location errors  is not a simple task. These errors are influenced by many factors. The most important are: the quality of velocity model, the configuration of stations in the observation network and the noise level recorded at stations. While the network configuration affects the error distribution in a deterministic manner, the noise level is largely random. It means that the uncertainties cannot be determined in a deterministic way and only statistical approach can be used. There are several methods for estimating location errors for particular seismic network. Some techniques use synthetic seismograms to calculate the detection range related to each station. However, this approach requires very precise knowledge of the geological model, which is not always possible. Instead, in this work we present a different approach, which uses only phase data for events included in the catalog. In this method, the detection range for each station is estimated using the detection probability (Schorlemmer & Woessner, 2008) used for both P- and S- waves first arrivals. The usefulness of this approach is discussed assuming the shape of  LUMINEOS seismic network which operates in the Legnica-Głogów Copper District (LGCD), Poland. In the LGCD region seismic activity is related to three deep underground copper mines. Every year thousand of seismic events with magnitudes up to M4.0 are registered here. Some of them are followed by tragic mining collapses and are widely felt by local residents.

How to cite: Kokowski, J. and Rudziński, Ł.: Estimation of earthquakes location errors distribution for LUMINEOS local seismic network in Poland. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7475, https://doi.org/10.5194/egusphere-egu21-7475, 2021.

EGU21-7269 | vPICO presentations | ERE6.1

Mining-Induced Tremors Source Modelling Applying InSAR

Wojciech Witkowski, Magdalena Łukosz, Artur Guzy, and Ryszard Hejmanowski

Mining exploitation is associated with the occurrence of adverse environmental effects. The most serious of such effects is land subsidence. Although land subsidence can be well predicted and mitigated by several methods, nevertheless, the extraction of mineral deposits is also associated with induced seismicity. The occurrence of seismic events causes ground surface vibrations, land surface displacements and, in many cases, has a negative impact on the safety of surface infrastructure and the inhabitants of endangered areas. Despite this, the issue of induced seismicity is much less recognized and often ignored in the assessment of the negative impacts of mining exploitation.

Induced seismicity is related to stress changes in the reservoir and surrounding rock mass that may be caused by a variety of mechanisms. Consequently, the patterns of induced seismicity vary greatly over time and space for different fields or events within the same field. It is often difficult to determine the correlation between seismicity and mining precisely because of the lack of data detailing the pattern of exploitation at the various wells. As a result, the source mechanism of mining-induced tremor remains a subject of active research.

The research aimed to better identify the phenomenon of induced seismicity caused by mining operations. Research has been conducted in the area of underground copper ore mining in Poland. Firstly, we investigate the pre-and post-seismic land-surface movements following 8 mining-induced Mw 3.6-4.8 earthquakes that occurred between 2016 and 2018. We use Sentinel 1 data to derive these movements 2 weeks before and 4 weeks after the mainshock. The results of these studies show that no substantial pre-seismic surface movements are indicating the possibility of a seismic event occurring. However, the co-seismic deformation fields are quite symmetrical, the maximum land subsidence is almost 10 cm and occurs within a few days after the mainshock. In addition, the time series of post-seismic deformation shows a gradual decay and a good correspondence with the post-shock distribution.

Secondly, we use the Mogi model, assuming the elastic half-space, to invert co-seismic deformation fields and to obtain the source parameters of the mine-induced earthquakes. The spatial distribution of the epicenters indicates a correlation with the fields of mining exploitation. The results also show that the average depth of the hypocenter tremor is approx. 650 m. This corresponds to the depth of the stiff sandstone layers adjacent to the exploration. These layers accumulate the stress of post-exploitation voids. In addition, the modeling results indicate an approx. the volume of the displaced rock layers of 1.2 x 105 m3. This value shows a high correlation with the volume of post-shock troughs determined based on InSAR data.

The results of this study contribute to research into activities related to mining operations resulting in an induced-earthquake occurrence. This demonstrates InSAR's potential for quasi-constant monitoring of large-scale areas against seismic hazards caused by ongoing mining operations.

How to cite: Witkowski, W., Łukosz, M., Guzy, A., and Hejmanowski, R.: Mining-Induced Tremors Source Modelling Applying InSAR, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7269, https://doi.org/10.5194/egusphere-egu21-7269, 2021.

EGU21-13040 | vPICO presentations | ERE6.1

Induced micro seismicity due to raising mine water level in former coal mines in the eastern Ruhr area (Germany)

Martina Rische, Kasper D. Fischer, Felix Allgaier, and Wolfgang Friederich

FloodRisk is an interdisciplinary project focusing on the effects of mine water level rise in abandoned coal mine regions in Germany. Such effects are heterogeneous ground uplift, stress changes due to the change in pore pressure and the reactivation of potential faults. One of the most directly measurable effects is certainly the induced micro seismicity. It is known from previous studies that the flooding of old mines can lead to a renewed increase level in induced micro seismicity in these regions.
In this study  the relationship between mine water rise, fluid-induced stress changes and induced seismicity in the Haus Aden dewatering area in the eastern Ruhr area (Germany) will be investigated in more detail. 
For this purpose, we operate a network of currently 21 short period seismic stations in the region of the former "Bergwerk Ost" colliery, which had the highest seismicity rate in the Ruhr area during active underground coal mining. This network is still to be expanded to cover the entire water drainage area, about 30 Raspberry Shake sensors are waiting for the possibility of installation. 
Nevertheless, the existing network registered almost 1000 induced micro seismic events in a magnitude range from -0.7 up to 2.6 MLv. Many of these events are  spatially clustered and some show quite high waveform similarity. This allows relative localisation  and can increase the accuracy of the location. The depth location of the earthquakes, within the limits of localisation accuracy, agrees very well with the distribution of seismicity at the time of active mining. The spatial distribution so far seems to be limited by a large inactive transverse fault in the west. It needs to be clarified what influence this fault has on the propagation of mine water in the  underground.
The measured temporal trend of the mine water level, after pumps were shut down in mid-2019, shows a strong correlation with the temporal evolution of the observed micro seismicity. In the first  months after the pumps are switched off, the water levels at the observation points rise only slowly and isolated microseismic events occur again. In November 2019, the rise in water levels doubled and at the same time, the strongest induced event in the measurement period was recorded with a magnitude of 2.6 MLv. In the following months, the seismicity rate ranged from 8 to 34 events above 0.5 MLv per month, some of which were felt. A structural geological 3D subsurface model is developed to help to understand the distribution of induced seismicity and the role of the raising mine water level.

How to cite: Rische, M., Fischer, K. D., Allgaier, F., and Friederich, W.: Induced micro seismicity due to raising mine water level in former coal mines in the eastern Ruhr area (Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13040, https://doi.org/10.5194/egusphere-egu21-13040, 2021.

EGU21-5495 | vPICO presentations | ERE6.1

Seasonal trends of reservoir-triggered seismicity in Song Tranh 2 reservoir, Vietnam

Grzegorz Lizurek, Konstantinos Leptokaropoulos, Jan Wiszniowski, Izabela Nowaczyńska, Nguyen Van Giang, Beata Plesiewicz, and Dinh Quoc Van

Reservoir-triggered seismicity (RTS) is the longest known anthropogenic seismicity type. It has the potential to generate seismic events of M6 and bigger. Previous studies of this phenomenon have proved that major events are triggered on preexisting major discontinuities, forced to slip by stress changes induced by water level fluctuations and/or pore-pressure changes in the rock mass in the vicinity of reservoirs. Song Tranh 2 is an artificial water reservoir located in Central Vietnam. Its main goal is back up the water for hydropower plant. High seismic activity has been observed in this area since the reservoir was first filled in 2011. The relation between water level and seismic activity in the Song Tranh area is complex, and the lack of clear correlation between water level and seismic activity has led to the conclusion that ongoing STR2 seismic activity is an example of the delayed response type of RTS. However, the first phase of the activity observed after impoundment has been deemed a rapid response type. In this work, we proved that the seismicity recorded between 2013 and 2016 manifested seasonal trends related to water level changes during wet and dry seasons. The response of activity and its delay with respect to water level changes suggest that the main triggering factor is pore pressure change due to the significant water level changes observed. A stress orientation difference between low and high water periods is also revealed. The findings indicate that water load and related pore pressure changes influence seismic activity and stress orientation in this area.

This work was partially supported by research project no. 2017/27/B/ST10/01267, funded by the National Science Centre, Poland, under agreement no. UMO-2017/27/B/ST10/01267.

How to cite: Lizurek, G., Leptokaropoulos, K., Wiszniowski, J., Nowaczyńska, I., Van Giang, N., Plesiewicz, B., and Quoc Van, D.: Seasonal trends of reservoir-triggered seismicity in Song Tranh 2 reservoir, Vietnam, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5495, https://doi.org/10.5194/egusphere-egu21-5495, 2021.

EGU21-13027 | vPICO presentations | ERE6.1

Seasonal stress inversion trends of RTS in Song Tranh2 reservoir, Vietnam

Izabela Nowaczyńska, Grzegorz Lizurek, Jan Wiszniowski, and Beata Plesiewicz

The Song Tranh 2 hydropower construction is located in the Quang Nam province (central Vietnam), it has a reservoir volume of 740 million cubic meters of water and a dam height of 96 m. The reservoir was filled to capacity for the first time in February 2011. The seismicity in the vicinity of reservoir is example of reservoir triggered seismicity(RTS). The natural seismic activity of the Song Tranh 2 reservoir is very low. After the reservoir was filled, the seismic activity increased, and the number and frequency of the tremors also changed as the water level changed. Water level changes are accelerating the tectonic process leading the critically stressed faults to slip. Data suggest that reservoir exploitation stress field changes as triggering origin of this seismicity. The stress inversion method was used to check if there were any seasonal trends. The inverted stress tensor and, in particular, the stress ratio, which is very sensitive to data quality and scope and difficult to accurately retrieve, can be influenced by porous pressure changes. Has been checked, how the average annual seismic activity is related to the change of the water level and if it implies the orientation of the principal stress during high and low water levels in the reservoir. The pore pressure changes and the stress ratio changes were also estimated in relation to the high and low water level periods.

How to cite: Nowaczyńska, I., Lizurek, G., Wiszniowski, J., and Plesiewicz, B.: Seasonal stress inversion trends of RTS in Song Tranh2 reservoir, Vietnam, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13027, https://doi.org/10.5194/egusphere-egu21-13027, 2021.

EGU21-6373 | vPICO presentations | ERE6.1

Do spatial and/or temporal b-value variations exist within the Groningen induced earthquake catalogue?

Annemarie Muntendam-Bos and Nilgün Güdük

EGU21-9913 | vPICO presentations | ERE6.1

Relating spatial-temporal b-value patterns of induced earthquakes of the Groningen gas field to differential stress changes due to reservoir extraction

Nilgün Güdük, Annemarie Muntendam-Bos, and Jan Dirk Jansen

It is important to distinguish between natural earthquakes and those induced by CO2 injection at carbon capture and storage sites. For example, the 2004 Mw 6.8 Chuetsu earthquake occurred close to the Nagaoka CO2 storage site during gas injection, but we could not quantify whether the earthquake was due to CO2 injection or not. Here, changes in pore pressure during CO2 injection at the Nagaoka site were simulated and compared with estimated natural seasonal fluctuations in pore pressure due to rainfall and snowmelt, as well as estimated pore pressure increases related to remote earthquakes. Changes in pore pressure due to CO2 injection were clearly distinguished from those due to rainfall and snowmelt. The simulated local increase in pore pressure at the seismogenic fault area was much less than the seasonal fluctuations related to precipitation and increases caused by remote earthquakes, and the lateral extent of pore pressure increase was insufficient to influence seismogenic faults. We also demonstrated that pore pressure changes due to distant earthquakes are capable of triggering slip on seismogenic faults. The approach we developed could be used to distinguish natural from injection-induced earthquakes and will be useful for that purpose at other CO2 sequestration sites.

This research was published in “Sustainability”, https://doi.org/10.3390/su12229723.

Keywords: pore pressure; CO2 injection; induced earthquakes; seasonal earthquakes; remote earthquakes; seismogenic faults.

How to cite: Chhun, C. and Tsuji, T.: Natural and artificial pore pressure variation for distinguishing earthquakes induced by CO2 injection from natural earthquakes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1725, https://doi.org/10.5194/egusphere-egu21-1725, 2021.

EGU21-9737 | vPICO presentations | ERE6.1

Initial effective stress controls the nature of earthquakes 

Francois Passelegue, Michelle Almakari, Pierre Dublanchet, Fabian Barras, Jerome Fortin, and Marie Violay

  Modern geophysics highlights that the slip behaviour response of faults is variable in space and time and can result in slow or fast ruptures. Despite geodetical, seismological, experimental and field observations, the origin of this variation of the rupture velocity in nature, as well as the physics behind it, is still debated. Here, we first discuss the scaling relationships existing for the different types of fault slip observed in nature and we highlight how they appear to stem from the same physical mechanism. Second, we reproduce at the scale of the laboratory the complete spectrum of rupture velocities observed in nature. Our results show that when the nucleation length is within the fault length, the rupture velocity can range from a few millimetres to kilometres per second, depending on the available energy at the onset of slip. Our results are analysed in the framework of linear elastic fracture mechanics and highlight that the nature of seismicity is governed mostly by the initial stress level along the faults. Our results reveal that faults presenting similar frictional properties can rupture at both slow and fast rupture velocities. This combined set of field and experimental observations bring a new explanation of the dominance of slow rupture fronts in the shallow part of the crust and in areas presenting large fluid pressure, where initial stresses are expected to remain relatively low during the seismic cycle.

How to cite: Passelegue, F., Almakari, M., Dublanchet, P., Barras, F., Fortin, J., and Violay, M.: Initial effective stress controls the nature of earthquakes , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9737, https://doi.org/10.5194/egusphere-egu21-9737, 2021.

