The SMILE network, part of the Marie Sklodowska-Curie doctoral network funded by the Horizon Europe (2021-2027) program, undertakes an innovative role in addressing geo-energy project challenges while promoting net-zero greenhouse gas emissions in line with global sustainability goals.

A segment of the SMILE network is dedicated to addressing the issue of ground deformation analysis. This research aims to develop a software tool that capitalizes on Global Navigation Satellite System (GNSS) data, coupled with Synthetic Aperture Radar (SAR) inputs and ground modeling information. This abstract outlines the methodological framework for the anticipated software development.

In the initial phase, we aim to integrate the high temporal resolution GNSS data with the high spatial resolution of SAR data. The goal of this process is to combine the advantages of both data types while minimizing their limitations. SAR provides extensive spatial detail but has limited temporal frequency and directional sensitivity. On the other hand, GNSS data provides comprehensive three-dimensional vectors with high temporal frequency, but spatially limited to the points where GNSS stations are located.

Merging the displacement measurements from GNSS and SAR requires temporal synchronization and the reconciliation of their different displacement vectors: GNSS captures vertical, east, and north components, and SAR measures in the line-of-sight direction. The optimal joint operation for this task is proposed through a Kalman filter. Due to the complexity of building a joint filter, the proposed method seeks to first analyze by considering the projected displacements only in the vertical direction. In this case, the measure in the line-of-sight of the SAR satellite will be projected in the vertical direction.

The next phase will focus on an innovative approach to enhance the covariance matrix within the Kalman filter algorithm. Instead of using a homogeneous and isotropic constant covariance in time, this enhancement strategy will harness observed data as input. Primarily, it will smooth the covariance evolution in time, exploiting past observations; this may improve the stability of the outcomes. The method under development proposes to improve the covariance modeling further by enabling the consideration of anisotropic and non-homogeneous scenarios. Finally, the proposed method aims to integrate the monitoring data into Thermo-Hydro-Mechanical (THM) modeling.

The proposed expansion is expected to bring significant advancements in ground deformation analysis, improving its resolution and precision. The tool will integrate GNSS and SAR datasets into a comprehensive ground deformation analysis suitable for geomatics applications within geo-energy projects.

How to cite: Aponte, O., Gatti, A., Realini, E., Barzaghi, R., and Sansò, F.: An Integrated GNSS-SAR Approach to Improve Ground Deformation Analysis in the Field of Geo-energies: activities planned within the SMILE project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1896, https://doi.org/10.5194/egusphere-egu24-1896, 2024.

PSI Technique remains a powerful remote sensing method in terms of ground deformation monitoring, which makes it useful for monitoring geo-energy projects such as geothermal and CO2 sequestration where movement is always detected. The monitoring is a crucial supporting component to ensure the smooth progress of geo-energy development. However, PSI Technique still faces some problems that affects the accuracy of the detection. This can be caused by data and related to the terrain of the study areas, such as vegetation, buildings, and the direction of the ground deformation. The goal is to counteract this is by combining multiple sensor images, both low resolution and high resolution. These can be obtained from the wide range of satellites available today such as Sentinel-1, TerraSAR, COSMO-SKYMED, and NISAR. This technique is supposed to increase the temporal sampling for a more comprehensive time series, redundancy to improve accuracy and robustness of PSI analysis, wider coverage by exploiting at each site the data that offers best performances. Aside from the expected improvement, some challenges in developing this technique will be presented. Most of the challenges are due to the difference in satellites’ characteristics, such as resolution, pixel spacing, wavelength, and geometry. The technique is planned to be applied on several study areas. The purpose of this is to study the effects of different terrain characteristics on the re-sampling process, tuning processes, and the result of the processing. One of the study areas will serve as the benchmark of the research.

How to cite: Ramlie, M. C., Olea-Encina, P., Crosetto, M., and Monserrat, O.: Improving PSI Capabilities on Ground Deformation Monitoring for The Application of Geo-Energy Projects. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6245, https://doi.org/10.5194/egusphere-egu24-6245, 2024.

2023 was claimed as the beginning of the “Global Boiling Era”. For this reason, geo-energies are key to provide a green and clean future. Geothermal energy, and geologic carbon injection/storage are the main types of geo-energies. Both have in common the underground fluid movement and the consequent ground motion dynamics.

