Orals: Wed, 30 Apr | Room -2.31
Induced seismicity is likely a major obstacle in front of the widespread deployment of geoenergy applications, such as geothermal energy or geologic carbon storage (GCS), which are indispensable components of efforts to mitigate the climate change emergency. Induced earthquakes may jeopardize the integrity of subsurface structures and, if felt at the surface, negatively impact the public perception of geoenergy projects. Thus, the effective and safe use of the subsurface to provide clean and sustainable energy and reduce atmospheric carbon emissions needs to properly address the risks and hazards posed by induced seismicity. In this Outstanding Early Career Scientist Award Lecture of the ERE Division, I discuss some important topics of induced seismicity in low-carbon geoenergies. First, I explain the potential mechanisms of seismic events that are unexpectedly induced far away from and/or long after operations related to geothermal energy developments. Such seismic sequences have been found problematic because of partial loss of control over their management. In particular, thermal stress is key in reactivating distant faults from a fluid circulation doublet after several years of operation in hydraulically bounded and unbounded hot deep sedimentary aquifers. The observed delays can be explained by the relatively large characteristic time scales of thermal effects (small thermal diffusivity). In enhanced geothermal systems, a sequence of processes, which can be identified when explicitly including fractures in numerical models, may give rise to post-injection seismicity. The stabilizing effect of poroelastic stress generated during reservoir stimulation rapidly attenuates after stopping injection, while the injection overpressure gradually diffuses away, which could bring distant faults to slip conditions with time delays as long as several months. Interestingly, bleed-off, i.e., flow back to relieve wellbore pressure, as an industrial practice to prevent post-injection seismicity may not effectively work under certain conditions. This is because the stimulated fractures become progressively less responsive to hydraulic perturbations with distance from the wellbore. In the second part of my presentation, I discuss induced seismicity within GCS at the gigatonne scale. Analysis of data from the global, multiphysics database of induced seismicity underscores some similarities between large-scale GCS and massive wastewater disposal that led to a drastic rise in seismic activity in central and eastern US in the 2010s – not to negate fundamental differences between the two technologies. Although GCS at the megatonne scale has been extensively demonstrated, its scale-up could face elevated risk of induced seismicity. We have developed the open-source tool CO2BLOCKSEISM that employs simplified physics models for screening subsurface CO2 storage resources at regional scales constrained by the risk of induced seismicity. The tool’s application is shown within the Utsira storage unit in the North Sea. Induced seismicity draws a more restrictive and realistic limit to the storage resource use at regional than at single-site scales. I conclude that reliable methodologies for induced seismicity forecasting and mitigation should be developed in light of the underlying physics and continuous characterization of the subsurface during operations to safely unlock the huge potential of the subsurface for a timely approach toward climate targets.
How to cite: Rahimzadeh Kivi, I., Makhnenko, R., Min, K.-B., Rutqvist, J., Carrera, J., Krevor, S., and Vilarrasa, V.: Energy transition and the challenge of induced seismicity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13579, https://doi.org/10.5194/egusphere-egu25-13579, 2025.
In underground hydrogen storage, mixing between Hydrogen and cushion gas could present a problem to the recoverability of working gas and may be a controlling factor in subsurface reactions. The conventional modelling approach focuses mainly on diffusion as the primary mixing process, while little attention is paid to dispersive mixing. Using the finite element simulator COMSOL this work focuses on assessing the relative magnitude of transport between the two processes, including diffusive processes such as thermodiffusion and surface diffusion. Molecular diffusion is shown to be the dominant segregative process, but still transports an order of magnitude less mass than mechanical dispersion. Necessary adjustments should be made when considering implementation of mixing processes in numerical models, with attention being given to the dispersion model and its reliance on a scale dependent dispersivity coupled with grid size.
How to cite: Marchbank, S., Molnar, I., Heinemann, N., and Wilkinson, M.: Hydrogen's Next Top Model: Exploring Processes and Practice in Hydrogen-Cushion Gas Mixing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10483, https://doi.org/10.5194/egusphere-egu25-10483, 2025.
Hydrogen storage within porous geological formations initiates the methanogenesis process, leading to the conversion of hydrogen into methane. Understanding and quantifying the impact of pore characteristics, including porosity, surface area, and interfacial area between liquid and gas phases on hydrogen conversion rates is crucial for evaluating both the risks of hydrogen loss during underground hydrogen storage and the potential benefits for efficient bio-methanation. This study explores the impact of surface area of reservoir rocks on methanogenic activity by employing various techniques including nitrogen physisorption, mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and X-ray micro-computed tomography (µCT). The research examines reservoir analogues for hydrogen storage, from the Cretaceous (Bentheimer Sandstone and Oberkirchner Sandstone) and Triassic periods (Red and Grey Weser Sandstone), varying from tight to permeable. The cell size of Methanothermococcus thermolithotrophicus ranges from 1 to 2 µm, suggesting that these archaea can access pores larger than this threshold. Microbial activity within the pore space of the reservoir rocks was assessed by monitoring pressure changes and gas compositions. Upon normalization of microbial activities on pore volume and interfacial area, the findings correlate with the specific surface area of accessible pores obtained from MICP, NMR, and SEM methods. These correlations emphasize the stimulating effect of surface area on microbial activity. The normalized activities demonstrate increments ranging from 0.19 to 0.44 mM/(h∙cm3∙cm2) as the specific surface area increases, varying depending on the method. Furthermore, a predictive model integrating pore volume, SSA, and interfacial area has been established to estimate reliable hydrogen conversion rates in porous media, crucial for assessing the economic viability of UHS and bio-methanation projects.
How to cite: Khajooie, S., Gaus, G., and Littke, R.: Experimental assessment of methanogenic activity in reservoir analogues for underground hydrogen storage: impact of pore volume, surface area, and gas-liquid interfacial area, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9430, https://doi.org/10.5194/egusphere-egu25-9430, 2025.
Underground hydrogen storage (UHS) in porous reservoir presents a promising solution for renewable energy storage; however, its safety and sustainability partly depend on its effects on the geomechanical stability and flow properties of reservoir rocks under injection-withdrawal cyclic operations. This study evaluates the effects of hydrogen exposure and pore pressure cycles including the rate and the number of cycles on reservoir sandstones. These experiments were carried out on two sandstones representing two different lithologies: Corsehill sandtone (clay rich), and Bentheimer sandtone (99% quartz). Rock plugs were exposed to hydrogen at 70°C and 18 MPa for 50 days, with nitrogen-exposed and unexposed samples used as controls to isolate hydrogen-specific effects. To evaluate impacts on geomechanical and flow properties, triaxial and flow tests were performed before and after each pore pressure cycle at in-situ reservoir stresses and temperatures relevant for reservoirs in the North Sea.
The geomechanical results revealed a progressive decrease in stiffness in Corsehill sandstones with increasing pressure cycles. This trend is more pronounced in hydrogen-exposed samples and samples undergoing slow pressure cycling. Specifically, the stiffness of Corsehill sandstone decreased by approximately 10% after 15 pore pressure cycles. In contrast, Bentheimer sandstone exhibited no substantial mechanical changes under cyclic loading, with the change being approximately 1%. Although gas-exposed samples showed higher stiffness compared to unexposed ones, highlighting a mechanical effect of gas exposure, no noticeable effect could be attributed to hydrogen exposure alone.