EGU21-5275 | vPICO presentations | ERE6.1

Fluid-induced Seismicity Depends on Injection Rate

Georg Dresen, Lei Wang, Grzegorz Kwiatek, Erik Rybacki, Audrey Bonnelye, and Marco Bohnhoff

Fluid injection causes fault slip that is partitioned in aseismic and seismic moment release. EGS stimulation campaigns have shown that in addition to total fluid volume injected also the rates of injection and fluid pressure increase affect seismic moment release. We investigate the effect of injection rate on slip characteristics, strain partitioning and energy budget in laboratory fluid injection experiments on reservoir sandstone samples in a triaxial deformation apparatus equipped with a 16-channel acoustic emission (AE) recording system. We injected fluid in sawcut samples containing a critically stressed fault at different pressurization rates. In general, fluid-induced fault deformation is dominantly aseismic. We find slow stick-slip events are induced at high fluid pressurization rate while steady fault creep occurs in response to low fluid pressurization rate. The released total seismic moment is found to be related to total injected volume, independent of fault slip behavior. Seismic moment release rate of AE is related to measured fault slip velocity. Total potential energy change and fracture energy release rate are defined by fault stiffness and largely independent of injection rate. Breakdown power density scales with slip rate and is significantly higher for fast injection and pressurization rates. The relation between moment release and injected volume is affected by fault slip behavior, characterized by a linear relation for slip at constant rate and fault creep while a cubic relation is evident for unstable and dynamic slip. Our experimental results allow separating a stable pressure-controlled injection phase with low rate of energy dissipation from a run-away phase, where breakdown power is high and cumulative moment release with injected volume is non-linear.

How to cite: Dresen, G., Wang, L., Kwiatek, G., Rybacki, E., Bonnelye, A., and Bohnhoff, M.: Fluid-induced Seismicity Depends on Injection Rate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5275, https://doi.org/10.5194/egusphere-egu21-5275, 2021.

EGU21-13656 | vPICO presentations | ERE6.1

Laboratory study on seismicity mitigation: The role of loading pattern and rate

Milad Naderloo, Auke Barnhoorn, Aukje Veltmeijer, and Jan Dirk Jansen

Reactivation of pre-existing faults/fractures in the reservoir due to the deep injection is a key concern in designing and running geothermal and water/CO2 injection projects. Therefore, we investigate potential methods to manage injection-induced seismicity. Recent laboratory and field studies recommend that changes in injection pattern (e.g., cyclic injection) might trigger less seismicity than monotonic injection. This study presents results from uniaxial compressive laboratory experiments performed on high porosity Red Felser sandstone that provide new information about the effect of loading pattern and rate on injection‐driven seismicity. Red Felser sandstone samples with identical porosity and dimensions were subjected to three different loading patterns, including cyclic recursive (CR), cyclic progressive (CP), and monotonic loading. Besides, three different loading rates (displacement control) were applied for each loading pattern: low, medium, and high rates that are 10-4 mm/s, 5×10-4 mm/s, and 5×10-3 mm/s, respectively. Microseismicity analysis shows that (i) the maximum magnitude of seismic events and seismic radiated energy at failure decrease for lower loading rates and during the cyclic loading scenario, (ii) the b-value (magnitude-frequency distribution of events) increases on average 40% for a low-rate cyclic recursive loading in comparison with high-rate cyclic recursive and monotonic loading at different rates. The largest b-value resulted from a low-rate cyclic recursive (LCR) loading pattern. The b-value was estimated and compared using different methods, including a least-square regression on either an incremental frequency distribution or a cumulative frequency distribution, and with the maximum likelihood method (MLM) to provide a reliable b-value estimation. The analyses indicate that by considering the accurate magnitude of completeness, MLM, and, with a least-square regression, the incremental frequency distribution, both result in a reliable b-value. From a mechanical perspective, a low loading rate reduces the sample's final strength by 19%. Moreover, samples subjected to cyclic loading display more complex fracture patterns and more disintegration. In our laboratory study, a combination of low-rate loading and a recursive cyclic loading pattern resulted in reduced seismicity through decreasing the maximum seismicity magnitude and increasing the b-value.

How to cite: Naderloo, M., Barnhoorn, A., Veltmeijer, A., and Jansen, J. D.: Laboratory study on seismicity mitigation: The role of loading pattern and rate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13656, https://doi.org/10.5194/egusphere-egu21-13656, 2021.

EGU21-11025 | vPICO presentations | ERE6.1

The STIMTEC-X hydraulic stimulation campaign at the URL Reiche Zeche Mine, Germany

Carolin Boese, Joerg Renner, and Georg Dresen and the STIMTEC-X Team

In 2018-2019, the STIMTEC hydraulic stimulation experiment was conducted at the Reiche Zeche underground laboratory in Freiberg, Saxony/Germany, to investigate the role of hydro-mechanical processes for the often required enhancement of hydraulic properties in deep geothermal projects. We applied the same injection protocol to each of the ten stimulated intervals in the 63 m-long injection borehole. Yet, we observed significant small-scale variability in the seismic and hydraulic responses to stimulation and in parallel stress field heterogeneity on the meter scale. While acoustic emission (AE) activity was high in the upper part of the injection borehole, no AE events were detected in its deepest part, ending in a high-permeability damage zone.

To investigate the stress field and seismic variability throughout the experimental volume and their interrelation further, we started the follow-on experiment STIMTEC-X. The initial phase involved eleven local stress measurements performed in October 2020 in three existing boreholes, previously used for monitoring purposes, with varying orientations and lengths. This phase of the experiment was seismically monitored in real-time using an adaptive, high-resolution seismic monitoring network comprising six AE-type hydrophones, six regular AE sensors and four accelerometers. The hydrophones were installed in combination with hydraulic gauges or the double packer probe used for localized injection to make best use of the existing infrastructure. Hydrophones were optimally placed for each measurement configuration anew with at least one deployed in the direct vicinity (~3-4 m) of the injection interval. We detected low-magnitude AE activity (M<-3.5) at high resolution, spatially distributed between distinct clusters identified previously during the STIMTEC experiment. Overall, these records indicate a doubling of the seismically active volume. We also performed eight dilatometer tests to determine deformation characteristics of induced hydrofracs and pre-existing fractures. A circulation experiment between the injection borehole and two newly drilled boreholes of 23 m and 30 m depth is pending. Here, we present the seismicity associated with the STIMTEC and STIMTEC-X hydraulic stimulation campaigns and focal mechanism solutions. We focus on how they contribute to 3-D volumetric stress field characterisation between local stress measurement points.

Figure 1: Borehole layout (cyan - injection borehole, yellow: seismic monitoring boreholes, green: hydraulic monitoring borehole, red: mine-back validation boreholes) and acoustic emission (AE) events during the STIMTEC (yellow and orange circles) and STIMTEC-X (purple circle) experiments at the Reiche Zeche underground laboratory in Freiberg, Germany. Damage zones (transparent red) and hydraulically stimulated (dark blue rings) and/or hydraulically tested intervals (light blue rings) are shown. Stimulation of the intervals resulted in >11000 AE events with most events occurring during the periodic pumping sequences following the hydrofracturing. The seismic clouds extend about 5 m radially around the boreholes.

How to cite: Boese, C., Renner, J., and Dresen, G. and the STIMTEC-X Team: The STIMTEC-X hydraulic stimulation campaign at the URL Reiche Zeche Mine, Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11025, https://doi.org/10.5194/egusphere-egu21-11025, 2021.

EGU21-8709 | vPICO presentations | ERE6.1

Analysis of anomalies in seismic ambient noise above fluid reservoirs

Christine El Khoury, Hervé Chauris, and Alexandre Kazantsev

Anomalies in seismic ambient noise, defined as strong spectral amplification of the vertical components at frequencies of several Hertz, are currently observed on sites located above hydrocarbon reservoirs. If properly understood, these anomalies could have a potential for applications such as geothermal reservoir exploration or underground gas storage monitoring. Under purely elastic modeling, the nature of these anomalies was mainly explained by the geological structure more than the fluid reservoir itself.  The main objective of the present work is to explain the exact origin of the anomalies by numerical simulations of the 3D wave propagation using specfem3D code. The simulated spectral anomalies are essentially static and determined by the typical geological reservoir environments. The effect of an anticline structure, which is a common characteristic of hydrocarbon reservoirs, is investigated using different types of sources. Results show that the spectral anomalies caused by the presence of the anticline structure have similarities with the anomalies observed in real data. More work is needed to extract laws linking geometrical characteristics of the anticline to spectral properties. Future works will also include analysis on real gas storage sites, followed by a transposition to the geothermal field applications, for which more complicated parameters appear to participate to the phenomenon.

How to cite: El Khoury, C., Chauris, H., and Kazantsev, A.: Analysis of anomalies in seismic ambient noise above fluid reservoirs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8709, https://doi.org/10.5194/egusphere-egu21-8709, 2021.

EGU21-2548 | vPICO presentations | ERE6.1

Systematic Investigation of Dynamic Earthquake Triggering in Japan

Bogdan Enescu and Yuki Takeda

Introduction. Previous studies (e.g., Harrington and Brodsky, 2006) documented a relative scarcity of remote triggering in Japan, compared to other seismic regions. For example, in California, dynamic triggering is reported to occur at levels of stress as small as 0.1 kPa, while in Japan it was reported that levels of 30 kPa or more are required to trigger detectable events (van der Elst and Brodsky, 2010). However, the threshold dynamic triggering level following the 2016 M7.3 Kumamoto earthquake was of just a few kPa (Enescu et al., 2016). Enescu et al. (2016) proposed that one of the possibilities to explain this observation is a change of stress triggering threshold that may have taken place after the 2011 M9.0 Tohoku-Oki earthquake.

Motivation. Given the above observations, this study investigates 1) the occurrence of dynamically triggered earthquakes in Japan after some large earthquakes from 2004, and 2) whether the threshold of dynamic triggering may have changed due to the 2011 Tohoku-Oki earthquake and why this threshold might have changed.

Analysis and Results. First, we investigated dynamic triggering throughout Japan, following some large earthquakes occurred after 2004. As a result, the  threshold appears to decrease following the 2011 Tohoku-Oki earthquake, however the number of earthquakes we have investigated was relatively small, so we could not draw statistically significant conclusions. In the second part of the study, we have focused on a few specific areas within Japan to systematically investigate dynamic triggering, which reduced significantly the computational costs. Thus, we focused on some areas in Tohoku and Hida, where swarm earthquakes occurred after the 2011 Tohoku-Oki earthquake. As a result, the change of the triggering level in an area close to the Yamagata-Fukushima border is considered to be statically significant at a 5% significance level. In other regions, the significance at a 5% level could not be established, however a decrease of this threshold is apparent, except for one region. We speculate that changes in the stress triggering threshold levels might be related to pore pressure changes in the crust following the 2011 Tohoku-Oki earthquake.

How to cite: Enescu, B. and Takeda, Y.: Systematic Investigation of Dynamic Earthquake Triggering in Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2548, https://doi.org/10.5194/egusphere-egu21-2548, 2021.

EGU21-8670 | vPICO presentations | ERE6.1

Spatial permeability variations of aquifers in North China Plain derived from large magnitude earthquake signals

Hongbiao Gu, Yirong Xu, Mingyuan Wang, Zhandong Su, Shuangshuang Lan, Nam Chil Woo, and Martin Sauter

Permeability changes induced by earthquakes have been widely studied. The question remains of how multiple large earthquakes influence permeability at different depths in the far-field and permeability changes could possibly be employed for hydraulic characterization of the aquifers has not yet been investigated. We study the change in permeability in fractured aquifers of the North China Paraplatform based on 11 years of groundwater hydrographs of 7 wells and 62 earthquakes. From 2008 to 2018, the permeability changes varied from well to well, all aquifers showed a consistent and distinct magnitude of change in permeability (decrease, increase and no change) following each earthquake. From the perspective of a single well to multiple shocks, the permeability variation of the JN well is the most sensitive to seismic events. From the perspective of multiple wells to one single earthquake, there were no cases of simultaneous permeability changes in all 7 wells induced by a single earthquake. Permeabilities varying within a wide range at a given depth implies that it could be considered as a dynamically self-regulating value, while permeability changes indicate great differences at varying depths. We found that the correlations between permeability changes and seismic energy density or depth are weak, however, the azimuths of seismic waves could greatly impact the changes in permeability, i.e., from 25° to 295°, and the most significant span is 250° to 295°, and fault distribution around the monitoring wells may also contribute to this result. Employing a seismic waves-pressure amplitude model, the mobilization of colloids driven by the oscillation of pressure head as a possible mechanism of permeability change. Distant, large magnitude earthquakes can alter the permeability, also can accelerate or slow down the rate of permeability change of the aquifer material.

How to cite: Gu, H., Xu, Y., Wang, M., Su, Z., Lan, S., Woo, N. C., and Sauter, M.: Spatial permeability variations of aquifers in North China Plain derived from large magnitude earthquake signals, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8670, https://doi.org/10.5194/egusphere-egu21-8670, 2021.

EGU21-3329 | vPICO presentations | ERE6.1

The impact of fault permeability on the nucleation of injection-induced earthquakes

David Santillán Sanchez, Juan Carlos Mosquera Feijoo, and Luis Cueto-Felgueroso Landeira

Injection-induced seismicity has become a central issue in the development of subsurface energy technologies such as enhanced geothermal energy, unconventional hydrocarbon production, wastewater injection, geologic carbon sequestration, or underground gas storage. The effect of the hydraulic properties of faults on the nucleation of earthquakes is a key aspect poorly understood. Our research question is how these properties may alter the onset of slip, the nucleation pattern, the nucleation length, and the time to nucleation.

We simulate earthquakes by means of sophisticated 2-dimensional computational models where earthquakes are triggered by fluid injection. The fault frictional contact is described by the Dieterich–Ruina rate-and-state law. Rock is simulated as a poroelastic solid and we couple fluid flow and rock mechanics.