One of the main techniques for analyzing ground motion is Persistent Scattered Interferometry (PSI), which allows us to estimate ground deformation over time from radar satellite data. PSI techniques calculate the temporal displacement in the so-called persistent scatterers by filtering the data based on amplitude value. Generally, the main cause for amplitude variability is the change in the surface properties over time, primarily due to changes in environmental factors (land cover/land use, vegetation dynamics, temporal water presence, or soil moisture). The main concern with these changes is that they may result in phase shifts, which could be misinterpreted as range displacements.

Improving the understanding of the environmental factors could improve the understanding of ground deformation over time. Therefore, environmental factors analysis and PSI can be integrated seamlessly into a workflow since the launch of the Copernicus Programme, combining Sentinel-1 and Sentinel-2 data. The goal of this research is to explore the relationship between environmental variables and amplitude values. This research is framed in the MultidiSciplinary and MultIscale approach for assessing coupLed processes induced by geo-Energies (SMILE) Project. The study site is the Illinois Basin – Decatur Project (IBDP), which is a carbon dioxide injection and storage located in the United States. IBDP is in the north part of Decatur city, the vegetation is mainly woodland and prairie; with a humid subtropical climate, with an annual precipitation over 1000 mm.

The analysis focuses on three areas near IBDP: wetland area, crop area, and woodland area. Performing a spatio-temporal analysis of the vegetation index (NDVI), soil moisture index (NDWI), and temporal water presence (NDWI) obtained from Sentinel-2 data between 2015 to 2023 and comparing these datasets with the amplitude time series from Sentinel-1 imagery for the same period. The results show that the woodland area has a high mean amplitude value with low dispersion; the wetland area has a low mean amplitude value with high dispersion; and the crop area has a medium mean amplitude value with medium dispersion.

The vegetation index for the woodland area has 7 month per year values over 0,4, showing a presence of high photosynthetic activity, which can be related to the low value of dispersion amplitude; while the wetland area only 3 months per year has a value over 0,4, that can be source of the high dispersion amplitude. While the crop area is 6 months over the threshold. The results of the analysis performed showed that the use of environmental indices can help in the interpretation of the dispersion amplitude in the PSI analysis. The next step is to consider more environmental variables such as snow cover, land cover/land use, or temperature in the analysis of amplitude, as well as consider different polarizations, among others.

How to cite: Olea-Encina, P., Ramlie, M. C., Monserrat, O., and Crosetto, M.: Relationship between Environmental Factors and Radar Amplitude: Illinois Basin – Decatur Project case study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6264, https://doi.org/10.5194/egusphere-egu24-6264, 2024.

Long-term seismic monitoring arrays are often deployed to shallow boreholes to reduce the seismic noise. We investigate noise level decay in shallow boreholes. A large number of publicly available data with such deployment is available at the seismic monitoring array near the town of Groningen, which allows also characterization of the seismic noise decay in shallow boreholes in urban environments. We study noise distribution at 4 sites from this array. Each site includes 5 receivers deployed in shallow vertical boreholes with 50 meters intervals between the surface and 200 m depth. We show there is no difference between noise levels during the summer and winter at the borehole instruments. However, we observe diurnal variation at all depth levels. We also show there are higher noise levels throughout weekdays and lower during weekends and state holidays. These changes are not only observed at the surface but also at the deepest receivers. This implies that the dominant source of this noise is anthropogenic and it penetrates to depths of 200 meters even at frequencies exceeding 5 Hz. This observation is contradicting the common assumption that the seismic noise consists of the surface waves.

How to cite: Kalinichenko, O., Eisner, L., Stanek, F., Waheed, U., Hanafy, S., and Jechumtalova, Z.: Decay of seismic noise at shallow boreholes: Observations from Groningen., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7497, https://doi.org/10.5194/egusphere-egu24-7497, 2024.

Subsurface uncertainty is large because we have limited access to it. Reducing uncertainty is important for geo-energies in order to increase the reliability of the simulation results used to define safe operation conditions. In particular, subsurface uncertainty can be reduced by analyzing ground deformation. A clear example of this is the CO₂ storage project at In Salah, Algeria, where a double lobe ground deformation shape revealed the presence of a vertical fault zone at depth. Here, we propose a workflow to reduce subsurface uncertainty by inferring the subsurface characteristics from ground deformation measurements. As a foundation step of the workflow, we train a supervised neural network-based regression approach for predicting ground deformation caused by reservoir pressurization due to fluid injection. To train the neural network, we use a recently developed analytical solution to assess ground displacement in response to pressurization of a reservoir that is intersected by a permeable or an impermeable fault (https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4503451). The instantaneous solution provided by the analytical solution allows us to generate a large dataset to train the neural network. We have varied eleven variables, including fault and reservoir geometry and mechanical properties. Simultaneously, a simplified parametric space analysis is also performed. Results show that the reservoir thickness, Biot´s coefficient, and the pore pressure buildup impact the displacement the most. This study highlights that an appropriately trained neural network can effectively predict the ground deformation and give insights into the corresponding subsurface characteristics.