Flow tests results indicated a progressive decline in permeability for Corsehill sandstone with increasing cycles, with faster cycles causing a more pronounced reduction compared to slower cycles. In contrast, Bentheimer sandstone showed varying trends: unexposed samples experienced an increase in permeability with increasing cycles, while gas-exposed samples exhibited a reduction. Notably, Bentheimer sandstone displayed a greater reduction in permeability during slow cycles compared to fast cycles.
These findings show the critical role of lithology, hydrogen exposure, and cyclic loading in determining the geomechanical and flow behavior of reservoir rocks. The pronounced decrease in permeability and stiffness in Corsehill sandstone compared to the stability of Bentheimer sandstone highlights the need for detailed evaluations of the targeted reservoirs and injection strategy in UHS operations.
Keywords: Underground hydrogen storage, geomechanical parameters, permeability, cyclic loading, hydrogen exposure
How to cite: Saricam, I. H., Soustelle, V., Abedi, S., Hassanpouryouzband, A., and Edlmann, K.: Impact of Hydrogen Exposure and Pressure Cycles on the Geomechanical and Flow Properties of Corsehill and Bentheimer Sandstones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20260, https://doi.org/10.5194/egusphere-egu25-20260, 2025.
Underground Hydrogen Storage (UHS) in saline aquifers and depleted gas reservoirs is a promising approach for large-scale energy storage; however, several challenges, including geomechanical challenges, must be addressed before widespread implementation. Hydrogen/brine-reservoir rock interactions, combined with cyclic stress conditions from hydrogen storage and withdrawal, may affect the geomechanical properties of the reservoir rock and its surroundings. It is essential to comprehensively assess the potential impact of hydrogen/brine-rock interactions on the geomechanical integrity of reservoir rock. In this study, we used two types of sandstone: quartz-rich (Red Felser) and clay-rich (Yellow Felser). These sandstones were subjected to two different exposure conditions, namely dynamic and static exposure, at high pressure and temperature. The quartz-rich sandstone was used for dynamic exposure, while the clay-rich sandstone was used for static exposure. The dynamic exposure is conducted using a core flood test under 100 bar, 80°C, for two months, while the static exposure is performed in an autoclave under 150 bar, 100°C, for six months. After exposure, triaxial cyclic laboratory experiments were conducted on both exposed (hydrogen-brine) and non-exposed (brine-only) samples at different confining pressures (10, 20, and 30 MPa). Additionally, eight stress cycles were applied in the linear regime (below the brittle yield point) before loading the sample to failure. The frequency, amplitude, and stress conditions of the cycles were adjusted for each confining pressure based on the brittle yield point. The results from dynamic exposure (hydrogen/brine-Red Felser sandstone) indicate minor changes in final strength and total inelastic deformation. However, alterations in the failure envelope (internal friction angle and cohesion) were negligible, and no changes were observed in Young’s modulus. The results from static exposure (Yellow Felser sandstone) suggest that six months of exposure had no impact on the failure envelope, elastic properties, total inelastic deformation, and acoustic characteristics. Our findings indicate that the interaction between hydrogen/brine and clay-rich and quartz-rich sandstones has a negligible effect on their geomechanical properties.
How to cite: Naderloo, M., Hajibeygi, H., and Pluymakers, A.: Static and Dynamic Exposure of Sandstone to a Hydrogen-Brine System: Geomechanical Alterations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20757, https://doi.org/10.5194/egusphere-egu25-20757, 2025.
Underground hydrogen storage (UHS) and utilization have gained considerable attention over the past few decades as major alternatives for fossil fuels. However, bulk of the challenges associated with its implementation lie within the foundation. One of such challenges is the (bio)geochemical interaction of stored hydrogen with reservoir materials. In particular, microbially induced redox reactions can pose threats to hydrogen storage due to fast consumption and subsequent generation of other gases (H2S, CH4 etc.). Recent experimental studies have suggested a variable degree of hydrogen consumption through redox interactions, when optimum conditions for such thermodynamic interactions are met inside reservoirs. One of the most abundant redox-sensitive phases is iron (oxy)hydroxide that can readily be reduced in the presence of hydrogen or other reducing gases. In this study, we experimentally evaluate the potential of iron (oxy)hydroxides in the presence of ultrapure hydrogen under reservoir P-T conditions. Using high P-T anoxic batch reactions, we obtain the reduction rate of iron (oxy)hydroxide phases under variable pH2, water chemistry and water-mineral ratios. We find that higher valence reactive iron (oxy)hydroxide phases readily transform into more stable mixed valence phases such as magnetite, even at abiotic conditions and high pH2 (>50 bars). We compare the results with ambient P-T batch experiments and find similar observations. Only the concentration of dissolved Fe(II) would determine the phase transformation of Fe(III) oxyhydroxides, not ultrapure H2. This implies that stored hydrogen may not be consumed even if iron rich oxyhydroxide phases are abundantly present inside reservoirs. In an additional study, effect of pH and matrix carbonates were also evaluated. Dissolution of carbonates (e.g. calcite) release bicarbonate and increase the pH of the porewater, which in turn, may impede further reduction of Fe(III) (oxy)hydroxide phases. This is currently being investigated inside the high P-T batch reactor with externally controlled pH and variable temperatures. In summary, our results suggest that surface controlled non-redox reactions associated with reactive iron bearing phases may be more effective in determining the fate of injected hydrogen. These studies aim at expanding our fundamental knowledge pertaining to iron redox systematics in the subsurface and a successful implementation of UHS.
How to cite: Pathak, A., Clark, A., and Sharma, S.: Ironic behavior of iron bearing phases during Underground Hydrogen Storage ?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13768, https://doi.org/10.5194/egusphere-egu25-13768, 2025.
The transition to a greener economy requires scalable, reliable, and efficient energy storage solutions. Hydrogen (H2), a key component of future renewable energy systems, must be stored in gigaton-scale quantities to balance supply and demand globally. Underground hydrogen storage (UHS) in salt rock caverns is emerging as the most promising solution due to the exceptional properties of rock salt (halite), such as low permeability, self-healing capacity, and geochemical stability. However, significant scientific and technological challenges remain, requiring further study to ensure the safe and efficient deployment of this technology (Berrezueta et al., 2024).
Among these challenges, the geomechanical and geochemical evolution of rock salt during cyclic H2 injection and extraction requires further knowledge to address potential integrity problems of the reservoir. Key uncertainties arise from the complex interplay of heterogeneous mineralogy, variable brine compositions, and the dynamic temperature and pressure conditions within the reservoir. Addressing these uncertainties begins with the development of a robust laboratory testing protocol to simulate and analyze the interaction of hydrogen within rock salt under reservoir-like conditions.
This study presents experimental data from an autoclave setup designed to replicate reservoir conditions of pressure and temperature. Samples of the Eocene Barbastro Fm. (Southern Pyrenees) were obtained from a deep borehole drilled in a salt structure considered for hydrogen storage. The experiments using pure halite samples and halite with various impurities provide insights into the reactivity of non-halite phases and their impact on the properties of the rock salt. The findings contribute to addressing critical knowledge gaps and improving the safety and reliability of underground hydrogen storage in salt caverns. By advancing our understanding of the processes governing UHS in salt formations, this research supports the development of robust, science-based solutions for the global energy transition.