Our model allows us to explain the impact of longitudinal and transverse fault permeability on the mechanisms that control the evolution of fault strength and shear stress during the nucleation. We find that the nucleation is controlled by the pressure and shear stress profiles along the fault, which in turn are driven by the fault hydraulic properties. Therefore, fault permeability exerts a fundamental control on the scaling of the nucleation length, the nucleation pattern, and the time to nucleation.

 Acknowledgements: Project supported by a 2019 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation. The BBVA Foundation accepts no responsibility for the opinions, statements and contents included in the project and/or the results thereof, which are entirely the responsibility of the authors.

How to cite: Santillán Sanchez, D., Mosquera Feijoo, J. C., and Cueto-Felgueroso Landeira, L.: The impact of fault permeability on the nucleation of injection-induced earthquakes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3329, https://doi.org/10.5194/egusphere-egu21-3329, 2021.

EGU21-13394 | vPICO presentations | ERE6.1

Three-dimensional aseismic ruptures driven by fluid injection

Alexis Sáez, Brice Lecampion, Pathikrit Bhattacharya, and Robert C. Viesca

Injection-induced seismicity is usually observed as an enlarging cloud of seismic events that grows in a diffusive manner around the injection zone. These observations are commonly interpreted as the triggering of instabilities in pre-existing fractures and faults due to the direct effect of pore pressure increase (Shapiro, 2015), whereas poroelastic stressing is usually associated with the occurrence of seismic events beyond the plausible zone affected by pore pressure diffusion (Segall and Lu, 2015). However, an alternative triggering mechanism based on the elastic transfer of stress due to injection- induced aseismic slip has been recently proposed (Viesca, 2015; Guglielmi et al, 2015). Previous studies have shown that in critically stressed faults, the aseismic rupture front can outpace fluid diffusion (Garagash and Germanovich, 2012; Bhattacharya and Viesca, 2019), and in turn be the primary cause that controls the evolution of seismicity as it has been recently inferred from in-situ experiments of fluid injection (Duboeuf et al., 2017) and recent cases of injection-induced earthquakes (Eyre et al, 2019).

Despite the great relevance of aseismic slip on injection-induced seismicity, the conditions that control the three-dimensional propagation of aseismic ruptures are still poorly constrained. This is in part due to the challenge of solving such a 3D moving boundary problem in which both fault slip and rupture shape are unknown. Here, we study the mechanics of injection-induced aseismic ruptures on a planar fault characterized by a strength equal to the product of a constant friction coefficient and the effective normal stress. We systematically track the temporal evolution of the rupture area relative to the evolution of the pressurized zone and focus on the effect of the initial stress state and injection scenario. For injection at constant flux, we derive a semi-analytical solution for circular ruptures (for a Poisson’s ratio equal to zero), which gives the ratio between the rupture radius and a nominal pore pressure front location, which we named as amplification factor λ. This amplification factor is a function of a unique dimensionless parameter that depends on the initial fault stress criticality and the fluid-induced overpressure. Then, we generalize the semi-analytical solution to the case of non-circular ruptures (for any value of the Poisson’s ratio) by solving numerically for the spatiotemporal evolution of fault slip using a fully implicit boundary-element-based solver with quadratic triangular elements. We show that the rupture front is nearly elliptical and the rupture area Ar evolves in a self-similar diffusive manner such that Ar(t) = 4παλ2t, where α is the fault hydraulic diffusivity and λ is the amplification factor for circular ruptures. The rupture area is greater than the nominal pressurized area if λ > 1. The semi-analytical solution for the rupture area provides a unique opportunity for verifying numerical hydro-mechanical solvers. After, we investigate numerically the case of circular and non-circular ruptures driven by injection at constant pressure instead of constant flux. We show that the self-similar property of the rupture growth is lost under this injection scenario.

How to cite: Sáez, A., Lecampion, B., Bhattacharya, P., and Viesca, R. C.: Three-dimensional aseismic ruptures driven by fluid injection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13394, https://doi.org/10.5194/egusphere-egu21-13394, 2021.

EGU21-1085 | vPICO presentations | ERE6.1

A common model to explain similarities between injection-induced and natural earthquake swarms

Philippe Danre, Louis De Barros, and Frédéric Cappa

Fluid injections at depth can trigger seismic swarms and aseismic deformations. Similarly, some natural sequences of seismicity occur clustered in time and space, without a distinguishable mainshock. They are usually interpreted as driven by fluid and/or aseismic processes. Those seismic swarms, natural or injection-induced, present similarities in their behavior, such as a seismic front migration. The effective stress drop, defined as a ratio between seismic moment and cluster size, is also weak for all swarms, when compared to usual earthquakes values. However, the physical processes that drive both types of swarms, and that can explain such similarities are still poorly understood. Here, we propose a mechanical model in which the fluid primarily induces an aseismic slip, which then triggers and drives seismicity within and on the edges of the active zone. This model is validated using a global and precise dataset of 16 swarms, from natural or induced origins, in different geological contexts. Consequently, our measurements of the migration velocity of the seismicity front, and of the effective stress drop for our swarms can be related to the seismic-to-aseismic moment. Using our model, we are then able to compute an estimate of the volume of fluids circulating during natural earthquake swarms, assuming the total moment is related to the volume of fluids. Our study highlights common characteristics and novel insights into the physical processes at play during seismic swarms.

How to cite: Danre, P., De Barros, L., and Cappa, F.: A common model to explain similarities between injection-induced and natural earthquake swarms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1085, https://doi.org/10.5194/egusphere-egu21-1085, 2021.

EGU21-8704 | vPICO presentations | ERE6.1

Effects of varying injection rate on dynamic slip nucleation along a frictional weakening fault

Federico Ciardo, Antonio Pio Rinaldi, and Stefan Wiemer

Anthropogenic injection of fluid into tight fractured reservoirs is known to alter the stress state of the Earth`s crust,  inducing micro-seismicity and eventually significant earthquakes. The injection scenario, in terms of injection pressure or injection rate, is one of the key controlling parameters for injection-induced seismicity. Although a number of studies have been carried out on understanding the effects of injection strategy on seismicity rates, less is known about its effect on the nucleation of dynamic slip on a pressurized fault, especially for non-stationary injection protocols.

In this contribution we study the effects of injection rate variation on the transition between aseismic and seismic slip along a frictional weakenig fault. Notably, we parametrize the injection strategy by assuming an initial linear increase of injection rate in time, up to a value after which it remains constant. We perform a scalying analysis and identify the governing parameters that control the fault response. We solve numerically the coupled hydro-mechanical problem using a fast boundary element solver for localized inelastic deformations [1]. Upon benchmarking the numerical results with the semi-analytical ones of Garagash and Germanovich [2] for the specific case of constant injection rate, we investigate the effect of injection rate variation on critically stressed and marginally pressurized faults. We derive analytical expressions for nucleation time and we confirm them via numerical results. Furthermore, we present a small scale yielding solution for marginallly pressurized faults and investigate the influence of injection scenario on shear crack run-out distances (when occuring).

 

References   

[1] Ciardo, F., Lecampion, B., Fayard, F., and Chaillat, S. (2020), A fast boundary element based solver for localized inelastic deformations, Int J Numer Methods Eng. 2020; 1–23.

[2] Garagash, D., and L. N. Germanovich (2012), Nucleation and arrest of dynamic slip on a pressurized fault, J. Geophys. Res., 117, B10310.

How to cite: Ciardo, F., Rinaldi, A. P., and Wiemer, S.: Effects of varying injection rate on dynamic slip nucleation along a frictional weakening fault, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8704, https://doi.org/10.5194/egusphere-egu21-8704, 2021.

EGU21-16385 | vPICO presentations | ERE6.1

Cascading earthquakes on a fracture network in a geo-energy reservoir

Kadek Hendrawan Palgunadi, Alice-Agnes Gabriel, Dimitry Garagash, and Paul Martin Mai

The increasing rate of induced seismicity in subsurface reservoirs, exceeding occasionally moment magnitude 5, has generated significant attention among earthquake scientists and regulators over the last decade. Fluid injection activity during the operation stage often produces a significant, sometimes even destructive, earthquake. Many approaches have been proposed to monitor, model, and predict the injection-related seismicity to avoid an earthquake larger than a threshold set by the regulator (e.g., Mw 2.0). However, unexpected higher magnitude events occur exceeding what is predicted by empirical models, theoretical relations, or computer simulations. 

Current models do not consider that subsurface reservoirs consist of complex fracture networks characterized by connected and unconnected individual fracture planes, often comprising a larger but inactive fault (unfavorably oriented with respect to regional stress). Fluid injection may then perturb stress conditions and trigger an initial rupture on fractures close to the injection well; this initial event may then dynamically trigger other fractures and potentially generate a large earthquake. 

We inspect conditions leading to induced earthquakes taking into account the complex fracture network intersected to an inactive fault using dynamic earthquake rupture simulations. We generate the fracture network using a nearest-neighbor method following statistical parameters (power-law distribution of fracture length and fracture density) based on field data. There are 134 fractures consisting of 95 connected fractures, 3 fractures connected with at least one fracture, and 38 unconnected fractures. We focus on two fracture populations oriented in strike N110E ± 10° and N210E ± 10°, respectively. The main fault has a depth-dependent dip orientation which results in a listric fault geometry. 

For our dynamic rupture simulations, we use the open-source software SeisSol (https://github.com/SeisSol/SeisSol), apply a laboratory-based rate-and-state with rapid velocity weakening friction law, and assign source radius-dependent characteristic length (L parameter) to the fractures. We vary stress conditions (maximum horizontal orientation, static-pore pressure, and prestress ratio) and conduct an initial static Mohr-Coulomb analysis before running the expensive dynamic rupture simulation. We choose conditions that lead to cascading rupture with (case 1) and without (case 2) the involvement of the main fault. Case 1 has higher artificial overstress within the nucleation area than case 2. Our simulation shows intricate rupture progression over small fractures via rupture branching with the parallel and orthogonal connected fractures. The rupture can also transfer to the unconnected fractures through dynamic triggering from the closest neighboring fracture. Case 1 produces a moment magnitude of Mw 6.36 that is equivalent to case 2. Our preliminary result reveals that connected fractures can generate a significant and potentially large induced earthquake if all fractures are favorable to the stress condition.

How to cite: Palgunadi, K. H., Gabriel, A.-A., Garagash, D., and Mai, P. M.: Cascading earthquakes on a fracture network in a geo-energy reservoir, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16385, https://doi.org/10.5194/egusphere-egu21-16385, 2021.

EGU21-8524 | vPICO presentations | ERE6.1

On the generation of geometry-independent noise models for microseismic monitoring purposes

Claire Birnie and Matteo Ravasi

As a result of the world-wide interest in carbon storage and geothermal energy production, increased emphasis is nowadays placed on the development of reliable microseismic monitoring techniques for hazard monitoring related to fluid movement and reactivation of faults. In the process of developing and benchmarking these techniques, the incorporation of realistic noise into synthetic datasets is of vital importance to predict their effectiveness once deployed in the real world. Similarly, the recent widespread use of Machine Learning in seismological applications calls for the creation of synthetic seismic datasets that are indistinguishable from the field data to which they will be applied. 

Noise generation procedures can be split into two categories: model-based and data-driven. The distributed surface sources approach is the most common method in the first category: however, it is well-known that this fails to capture the complexity of recorded noise (Dean et al., 2015). Pearce and Barley (1977)’s convolutional approach offers a data-driven procedure that has the ability to accurately capture the frequency content of noise however imposes that noise must be stationary. Birnie et al. (2016)’s covariance-based approach removes the stationarity requirement accurately capturing spatio-temporal characterisations of noise, however, like all other data-driven approaches it is constrained to the survey geometry in which the noise data has been collected. 

In this work, we propose an extension of the covariance-based noise modelling workflow that aims to generate a noise model over a user-defined geometry. The extended workflow comprises of two steps: the first step is responsible for the characterisation of the recorded noise field and the generation of multiple realisations with the same statistical properties, constrained to the original acquisition geometry. Gaussian Process Regression (GPR) is subsequently applied over each time slice of the noise model transforming the model into the desired geometry.

The workflow is initially validated on synthetically generated noise with a user-defined input covariance matrix. This allows us to prove that the noise statistics (i.e., covariance and variogram) can be kept almost identical between the noise extracted from the synthetic dataset and the various steps of the noise model procedure. The workflow is further applied to the openly available ToC2ME passive dataset from Alberta, Canada consisting of 69 geophones arranged in a pseudo-random pattern. The noise is modelled and transformed into a 56-sensor, gridded array, which is shown to a very close resemblance to the recorded noise field. 

Whilst the importance of using realistic noise in synthetic datasets for benchmarking algorithms or training ML solutions cannot be overstated, the ability to transform such noise models into arbitrary receiver geometries opens up a host of new opportunities in the area of survey design. We argue that by coupling the noise generation and monitoring algorithms, the placement of sensors can be optimized based on the expected microseismic signatures as well as the surrounding noise behaviour. This could be of particular interest for geothermal and CO2 storage sites where processing plants are likely to be in close proximity to the permanent monitoring stations.

How to cite: Birnie, C. and Ravasi, M.: On the generation of geometry-independent noise models for microseismic monitoring purposes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8524, https://doi.org/10.5194/egusphere-egu21-8524, 2021.

EGU21-12859 | vPICO presentations | ERE6.1

Reliability tests of moment tensor inversion of anthropogenic seismicity

Anna Tymińska and Grzegorz Lizurek

Seismic moment tensor becomes part of basic seismic data processing. For anthropogenic events mostly common and available method to determine mechanism is amplitude inversion. However essential for correct amplitude inversion are good quality data. Factors commonly occurring in anthropogenic seismicity like high noise to signal ratio, low magnitude and shortage of seismic stations with unfavorable focal coverage can introduce undetected errors to inversion solution. In this work, synthetic tests for two seismic networks are presented to examine the reliability of P-wave first peak amplitude inversion for these areas. The synthetic tests of the noise influence on the results of full MT solutions were carried out for two surface networks monitoring anthropogenic seismicity: VERIS network in Vietnam and LUMINEOS network in Poland. Various mechanisms with double couple component variability from 10% to 100% were considered to take into account mechanisms caused by different types of human activity. High variability of solutions in tests shows that some spurious components cannot be avoided in full moment tensor solutions obtained for presented networks in certain cases.