How to cite: Guo, T., Wu, H., and Vilarrasa, V.: A Neural Network to Reduce Subsurface Uncertainty Based on Ground Deformation Measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5492, https://doi.org/10.5194/egusphere-egu24-5492, 2024.

Injection of dense-phase CO2 in a saline sandstone aquifer involves several processes which ideally work together to ensure effective long-term storage. The main processes are flow of free-phase CO2 (controlled by viscous and gravity forces), residual trapping at the pore scale, structural trapping at the scale of geological heterogeneities and dissolution in the aqueous phase.  Assessment of possible lateral and vertical migration along high-permeability layers or faults and fractures will also require stress-sensitive flow models which consider the phase behaviour of CO2, and the associated coupled thermal-hydraulic-mechanical-chemical processes.
Many insights into these complex processes can be obtained by analysis of the time-lapse seismic data at Sleipner CO2 storage project in Norway, in conjunction with findings derived from the quantitative and qualitative uncertainty analysis of the medium-scale flow experiments at the Mont Terri Rock Laboratory (Switzerland), involving periodic injections over long-term (CO2LPIE). The insights at Sleipner include the effects of internal shale layers and shale breaks in controlling the actual multi-layer CO2 distributions, the likely contribution of different of trapping mechanisms and the effectiveness of the overlying caprock. Another set of insights gained from these data are estimates of the effective use of the pore space at different length scales. The seismic imaging datasets can be used to show that at the scale of whole storage unit the overall storage efficiency is in the range of 2-5%, with the result depending very much on how the storage volume is defined. When the effects of areal and vertical sweep efficiency are considered, the fraction of the pore space occupied by CO2 rises to around 40-50%.
We illustrate these multi-scale processes using seismic data, analytical analysis, example flow models and 3D/4D visualization. Use of Invasion Percolation (IP) flow models is contrasted with multiphase (finite difference) flow simulators. With this approach CO2 migration problems will be addressed, as well as various open-source research codes will be used to develop enhancements for handling fluid mixing between hydrocarbon and CO2 phases in brine-saturated media. Moreover, coupled thermal modelling is found to be important at this site due to significant temperature changes as the CO2 plume expands and rises within the formation. Next to classic PC screen display, we empower the visualization by using the extended reality (XR) platform for geoscience, BaselineZ. This allows for true 3D (holographic) display in virtual reality (VR) as well as remote and interactive collaboration around the Sleipner dataset and thus leads to new insights. 

How to cite: Yun, T. K., Macut, M., Schulze, K., Ringrose, P., and Berg, C. F.: CO2 storage in saline aquifers: multi-scale processes visualized using the Sleipner case, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8100, https://doi.org/10.5194/egusphere-egu24-8100, 2024.

Deep geological repositories rely on a natural geological barrier with a low permeability to ensure radioactive waste containment and prevent radionuclide transport into the biosphere. For the Swiss repository concept, the Opalinus Clay formation is considered as the natural geological barrier. After high-level radioactive waste are disposed of in a repository within the host-rock, corrosion of metal containers in anaerobic conditions can result in the release of hydrogen. Due to the low-permeability of the host-rock, elevated gas pressures are expected. If the gas pressure exceeds the minimum principal stress, fracturing of the rock could occur. It is therefore important to assess the possible impacts of this process on the integrity of the repository such as a possible increase of the permeability of the host formation.

Production of hydrogen is anticipated to span more than 100,000 years, and understanding how gas transport occurs in a low-permeable host-rock is therefore an important aspect for the long-term safety of the repository. Gas transport can generally be subdivided in four different mechanisms: (1) advective-diffusive flow, (2) visco-capillary two-phase flow, (3) dilatancy-controlled gas flow and (4) gas transport along macroscopic tensile fractures. Gas flow rate and the microstructure of the host rock largely control the dominating gas transport mechanism, but the exact variables determining the process are poorly quantified.