This work is funded by the Project UES365 of the Convocatoria Misiones-CDTI (Spain).
References:
Berrezueta, E.; Kovács, T.; Herrera-Franco, G.; Caicedo-Potosí, J.; Jaya-Montalvo, M.; Ordóñez-Casado, B.; Carrión-Mero, P.; Carneiro, J. Laboratory Studies on Underground H2 Storage: Bibliometric Analysis and Review of Current Knowledge. Appl. Sci. 2024, 14, 11286. https://doi.org/10.3390/app142311286
How to cite: Kovács, T., Mediato, J., Ordóñez, B., Garcia, N., Pueyo, E., Sanchez Guzman, J., Gracia, J., and Berrezueta, E.: Preliminary Laboratory Studies on Hydrogen Storage in a Salt Cavern of the Eocene Barbastro Formation, Southern Pyrenees, Spain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6528, https://doi.org/10.5194/egusphere-egu25-6528, 2025.
How to cite: Zargar, A. R., Menke, H., Maes, J., and Boon, M.: Visualization and characterization of spreading and mixing at the pore-scale relevant for Geological Carbon Sequestration and Underground Hydrogen Storage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8229, https://doi.org/10.5194/egusphere-egu25-8229, 2025.
Naturally occurring CO2 reservoirs across the USA are critical natural analogues of long-term CO2 storage in the subsurface over geological timescales and provide valuable insights into the fate of CO2 in the subsurface (Fig. 1). Previous measurements of CO2 to 3He ratios within gas samples obtained from six natural CO2 reservoirs, located in the United States, show that the CO2 originated from magmatic degassing[1]. Variation in CO2/3He across each reservoir suggests that significant amounts of CO2, equivalent to hundreds of megatonnes, have been stored by solubility trapping[2]. However, the key question of whether CO2 dissolution occurred during emplacement, or by diffusion and convection over geological time remains unanswered.
Here we present the results of integrating geochemical measurements with reservoir modelling to quantify both the mass of CO2 emplaced and the proportion dissolved within each of the six natural CO2 reservoirs. Given the magmatic origin of the CO2, we use the known age dates of associated igneous rocks to estimate the timing of CO2 emplacement in each reservoir. Using these emplacement ages, we show there is no relationship between the duration of CO2 storage and the proportion of solubility trapping that has occurred. This shows that the proportion of dissolved CO2 does not significantly increase over geological timescales.
Further, we find that the original mass of CO2 does not influence the proportion of CO2 that is solubility trapped. We also find that rock properties, the present-day pressure, temperature and salinity of the reservoirs do not control the fraction of CO2 dissolved, suggesting that the circumstances of CO2 migration and filling are more critical. Our conclusion is supported by reservoir simulation at our exemplar site, Sheep Mountain in Colorado (Fig. 1), where we show that CO2 dissolution after structural trapping is a minor contribution to amount of CO2 residually trapped.
Our findings support a model where the majority of solubility trapping occurs on CO2 injection and during the migration of the CO2 plume. This indicates that the proportion of solubility trapping after the CO2 has become structurally trapped is comparatively minor. Therefore, in engineered CO2 stores, considerable amounts of injected CO2 can be solubility trapped within CO2 injection and post-injection monitoring timescales.
References
[1] Gilfillan et al., 2008, Geochimica et Cosmochimica Acta, 72 (4), 1174-1198
[2] Gilfillan et al., 2009, Nature, 458 (7238), 614-618
Fig. 1 (a) Location map of the west and central United States, showing the location of the natural CO2 reservoirs investigated in this study. (b) Map of Four Corners area USA, showing the location of significant natural CO2 reservoirs, topographic elevation and Cenozoic-age igneous rocks. The CO2/3He ratio of samples from Bravo Dome, St Johns Dome, McElmo Dome, Sheep Mountain and McCallum Dome show a magmatic CO2 source.
How to cite: Leslie, R., Johnson, G., Holdsworth, C., Haszeldine, S., and Gilfillan, S.: Rapid Large-scale Trapping of CO2 via Dissolution in US Natural CO2 Reservoirs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18526, https://doi.org/10.5194/egusphere-egu25-18526, 2025.
The study explores the potential of repurposing decommissioned mine shafts and underground workings as lower reservoirs for pumped-storage hydropower systems (USPS). A comprehensive analysis was conducted to evaluate the challenges and opportunities associated with converting these infrastructures, focusing on key factors such as structural stability, water tightness, and economic feasibility.
The limitations of using horizontal corridor workings, particularly their lack of tightness, susceptibility to convergence, and high adaptation costs, were highlighted. Conversely, mine shafts emerged as more viable candidates due to their robust construction and potential for cost-effective adaptation. A scoring system was developed to assess the suitability of mine shafts and neighboring workings, incorporating criteria such as shaft dimensions, methane hazard, drainage capacity, and proximity to surface reservoir development sites.
Logical functions and mathematical formulas were applied to automate scoring and calculate total suitability scores for individual shafts. This approach enables prioritization and ranking of shafts based on technical and environmental conditions, facilitating the selection of optimal sites for USPS projects. The results underscore the importance of post-mining revitalization and propose a framework for integrating renewable energy storage into existing infrastructure. Further economic and site-specific assessments are recommended to refine project feasibility.
How to cite: Lutyński, M., Kołodziej, K., Matusiak, P., and Kowol, D.: Assessment and Adaptation of Mine Shafts and Underground Workings for Pumped-Storage Hydropower: A Multi-Criteria Scoring System Approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7376, https://doi.org/10.5194/egusphere-egu25-7376, 2025.
Microbial processes such as biofilm formation (biofouling), microbially induced mineral dissolution, mineral precipitation and corrosion can affect the thermal, chemical and physical stability of mine thermal energy storages (MTES). High concentrations of sulfate and metals, typical for mine water, enable microbial iron and sulfur cycling. Oxic conditions promote acidification through iron and sulfur oxidation, while anoxic conditions enable the production of H2S or methane, that are not only climate but also safety relevant. Processes such as sulfate reduction and iron oxidation can corrode technical components of the heat pump system. Together with biofouling and mineral precipitation on technical equipment as well as in the water-bearing mine galleries, microbial processes can compromise the efficiency of MTES. To evaluate the microbial impact on the performance of MTES, it is crucial to characterize the site-specific hydrogeochemical conditions, the microbiome inherent to the MTES site, and its response to the changing thermal conditions.
At the MTES real laboratory site Reiche Zeche, Freiberg (Germany), we monitored the microbial community in a mine water filled rock pool, its responses to several cycles of charging and discharging and their implications on different materials used in the heat exchangers. We analyzed the microbial abundance via quantitative PCR and the community composition based on amplicon sequencing in water and biofilm samples as well as the hydrogeochemical conditions after every heating and cooling cycle.
The test site is located at 147.5 m below surface in the first level of the mine. The mine water was characterized by an in-situ temperature of 11 °C, hyperacidic conditions (pH 2.6), concentrations of 1.1 mg L-1 DOC, ~700 mg L-1 of sulfate and 13-30 mg L-1 of iron. The microbial community was dominated by aerobic, acidophilic autotrophs related to iron and sulfur oxidation. During 1.5 years of construction at the test site, the bacterial taxa dominating the mine water shifted from the iron-oxidizing Gallionella and Sideroxydans to Ferrovum, Leptospirillum and Thiomonas, the latter potentially capable of both iron and sulfur oxidation. These taxa and their potential activity involve the risk of corrosion, biofilm formation and iron mineral scaling as well as further acidification. Especially Leptospirillum, a meso- to thermophilic genus, is expected to play a crucial role also during the heating cycles up to 50°C.