This work was partially supported by research project no. 2017/27/B/ST10/01267, funded by the National Science Centre, Poland, under agreement no. UMO-2017/27/B/ST10/01267.

How to cite: Tymińska, A. and Lizurek, G.: Reliability tests of moment tensor inversion of anthropogenic seismicity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12859, https://doi.org/10.5194/egusphere-egu21-12859, 2021.

ERE6.2 – Faults and fractures in geoenergy applications 1: Numerical modelling and simulation

EGU21-658 | vPICO presentations | ERE6.2

Numerical modelling of deformation and fracturing of thermo-poroelastic media

Ivar Stefansson, Eirik Keilegavlen, and Inga Berre

In addition to significantly impacting flow properties, fractures may deform and propagate due to changes in the stress state. Such stress changes may e.g. be caused by changes in fluid pressure or rock temperature. Accounting for all interacting processes and structures leads to a tightly coupled and highly complex system.

We apply a mixed-dimensional model explicitly accounting for both rock matrix and fractures, the latter as two-dimensional objects. This framework enables tailored modeling in the different parts of the domain. We impose conservation of mass and energy in both fractures and matrix and conservation of momentum in the matrix. At the fractures, we impose contact mechanics relations and propagation criteria based on the local stress state. Coupling between fractures and matrix is formulated as interdimensional fluid and heat fluxes and displacement at the two fracture surfaces.

We demonstrate the model through three-dimensional transient simulations focusing on process-structure interaction. That is, we investigate the interplay between thermo-hydraulic processes and fracture deformation, including propagation of pre-existing fractures.

How to cite: Stefansson, I., Keilegavlen, E., and Berre, I.: Numerical modelling of deformation and fracturing of thermo-poroelastic media, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-658, https://doi.org/10.5194/egusphere-egu21-658, 2021.

We present a fully-coupled hydro-mechanical simulation of fluid injection-induced activation of pre-existing discontinuities, propagation of new damages, development of seismic activities, and alteration of network connectivity in naturally faulted and fractured rocks, which are represented using the discrete fracture network approach. We use the finite element method to compute the multiphysical fields including stress, strain, damage, displacement, and pressure by solving governing and constitutive equations of coupled solid and fluid domains. Essential hydro-mechanical coupling mechanisms are honoured such as pore pressure-induced shear slip of natural discontinuities, poro-elastic response of rock matrix, and stress-dependent permeability/storativity of both fractures and rocks. We use the numerical model developed to investigate the hydro-mechanical behaviour of deeply buried fractured rocks and fault zones in response to high-pressure fluid injection, with a specific focus on the system either below or above the percolation threshold. We observe a strong control of fracture network connectivity on the damage emergence, seismicity occurrence and connectivity change in the rock mass subject to hydraulic stimulation. We highlight the strong poro-elastic effect that tends to drive heterogeneous connectivity evolution of fracture systems during fluid injection. The results of our research and insights obtained have important implications for injection-related geoengineering activities such as the development of enhanced geothermal systems and extraction of hydrocarbon resources.

How to cite: Qinghua, L. and Tsang, C.-F.: Numerical simulation of fluid injection in faulted and fractured rocks based on a fully-coupled hydro-mechanical model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7087, https://doi.org/10.5194/egusphere-egu21-7087, 2021.

EGU21-5064 | vPICO presentations | ERE6.2

Numerical simulation of coupled processes in a single fracture employing a continuum approach

Iman Vaezi, Víctor Vilarrasa, Francesco Parisio, and Keita Yoshioka

Fractures control fluid flow and the coupled geomechanical response of geological media in many geo-engineering applications. For instance, fractures dominate fluid flow and deformation in enhanced geothermal systems, underground radioactive waste repositories, and CO2 storage. Coupled thermo-hydro-mechanical processes in rock masses are a result of perturbations in the pore pressure, as in fluid injection and/or production, and/or temperature, as in cold fluid injection and disposal of radioactive waste. For example, fractures open as a result of pore pressure increase, which simultaneously increases permeability and reduces overpressure.

Geo-engineering and geo-energy applications involve a large portion of rock masses that include several fractures. Numerical computations of coupled processes occurring in rock masses while considering a large number of fractures pose several challenges. In this study, we firstly focus on a simple problem to fully understand the hydro-mechanical behavior of a single fracture subjected to a constant injection flow rate. We use the FEM software CODE_BRIGHT, which solves the thermo-hydro-mechanical governing equations in a fully coupled way. Since standard FEM can solve equations in continuum media, we investigate the behavior of a single fracture by analyzing the hydro-mechanical parameters that control the fracture response in a continuum fashion. However, simulating fractures with the real aperture is not simply feasible, hence, we search the equivalent properties of thicker fractures that are more feasible to be discretized in large-scale models with several fractures.

As the pore pressure increases inside a fracture, the fracture aperture increases and enhances its transmissivity. The embedded model uses variable permeability as a function of the cubic law. The simulation results show that a continuum approach can represent a fracture with a relatively large thickness (in the cm order) instead of the real aperture dimension (in the order of the micron).

How to cite: Vaezi, I., Vilarrasa, V., Parisio, F., and Yoshioka, K.: Numerical simulation of coupled processes in a single fracture employing a continuum approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5064, https://doi.org/10.5194/egusphere-egu21-5064, 2021.

Geothermal provides nearly 20% of New Zealand’s electricity as well as increasing opportunities for direct use. In New Zealand’s ~20 high temperature geothermal systems, fluids flow dominantly through fractured rocks with low matrix permeability. It is important to understand the nature of these fracture systems, and how fluids flow through them, so that the geothermal systems may be more efficiently and sustainably used. Here we present fluid flow calculations in several distinct discrete fracture models, each of which is broadly consistent with the fracture density and high dip magnitude angle distributions directly observed in borehole image logs at the Rotokawa Geothermal Field (>300°C, 175 MWe installed capacity). This reservoir is hosted in fractured andesites. In general, fractures are steeply dipping, and the reservoir is known to be compartmentalized.

Our new code describes fluid flow through large numbers (e.g., thousands) of stochastic fracture networks to provide statistical distributions of permeability, permeability anisotropy and fluid dispersion at reservoir scale (e.g., 1 km2). Calculations can be based on both the cubic flow law for smooth-walled fractures and the Forchheimer flow model, which includes an additional term to describe the nonlinear drag (i.e. friction) in real fractures caused by surface roughness of the fracture walls.

Models with fracture density consistent with borehole observations show pervasive connectivity at reservoir scales, with fluid flow (hence permeability) and tracer transport predominantly along the mean fracture orientation. As the fracture density is varied, we find a linear relationship between permeability which holds above a well-defined percolation threshold. Permeability anisotropy is in general high (~10 to 15), because of the steeply dipping fractures. As fracture density decreases, mean anisotropy decreases while its variability increases. Significant dispersion of fluid occurs as it is transported through the reservoir. These fracture models will inform more traditional continuum models of fractured geothermal reservoirs hosted in volcanic rocks, to provide a better description of fluid flow within reservoirs and aid the responsible and sustainable use of that resource in the future.

How to cite: Kissling, W. and Massiot, C.: Anisotropic permeability and fluid dispersion in pervasively fractured lavas, Rotokawa Geothermal System, New Zealand., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3564, https://doi.org/10.5194/egusphere-egu21-3564, 2021.

EGU21-4050 | vPICO presentations | ERE6.2

Influence of Aperture Distribution on Flow in Fractal-Fracture Networks

Ajay Kumar Sahu and Ankur Roy

While fractal models are often employed for describing the geometry of fracture networks, a constant aperture is mostly assigned to all the fractures when such models are flow simulated. While network geometry controls connectivity, it is fracture aperture that controls the conductivity of individual fractures as described by the well-known cubic-law. It would therefore be of practical interest to investigate flow patterns in a fractal-fracture network where the apertures also scale as a power-law in accordance to their position in the hierarchy of the fractal. A set of synthetic fractal-fracture networks and two well-connected natural fracture maps that belong to the same fractal system are used for this purpose. The former, with connectivity above the percolation threshold, are generated by spatially locating the fractured and un-fractured blocks in a deterministic and random manner. A set of sub-networks are generated from a given fractal-fracture map by systematically removing the smaller fracture segments. A streamline simulator based on Darcy's law is used for flow simulating the fracture networks, which are conceptualized as two-dimensional fracture continuum models. Porosity and permeability are assigned to a fracture within the continuum model based on its aperture value and there is nearly no matrix porosity or permeability. The recovery profiles and time-of-flight values for each network and its dominant sub-networks at different time steps are compared.

The results from both the synthetic networks and the natural maps show that there is no significant decrease in recovery in the dominant sub-networks of a given fractal-fracture network. It may therefore be concluded that in the case of such hierarchical fractal-fracture systems with scaled aperture, the smaller fractures do not significantly contribute to the fluid flow.

Key-words: Fractal-fracture; Connectivity; Aperture; Dominant Sub-networks; Streamline Simulator; Recovery

How to cite: Sahu, A. K. and Roy, A.: Influence of Aperture Distribution on Flow in Fractal-Fracture Networks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4050, https://doi.org/10.5194/egusphere-egu21-4050, 2021.

EGU21-8400 | vPICO presentations | ERE6.2

Fracture network connectivity devolution monitoring using transdimensional data assimilation

Márk Somogyvári, Mohammadreza Jalali, Irina Engelhardt, and Sebastian Reich

In fractured aquifers, the permeability of open fractures could change over time due to precipitation effects and hydrothermal mineral growth. These processes could lead to the clogging of individual fractures and to the complete rearrangement of flow and transport pathways. Existing fractured rock characterization techniques often neglect this dynamicity and treat the reconstruction as a static inversion problem. The dynamic changes then later added to the model as an independent forward modeling task. In this research we provide a new data assimilation-based methodology to monitor and predict the dynamic changes of fractured aquifers due to mineralization in a quasi-real-time manner.

We formulate the inverse problem as a dynamic ‘hidden Markov process’ where the underlying model dynamicity is just partly known. Data assimilation methods are specifically designed to model such systems with strong uncertainties. A typical example for such problems is weather forecasting, where the combination of nonlinear processes and the partial observations make the forecasting challenging. To handle the strong random behavior, data assimilation approaches use stochastic algorithms. In this study we combine DFN-based stochastic aquifer reconstruction techniques with data assimilation algorithms to provide a dynamic inverse modelling framework for fractured reservoirs. We use the transdimensional DFN inversion of (Somogyvári et al., 2017) to initialize the data assimilation. This method uses a transdimensional MCMC approach to identify the most probable DFN geometries given the observations. Because the method is transdimensional it can adjust the number of model parameters, the number of fractures within the DFN. We developed this idea further by enhancing a particle filter algorithm with transdimensional model updates, allowing us to infer DFN models with changing fracture numbers.

We demonstrate the applicability of this new approach on outcrop-based synthetic fractured aquifer models. To create a dynamic DFN example, we simulate solute transport in a 2-D fracture network model using an advection-dispersion algorithm. We simulate fracture sealing in a stochastic way: we define a limit concentration above which the fractures could seal with a predefined probability at any timestep. At the initial timestep, a hydraulic tomography experiment is performed to capture the initial aquifer structure, which is then reconstructed by the transdimensional DFN inversion. At predefined timesteps hydraulic tests are performed at different parts of the aquifer, to obtain information about new state of the synthetic model. These observations are then processed by the data assimilation algorithm, which updates the underlying DFN models to better fit to the observations.

How to cite: Somogyvári, M., Jalali, M., Engelhardt, I., and Reich, S.: Fracture network connectivity devolution monitoring using transdimensional data assimilation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8400, https://doi.org/10.5194/egusphere-egu21-8400, 2021.

EGU21-10581 | vPICO presentations | ERE6.2

A model for off-fault plastic poroelastic deformation and its effects on permeability

Bora Yalcin, Olaf Zielke, and Martin Mai

Fractured reservoirs comprise finite or discrete fracture networks; if these are conductive, they
form heterogeneously distributed high-permeability streaks. These are generally referred as
fracture corridors. Unless they occur as joint swarms, fracture corridors are simply seismic or sub-
seismic fault zones with connected fractures in the near-fault damage zone. Several studies
document the decrease in rock-matrix permeability adjacent to the fault surface, within the
damage zone. Although the damage zone creates fracture connectivity and high permeability
anisotropy for reservoirs, the matrix fracture feeding mechanism is related to matrix permeability
generally described by a transfer function. This transfer function accounts for fracture properties
(i.e. fracture density, length and connectivity), relative fluid mobilities, imbibition and reservoir
properties (i.e. matrix permeability). Commonly, the matrix permeability for all transfer functions
is considered in terms of a representative rock type permeability. However, observational
evidence and our numerical model show that slip induced deformation causes significant strain on
matrix in vicinity to the fault surface causing a permeability decrease in the matrix.

In this study, we present a new approach to model strain in a porous medium and related
permeability changes due to stress perturbation from slip around pure strike slip faults. The fault
length is used to scale the amount fault slip. For given/computed dislocation (slip) the off-fault
strain is then calculated to derive porosity and permeability changes. In our study we propose an
off-fault plastic-poroelastic deformation model for any known fault length and known rock
mechanical and petrophysical properties of the surrounding material. Our modeling technique will
help to better quantify fault transmissivity in geo-reservoirs.

How to cite: Yalcin, B., Zielke, O., and Mai, M.: A model for off-fault plastic poroelastic deformation and its effects on permeability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10581, https://doi.org/10.5194/egusphere-egu21-10581, 2021.