The GT (Gas Transport) experiment at Mont Terri was designed to study the pressure and deformation effects after injecting gas into the Opalinus Clay. Helium was injected with increasing pressure increments until a gas breakthrough was observed. The borehole into which the helium was injected was surrounded by eight observation boreholes providing deformation and pore pressure observations.The results of the experiment have been used to create a coupled hydro-mechanical model using TOUGH-FLAC, which couples the multiphase flow and heat transport simulator TOUGH3 with the geomechanical simulator FLAC3D. The model uses the helium injection rates as input and computes the resulting pressure and deformation responses. By running models with different transport mechanisms (e.g. two-phase only, both two-phase and dilatancy, allowing fracture formation) and by comparing the pressure and deformation results with the observations, insight is gained into the dominant transport mechanisms in the Opalinus Clay. Preliminary results reveal a slow build-up of strain and a relatively small pressure drop after gas injection begins, suggesting that dilatancy-controlled gas flow occurred.

How to cite: Nuus, M., Rinaldi, A. P., Cuss, R., Sentis, M., Gisiger, J., Graupner, B., Magri, F., Bernier, F., and Jaeggi, D.: Modelling coupled hydro-mechanical processes of gas flow in the Opalinus Clay, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17949, https://doi.org/10.5194/egusphere-egu24-17949, 2024.

Within the context of CO₂ injection, understanding the properties of potential caprocks, particularly clay-rich ones such as Opalinus Clay and their potential evolution is crucial for safe and effective carbon capture and storage (CCS) initiatives. This study presents hydrogeochemical models developed to investigate interactions between groundwater, Opalinus Clay caprock and CO₂, focusing on chemical evolution under varying pCO₂ levels across different layers of the clay.

Utilizing a comprehensive dataset derived from CO₂ injection experiments conducted at the Mont Terri Rock Laboratory and published pore water chemistry of Opalinus Clay, hydrogeochemical models of a potential reservoir and caprock system were constructed employing PHREEQC and CHESS geochemical modeling softwares. These models were designed to simulate and comprehend the intricate processes governing groundwater-CO₂-rock interaction within the reservoir-caprock interface and through the stratified layers of Opalinus Clay.

The models aimed to elucidate the chemical evolution of the groundwater as it interacts with the Opalinus Clay under different pCO₂ conditions. By considering variations in pCO₂ levels representative of potential CCS scenarios, the simulations provided insights into the geochemical alterations occurring within the caprock and their implications for its integrity over time.

The findings of these hydrogeochemical models offer valuable insights into the potential consequences of CO₂ injection into reservoirs whose caprocks are formed of Opalinus Clay, informing risk assessment and mitigation strategies for CCS applications. Moreover, these constructed hydrogeochemical models not only serve as a crucial foundation for comprehending the intricate thermal-hydro-mechanical-chemical (THMC) coupling mechanisms within caprocks like Opalinus Clay but also contribute to a deeper understanding of the complex interplay between pore water chemistry, rock properties, and varying pCO₂ levels, essential for ensuring the long-term security and effectiveness of subsurface CO₂ storage.

How to cite: Koç, Ü., Corvisier, J., Bruel, D., and Blanco Martin, L.: Hydrogeochemical Modeling of Opalinus Clay: Insights from CO2 Injection Experiments at Mont Terri Rock Laboratory, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3952, https://doi.org/10.5194/egusphere-egu24-3952, 2024.

In the realm of harnessing geothermal energy, groundwater heat pumps exhibit superior thermal efficiency when compared to closed-loop geothermal heat pumps. However, the outlook for progress remains less than promising. A primary obstacle stems from the improper extraction of groundwater, which can disrupt the stress field in subsurface structures and potentially trigger land subsidence. This concern is particularly pronounced in unconsolidated soils found in coastal sedimentary plains, where the additional threat of severe flooding disasters looms. Furthermore, artificial pumping processes may give rise to coupled hydraulic phenomena, exemplified by the reverse water level fluctuations. This transient anomalous changes in hydraulic head occurs in adjacent aquifers during the initial stages of pumping from a confined aquifer, induced by strain propagation. The magnitude of the hydraulic head elevation varies from a few centimeters to several tens of centimeters, posing a challenge to the accurate interpretation of groundwater monitoring data for land subsidence prevention. Geothermal heat pump systems can also induce changes in the temperature and thermal strain of geological layers. Consequently, understanding how this strain-induced hydraulic head responds to temperature fluctuations becomes a research question. In our investigation, the hydraulic and mechanical responses of a three-layer aquifer system to groundwater pumping were assessed through thermoporoelastic numerical simulations. The simulated reverse hydraulic head changes align with field observations documented in the literature. The findings of this numerical investigation indicate that when we recharged the water into the ground, the initial head decrease is likely to occur in proximity to a recharge well within an unpumped clay layer. These deformation-induced head changes eventually dissipate following the hydraulic propagation of unsteady state drawdown from the pumped aquifer into adjacent layers. In the event of reverse water level fluctuation, it is shown that temperature has no obvious influence on the hydraulic variation, both the head variation and happening time. It is also suggested that the propagation of thermally induced strain is slower than that of hydraulically induced strain and the effect appears much later.

