We invite contributions across the spectrum of geothermal technologies: hydrothermal, petrothermal, closed-loop, enhanced geothermal systems (EGS), and aquifer or borehole thermal energy storage (ATES/BTES). Reliable forecasting and sustainable geothermal utilization require solid understanding of the subsurface structure and physical properties. Integrated exploration strategies—seismic, geological, and geophysical studies—combined with consistent monitoring during operation is vital for optimal reservoir management and for minimizing environmental impacts.
The session further addresses the complex interaction between reservoir heterogeneity, imposed perturbations by operation, and impact on governing physical processes. These coupled mechanisms may cause stress redistribution or rock deformation and—in faulted/fractured reservoirs or EGS projects—enhance the seismic risk. Understanding the coupled thermal-hydraulic-mechanical-chemical (THMC) response of geothermal systems is thus crucial for predictive analyses, sustainable operation, and risk mitigation. Contributions on predicting and mitigating induced seismicity, including risk management approaches such as traffic light systems, are especially encouraged.
To this end, we welcome diverse methodological approaches: analytical studies, laboratory and field experiments, multiphysics numerical modeling, and data-driven or machine learning approaches resolving the relevant physical mechanisms across spatial and temporal scales. Case studies and operating geothermal projects highlighting engineering challenges (e.g. wellbore stability, scaling), successful methodologies and engineering solutions, or novel geothermal concepts are especially valuable.
Beyond engineering innovation, the session addresses the broader context of geothermal deployment in urban environments. We invite contributions on management strategies of the geothermal resource and integration into urban energy planning. By showcasing innovative research and practical applications, this session highlights the multifaceted potential of geothermal energy in advancing the urban energy transition.
Orals: Tue, 5 May, 14:00–15:45 | Room -2.43
As the global energy transition accelerates, Geothermal Systems are increasingly recognized for their potential to provide baseload renewable power and heat. However, the deployment of geothermal projects near urban centers faces significant challenges related to induced seismicity, as evidenced by discontinued projects in Basel and St. Gallen. This presentation details the comprehensive seismic risk mitigation strategy developed for the Haute-Sorne EGS pilot project in Switzerland and discusses its critical relevance for future geothermal deployment in densely populated settings.
The Haute-Sorne project employs a multi-faceted approach to risk management that surpasses the current state of the art. Central to this strategy is a shift from single, large-scale stimulations to a multi-stage stimulation concept. By dividing the reservoir into smaller, engineered segments, the project aims to limit the maximum magnitude of induced events, a crucial prerequisite for operating in urban environments where tolerance for felt vibrations is minimal.
To further ensure safety in sensitive locations, the project integrates Adaptive Traffic Light Systems (ATLS). Unlike conventional reactive systems, ATLS utilizes real-time data and earthquake forecasting to predict the evolution of seismicity based on planned injection schedules. This proactive capability allows operators to adjust or halt operations before adverse events occur, providing the high level of operational control necessary for city-based projects.
Finally, addressing social acceptance in populated areas requires transparent risk communication. We present results from a probabilistic risk assessment comparing the geothermal project's risk profile to accepted community risks, such as fire. This comparison demonstrates that with rigorous mitigation, EGS risks can be managed to levels comparable to everyday urban hazards. These lessons from Haute-Sorne provide a vital blueprint for the safe, socially acceptable integration of geothermal energy into the urban landscape.
How to cite: Bethmann, F., Alcolea, A., Dyer, B., Karvounis, D., Meier, P., Ollinger, D., and Zingg, O.: Seismic Risk Mitigation for Geothermal Projects in Densely Populated Areas: Lessons from the Haute-Sorne Pilot Project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5856, https://doi.org/10.5194/egusphere-egu26-5856, 2026.
The exploitation of Deep Hydrothermal Systems (DHS) offers significant potential for decarbonizing district heating networks by providing renewable baseload energy. However, the sustainable management of these resources requires balancing conflicting physical phenomena. DHS operations extract hot fluid from deep aquifers and reinject heat-depleted water. This process creates a hydraulic head loss near production wells, increasing pumping costs, while simultaneously driving the cold-water plume toward the producer. While placing injection wells nearby mitigates hydraulic pressure drop, it accelerates thermal breakthrough, reducing the system’s thermal capacity.