EGU21-7810 | vPICO presentations | ERE6.2

Challenges in correctly assessing fracture growth in subsurface applications

Morteza Nejati, Mahsa Sakha, Bahador Bahrami, Saeid Ghouli, Majid R. Ayatollahi, and Thomas Driesner

Accurate predictions of fracture growth path resulted from fluid injection in subsurface is an important topic in geoscience projects such as wastewater injection, CO2 sequestration and geothermal energy extraction. Pressurised fluid not only creates new fractures in form of hydraulic fractures, but also potentially propagates pre-existing ones. A precise assessment of fracture growth path is pivotal in characterising the connectivity of the fracture network, and as a result, the hydraulic response of the rock volume. Numerical modelling provides a strong platform to help better understand fracture growth path during hydraulic stimulations. Despite significant progress in the computational power and advanced numerical algorithms in recent years, the numerical simulation of fracture growth still faces many challenges. Some of these challenges are related to the robustness of the numerical schemes used to model evolving fractures. The development of methods such as extended finite element and phase-field have greatly helped in recent years to tackle the evolution of fractures in complex trajectories. A second group of challenges is related to the development of accurate fracturing laws and their implementation into numerical codes in order to obtain realistic fracture growth trajectories. In this paper, we address some of the challenges in the second group and share our findings on how we can more accurately predict fracture path in subsurface. At first, we present our evaluation of the measured values of the fracture toughness in laboratory, and discuss why those values are mostly underestimating fracture toughness in rock masses. We then introduce a method to correct these values, that are obtained from small laboratory-sized specimens, to be able to use them in numerical codes that predict fracture growth in large rock volumes in subsurface. The second contribution is related to the rock anisotropy and its influence on the fracture growth path. We present experimental results on the anisotropy of fracture toughness, and show how important it is to take into account the directional-dependence of fracture toughness when modelling fracture growth in anisotropic formations. Lastly, the third contribution is to distinguish between tension-based and shear-based fracture growth mechanisms. Most numerical models in literature use the maximum tangential stress criterion to predict fracture growth path. We show that this criterion is not able to predict shear-based fracturing that often occurs in the subsurface. We conclude that a reliable numerical code needs to implement a fracturing law that is able to predict both tensile- and shear-based fracturing types.

How to cite: Nejati, M., Sakha, M., Bahrami, B., Ghouli, S., Ayatollahi, M. R., and Driesner, T.: Challenges in correctly assessing fracture growth in subsurface applications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7810, https://doi.org/10.5194/egusphere-egu21-7810, 2021.

EGU21-13704 | vPICO presentations | ERE6.2

Modelling hydraulic fracturing with the J-integral

Edoardo Pezzulli, Morteza Nejati, Saeed Salimzadeh, Stephan Matthai, and Thomas Driesner

Hydraulic fracturing plays a central role in engineering fractured reservoirs. To simulate the propagation of “dry” fractures, the J-integral has been a standard technique. Its superior accuracy at coarser resolutions make it particularly attractive, especially for reservoir-scale simulations. However, the extension of the J-integral to hydro-mechanical simulations of fluid-driven fracturing has not received the same attention or success. In particular, while several studies have highlighted the capacity of the method in simulating viscosity-dominated propagation, detailed investigations into the performance of the method are still missing. In this work, we find that the extent of hydraulic fracturing is typically overestimated by the J-integral in the viscosity-dominated propagation regime.  A finite element analysis is conducted which sheds light on the source of the error. The case is put forward that the inaccurate numerical solution for fluid pressure is exclusively responsible for the loss in accuracy of the J-integral. With this new understanding, the J-integral is reformulated to minimise its dependence on inaccurate fluid pressures, bypassing the aforementioned sources of error. The reformulation, termed the JV-integral, is both simple to implement, and general to the numerical method. Within the framework of finite elements, a propagation algorithm using the novel JV-integral is subsequently constructed with two distinct abilities compared to the original J-integral. The first is an increased ability to capture the viscosity-dominated regime of propagation at significantly coarser resolutions. Finite element simulations conducted at various levels of refinement detail the promising results relevant to hydro-mechanical simulations at reservoir scale.  The ability of the method in simulating the toughness regime remains as performant as the original J-integral.  The second, is the ability of the JV-integral in extracting the propagation velocity of the fracture; a feature particular to methods arising from hydraulic fracture mechanics. Consequently, the method demonstrates an inherent advantage when converging on the fracture length, requiring significantly fewer iterations compared to the original formulation. Fundamentally, the velocity obtained via the JV-integral has the potential to be used in combination with front-tracking schemes like the implicit level set method. As a result, the JV-integral appears to be a promising method when simulating hydraulic fracturing in geoenergy applications and beyond. 

How to cite: Pezzulli, E., Nejati, M., Salimzadeh, S., Matthai, S., and Driesner, T.: Modelling hydraulic fracturing with the J-integral, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13704, https://doi.org/10.5194/egusphere-egu21-13704, 2021.

EGU21-6756 | vPICO presentations | ERE6.2

In-plane and out-of-plane shear fracture toughness of rocks

Bahador Bahrami, Morteza Nejati, Majid Reza Ayatollahi, and Thomas Dreisner

Rocks in the subsurface are exposed to high amount of confinement which can potentially suppress the formation or the development of tensile-based cracks and thus, give rise to shear-based fracture growth. However, measuring the shear fracture toughness of rocks have been studied less in the literature, as providing the required confinement to force the shear fracturing precede tensile fracturing is not an easy task. In the current study, two new tests namely the double-edge notched Brazilian disk (DNBD) and the axially double-edge notched Brazilian disk (ANBD) are proposed to measure the in-plane (true mode II) and the out-of-plane (true mode III) shear fracture toughness of rocks, KIIc and KIIIc, respectively. We use the term true to emphasis that not only sustains the crack shear loading, but also the type of fracturing is shear-based. Finite element method is used to study the variations of stress field around the crack tip in these tests and to prove the applicability of the tests in providing mode II and mode III loading conditions. It is argued that both tests are straightforward and have several advantages compared to the existing ones. The effectiveness of the tests is empirically corroborated by conducting some experiments on Bedretto Granite. The pulverized surface of fracture in both the tests denotes the existence of friction which indicate the shear-based nature of fracture. Finally, the measured values of KIIc and KIIIc for Bedretto granite are compared to each other and to the reported values of KIc in the literature. It is shown that KIIc and KIIIc values are close to each other while both are more than two times greater than KIc.

How to cite: Bahrami, B., Nejati, M., Ayatollahi, M. R., and Dreisner, T.: In-plane and out-of-plane shear fracture toughness of rocks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6756, https://doi.org/10.5194/egusphere-egu21-6756, 2021.

EGU21-10155 | vPICO presentations | ERE6.2

Stress field perturbations from faults

Karsten Reiter and Oliver Heidbach

Faults are crucial structures in the subsurface with respect to seismic hazards or the exploitation of the subsurface. However, even though it is clear that the released elastic energy changes the stress field, it is not well known at what distance these change leave a significant imprint on the stress tensor components. In particular, it is assumed that stress tensor rotations are a measure of these changes. Furthermore, from a technical point of view, the implementation of faults in geomechanical models is a challenging task. There are several implementation concepts are to mimic faults in geomechanical models. The two main classes are the continuous approach (soft of low plastic elements) and the discontinuous approach (contact surfaces). However, only partial aspects of the complex behaviour of faults or fault zones are represented by these techniques.

Knowing this limitation, we investigate the influence of the implementation concepts, fault properties and numerical resolution on the resulting stress field in the vicinity of a fault. The main focus of the generic models is to investigate, up to which distance from a fault, significant stress changes of the stress tensor components can be observed. In doing so, the respective models undergo a deformation that produces a similar stress state. The resulting stress magnitudes are investigated along a horizontal line at a depth of 660m, parallel to the shortening direction.

The result indicates, that stress magnitude pattern varies significantly close to the modelled fault, depending on the used implementation concept. However, beyond 500 m distance from the fault, the changes in stresses are < 0.5 MPa, regardless of the concept. Even a significant coarser resolution causes comparable stress patterns and magnitudes away from the implemented fault. Similarly, the dip angle, as well as the strike angle, have little effect on the observed distance effect. For stiff rocks having a higher Young's modulus, significant stress changes can also exceed the distance of 1000 m away from the fault.

The results indicate, that faults alone have limited effect on the far-field stress pattern. On the other hand, data of stress magnitudes or the stress tensor orientation close to a fault (< 500 m) are most likely affected by the particular fault geometry and fault characteristics. This is also the case for the vertical stress magnitude.

How to cite: Reiter, K. and Heidbach, O.: Stress field perturbations from faults, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10155, https://doi.org/10.5194/egusphere-egu21-10155, 2021.

Well-logging data show that geothermal formations typically feature layered heterogeneities. This imposes a challenge in numerical simulations, in particular in the upscaling of geothermal processes. The goal of our study is to develop an approach to (1) simplify the description of heterogeneous geothermal formations and (2) provide an accurate representation of convection/dispersion processes for simulating the up-scaled system.

In geothermal processes, transverse thermal conduction causes extra spreading of the cooling front: thermal Taylor dispersion. We derive a model from an energy balance for effective thermal diffusivity, αeff, to represent this phenomenon in layered media. αeff, accounting for transverse heat conduction, is much greater than the longitudinal thermal diffusivity, leading to a remarkably larger effective dispersion. A ratio of times is defined for longitudinal thermal convection and transverse thermal conduction, referred to as transverse thermal-conduction number NTC. The value of NTC is an indicator of thermal equilibrium in the vertical cross-section. Both NTC and αeff equations are verified by a match with numerical solutions for convection/conduction in a two-layer system. For NTC > 5, the system behaves as a single layer with thermal diffusivity αeff.

When NTC > 5, a two-layer system can be combined and represented with αeff and average properties of the two layers. We illustrate upscaling approach for simulation of geothermal processes in stratified formations, by grouping layers based on the condition of NTC > 5 and the αeff model. Specifically, NTC is calculated for every adjacent two layers, and the paired layers with a maximum value of NTC are grouped first. This procedure repeats on the grouped system until no adjacent layers meet the criterion NTC > 5. The upscaled layer properties of the grouped system are used as new inputs in the numerical simulations. The effectiveness of the upscaling approach is validated by a good agreement in numerical solutions for thermal convection/dispersion using original and average layer properties, respectively (Figs. 1 and 2 in the Supplementary Data File). The upscaling approach is applied to well-log data of a geothermal reservoir in Copenhagen featuring many interspersed layers. After upscaling, the formation with 93 layers of thickness 1 – 3 meters is upscaled to 12 layers (Fig. 3 in the Supplementary Data File). The effective thermal diffusivity αeff in the flow direction is about a factor of 10 times greater than original thermal diffusivity of the rock. Thus, αeff should be used as simulation inputs for representing more accurately geothermal processes in the up-scaled system.

 

 

How to cite: Tang, J. and Rossen, W. R.: Application of Thermal Taylor Dispersion to Upscaling of Geothermal Processes in Heterogeneous Formations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10564, https://doi.org/10.5194/egusphere-egu21-10564, 2021.

EGU21-12766 | vPICO presentations | ERE6.2

Fracture-generated frequency-dependent seismic Q measured from a VSP in granite

Victoria R. Bourne, C. Dario Cantu Bendeck, Mark W. Hildyard, Roger A. Clark, and William Wills

We integrate two topics – seismic characterisation of fractures, and seismic attenuation quantified as the frequency-dependent Seismic Quality Factor Q, Q(f). The former is vital for predicting and monitoring fluid movement and containment in energy-related settings (hydrocarbons; geothermal; CO2, hydrogen or compressed air storage; radwaste). Fractures control the fluid flow and structural behaviour of a rock mass, yet their expression in Q is poorly studied and not well understood despite it typically being more sensitive than wavespeeds as a rock physics parameter. The latter is long-recognised, little-studied, and a paradigm shift from frequency-independent Q (‘constant-Q’, a routine signal-processing and image enhancement tool in hydrocarbon exploration), despite theory, laboratory, and field data showing that Q must be frequency dependent due to varying scale-lengths of the physical-mechanical phenomena causing attenuation.

We therefore measure Q(f) from the downgoing direct P-wave arrival in a near-offset vertical seismic profile in granite at a former geothermal test site in Cornwall, SW England, where vertical and horizontal fracturing is seen at surface: horizontal fractures are confirmed at depth by well-log data. Sensors were 3-component 15Hz geophones at 15m depth spacing: the source was a single vibrator, linear 8-100Hz up-sweep, 30m offset from the wellhead in the azimuth of well deviation: record length was 1000ms at 1ms sample interval. We analyse only the deeper cased interval, from 700m to 1735m. Pre-processing was geometric spreading correction, hodogram-based component rotation toward the source, and wavefield separation using a 7-point median filter to suppress interference from upgoing energy. Measured attenuation Qeff is the harmonic sum of intrinsic Q, Qint, and apparent attenuation, Qapp. Qint in massive granite is typically 500-1000, yet we find Qeff(f) is 50-70 at >60Hz and only ≈30 at <30-35Hz, features masked in the constant-Q result of 55±11 over our working bandwidth of 25-90Hz.

One contribution to Qapp is ‘stratigraphic attenuation’, forward-scattering interference of short-path internal multiple reflections superimposed on direct arrivals, and quantifiable from sonic and density well-logs using O’Doherty-Anstey-Shapiro methodology. We find it is indeed frequency-dependent (peaking at ≈50-60Hz, 10-40% lower at our bandwidth limits) but its absolute magnitude is insignificant (Q≈20,000-30,000) and unable to explain the measured Qeff(f). We therefore investigate the effect of fracturing directly using finite difference models in which fractures are defined explicitly as displacement discontinuities with opposing surfaces connected by a normal and shear stiffness. An individual fracture acts somewhat like a low pass filter: more complex frequency behaviour emerges from multiple fractures, particularly when fracture stiffness, spacing and size can vary. We concentrate first on large horizontal fractures perpendicular to the borehole receiver array, and find that these can indeed influence effective attenuation within the 25-90Hz bandwidth. We then discuss the range of fracture spacings and stiffnesses capable of explaining the data and whether they are sufficiently physically credible as an explanation of the observed Q(f).