Results of this study will help to better understand the microbial response to changing thermal conditions in an oxic, acidic mine environment and its impact on technical equipment of different metal-based materials.
How to cite: Mitzscherling, J., Gabler, L., Oppelt, L., Wiedener, R., and Wagner, D.: Thermal energy storage and extraction at the MTES real laboratory site Reiche Zeche: microbial response and implications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5746, https://doi.org/10.5194/egusphere-egu25-5746, 2025.
The Chattian-Oligocene interval of the Northern Upper Rhine Graben (URG) is characterized by a complex stratigraphic and structural framework influenced by several phases of tectonic activity and variations of crustal stress fields. The deposition of the fluviatile-lacustrine Niederrödern Formation coincides with the major Chattian regression phase overlaying unconformably the brackish-marine uniform Grey Bed Series (Froidefontaine Formation). The Niederrödern Formation is characterized by colorful marls hosting sand layers and lenses that were partly exploited for hydrocarbons more than 40 years ago. Detailed investigations of 3D seismic data were conducted due to the direct link between channel geometry and the depositional regime with the storage potential of the sandstone layers for heat, CO2, or hydrogen.
A subset of a 3D seismic survey carried out in 2012, covering an area of 10 km × 4 km close to the Karlsruhe Institute of Technology (KIT) Campus North and including more than 20 in-field wells, was used for structural-stratigraphic analysis and advanced spectral decomposition analysis. Advanced spectral decomposition techniques could enhance seismic resolution and enable – for the first time in the Upper Rhine Graben – the delineation of meandering fluvial channels of up to 25 m width, providing constraints for the depositional system of the Niederrödern Formation. The delineation of meandering fluvial channels provides not only a better sedimentological understanding of the graben filling development but also geometric constraints for the thermo-hydraulic modeling of HT-ATES (High Temperature Aquifer Thermal Energy Storage) of former hydrocarbon reservoirs. This work highlights the potential of the Northern URG as a key region for geothermal energy utilization and subsurface storage, paving the way for future research and applications in renewable energy technologies.
How to cite: Tolba, A. T., Bauer, F., Grimmer, J. C., Dashti, A., and Kohl, T.: First identification of fluvial channels by advanced spectral decomposition in Chattian syn-rift successions of the central Upper Rhine Graben: Implications for subsurface energy storage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10539, https://doi.org/10.5194/egusphere-egu25-10539, 2025.
Underground Hydrogen Storage (UHS) seems like a very promising new technology to balance the seasonal variance of renewable energy production. The excess energy of renewables can be used for water splitting to produce ‘green’ hydrogen, which can be stored in UHS sites. However, due to the high mobility and small molecular size of hydrogen, the risk of leakage through faults and caprock is large compared to gas or carbon-dioxide. Thus, a complex monitoring system is a critical part of every UHS project. Borehole geophysical measurements are parts of this system. One of the key monitoring parameters is the hydrogen saturation in the vicinity of wells. The aim of our research is to investigate the applicability of nuclear borehole measurements for hydrogen saturation estimation in the presence of borehole casing, independently of water salinity. To achieve this goal, systematic simulation runs were carried out using the MCNP particle transport code. We present a method based on the ratio of gamma counts acquired from two detectors of a pulsed neutron logging (PNL) tool and the results of a sensitivity study focused on the most crucial model parameters of the measurement: hydrogen saturation, porosity, lithology, borehole diameter. Model results demonstrate that the sensitivity of the method is larger in high porosity reservoirs and smaller borehole diameters but there is a still reasonable sensitivity in wells with up to 8-inch casings. Additionally, an alternative technique is presented to improve the sensitivity of the method used in sandstone reservoirs which yields 10% sensitivity increase, when the rock consists of more than 50% sandstone. The improvement is independent of porosity, that is especially advantageous in reservoirs with lower porosity (10–15%). The simulation results prove that, in deep saline aquifers, the hydrogen saturation of the reservoir rock can be monitored independently of water salinity by using only one nuclear borehole geophysical method.
How to cite: Szucs, J. G., Galsa, A., and Balazs, L.: Simulation of monitoring Underground Hydrogen Storage (UHS) using nuclear borehole geophysics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-609, https://doi.org/10.5194/egusphere-egu25-609, 2025.
The East Midlands (UK) is poised to become the largest inland hydrogen cluster in the UK, supplied via Cadent’s East Coast Hydrogen pipeline. The storage of hydrogen will become an important enabler, allowing the gas to be produced when renewable energy is abundant, stored, and then used by industry and power generators during times of energy needs.
Project East Midlands Storage (EMStor) is a Strategic Innovation Funded feasibility study on the development of hydrogen storage in repurposed hydrocarbon fields. In this project, we investigate the feasibility of one of the East Midland depleted oil reservoirs in close proximity to the proposed hydrogen pipeline network that could potentially be used to store hydrogen, subject to technical feasibility and further development work. Initial promising calculations predicted combined capacities in the TWh-scale of nearby fields, and current research focusses on unlocking meaningful storage capacity while ensuring safety and commercial success.
Project EMStor will demonstrate at scale the technology readiness of underground hydrogen storage in the East Midlands and develop our understanding of technical, social and economic facets. A screening of available sites has resulted in the selection of the “Long Clawson” oil field for a pre-feasibility study. Oil-rich reservoirs are often not the primary targets for hydrogen storage due to the scientific complexities. Additionally, the field of the interest is relatively shallow (680m), has reservoir layers with an average thickness of ~10m, and have low oil depletion rates. Using an efficient black-oil simulator, reservoir modelling is used to test and optimise the feasibility of cyclic hydrogen storage in these reservoir layers, with a focus on cushion gas demand and dynamic storage capacity.
Gas leakage via pre-existing reservoir wells poses a potential risk for hydrogen storage. An assessment of the integrity of Long Clawson’s operational and legacy wells, conducted using existing available data, including well schematics and reports, will determine the preliminary suitability of these wells for safe and reliable hydrogen storage.
To address questions around possible reaction between stored hydrogen and reservoir materials batch reactions are conducted on the nominal well cement as well as reservoir rock samples, together with synthetic formation brine and hydrogen gas at reservoir conditions, in order to characterise any reaction within the system. These experiments will provide a basis for demonstrating the long-term stability and safety of these stores for hydrogen from a geochemical point of view, where loss of stored hydrogen to reaction, generation of undesirable by-products (such as H2S) and infrastructure compatibility are of primary concern.
Additional research includes public’s perception of hydrogen storage in East Midlands (UK), an economic analysis, the approach to regulatory, permitting and planning for any subsequent demonstration and finally decisions on next steps and future phasing.
By showcasing the potential storage in the East Midlands, project EMStor may demonstrate the technical viability of underground hydrogen storage in a methodology that is widely replicable for other repurposed hydrocarbon fields.