In this work, we present a computational framework to maximize the net energy extraction of DHS—defined as thermal energy production minus pumping energy consumption—by optimizing well flow rates and positions. We formulate the problem as a PDE-constrained optimization governed by a coupled thermo-hydraulic (TH) model. To solve this efficiently, we utilize the Finite-Element Method (FEM) combined with the adjoint approach to compute gradients, allowing for the use of the Interior Point Optimizer (IPOPT). This is paired with a multi-start strategy to approximate global optimality. Compared to gradient-free algorithms, this gradient-based method offers superior convergence rates, making the optimization of large-scale systems computationally tractable.
We validate the proposed framework by benchmarking against analytical solutions for homogeneous reservoirs, subsequently demonstrating its efficacy through numerical examples in 2D aquifers with heterogeneous hydraulic properties. The results illustrate how optimal well configurations shift based on subsurface permeability structures. Ultimately, this gradient-based framework provides a computationally efficient foundation for optimizing DHS in structurally complex 3D geothermal reservoirs.
How to cite: Steindl, U., Hamacher, T., and Halilovic, S.: Optimization of deep hydrothermal systems via the adjoint approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15015, https://doi.org/10.5194/egusphere-egu26-15015, 2026.
High-resolution diagnostics of flow and heat transfer in deep geothermal wells are commonly constrained by sparse downhole instrumentation and production-logging tools that require well intervention, interrupting steady-state operations. Here, we demonstrate continuous flow profiling and convection-regime identification (pump-driven forced convection vs. buoyancy-driven natural convection) using fiber-optic sensing methods. We used a combination of the Low-Frequency Distributed Acoustic Sensing (LF-DAS) approach, which measures axial strain-rate changes along a fiber, and Distributed Temperature Sensing (DTS) in a 4.1 km MD (Measured Depth) geothermal injection well within Munich, Germany.
During shut-in, LF-DAS reveals three persistent, depth-localized natural convection cells, characterized by distinct strain-rate patterns and coincident with rapid warming with depth, as observed in the DTS data. In quasi-steady-state injection, operationally occurring temperature changes as small as 10 mK/min in the injected fluid induce thermo-mechanical deformation along the fiber. These downward-propagating thermal fronts initially reflect pump-driven forced convection and enable flow profiling based on advective heat transport. From a depth of 3580 m MD, these fronts are blurred by the onset of buoyancy-driven natural convection. LF-DAS allows estimation of the plume-shedding frequency, plume height, travel distance, and velocity, all related to the temperature gradient measured with DTS. The accuracy of a threshold criterion for the onset of buoyancy-driven flow based on the temperature gradient is currently limited by the precision of the reference DTS measurement. Across all operational states, values range from 39 to 44 °C/km of true vertical depth.
These findings show that fiber-optic sensing can detect fluid-flow pathways, convection behavior, and regime changes without well intervention, thereby improving continuous monitoring and reservoir characterization for sustainable geothermal operation.
How to cite: Hart, J., Wollin, C., Andy, A., Ledig, T., Reinsch, T., and Krawczyk, C.: Low-Frequency Distributed Acoustic Sensing reveals transient flow and heat-transfer regimes during geothermal injection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16969, https://doi.org/10.5194/egusphere-egu26-16969, 2026.
Aquifer Thermal Energy Storage (ATES) systems play an increasingly important role in balancing urban heating and cooling demand. Their sustainable operation requires high‑resolution monitoring of subsurface thermal and hydraulic processes, particularly the movement of thermal plumes, groundwater flow dynamics, and operational disturbances during injection and extraction. Traditional monitoring approaches provide only sparse spatial information, limiting the ability to characterize key ATES behaviors. Distributed fiber‑optic sensing (DFOS) offers a step‑change in monitoring capability by enabling continuous measurements along the full depth of wells and monitoring infrastructure.
We present a use case of the ATES system on the Deltares campus in Delft using a multi‑sense DFOS approach that combines Distributed Temperature Sensing (DTS), Active‑Heating DTS (AH‑DTS) and Distributed Acoustic Sensing (DAS). DTS provides the temperature distribution along the well filters and how this evolves over time to get insights into plume migration. AH‑DTS provides estimates of (changes in) groundwater flow velocity by analyzing heating curves measured by the fiber, enabling analysis of preferential flow at specific depth intervals paths. DAS can capture hydrodynamic and operational acoustic signals associated with injection, production, and well hydraulics, offering additional insight into transient system behavior.