How to cite: Bourne, V. R., Cantu Bendeck, C. D., Hildyard, M. W., Clark, R. A., and Wills, W.: Fracture-generated frequency-dependent seismic Q measured from a VSP in granite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12766, https://doi.org/10.5194/egusphere-egu21-12766, 2021.

EGU21-13206 | vPICO presentations | ERE6.2

Impact of fracture sealing on their hydraulic and mechanical properties

Qinglin Deng, Jean Schmittbuhl, Guido Bloech, and Mauro Cacace

In deep tight reservoirs like Enhanced Geothermal Systems (EGS), the fracture flow often plays a dominant role. The hydraulic and mechanical behaviors of the fracture are affected by a couple of factors such as the sealing deposits owing to mineral cementation. Here we aimed to investigate the impact of the sealing material on the hydro-mechanical properties of a rough fracture using a well-established self-affine rough fracture model. We developed finite element model based on the MOOSE/GOLEM framework dedicated to modeling coupled Hydraulic-Mechanical (HM) process of the rock-fracture system. We conducted numerical flow through a granite reservoir hosting one single large and partly sealed fracture of size 512x512 m2. Navier-Stokes flow and Darcy flow are solved in the 3-dimensional rough aperture and in the embedding poro-elastic matrix, respectively. In order to mimic the impact of the fracture sealing material on the physical properties of the rock-fracture system, we sequentially increased the amount of the fracture-filling material in the rough fracture by changing the thickness of the sealing deposits.  The evolution of the contact area, fracture permeability, fracture diffusivity and normal fracture stiffness, is monitored up to the percolation threshold of the fluid flow. We show that sealing induces strong permeability anisotropy, significant decrease of hydraulic diffusivity and increase of fracture stiffness. The results have strong implications for optimizing the stimulation strategy like chemical stimulation of fractured reservoirs, as well as understanding the fluid-induced seismicity.

How to cite: Deng, Q., Schmittbuhl, J., Bloech, G., and Cacace, M.: Impact of fracture sealing on their hydraulic and mechanical properties, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13206, https://doi.org/10.5194/egusphere-egu21-13206, 2021.

Reservoir characterization and flow studies require accurate inputs of petrophysical properties such as porosity, permeability, water and residual oil saturation and capillary pressure functions. All these parameters are necessary to evaluate, predict and optimize the production of a reservoir.

This study is the continuity of a previous work that summarize the construction of a net rock aerial map by combining stochastic simulation of rock types and processed seismic data. In this case study; petrophysical data are integrated to construct a 3D model of porosity corresponding to the 3D model of rock type. This is in order to further understand the intricacies of the geostatistical methods used and the impact of the technique on the resulting uncertainty profile

For the construction of 3D model of porosity corresponding to the 3D model of rock types, a geostatistical workflow encompassing the modelling of experimental variograms and sequential Gaussian simulation (SGS) were used. The geostatsitical methodologies of stochastic simulation such as SGS enabled the generation of several realistic scenarios of constinuous data, such as porosity, within a volume, thus facilitating the association of local probabilities of occurrence of each rock type.

The resulting porosity image properly combines the available seismic and well data and balance the local and regional uncertainty of the studied reservoir volume.

Keywords: Geostatistics, Sequential Gaussian Simulation (SGS), Rock types, Porosity, Uncertainty, Spatial resolution.

How to cite: Boussa, L., Boudella, A., and Almeida, J.: Assessing of tight reservoir by combining the porosity of geological units, and simulated images of rock types: A case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15250, https://doi.org/10.5194/egusphere-egu21-15250, 2021.

ERE6.3 – Faults and fractures in geoenergy applications 2: Monitoring, laboratory and field work results

EGU21-13636 | vPICO presentations | ERE6.3 | Highlight

Hengill, SW-Iceland: Operating a fractured reservoir for geothermal production and carbon storage

Sandra Snæbjörnsdóttir, Thomas Ratouis, and Sveinborg Gunnarsdóttir

Fractures and fracture networks play fundamental roles in the operation of subsurface systems such as geothermal production and geological carbon storage: Fractures are the circulatory systems of such reservoirs, driving them via transport of fluids, gases, heat, and dissolved elements, channelling the flow as both carriers and barriers, and providing connection to the rock matrix. Furthermore, due to their role, they provide important insights into the reservoirs, such as the dominant flow paths, the thermal evolution and the dominant chemical processes taking place and affecting e.g. the permeability via dissolution, precipitation and mechanics within the subsurface.

At Hengill central volcano, SW-Iceland, the subsurface reservoir is utilised for geothermal production, re-injection of geothermal fluids and injection of carbon dioxide (CO2) for the means of mineral CO2 storage, at the two field sites in Nesjavellir and Hellisheidi. The operation involves thousands to millions of tonnes of fluid, steam, and gases that are circulated annually through the subsurface bedrock via extraction and injection. Over 100 production and injection wells have been drilled in the two fields, ranging in depths from 800 m to 3300 m. The increased emphasis on the mapping of surface and subsurface faults and structures, and the opportunity of tracing the fluid flow via injection of tracers into the reinjection wells of the fields has provided deeper understanding of the role of fractures in this fracture dominated reservoir. This knowledge has benefitted the field operation by the drilling of very powerful production wells, and successful injection wells – both in terms of injectivity and their locations, providing pressure support to the geothermal production while preventing thermal breakthrough of colder fluids. Furthermore, the use of tracers has been an invaluable tool for managing injection of dissolved CO2 into fractured basaltic reservoirs for mineral carbon storage, both in terms of quantitative monitoring and detection of dissolved and mineralised CO2.

The utilisation of the Hengill field sites at Nesjavellir and Hellisheidi offers unique opportunities to increase our understanding of subsurface processes, providing large-scale field laboratories with enormous datasets, and building bridges between industry and academia.

 

How to cite: Snæbjörnsdóttir, S., Ratouis, T., and Gunnarsdóttir, S.: Hengill, SW-Iceland: Operating a fractured reservoir for geothermal production and carbon storage, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13636, https://doi.org/10.5194/egusphere-egu21-13636, 2021.

EGU21-16442 | vPICO presentations | ERE6.3

Fracture network analysis for carbon mineralization in basalts of the Oligocene Jizan volcanics, Saudi Arabia

Murtadha Al Malallah, Jakub Fedorik, Giacomo Losi, Yuri Panara, Niccolo Menegoni, Abdulkader Alafifi, and Hussein Hoteit

This study aims to characterize fracture permeability in altered Oligocene-Early Miocene basalts of the Jizan Group, which accumulated in half grabens during the continental rift stage of Red Sea evolution. Unlike fresh basalts, the Jizan Group was affected by low temperature hydrothermal metamorphism, which plugged the original matrix porosity in vesicles, breccias, and interflow layers with alteration minerals. On the other hand, the basalts are pervasively shattered by open closely spaced fractures in several directions. Characterization of these fractures is essential to reducing the fracture permeability uncertainty for mineral carbonation by the dissolved CO2 process such as Carbfix.
Conventional measurements of fracture orientations and densities were initially taken at outcrops of the Jizan Group to characterize the fracture network. Photogrammetry of drone images covering larger areas were then used to create 3D models of the outcrops using Agisoft Metashape, which were analyzed for fracture geometries using Cloud Compare. The automated analysis of fracture orientations and densities compared well with conventional manual measurements. This gives confidence in semi-automated dronebased fracture characterization techniques in 3D, which are faster and less labor intensive, especially for characterization of large and difficult to reach outcrops.
Our fracture characterization will be used to construct 3D fracture permeability models of the Jizan Group for combined physical and chemical simulation of injection of dissolved CO2 from industrial sources into basalts. This will provide essential parameters to mitigate geological risks and to determine depth, spacing, and injection rates in CO2 disposal wells.

How to cite: Al Malallah, M., Fedorik, J., Losi, G., Panara, Y., Menegoni, N., Alafifi, A., and Hoteit, H.: Fracture network analysis for carbon mineralization in basalts of the Oligocene Jizan volcanics, Saudi Arabia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16442, https://doi.org/10.5194/egusphere-egu21-16442, 2021.

EGU21-8517 | vPICO presentations | ERE6.3 | Highlight

Role of fault and fracture networks to de-risk geological leakage from subsurface energy sites

Roberto Emanuele Rizzo, Hossein Fazeli, Florian Doster, Niko Kampman, Kevin Bisdom, Jeroen Snippe, Kim Senger, Peter Betlem, and Andreas Busch

The success of geological carbon capture and storage projects depends on the integrity of the top seal, confining injected CO2 in the subsurface for long periods of time. Here, faults and related fracture networks can compromise sealing by providing an interconnected pathway for injected fluids to reach overlying aquifers or even the surface or sea bottom. In this work, we apply an integrated workflow [1] that, combining single fracture stress-permeability laboratory measurements and detailed fault and fracture network outcrop data, builds permeability models of naturally faulted caprock formations for in situ stress conditions.

We focus our study on two-dimensional (2D) fault-related fracturing within caprock sequences cut by extensional faults. 2D data of fault and fracture networks were collected from an Upper Jurassic to Lower Cretaceous shale-dominated succession in the Konusdalen area (Nordenskioldland, Svalbard, Norway). The studied rock succession represents the regional caprock and seal for the reservoir of the nearby Longyearbyen CO2 Lab. By digitising all the visible features over the images and then inputting them into the open-source toolbox FracPaQ [2], we obtain information about the fault and fracture networks. In particular, we study the variations in fracture size (i.e., length, height) and density distribution near and away from the fault zone(s), together with the connectivity of fractures within the network. These three parameters are fundamental to establish if the network provides permeable pathways. They also enable us to statistically reproduce and upscale a fracture network in a realistic way.

Combining laboratory single fracture stress-permeability measurements with outcrop fracture network data allow us to create an accurate coupled mechanical-hydromechanical model of the natural fracture network and to evaluate the effective permeability of a fault related fracture network. These results are also compared against analytical estimates of effective permeability [3]. With this workflow, we overcome the geometrical simplifications of synthetic fracture models, thus allowing us to establish representative stress-permeability relationships for fractured seals of geological CO2 storage.

Reference: [1] March et al., 2020, Preprint; [2] Healy et al., 2017, JSG; [3] Seavik & Nixon, 2017, WRR

How to cite: Rizzo, R. E., Fazeli, H., Doster, F., Kampman, N., Bisdom, K., Snippe, J., Senger, K., Betlem, P., and Busch, A.: Role of fault and fracture networks to de-risk geological leakage from subsurface energy sites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8517, https://doi.org/10.5194/egusphere-egu21-8517, 2021.

EGU21-2103 | vPICO presentations | ERE6.3

On the multiscale quantification of fracture network geometry from lineament maps of crystalline basement units

Alberto Ceccato, Giulia Tartaglia, Giulio Viola, and Marco Antonellini

Fractured crystalline basement units are attracting increasing attention as potential unconventional reservoirs for natural (oil, heat and water) resources and as potential waste (nuclear, CO2) disposal sites. The focus of the current efforts is the characterisation of the structural permeability of fractured crystalline basement units, which is primarily related to the geology, geometry, and spatial characteristics of fracture networks. Fracture network properties may be scale–dependent or independent. Thus, a multi–scale characterisation of fracture networks is usually recommended to quantify the scale–variability of properties and, eventually, the related predictive scaling laws. Fracture lineament maps are schematic representations of fracture distributions obtained from either manual or automated interpretation of 2D digital models of the earth surface at different scales. From the quantitative analysis on fracture lineament maps, we can retrieve invaluable information on the scale–dependence of fracture network properties.

Here we present the results of the quantification of fracture network and fracture set properties (orientation, length, spacing, spatial organisation) from multi– (outcrop to regional) scale 2D lineament maps of two crystalline basement study areas of Western Norway (Bømlo island and Kråkenes). Lineament maps were obtained from the manual interpretation of orthophotos and 2D digital terrain models retrieved from UAV–drone and LiDAR surveys.

Analyses aimed at the quantification of: (i) scaling laws for fracture length cumulative distributions, defined through a statistically–robust fitting method (Maximum Likelihood Estimations coupled with Kolmogorov–Smirnov tests); (ii) variability of orientation sets as a function of scale; (iii) spatial organisation of fracture sets among scales; (iv) fractal characteristics of fracture networks (fractal exponent). Results suggest that: (i) a statistical analysis considering variable censoring and truncation effects allows to confidently define the best–fitting scaling laws; (ii) the analysis of orientation variability of fracture sets among different scales may provide important constraints about the geometrical complexity of fracture and fault zones; (iii) the statistical analysis of 2D spacing variability and fracture intensity can be adopted to quantify fracture spatial organisation at different scales.

A statistically robust analysis of the scaling laws, length distributions, spacing, and spatial organisation of lineaments on 2D maps provides reliable results also where only partial or incomplete dataset/lineament maps are available. Such properties are the fundamental input parameters for conceptual (geologic) and numerical (discrete fracture network, DFN) models of fractured crystalline basement reservoirs. Therefore, a statistically robust analysis of fracture lineament maps may help to improve the accuracy of conceptual and numerical models.

How to cite: Ceccato, A., Tartaglia, G., Viola, G., and Antonellini, M.: On the multiscale quantification of fracture network geometry from lineament maps of crystalline basement units, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2103, https://doi.org/10.5194/egusphere-egu21-2103, 2021.

EGU21-5593 | vPICO presentations | ERE6.3

Fractures in Granite: Results from United Downs Deep Geothermal well UD-1

Mark W. Fellgett and Richard Haslam

The geothermal potential of the granites of SW England has long been known. The first significant exploration of the resource was in the Carnmenellis Granite under the ‘Hot Dry Rock (HDR) Project’ during the 80’s and early 90’s. Following completion of the HDR project there was little further exploration in the area for geothermal power generation. Recently however, development of the United Downs Deep Geothermal Power (UDDGP) project marks a significant leap forward, and this aims to be the first commercial project to explore deep geothermal power generation in SW England.