How to cite: Heinemann, N., Williams, H., Hemming, C., Kilpatrick, A., Armitage, T., Edlmann, K., Hough, E., Gregory, S., Lewis, A., Brewis, S., Evans, R., Morris, D., McAnulla, F., McClane, C., and Shillinglaw, K.: Hydrogen storage in the East Midlands (UK): The EMStor Project, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13399, https://doi.org/10.5194/egusphere-egu25-13399, 2025.
Effects of microbial activity on permeability of porous rock is a significant research topic in the context of underground hydrogen storage. However, the introduction of microorganisms into conventional experimental setups for permeability measurements under in situ pressure and temperature conditions might cause several risks for the outcome. Maintaining sterile conditions is important as well as the exclusion of oxygen and the avoidance of toxic materials such as lead foil. Thus, careful planning and consideration of the experimental set up is crucial to avoid incorrect assessment of microbial rock interactions. This study presents the interdisciplinary development of a simple experimental setup to gain basic knowledge on microbial rock interactions. The system was successfully used to introduce microorganisms into porous rocks while the anaerobic microorganisms stayed alive and active and no contamination was observed. At the same time, the setup was sensitive enough to detect a permeability reduction induced by the introduced microorganisms. Consequently, this experimental setup helps gaining fundamental knowledge needed for more complex experiments e.g. in high pressure Hassler cells where in situ pressure, temperature and flow conditions can be simulated.
How to cite: Krueger, M. and Dohrmann, A.: Simple experimental setup to study effects of microbial activity on rock permeability important for hydrogen storage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14813, https://doi.org/10.5194/egusphere-egu25-14813, 2025.
The Bulqizë Ophiolite in Albania is a site of active hydrogen degassing (84 vol% H2, ~200 tons/year) observed in a deep chromite mine (Truche et al., 2024). This intense degassing may result from serpentinization at depth, a process where ultramafic rocks react with water, producing H₂ as a byproduct. The depth, shape, and major structures of this ophiolite are currently poorly constrained. Gaining insights into these key parameters is essential to understand the conditions that promote H2 generation, migration and eventual trapping whithin these ultramafic rocks. To fill this gap, we conducted a magnetotelluric (MT) survey across a east-west transect of seven measurement points crosscutting the ophiolite and encompassing the adjacent sedimentary units. Data processing and analysis, including a 2D inversion executed using Geotools software, unveiled the subsurface structural configuration of the area.
Our results confirmed the existence of a bowl-shaped ophiolite structure at approximately 6 km depth, surrounded by sedimentary rocks and consistent with existing geological cross-sectional data. The structure displays an asymmetric elongation towards the East, with a thicker profile towards the West. This left-leaning bowl shape aligns with the geological characteristics of the Supra-Subduction Zone region. Additionally, our analyses identified that the ophiolite rock consists of an upper layer of fresh Peridotite transitioning to serpentinised Peridotite at greater depths. This transition zone, marked by significant chromite deposits – Bater, aligns with the observations that the chromite deposits tend to be accumulated in Ophiolite transition zones.
This geophysical characterization enhances our understanding of the subsurface configurations crucial for targeting potential H2 reservoirs. While this study primarily focuses on mapping and characterizing the subsurface structures, the implications for H2 exploration are significant. Our findings lay the foundation of a workflow for H2 exploration in ophiolite and ultramafic mantle bodies emplaced at shallow depth in the crust.
How to cite: Yao, Y., Donze, F. V., Truche, L., Vujevic, I., and Persem, M.: Imaging the root of the Bulqizë ophiolite and it associated H2 system through magnetotellurics , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19496, https://doi.org/10.5194/egusphere-egu25-19496, 2025.
Underground Hydrogen Storage (UHS) in porous media, such as saline aquifers and depleted oil and gas reservoirs, are promising options for storing renewable energy, enabling large-scale energy storage, and balancing supply-demand fluctuations in a decarbonised energy system. The availability and extent of these underground formations may provide long term TWh-scale capacity compared to other storage technologies such as surface infrastructure or salt caverns. The suitability of a storage site for UHS encompasses a variety geological, economy, environmental, legal, regulatory, and social aspects. In this paper, we focus on the subsurface elements and postulate what ‘UHS site suitability’ could be by framing it through the integration of three deeply interrelated aspects of the UHS operation: safety, efficiency, and cost. Here we explore the relationships and trade-offs to determine how safety, efficiency, and cost affects UHS site suitability. Factors influencing the safety, efficiency, and cost of an UHS operation include potential leakage pathways and the cyclical hydrogen injection and production are discussed. By doing so, the ideal conditions for UHS site in porous media are proposed and unsuitable options in terms of safety, efficiency, and cost are highlighted. Lastly, different considerations when selecting suitable UHS site in aquifers and depleted oil and gas reservoirs such as fluid composition and cushion gas selection are identified and discussed. The outcome of this paper can be used to guide UHS site selection and optimisation, providing a framework for evaluating the suitability of UHS site in porous media.
How to cite: Dzulkefli, M., Alcalde, J., and Iacopini, D.: What makes a suitable underground hydrogen storage site in porous media?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19059, https://doi.org/10.5194/egusphere-egu25-19059, 2025.
Understanding the flow and transport dynamics of hydrogen in heterogeneous porous media is crucial for advancing research on Underground Hydrogen Storage (UHS), a promising solution for the large-scale storage of renewable energy. Currently, there exist robust theoretical frameworks to predict transport properties (e.g., mixing and macrodispersion) of chemical components that are passively transported by flows, namely, where the hydrodynamic fluid properties (HP), density and viscosity, remain independent of the two primary variables (PV), pressure and mass fraction. However, gases feature a strong dependency of HP on PV that has been seldom taken into account to predict hydrogen transport dynamics in the context of UHS. Here, we investigate the impact on transport properties exerted by the non-linear relationship between PV and HP, both numerically and analytically in the context of heterogeneous UHS reservoirs. We simulate gas injection at different rates into gas- and water saturated reservoirs exhibiting a heterogeneous distribution of permeability. By considering test cases with different relationships between PV and HP, we observe and quantify the isolated effect of variability in each HP on the mixing and dispersion dynamics of the invading gas front.
How to cite: Fernandez Visentini, A., Hidalgo, J. J., and Dentz, M.: The coupling between gas flow and transport dynamics in the context of heterogeneous Underground Hydrogen Storage reservoirs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21204, https://doi.org/10.5194/egusphere-egu25-21204, 2025.
Underground hydrogen storage (UHS) in depleted reservoirs presents a promising solution for managing seasonal variations in renewable energy during the global energy transition. However, the impact of reservoir heterogeneity, particularly permeability anisotropy and interlayer characteristics, on hydrogen recovery efficiency remains insufficiently understood. To bridge this knowledge gap and improve storage site selection accuracy, we developed a systematic box model to evaluate the effects of reservoir heterogeneity and validated our findings using New Zealand's Ahuroa gas storage field.