How to cite: Yue, L. and Aichi, M.: Numerical Investigation of Reverse Water Level Fluctuations under Non-Isothermal Conditions with a Fully Coupled Thermal-Hydro-Mechanical Model for Geothermal Heat Pump Systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5401, https://doi.org/10.5194/egusphere-egu24-5401, 2024.

In the context of geological CO₂ sequestration, understanding the complex interaction between reactive fluids and the rock matrix is pivotal in efficient and safe carbon storage. This paper presents a recently initiated research plan, spanning laboratory and pilot scale, covering two main scenarios: A) reactive reservoir rocks (e.g. basalt and peridotite), and B) claystone saline aquifers with sandstone reservoir rocks and claystone caprock. To investigate the specific effects of CO₂ exposure on rock properties, we propose a 1-2 year exposure experiment on intact rock core samples. The experiment will be conducted using a batch reactor system equipped with continuous pH monitoring and carefully controlled to replicate in situ salinity, pressure and temperature levels. Before, during and after exposure, samples will be analysed using CT scanning to detect changes in porosity, and mechanical and physical properties will be assessed before and after exposure. Preliminary characterisation of the cores prior to exposure to CO₂ will also be presented.

In parallel decameter scale experiments spanning many months of CO₂ injection are conducted at the Mont Terri underground rock laboratory in Switzerland. The experiments involve observing the injection of CO₂-saturated brine into a fault zone within Opalinus Claystone—an analogue caprock. This contributes to a more comprehensive understanding of fluid injection on fault reactivation, particularly within the context of leakage processes at shallow depths crucial to CO₂ storage security. Preliminary results on clay deformation in response to rapid increase of injection pressure will be presented.

This research plan aims to understand reactive processes in different geological contexts fundamental to carbon storage strategies. Operating at multiple scales - from laboratory to pilot scale analysis - our study aligns with the session's broader goal of advancing the understanding and predictive capabilities of coupled processes induced by geoenergy applications. By sharing preliminary results and fostering collaboration, we aspire to maximise the scientific results of our laboratory experiments and contribute to the scientific community's search for sustainable solutions in carbon storage strategies.

How to cite: Annan, P., Madonna, C., Rinaldi, A. P., and Zappone, A.: Multi-scale study on fluid-rock interaction in caprock and reservoir rocks for enhanced CO2 sequestration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18886, https://doi.org/10.5194/egusphere-egu24-18886, 2024.

The extraction of geothermal energy faces the hazard of H₂S, a highly toxic and strongly corrosive gas. H₂S exposure can lead to the failure of oilwell cement, decreased extraction efficiency, and even pose serious risks to operational personnels near the wellsite. High temperature is a prominent environmental feature in geothermal resource extraction. However, current research works primarily focus on the corrosion effects of H₂S on cement at moderate to low temperatures. This study utilizes Class G oilwell cement to conduct corrosion experiments of cement by H₂S under high temperature in a H₂S-rich reaction vessel. The impact of H₂S on the structure, chemical composition, and mechanical strength of oilwell cement is analyzed via SEM-EDS, XRD, nanoindentation tests, and unconfined compressive strength tests. The results indicate a reduction in compressive strength for cement samples corroded by H₂S. The surface nano-hardness and elastic modulus of cement samples decrease while the internal values of nano-hardness and elastic modulus significantly increase. Under the corrosion of H₂S, the structure of cement is characterized by a yellow and black surface layer and stratified cracks. The external surface of the cement exhibits a yellow color due to the formation of pyrite (FeS₂), while internally, pyrrhotite (FeS) and gypsum (CaSO₄^.2H₂O) are generated.

How to cite: Zhang, L., Yin, Y., Mei, K., Cheng, X., Wang, Y., and Wang, H.: Degradation pathways and mechanisms of oilwell cement exposed to H2S under high temperatures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2815, https://doi.org/10.5194/egusphere-egu24-2815, 2024.