 

The UDDGP project targets the Porthtowan Fault zone, a regional scale NW to NNW striking strike-slip fault that is inferred to transect the NE margin of the Carnmenellis Granite. Two directional wells were drilled to intersect this fault zone, maximising the surface area of the fault exposed. A production well with a measured depth of 5275 m true vertical depth of 5054 m and an injection well vertically above the production well at a measured depth of 2393 m and a true vertical depth of 2214 m. A full suite of geophysical wireline logs were collected for the production well, including borehole image logs from 900 mMD to 5160 mMD (900 - 4097mTVD).

 

Interpretation of the borehole imaging across the 4260 m identified a total of 12031 discontinuities. The features were classified using a simple schema and provide new insights into the complex nature of faulting and fracturing within the Granite. Stress field indicators including Borehole Breakouts and Drilling Induced Tensile Fractures (DIFs) were also interpreted.

 

The orientations of the borehole breakouts and DIFs are consistent and are comparable to previous measurements in the region and the regional stress field, indicating the direction of maximum compression is, approximately horizontal trending towards 320°.

 

The data show variable fracture density along the imaged section of the well with the maximum density tentatively associated with discreet fault zones. At least 3 fracture sets are identified with the largest concentration of fractures approximately parallel to inferred Porthtowan Fault Zone, suggesting UD-1 intersected the target fault zone. Key fracture attributes are explored and discussed including orientation, spacing, intensity, and spatial correlation.

How to cite: Fellgett, M. W. and Haslam, R.: Fractures in Granite: Results from United Downs Deep Geothermal well UD-1, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5593, https://doi.org/10.5194/egusphere-egu21-5593, 2021.

EGU21-8921 | vPICO presentations | ERE6.3

Depth-dependent Clustering Analysis of Fractures in Crystalline Basement Rocks

Mohammad Javad Afshari Moein, Keith Evans, Benoît Valley, Kristian Bär, and Albert Genter

Understanding the complex seismic, thermal, hydraulic and mechanical processes active during the hydraulic stimulation or continuous operation of Enhanced Geothermal Systems (EGS) requires an accurate description of the pre-existing fractures and faults. However, the three-dimensional characterization of the fracture network is challenging, as direct observation of the discontinuity network at great depth is limited. Fracture image logs and continuous core, which provide line samples through the fracture network, are most valuable in this regard as they provide the most precise option to place constraints on network attributes in stochastic realizations of the fractured rock mass. Among various geometrical attributes, the spatial clustering of fractures plays a critical role on the rock mass properties. 

Here, we analyzed the spatial distribution of fractures derived from image log runs in six deep boreholes in crystalline basement rock. In one well, the fracture distribution from continuous core was also available. The wells were drilled to depths between 2-5 km, and were all located in the same tectonic setting of the Upper Rhine Graben, which is recognized for its high geothermal potential. The normalized correlation integral method was employed to define the scaling relationships of fracture patterns. This methodology is demonstrated to be less affected by the finite size effects, delivering reliable estimates of scaling laws.

Detailed analyses of image log datasets revealed fractal scaling with similar fractal dimensions (between 0.85 and 0.96), prevailed over almost two orders of magnitude of scale. The same was true for the fracture distribution derived from the continuous core, although this distribution was found to be more clustered than that derived from image logs in the same well (i.e. the fractal dimension was lower, which may be due to the partial fracture sampling of image logs which have a coarser resolution than continuous core analyses). Analysis of fractures in sub-sections of the core dataset from progressively increasing depths revealed no systematic depth-dependency for the fractal dimension, although a local variation at a scale of hundreds of meters was identified.

How to cite: Afshari Moein, M. J., Evans, K., Valley, B., Bär, K., and Genter, A.: Depth-dependent Clustering Analysis of Fractures in Crystalline Basement Rocks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8921, https://doi.org/10.5194/egusphere-egu21-8921, 2021.

EGU21-9940 | vPICO presentations | ERE6.3

Multiscale fracture analysis of the Vallès fault zone in La Garriga-Samalús geothermal system

Gemma Mitjanas, Gemma Alías, David García-Martínez, Pilar Queralt, and Juanjo Ledo

La Garriga-Samalús geothermal system is located in the Catalan Coastal Ranges (CCR) (NE Spain). The CCR is a NE-SW horst and graben system with two lifted mountain chains, the Precoastal (PR) and Coastal ranges (CR), separated by the Vallès basin. An Hercynian highly fractured granodiorite thrusts the Paleozoic metamorphic units in the northern part of the PR. Towards the south, the intrusive unit is in contact with the Miocene rocks of the Vallès basin by a major Neogene normal fault, the Vallès fault.

Previous works in this area showed that the fractured zone associated to the Vallès normal fault, located in the Hercynian granodiorite, could act as the geothermal reservoir as well as the fast-ascending path for the hot fluids. Although some geophysical prospections and exploration boreholes have been made in La Garriga-Samalús area, it is still necessary to understand and model the fracture network.

This study presents a multiscale fracture analysis of the granodiorite from outcrops and boreholes samples. This multiscale analysis combines satellite pictures, field studies and laboratory measurements of both field and borehole samples.

The fracture data collection has allowed the identification of 3 major fracture sets related to the main tectonic events of the CCR, in addition to 7 other minor fracture groups. Through the variation of fracture density in the footwall, a 10 meters fault core, and an asymmetric damage zone of approximately 300 m, have been identified. The damage zone shows an increasing fracture density towards the northern and southern limits of the granodiorite, which are an alpine thrust and the Vallès fault, respectively. In the fault core, the presence of cemented rocks like cataclasites with hydrothermal sealed fractures result in low porosity and permeability. Contrary, the damage zone consists of minor faults and related fractures which may enhance fault permeability with respect the core and its protolith.

In order to characterize fractures in depth, the borehole samples have been digitized via photogrammetry method. The study of the point cloud related to this samples have allowed the identification and characterization of some of the fractures sets at greater depths. The permeability differences between the fault core and the damage zone can be also identified in the borehole samples. The presence of centimetric open fractures, cavities, and hydrothermal minerals, confirm the circulation of thermal fluids. Meanwhile, other samples within the fault trace are compact rocks, with slickensides and high-pressure alteration minerals.

These fracture results have been also correlated with a previous 2D magnetotelluric (MT) model which shows the Vallès fault zone as a low resistivity unit. The fault zone may give a low resistivity value only if it is permeable and water saturated. Therefore, our results identify the damage zone of the Vallès fault as the potential reservoir of La Garriga-Samalús geothermal system.

How to cite: Mitjanas, G., Alías, G., García-Martínez, D., Queralt, P., and Ledo, J.: Multiscale fracture analysis of the Vallès fault zone in La Garriga-Samalús geothermal system, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9940, https://doi.org/10.5194/egusphere-egu21-9940, 2021.

EGU21-13435 | vPICO presentations | ERE6.3

First-order discontinuity in tracer mass recovery: indicative of (large) induced fracture(s)?

Horst Behrens Julia Ghergut and Martin Sauter

Forced-gradient flow sustained by a geothermal well doublet in a porous-fissured reservoir (more or less karstified, Jurassic formation, cf. Behrens et al. 2020 for a conceptual-hydrogeologic model outline and competing hypotheses as to what role large fractures might play) is subject to a tracer test anew, following a significant augmentation of fluid turnover rates. The distinct aromatic sulfonates (N2S and P4S) used as tracers in the first (lower-rate) and the second (higher-rate) test are supposed to be transported conservatively and similarly under this reservoir’s in-situ conditions; in terms of solute diffusivity, the larger molecule size of P4S ought to be roughly matched by N2S’s stronger hydratization in-situ, and for assuming else physicochemically conservative behavior one may invoke vast evidence from past applications in mineralogically variate, saline, hot reservoirs (Behrens 1992ff; Rose 1997ff). Cumulative mass recovery for each tracer can be calculated based on its theoretical ‘single-passage’ signal, deconvolved from its measured signal (eliminating ‘redundant’ contributions from fluid recirculation; to account for flow-rate variability, we set up an ad-hoc deconvolution algorithm). From tracer sampling to date, CMR amounts to ~28% for P4S, and ~70%* for N2S – whose first 20-30%* mass amounts were swept through the reservoir under the lower-rate flow regime, and its subsequent amounts under the higher-rate regime, reaching 60-65%* by the time P4S was added (for the latter, a certain time lag after flow rate augmenting was allowed, not having in pectore whether the higher flow rate would prove sustainable, and how long it would take for the flow field to reach a new ‘quasi-steady’ state at reservoir scale; pressure buildup/drawdown changes at injection/production wells stayed uninterpretably low). Those N2S %* cannot be told accurately due to short-term flow-meter (instrumental) failures during precisely this transition. CMR for P4S exhibits a significantly lower growth rate than for N2S (even when plotted against cumulative fluid turnover, which should compensate for flow-rate disparities), and, more strikingly, a marked first-order discontinuity (tangent drop) after reaching ~20% (which would correspond to ~30% N2S after the same cumulative fluid turnover, counted since tracer injection). Three hypotheses which might explain these findings are evaluated: P4S decay? reservoir ‘stimulation’ → stronger P4S dilution? reservoir ‘compartmenting’ → P4S ‘loss’ into some ‘non-pay’ zone? Accordingly, special monitoring options that would allow to disambiguate (or refute) some ‘induced fracture’ / ‘activated fault’ / ‘karst window’ scenarios are discussed. [*Note: not only these particular values for N2S, but its entire subsequent CMR calculation is impeded by the flow-meter data gap; as a substitute, one may attempt to reconstruct the missing flow-rate data from ‘geothermal’ power generation data, but here operator-provided information is insufficient. For P4S however, being injected way later after this metering gap, its tangent discontinuity in CMR stays independent upon the missing data] – – Reference: SGP-TR-216, pp.195-201, pangea.stanford.edu/ERE/db/GeoConf/papers/SGW/2020/Behrens.pdf (for a reservoir model outline, and early tracer signal illustrations)

How to cite: Ghergut, H. B. J. and Sauter, M.: First-order discontinuity in tracer mass recovery: indicative of (large) induced fracture(s)?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13435, https://doi.org/10.5194/egusphere-egu21-13435, 2021.

EGU21-10324 | vPICO presentations | ERE6.3

The response of a fractured crystalline reservoir to natural pressure buildup: Experiment results from the Bedretto Lab

Alexis Shakas, Nima Gholizadeh, Marian Hertrich, Quinn Wenning, Hansruedi Maurer, Bernard Brixel, Alba Zappone, Antonio Rinaldi, Anne Obermann, Xiaodong Ma, Philipp Kaestli, Paul Linwood, Rebecca Hochreutener, Stefan Wiemer, and Domenico Giardini

The Bedretto Underground Laboratory for Geosciences and GeoEnergies, located in the Swiss Alps and situated under more than 1 km of granitic overburden, offers a unique field site to study processes in fractured rock. Currently, a total of six boreholes are available, four of them being permanently instrumented with monitoring equipment, and two dedicated as stimulation boreholes. One of the monitoring boreholes contains permanent packed-off intervals which record pressure changes and flow rate. The remaining three are instrumented with a variety of sensors, including fiber-optic micro-strain sensors, temperature monitoring, permanent geophones and accelerometers. All monitoring boreholes are either sealed with packers or cemented, and only the stimulation boreholes allow for outflow. During a period of several weeks, we were able to seal the two stimulation boreholes and allow the reservoir to approach ambient pressure conditions (more than 3 MPa at the wellhead) while we monitored the response of the reservoir. The pressure buildup shows not only in the pressure data, but also as stress changes in the reservoir. During a depressurization phase, we quickly opened one borehole and subsequently performed time-lapse single-hole Ground Penetrating Radar (GPR) measurements. At a second depressurization phase, we continued the GPR measurements while opening the second borehole in a controlled manner. The changes in strain, pressure and GPR reflectivity illuminate the response of the reservoir when moving from ambient to atmospheric pressure at the wellhead, and reveal processes such as wellbore storage, pore-pressure variations and ultimately permeability changes in the reservoir.

How to cite: Shakas, A., Gholizadeh, N., Hertrich, M., Wenning, Q., Maurer, H., Brixel, B., Zappone, A., Rinaldi, A., Obermann, A., Ma, X., Kaestli, P., Linwood, P., Hochreutener, R., Wiemer, S., and Giardini, D.: The response of a fractured crystalline reservoir to natural pressure buildup: Experiment results from the Bedretto Lab, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10324, https://doi.org/10.5194/egusphere-egu21-10324, 2021.

EGU21-361 | vPICO presentations | ERE6.3

FSAT - An Open-Source Fracture Surface Analysis Toolbox

Thomas Heinze, Sascha Frank, and Stefan Wohnlich

Fracture morphology influences various physical processes within a fracture, such as fluid flow, contaminant, and heat transport as well as mechanical shearing. Through the increasing availability of affordable high-precision scanning technology of open surfaces, drill cores, and broken rock samples, digital rock surfaces are easy to obtain and become a common tool to study hydraulic and mechanical processes inside fractures. Through statistical fracture generation and 3D printing technology, even custom-made fracture surfaces have been applied in numerous studies.

However, the complexity to describe and quantify fracture surface morphology is a major obstacle in evaluating and comparing results from laboratory and numerical experiments across studies and rock samples. While many so-called roughness parameters exist, there is no single parameter representing all features of a fracture surface. Only through a combination of parameters, which often is problem depending, a fracture surface can be suitably characterized to enable reproducibility of experiments and analysis across samples and studies. The effort of calculating various parameters is impeding scientists to sufficiently and quantitatively describe fracture surfaces.

We introduce an open-source MATLAB toolbox that allows the determination of over 25 different roughness parameters for height profiles as well as full 3D fracture surfaces. The selection of parameters includes statistical parameters, amplitude and spatial metrics, joint roughness coefficients, and fractal parameters. Variation of those parameters across as fracture surface as well as anisotropy is also calculated. For three-dimensional profiles, also surface measures are determined. If the top and bottom surfaces of a fracture are provided, even an estimated aperture distribution can be obtained, which is analyzed as well as provided for subsequent calculations, e.g., regarding the flow field. Further, the toolbox includes pre-processing routines for digital fracture surfaces of different sizes, shapes, and orientations. The toolbox is validated with standard profiles and synthetically generated fractures with known characteristics.