Our investigation revealed that permeability anisotropy affects hydrogen recovery efficiency, with variations depending on well patterns. For well patterns with vertical wells only, both lateral (kx/ky) and horizontal-to-vertical (kh/kv) permeability anisotropy enhanced hydrogen recovery efficiency. For combined vertical and horizontal well patterns, the effect varied by anisotropy type. Lateral (kx/ky) anisotropy enhanced efficiency when horizontal wells aligned with the maximum permeability direction. In contrast, when horizontal wells aligned with the minimum permeability direction, kh/kv anisotropy exhibited an optimal ratio, beyond which efficiency began to decline. Analysis of interlayer effects revealed that reducing permeability from 1 mD to 10-3 mD led to an enhancement in hydrogen recovery efficiency, increasing from 61% to 75%. Additionally, our investigation demonstrated that the presence of interlayer pinch-outs and discontinuities along vertical hydrogen migration pathways reduced hydrogen recovery efficiency. A realistic geological model corroborated the box model findings: hydrogen recovery efficiency improved from 66.6% to 77.9% as the kx/ky ratio increased from 1 to 10, and from 66.6% to 76.2% when the kh/kv ratio increased similarly. Furthermore, inaccurate estimation of interlayer permeability could result in an 11.3% deviation in hydrogen recovery predictions.
These results underscore the importance of accurately characterizing reservoir heterogeneity, including permeability anisotropy and interlayer properties, to ensure reliable hydrogen recovery predictions and improve site selection for UHS.
How to cite: Liu, J., Dempsey, D., Nicol, A., and Parker, M.: Implications of Reservoir Anisotropy and Interlayer Heterogeneity for Hydrogen Recovery in Underground Storage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3349, https://doi.org/10.5194/egusphere-egu25-3349, 2025.
The integrity of cementing in oil and gas wells is vital for ensuring wellbore stability and preventing environmental contamination. However, the extreme conditions encountered during production and abandonment, such as the combined high pressure, temperature, and chemical exposure, pose significant challenges to the long-term performance of wellbore cement. This may lead to cracking, debonding and structural failure of cementing, ultimately causing leakage of gas. Existing research is mainly focused on analysing the potential parthway of leackage and some simplified experimental test for estimating the long-term behaviour of cementing. However, to accurately understand the whole life performance of cementing in Oil/Gas wells requires realistic reproduction of the in-situ environment for cement curing and testing the material properties such as permeability especially for the interface between cementing and rock formation rather than cementing itself. This study is therefore aimed to provide an innovative experimental analysis on quatntifying the cementing integirity in Oil/Gas wells by reproducing a model size of a section of rock-cementing section under the in-situ real environment. A seiries of experimental tests are then conducted to obtain the physical and mechanical performance for, in particular, the interface of the cement and rock. Whole life service condition is also considered and the long-term deterioration on the cementing and its interface with rock is quantitatively determined. The findings of this research are expected to contribute to the acucurate and comprehensive understanding of the whole life performance for cementing in Oil/Gas wells and more resilient cementing solutions with broader implications for other subsurface engineering applications, including underground energy storage and low-carbon infrastructure.
How to cite: Yin, Z., Xi, X., and Yang, S.: Experimental Investigation on Cementing Integrity of Oil/Gas Wells , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2955, https://doi.org/10.5194/egusphere-egu25-2955, 2025.
Berrezueta, E.; Kovacs, T.; Herrera-Franco, G.; Mora-Frank, C.; Caicedo-Potosí, J.; Carrion-Mero, P.; Carneiro, J. Laboratory Studies on CO2-Brine-Rock Interaction: An Analysis of Research Trends and Current Knowledge. Int. J. Greenh. Gas Control 2023, 123, 103842, doi:10.1016/j.ijggc.2023.103842.
Berrezueta, E.; Kovacs, T.; Herrera-Franco, G.; Caicedo-Potosí, J.; Jaya, M.; Ordóñez-Casado, B.; Carrion-Mero, P.; Carneiro, J. Laboratory Studies on Underground H2 Storge. Bibliometric Analysis and Review of Currant Knowledge. Applied Sciences 2024, 14 (23), 11286, doi:10.3390/app142311286.
How to cite: Berrezueta, E., Kovacs, T., Caicedo-Potosí, J., Carneiro, J., Ordóñez-Casado, B., Baragaño, D., Carrión, P., Roces, S., and Mediato, J.: Geological Storage of CO2 and H2: A Comparative Bibliometric Analysis of Global Challenges and Laboratory Advances., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7392, https://doi.org/10.5194/egusphere-egu25-7392, 2025.
This study leverages data on deep (>500 m) groundwater from the Dutch subsurface to assess the potential impacts of (re)using depleted natural gas fields and aquifers for (large) scale underground storage (e.g., UHS, CO2), and geothermal (heat) extraction/storage (GHE/S). To date, we have collected data from 700 deep groundwater samples obtained from 161 onshore and offshore wells. This data comes from the Dutch public geological archive (www.nlog.nl), which contains extensive and valuable information accumulated over six decades of oil, natural gas and geothermal exploration and production in the Netherlands. In addition to groundwater composition, we also gathered information on groundwater sampling and laboratory methodologies, rock properties, mineralogy and environmental conditions of underground reservoirs, and the composition of drilling fluids and unrecovered natural gas, among others. Our primary focus is to evaluate the quality of this data and determine its suitability for biogeochemical modelling. These findings are being integrated with laboratory experiments conducted on groundwater samples from operational oil/gas/geothermal wells in the Netherlands. This allows us to reproduce, quantify, and predict the effects of environmental changes that may occur in specific underground reservoirs due to current and planned underground production and storage projects. The results are particularly valuable for the growing number of performance screening studies on UHS, CCS, and geothermal projects, many of which may have yet to fully account for the impact of biogeochemical processes on their estimates of production/injection rates and/or storage capacities. Our findings also offer practical recommendations for optimal sampling and analysis practices for biogeochemical monitoring studies, which may differ from those typically employed by oil, gas, and geothermal companies. The ultimate goal of this study is to better characterize, quantify, and predict the potential short- and long-term impact and risks of microbial activity and geochemical reactions in the various geological formations targeted for underground activities in the Netherlands.
How to cite: Juez-Larré, J., Jansen, S., Leentvaar, E., Grunder, J., Van Baak, C., and Gerritse, J.: Deep groundwater and its potential effects on underground storage and geothermal heat extraction activities in the Netherlands, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8474, https://doi.org/10.5194/egusphere-egu25-8474, 2025.
When a porous rock is subjected to compressive stress, rock failure may occur due to either an increase in pore pressure or a decrease in confining pressure. The stress path and the rate of effective pressure change can influence the initiation and propagation of fractures within brittle materials. Understanding these mechanisms is key for applications in underground engineering, as well as in geo-energy exploration and storage. We conducted triaxial compression tests on Bentheim sandstone samples under different stress paths and effective pressure change rates. First, intact cylindrical samples were loaded axially at a constant confining pressure of 35 MPa and a pore pressure of 5 MPa, up to about 85% of the peak strength. We then fixed the axial piston and either increased the pore pressure or decreased the confining pressure at two different rates (0.5 MPa/min or 2 MPa/min), leading to final macroscopic failure. Comparison of located Acoustic Emission (AE) events with post-failure microstructures of deformed samples shows a good agreement, indicating a location accuracy of AE events of about 2 mm. The AE source types, determined by P-wave first-motion polarities, indicate that shear failure mechanisms are dominant as the rock approaches failure at the expense of tensile cracking and compaction events. Approaching failure, we observe a significant decrease in Gutenberg-Richter b-values in all tests. Our results show that samples subjected to faster rates of decreasing effective confining pressure experience larger stress drops, higher slip rates, greater total breakdown work, higher rates of AE before failure, and faster post-failure AE decay rates. In contrast, the applied stress path did not significantly affect the deformation microstructures and rock failure characteristics.