Integrating DTS, AH‑DTS and DAS provides low-cost monitoring at aquifer depth that can help reduce uncertainty and provides insights in thermal–hydraulic processes governing ATES performance. This multi‑sense DFOS approach enhances predictive modelling, enables early detection of thermal short‑circuiting or unintended flow pathways, and supports more efficient, reliable and sustainable ATES operation.
How to cite: Nieboer, R., Doornenbal, P., Ahlrichs, E., Kooi, H., Obando Hernandez, E., Pefkos, M., and Pauw, P.: Multi‑sense monitoring using Distributed Fiber‑Optic Sensing for temperature, groundwater flow and acoustics in Aquifer Thermal Energy Storage Systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20547, https://doi.org/10.5194/egusphere-egu26-20547, 2026.
Dense urban areas like Berlin face unique challenges when instituting geothermal energy, especially understanding how subsystems (e.g., transportation, people, legal framework, deep subsurface, drinking water, etc.) are linked and how the larger system is affected by changes to subsystems. The innovative approach to viewing a city as a system composed of subsystems and integrating the subsystems in a holistic energy efficiency framework is required to prevent unforeseen adverse consequences of actions such as heat pollution from thermal energy storage in deep reservoirs. The interaction between U-Bahn tubes, HT-ATES/BTES systems, groundwater flow, and the urban heat island creates a tightly coupled thermomechanical environment in which temperature, pore pressure, strain, and geochemical states evolve simultaneously and govern system efficiency and structural stability. In Berlin-Adlershof, an HT-ATES research well was completed in 2024 and drilling of the injection and production wells are slated for this year. Our new work will demonstrate the efficacy of: 1. HT-ATES in Berlin for thermal heat storage and production, 2. Using the subway system to collect heat and mitigate heat waste from the shallow subsurface heat island and heat pollution produced by HT-ATES wells. The interaction data from monitoring wells and a fiber optic experiment within the subway will provide parameters for thermomechanical models on granular scales (e.g., directly adjacent to wells, subway) and we will scale up models to interconnect ATES, subway, and groundwater, and then to district, city, and national levels. Social science and humanities data will be incorporated into the large-scale models to produce a structure for establishing UTES in other cities with unique settings in terms of geology, legal framework, drinking water sources, presence/ absence of mining, and other differences.
How to cite: Potter-McIntyre, S. and Blöcher, G.: UTES in Berlin: a systems approach to heat storage, usage, and heat pollution mitigation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16775, https://doi.org/10.5194/egusphere-egu26-16775, 2026.
Deep geothermal energy is a renewable energy source with broad distribution, vast resource potential, and promising development prospects. The current main extraction methods include enhanced geothermal systems（EGS）, annular heat exchange well systems（AGS）, fault zone fluid circulation extraction, and coaxial casing extraction methods. However, challenges such as unstable heat extraction power, high seismic risks, and low heat extraction efficiency persist. Addressing the bottlenecks in current deep geothermal extraction technology, we adheres to the principle of energy exchange without material exchange during the extraction process and aims for large-scale, sustainable, and stable development of deep dry hot rock geothermal resources. We propose the clustered multi-branch U-shaped well heat extraction method（UMW-DGS） and its key technologies. On this basis, an axisymmetric thermal conduction model for the wellbore is established. We calculated the spatiotemporal evolution of the temperature field and heat extraction power around the well under constant wellbore diameter conditions and analyzed the effects of three sensitive factors—temperature difference, thermal conductivity, and wellbore diameter—on heat extraction power. In addition, to address the boundary value problem of the UMW-DGS, a three-dimensional thermo-hydro-mechanical coupling numerical algorithm based on the finite volume method（FVM） was developed. This algorithm was used to study the heat exchange efficiency of a single horizontal well section of the UMW-DGS and the spatiotemporal evolution of the temperature field under different injection flow conditions. By analyzing the effective heat exchange amount, duration, and power at different flow rates, we found that increasing the injection flow rate decreases the effective heat exchange energy and duration while causing the effective heat exchange power to first increase and then decrease. The research results indicate that deep geothermal energy development requires designing injection flow rates under the condition of balancing heat exchange temperature and power to achieve optimal heat exchange efficiency.