The toolbox massively simplifies the quantitative description of fracture surfaces, unifies the methodology of determining roughness parameters, and allows an easy generation of digital fractures with known characteristics. On the other hand, the toolbox enables easy customization for advanced users with specific demands. The toolbox consists of well-documented MATLAB scripts and functions that require a minimum of user-defined metadata. Extensive examples are also provided. The source code is freely available for download at https://gitlab.com/thomhGeoCode/fsat

How to cite: Heinze, T., Frank, S., and Wohnlich, S.: FSAT - An Open-Source Fracture Surface Analysis Toolbox, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-361, https://doi.org/10.5194/egusphere-egu21-361, 2021.

EGU21-7687 | vPICO presentations | ERE6.3

Two-Phase Flow in Rough Fractures – Insights from 3D-Printed Fractures

Tomos Phillips, Jeroen Van Stappen, Tom Bultreys, Stefanie Van Offenwert, Arjen Mascini, Shan Wang, Veerle Cnudde, and Andreas Busch

Fractures can provide principal fluid flow pathways in the Earth’s crust, making them a critical feature influencing subsurface geoenergy applications, such as the storage of anthropogenic waste, emissions or energy. In such scenarios, fluid-conductive fault and fracture networks are synonymous with two-phase flow, due to the injection of an additional fluid (e.g. CO2) into an already saturated (e.g. brine) system. Predicting and modelling the resulting (partly-)immiscible fluid-fluid interactions, and the nature of fluid flow, on the field-scale, requires an understanding of the constitutive relationships (e.g. relative permeability and capillary pressure) governing fluid flow on the single-fracture scale. In addition to capillary and viscous forces, fracture relative permeability is influenced by aperture heterogeneity, arising from surface roughness. The degree to which surface roughness controls relative permeability behaviour in fractures remains unclear. As all fractures display roughness to various degrees, furthering our understanding of two-phase flow in fractures benefits from a systematic investigation into the impact of roughness on flow properties. To this end, we performed co-injection experiments on two 3D-printed (polymeric resin) fractures with different controlled and quantified surface roughness distributions (Joint Roughness Coefficients of 5 & 7). Brine and decane were simultaneously injected at a series of incrementally decreasing brine fractional flow rates (1, 0.75, 0.5, 0.25, and 0), at low total volumetric flow rates (0.015 mL/min). Steady-state fluid occupancy patterns, preferential flow pathways and overall fluid saturations in each fracture were imaged and compared using an environmental laboratory-based μ-CT scanner with a 5.8 μm voxel size (EMCT; Ghent University Centre for X-ray Computed Tomography). Experimental results highlight the importance of roughness on the relative permeability behaviour of fractures, which is, for example, a principal control on leakage rates from geological stores.

How to cite: Phillips, T., Van Stappen, J., Bultreys, T., Van Offenwert, S., Mascini, A., Wang, S., Cnudde, V., and Busch, A.: Two-Phase Flow in Rough Fractures – Insights from 3D-Printed Fractures, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7687, https://doi.org/10.5194/egusphere-egu21-7687, 2021.

EGU21-16156 | vPICO presentations | ERE6.3

An exploration of the rate-dependent rupture of granites in compression and tension

Jackie E. Kendrick, Anthony Lamur, Julien Mouli-Castillo, Andrew Fraser-Harris, Alexander Lightbody, Andrew Bell, Katriona Edlmann, Christopher McDermott, and Zoe Shipton

The rupture of geomaterials is integral to multiple areas of geoscience and engineering, and is of particular importance to subsurface engineering projects that address decarbonisation, such as geothermal energy extraction and carbon capture and storage. Laboratory experimentation has led to the development of numerous, elegant micro-mechanical solutions that detail the accumulation of damage during deformation. Yet few studies have constrained the impact of deformation rate (which spans 10’s of orders of magnitude in nature and during subsurface stimulation) on material strength, rupture architecture and associated geophysical signals.

Here, we perform a suite of uniaxial compressive strength (UCS) and Brazilian disc tests with acoustic emission monitoring at 4 deformation rates (0.0004, 0.004, 0.04 and 0.4 mms-1) using a dense (1% porosity), low permeability (7x10-19 m2 at 10 MPa effective pressure) medium-fine grained monzogranite. Rates chosen equate to strain rates (for UCS) and diametric equivalent strain rates (Brazil tests) span 10-5 to 10-1, encompassing and expanding upon standard conditions for reporting of material strength. We find that materials undergo apparent strengthening under increasing deformation rate in both compression and tension. UCS is increased by ~45 % and Brazilian tensile strength by ~35 % across the rates tested. Young’s Modulus also shows an apparent increase of ~17 % across the rates tested. In UCS, increasing rate results in increasingly localised rupture and increasingly efficient grain size reduction along the fracture plane, suggesting that the rate of rupture impacts development of permeable pathways and hence fracture conductivity in deformed media.

Acoustic emission monitoring shows that ruptures developed in compression and tension follow different characteristic rates of acceleration, driven by the initiation, propagation and coalescence of fractures which differs under the two regimes. Moreover, b-value, calculated for the frequency-amplitude distribution of AEs is shown to be higher in tension than in compression. As a function of rate in both compression and tension, we find a higher prevalence of higher energy AE events with increasing deformation rates, which also serves to reduce b-value. This demonstrates that the predictability of failure events is dependent on stress regime (tensile/ compressive) and deformation rate, which impacts our ability to accurately forecast behaviour; however monitoring and predictive strategies largely fail to account for these controls. One of the most robust strategies for monitoring changes in material response to deformation may thus be tracking b-value with fixed sampling windows. A better understanding of the signals that accompany rate-dependent deformation will aid in the interpretation of seismicity both in natural phenomena and during geoenergy applications.

How to cite: Kendrick, J. E., Lamur, A., Mouli-Castillo, J., Fraser-Harris, A., Lightbody, A., Bell, A., Edlmann, K., McDermott, C., and Shipton, Z.: An exploration of the rate-dependent rupture of granites in compression and tension, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16156, https://doi.org/10.5194/egusphere-egu21-16156, 2021.

EGU21-13759 | vPICO presentations | ERE6.3

Permeability evolution during carbon mineralization in peridotite: an experimental determination of chemo-mechanical feedbacks

Catalina Sanchez Roa, Jacob Tielke, Christine McCarthy, Peter Kelemen, Soyoung Choi, James Andrew Leong, Marc Spiegelman, Owen Evans, and Alissa Park

Carbon Capture and Storage (CCS) aims to gather and store atmospheric CO2, often in geologic reservoirs, to mitigate the increasing atmospheric CO2 concentrations that lead to climate change. While the majority of CCS projects to date focus on structurally trapping CO2 in gaseous form in porous sedimentary rocks, carbon mineralization approaches storage from a much more secure perspective by storing CO2 as a solid carbonate mineral phase.

 

During the carbon mineralization process, interactions between the host rock and the fluids flowing through the rock’s permeable pathways exert a primary control on the evolution of permeability of the system. Precipitation of mineral phases within the fracture network can significantly reduce the permeability of the overall system (clogging), whereas mineral dissolution and volume positive mineral reactions (leading to cracking) can enhance permeability. The coupling between these competing processes dictates reservoir permeability and thus the long-term storage capacity and lifetime of CO2 storage reservoirs. Experimental studies are therefore vital to understand the chemo-mechanical controls on dissolution, precipitation, and carbonation-induced cracking, as well as to quantify their effect on the permeability of the system.

 

In this study, we perform experiments using a new AutoLab triaxial deformation apparatus equipped with independently servo-controlled axial load, confining, and fluid pressures. Samples are prepared via cold press from Twin Sisters peridotite powdered to a mean particle size of 94 µm. Experimental conditions are set to reproduce shallow crust conditions at viable injection depths and are controlled at a confining pressure of 20 MPa and fluid pressures of 10 MPa. Experimental temperatures range from 20 to 150 °C. Pore fluids are mixed in a joint mixing vessel using deionized water and sodium bicarbonate forming a solution of 0.6 M concentration. The solution is then pressurized using CO2 (99.9% purity) to a pressure of 3.5 MPa serving both as a vehicle for CO2 transport and as pH buffer. Permeability, ultrasonic wave velocities, axial strain, pH and fluid composition are monitored during these flow-through experiments. 

 

Preliminary results relate progress of the mineral carbonation reaction through the sample with a systematic decrease in permeability and an associated increase in P wave velocity. The results of this experimental study will be used to constrain the most favourable conditions for CO2 storage in a solid form, which is fundamental to the upscaling of carbon mineralization as an innovative, efficient and safe method for CO2 storage.

How to cite: Sanchez Roa, C., Tielke, J., McCarthy, C., Kelemen, P., Choi, S., Leong, J. A., Spiegelman, M., Evans, O., and Park, A.: Permeability evolution during carbon mineralization in peridotite: an experimental determination of chemo-mechanical feedbacks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13759, https://doi.org/10.5194/egusphere-egu21-13759, 2021.

EGU21-12764 | vPICO presentations | ERE6.3 | Highlight

Frictional properties of a faulted shale gas play: implications for induced seismicity 

Michael John Allen, Tom Kettlety, Daniel R Faulkner, J. Michael Kendall, and Nicola De Paola

Injecting fluids into the subsurface is necessary for a number of industries to facilitate the energy transition (e.g., geothermal, geologic CO2 sequestration or hydrogen storage). One of the biggest challenges is that fluid injection induces seismicity, which can lead to damaging events. It is currently not possible to predict the exact nature of seismicity that will occur due to fluid injection prior to operations.

Using laboratory friction experiments and in-situ microseismic analyses, we investigate the role frictional behaviour may have on the rate and magnitude of induced seismicity. This study focuses on the Horn River Basin shale gas play (British Columbia, Canada), where hydraulic fracturing activity has resulted in felt induced seismicity. Microseismic data from this field highlights fault planes that cut across the stratigraphy, including overburden and reservoir shales of varying mineralogy and underburden dolomites.

Our experimental friction results on samples recovered from core at reservoir depths show that both the frictional strength and stability vary considerably across the different lithologies; transitioning from very velocity-strengthening with friction coefficients of 0.3 – 0.4 in the overburden shales to more velocity-weakening and friction coefficients of 0.55 – 0.7 in the reservoir shales and an analogue of the underburden dolomite.

Spatial clustering analysis of the microseismicity allowed us to discriminate the operationally induced fracturing from fault reactivation events. We then examined the variations in the seismic b-value of the event magnitude-frequency distribution. These events were further differentiated by depth, separating them into their lithological horizons. The results show, for both fracturing and faulting events, higher seismic b-values of 1.4 – 1.5 occur in the overburden shales, which then decrease into the upper reservoir shales to 0.8 – 1.1, and then increase into the lower reservoir shales and underburden dolomite to 1.1 – 1.4. These trends correlate well with the laboratory measurements of frictional a-b values that define the degree of velocity-strengthening to velocity-weakening in the different gouges across the same lithological units.

These results suggest that knowledge of the frictional behaviour of the subsurface prior to operations, derived from mineralogical compositions and laboratory testing on cored material, may help improve our understanding of the potential rate and magnitude of induced seismicity that may occur due to subsurface fluid injection.

How to cite: Allen, M. J., Kettlety, T., Faulkner, D. R., Kendall, J. M., and De Paola, N.: Frictional properties of a faulted shale gas play: implications for induced seismicity , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12764, https://doi.org/10.5194/egusphere-egu21-12764, 2021.

EGU21-12187 | vPICO presentations | ERE6.3

Long-term evolution of fracture permeability in slate as potential target reservoirs for Enhanced Geothermal Systems (EGS)

Chaojie Cheng, Johannes Herrmann, Erik Rybacki, and Harald Milsch

The long-term sustainability of fractures in Variscan metamorphic rocks will determine whether it is reasonable to utilize such formations as potential unconventional EGS reservoirs. During long lasting fluid flow within fractures, dissolution, precipitation, and chemical reactions between the fluid and the rock matrix may alter the flow pathway structure and flow properties. Within the framework of the European Union's Horizon 2020 initiative "MEET (Multi-Sites EGS Demonstration)", we performed long-term fracture permeability experiments on saw-cut slate samples from the Hahnenklee drill site, Harz Mountains, Germany, under constant pressure and temperature conditions. Two experiments were performed using deionized water as pore fluid with intermittent flow for more than one month at 10 MPa confining pressure and 1 MPa pore pressure. Three sequential investigations were performed, including (1) an initial continuous flow tests at room temperature, (2) temperature cycles between room temperature and up to 70 °C or 90 °C, and (3) measurement of the time-dependent permeability evolution at 70 °C or 90 °C. During stage (3), the effluents were sampled in time intervals of 6 days and analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). The results show that (1) sample permeability first continuously decreases, but progressively converges within about three days, (2) increasing temperature leads to an additional permeability decline that is irreversible, and (3) the time-dependent permeability reduction is much more pronounced at 90 °C in comparison to that at 70 °C. The effluents are enriched with Na, Fe, K, Ca, Si, where the Na concentration is always an order of magnitude higher than the others. Except for Si, concentrations are progressively decreasing with time. During the entire experimental period, sample permeability was reduced by approximately 90% at 90 °C and 60% at 70 °C compared to their initial values. In contrast, both samples showed a negligible permeability decline with time at room temperature after cooling. Our results demonstrate that thermally-enhanced fluid-rock interactions lead to a permanent and at least partial closure of fracture aperture, which is unfavorable for geothermal exploitation. However, the degree of permeability reduction may strongly depend on initial fracture roughness, which remains to be investigated.

How to cite: Cheng, C., Herrmann, J., Rybacki, E., and Milsch, H.: Long-term evolution of fracture permeability in slate as potential target reservoirs for Enhanced Geothermal Systems (EGS), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12187, https://doi.org/10.5194/egusphere-egu21-12187, 2021.

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