How to cite: Han, X., Wang, L., Bohnhoff, M., and Dresen, G.: Fracturing of Porous Sandstone by Decreasing Effective Pressure: The Roles of Stress Path and Rate Dependence , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9097, https://doi.org/10.5194/egusphere-egu25-9097, 2025.
Hydrogen storage in underground salt caverns provides a possible solution for quickly managing fluctuations in energy demand, allowing for rapid retrieval and the ability to accommodate frequent injection and withdrawal cycles. However, the limited cavern volume constrains its capacity for long-term grid support. An alternative approach involves storing hydrogen in chemically bonded forms, such as Dimethyl Ether (DME), which has an energy density 14 times higher than hydrogen, presenting a promising solution to overcome this limitation.
This proof-of-concept study investigates the mechanical and petrophysical properties of salt caverns under conditions representative of DME storage. An interdisciplinary approach combines compaction experiments, petrophysical analyses, and advanced imaging techniques to assess variations in hydromechanical properties. Experimental works utilize an X-ray transparent oedometer to evaluate the deformation behaviours of DME-saturated NaCl aggregates under constant load, simulating long-term creep, and under cyclic loading to assess damage accumulation. The impact of applied stress on permeability is also measured, providing qualitative insights into in-situ integrity.
Additionally, time-resolved (4-D) X-ray microtomography is used to quantify displacement and strain fields, offering insights into deformation mechanisms such as dislocation creep, pressure solution creep, and the initiation and propagation of micro-cracks and fractures. This novel, multi-scale approach provides a foundational framework for understanding the hydromechanical behaviours of salt rocks under complex loading conditions. The findings pave the way for future studies on heterogeneous samples and more complex conditions, contributing to the development of safe and efficient DME storage systems and supporting the integration of chemical hydrogen carriers into energy storage infrastructures.
How to cite: Fusseis, F., Khajooie, S., and Gaus, G.: Experimental Proof-of-Concept Study on the Hydromechanical Properties of Salt Caverns during Dimethyl Ether Storage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9256, https://doi.org/10.5194/egusphere-egu25-9256, 2025.
With rising global energy demands, shale gas and coal bed methane are increasingly recognised as essential unconventional hydrocarbon sources offering lower carbon emissions and reducing dependence on conventional fossil fuels. These unconventional sources are generated through the thermal maturation of organic matter, influenced by geothermal gradient, burial depth, and heat exposure duration. In certain cases, coal and shale formations are even subjected to igneous intrusions, causing localised thermal metamorphism. The proximity to these intrusions elevates the thermal maturity of organic matter and significantly modifies the porosity of these formations, which differs from burial-induced maturation. To investigate these effects, a comparative analysis was conducted on two heat-altered and two non-heat-altered samples comprising both coal and shale from the Raniganj basin. An integrated approach of Rock-Eval analysis and low-pressure gas adsorption (LPGA) techniques reveals advanced thermal maturity, increased micropore volumes and enhanced adsorption capacities due to thermal stress caused by intrusions. Such changes suggest an improved capacity for carbon dioxide storage in heat-altered samples, making them viable candidates for carbon sequestration projects. These findings provide valuable insights into thermally altered sedimentary sequences, contributing to carbon emission mitigation and sustainable carbon management strategies.
How to cite: Chowdhury, M., Sarkar, K., Hazra, B., and Vishal, V.: Thermal Alteration Effects on Shale and Coal: Insights into Porosity Evolution, Hydrocarbon Potential, and Carbon Sequestration Capacity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9396, https://doi.org/10.5194/egusphere-egu25-9396, 2025.
Mineral carbonation of subsurface basalt by CO2-rich fluids is a proven CO2 sequestration method. Aqueous and supercritical CO2 fluids permeate through variably porous lava layers away from the injection well, and somewhere along this flow pathway, mineral carbonation reactions initiate. Mineral carbonation is a two-stage process of dissolution of silicate phases by carbonic acid followed by precipitation of carbonate minerals from solution. Where along the flow pathway and when, relative to the start of injection, mineral carbonation begins is largely unconstrained. Sub-millimetre-scale x-ray tomography reveals the vesicle (i.e. porosity) structure in 3D. Scans reveal a bimodal vesicle size distribution in macroscopically vesicle-rich samples. Small (<1 mm-diameter) vesicles are isolated pores formed either by volatile exsolution (i) into a liquid (a sub-spherical bubble) or (ii) during groundmass crystallization (interstitial ‘ditytaxitic’ pores). A few anomalously large voids of connected porosity are formed when individual bubbles nucleate - these represent the only connected porosity and efficient permeability in unfractured basalt. We investigate further if mineral carbonation reactions can reach and act on isolated pores. Millimetre-sized samples were scanned after being immersed in aqueous CO2 for between 2 and 4 months. Some but not all samples show evidence of cation-dissolution along fractures and external surfaces. New results will be presented.
How to cite: Andrews, G., Brown, S., Ditscherlein, R., and Crandall, D.: Investigation of fluid-flow and mineral carbonation reaction processes in vesicular basalt by computed x-ray tomography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11423, https://doi.org/10.5194/egusphere-egu25-11423, 2025.
Even if emissions were halted immediately, the excess CO2 already present in the atmosphere would continue to contribute to global warming for centuries. This legacy carbon necessitates the deployment of technologies that can actively remove CO2 from the atmosphere, a process known as carbon dioxide removal (CDR). Among the suite of CDR technologies, Direct Air Capture (DAC) stands out as a scalable and targeted approach to directly reduce atmospheric CO2 concentrations.
This escalating urgency to mitigate atmospheric CO2 levels has driven significant advancements in direct air capture (DAC) technologies, particularly in the development and application of molecular sieves tailored for efficient CO2 adsorption. This presentation explores both the synthesis of zeolites, which are a subset of molecular sieves, as well as their performance in DAC systems.
Zeolites are crystalline microporous aluminosilicate materials with a highly regular and tunable pore structure, making them highly effective for direct air carbon capture (DAC). Their unique framework allows for selective adsorption of CO2 over other gases like nitrogen or oxygen, thanks to their surface chemistry and pore size. They are also easily regenerable, as CO2 can be released by altering pressure or temperature, enabling repeated use.
Our research has primarily focused on the experimental evaluation of existing zeolites, particularly spherical molecular sieves derived from them, to enhance their performance in achieving faster, more efficient capture and regeneration cycles. This optimization is key to reducing both operational costs and energy demands. Additionally, we are beginning to investigate the synthesis of zeolites, and by extension, molecular sieves, from volcanic ash, an abundant and sustainable resource in the Canary Islands, to develop a locally sourced solution. To complement these efforts, based on the experimental results, we are designing an integrated DAC system prototype that combines heating for regeneration and cooling within a single integrated unit, enhancing operational efficiency.
We are also beginning to study the integration of DAC systems with green hydrogen production to synthesize electrochemical Sustainable Aviation Fuel (eSAF), providing a sustainable alternative for aviation fuel. By utilizing renewable energy for water electrolysis, green hydrogen can be produced and combined with captured CO2 from the atmosphere to synthesize eSAF. Since Fischer-Tropsch synthesis primarily uses CO and H2, the captured CO2 is first converted into CO via the Reverse Water-Gas Shift (RWGS) reaction, where CO2 reacts with H2 to produce CO and water. The resulting syngas (CO and H2) is then fed into the Fischer-Tropsch process, producing hydrocarbons that can be refined into jet fuel. Alternatively, CO2 and H2 can be directly hydrogenated into hydrocarbons or converted to methanol, which is subsequently upgraded to aviation fuel.
Recent regulatory developments emphasize the growing importance of sustainable aviation fuels (SAF). The European Union’s ReFuelEU Aviation initiative mandates a minimum of 2% SAF usage for flights departing from EU airports starting in 2025, with incremental increases to 6% by 2030, 20% by 2035, 34% by 2040, 42% by 2045, and 70% by 2050. These ambitious targets reflect the critical role of SAF in decarbonizing aviation and meeting climate goals.
How to cite: Signorelli Pacheco, L. and Hernández-Gutiérrez, L. E.: Advancing Direct Air Capture Technologies: From Carbon Removal to Sustainable Aviation Fuels, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12733, https://doi.org/10.5194/egusphere-egu25-12733, 2025.
Seismic monitoring plays a critical role in ensuring the safety and effectiveness of carbon capture and storage (CCS) operations, as it offers essential insights into fault stability and potential risks to storage integrity. Focal mechanism analysis provides knowledge on stress field orientation, fault slip directions, and seismic source characteristics, aiding the understanding of subsurface fault dynamics and stress changes within the reservoir. Analysing focal mechanisms of small, local earthquakes before, during and after CO₂ injection is crucial for understanding seismic response and, as a result, assessing the risk of significant future events.
Within the ACT SHARP Storage project framework, a newly compiled detailed earthquake bulletin (Kettlety et al., 2024) and waveforms collected in the North Sea region were utilised to invert for moment tensors. Proposed CO2 storage sites in the North Sea are often located far from existing onshore seismological networks, resulting in sparse records and large azimuthal gaps, leading to significant uncertainties in earthquake parameters estimation, such as epicentre coordinates and hypocentral depth, making it very challenging to discriminate natural and induced events.
To address these limitations, we conducted a synthetic study to optimise the placement of offshore stations to improve the monitoring of CO₂ storage sites. Using the open-source Fomosto package, we modelled seismic responses from various double-couple sources and incorporated noise data from existing OBS deployments in Germany and Denmark. The results highlight optimal station configurations and strategies to enhance seismic monitoring, enabling better recovery of focal mechanisms and detecting micro-seismicity that may constitute induced seismicity or early precursors of CO₂ storage containment failure.
This study provides practical advice on designing robust seismic networks, paving the way for improved stress field knowledge and safer CCS operations in the North Sea.
How to cite: Martuganova, E., Naranjo, D., Kühn, D., and Barnhoorn, A.: Ensuring safe North Sea CO2 storage: the design of robust seismic networks to enable focal mechanism analyses for stress field orientation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-615, https://doi.org/10.5194/egusphere-egu25-615, 2025.
Energy systems models analyzed by the UN Intergovernmental Panel on Climate Change (IPCC) suggest that geologic carbon storage (GCS) at annual rates of several gigatonnes may be required to effectively mitigate the climate change crisis. Deployment of GCS at such large scales needs to address uncertainties about the availability and use of subsurface resources. A major concern is the growing risk of induced seismicity with the scale of implementation as wastewater disposal at comparable rates led to a surge in seismic activity in the central and eastern US in the 2010s. We develop an open-source tool, named CO2BLOCKSEISM, for screening subsurface storage resources constrained by the risk of induced seismicity. It relies on (1) analytical solutions of the pressure response of saline aquifers to multi-site CO2 injection at time-varying rates and (2) Monte Carlo simulations for estimating slip probability on mapped faults under inherent uncertainties of the geomechanical parameters. Employing simplified physics models in this tool enables the evaluation of storage resources at regional scales under different scenarios of site number and distance between them. We demonstrate the application of the tool to estimating storage resources in the Utsira Formation in the Norwegian North Sea. We find that nearly 12.5 Gt CO2 can be safely stored in this region over 50 years of continuous injection. The estimated storage capacity, although large, is much smaller than estimates of around 18 Gts subject to the caprock fracturing limit. We conclude that the use of induced seismicity as the leading physical constraint allows for more reliable estimates of the potential rates of GCS scale-up at regional and global scales.
How to cite: Rahimzadeh Kivi, I., De Simone, S., and Krevor, S.: CO2BLOCKSEISM, a tool for screening CO2 storage resources constrained by the risk of induced seismicity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13159, https://doi.org/10.5194/egusphere-egu25-13159, 2025.
Thermal energy storage can help to bridge temporal fluctuations of renewable energy provision, e.g. from wind and solar energy, and demand, e.g. to avoid system shutdown and associated negative effects on technical equipment and reservoir in geothermal energy production.
Storing thermal energy in rocks or rock beds is interesting as the material is abundant and inexpensive. In addition, rock has good, suitable thermal properties and is available directly where it is needed.
We investigated the effect of cyclic thermal energy storage a sandstone (Buntsandstein) from the Upper Rhine Graben, a region in Germany with high geothermal gradient and therefore a target region for present and future geothermal projects. To characterise the rock before and after different cyclic thermal loading conditions, the sandstone specimens were subjected to an initial temperature of 150 °C in a muffle furnace, then heated to 200 °C, 500 °C or 600 °C, and finally cooled to 100 °C in varying numbers of thermal cycles (2, 5, 10, 25 or 35).
After thermal treatment the sandstone showed changes e.g. in uniaxial and triaxial compressive strength, and P-wave velocity.
How to cite: Neumann, K. M., Zinke, B., Duda, M., and Backers, T.: Experimental investigation of the effect of thermal cycling loading on physical properties of a sandstone from the Upper Rhine Graben, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15455, https://doi.org/10.5194/egusphere-egu25-15455, 2025.
Posters virtual: Thu, 1 May, 14:00–15:45 | vPoster spot 4
EGU25-20467 | ECS | Posters virtual | VPS17
Quantification of the Impact of temperature variation on tiltmeter recordings for ground deformation monitoringThu, 01 May, 14:00–15:45 (CEST) | vP4.9
Geothermal energy, driven largely by the push towards achieving net-zero emissions, has garnered increasing interest in the past decades for electricity generation. Geothermal-related activities, as any other activity for energy projects that utilise the subsurface, could induce subtle deformations on the near-surface. Tiltmeters is a technology capable to detect submillimetre ground deformations but can be significantly affected by ambient temperature variations. This effect can mask potential minute deformation signals. The effect of ambient temperature variations on tiltmeter recordings still lacks systematic understanding due to the absence of precise monitoring data and appropriate interpretation guidelines. In this study we analysed continuous tiltmeter recordings for a full year period and quantified the close correlation between the ambient temperature and ground displacement in both east-west (EW) and north-south (NS) directions. This close relationship has also been suggested by their wavelet coherence (WTC) results with only small time-lag observed. Overall, appropriate recognition of temperature-related ground motions can benefit the understanding of shallow crust and promote the establishment of baseline for future geothermal-related practices.
How to cite: Qiu, C. and Pytharouli, S.: Quantification of the Impact of temperature variation on tiltmeter recordings for ground deformation monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20467, https://doi.org/10.5194/egusphere-egu25-20467, 2025.