How to cite: Li, S., Zhang, S., Xu, T., Zhang, Z., and Li, X.: Numerical Study on Heat Transfer of Multibranch U-shaped Wells for Closed-Loop Geothermal Systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1429, https://doi.org/10.5194/egusphere-egu26-1429, 2026.
Cities aiming to decarbonize space heating increasingly consider ground source heat pumps, but in densely built-up urban areas permission and practical installation is spatially constrained, e.g., by property boundaries, minimum distances to buildings, exclusion zones, and subsurface conditions. Planners and permitting authorities therefore need transparent tools at the lot-scale for borehole heat exchanger (BHE) array design in accordance with the building’s heat demand, and in compliance with local regulations. We present an open-data workflow implemented in QGIS and python to estimate the technical shallow geothermal potential for cities based on the lot level under relevant regulatory rules. The workflow is designed to rely on public datasets as far as possible, i.e. cadastral lots, building footprints, transport and land use restrictions, tree locations, and subsurface thermal conductivity. Lot-level annual heat demand is estimated based on LOD2 data by assigning standard residential building archetypes to 3D building models, scaling specific demands with floor area. All key distance and BHE array design parameters are considered as user-defined inputs, which facilitates sensitivity and scenario analyses.
The workflow comprises four major steps. First, available installation space is derived for each lot by assigning buffer zones around buildings, lot boundaries, tree locations and other restricting features in order to exclude the placement of BHEs in their direct vicinity. Furthermore, all exclusion zones are subtracted, e.g. drinking water protection zones or natural reserves. Second, within each available space polygon, candidate BHE positions are placed on a rotated and shifted hexagonal grid to approximate the densest location of BHEs for a given minimum separation distance. Third, thermal conductivity along the BHE length is sampled at every BHE position and combined with design tables for vertical BHE systems to estimate specific heat extraction rates and annually extractable geothermal energy. Finally, potentials are aggregated within lots and compared to lot-level heat demand. An energy index is derived to quantify the fraction of demand that can be covered on each lot.
The workflow was exemplarily applied to a city district, containing 1823 lots with a total annual heat demand of about 98 GWh. In a base-case scenario with all distances in compliance to local guidelines, roughly two-thirds of all lots (accounting for 88% of the district’s total heat demand) are suitable for BHE installation. The total technical potential exceeds total demand by about a factor of 1.5, but when limited to the demand per lot, only about half of the district’s heat demand can be met by BHEs on the same lot, and only about one quarter of lots with a non-zero heat demand are self-sufficient. Scenario analyses show that the geothermal potential is most sensitive to borehole depth, spacing between BHEs and distance to neighboring lots, while building and tree distance buffers have smaller effects. A scenario using deeper BHEs and slightly relaxed spacing rules increases district-wide demand coverage to about three quarters and more than doubles the number of self-sufficient lots.
How to cite: Shakeri, A., Beyer, C., Witte, F., Haller, J., Löschner, E., and Bauer, S.: An open-data QGIS-workflow for lot-scale shallow geothermal planning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4987, https://doi.org/10.5194/egusphere-egu26-4987, 2026.
Geothermal systems are frequently used as a source of low-emissions energy. However, reservoirs with high amounts of dissolved CO2 can produce substantial power plant emissions, exceeding 100 kt/yr in some cases. Accurately accounting for the net anthropogenic emissions at geothermal systems is difficult because these systems also naturally flux CO2, sometimes at a magnitude similar to plant emissions, and this natural flux may increase or decrease due to plant operations. Furthermore, recent efforts in Iceland and New Zealand to capture and reinject geothermal emissions can further alter CO2 fluxes and raise the amount of CO2 stored in the subsurface.
In the absence of direct monitoring data, mathematical models can be used to estimate geothermal CO2 emissions. Here, I describe a lumped parameter model of CO2 flux through a liquid geothermal reservoir. The model parameterises CO2 influx due to magmatic degassing, CO2 loss from vertical migration through caprock or lateral outflow, degassing due to pressure or boiling driven solubility changes, CO2 extraction and reinjection through wells, and permanent storage through mineralisation reactions. Under constant mass extraction and suitable simplifying assumptions, the model can be solved exactly yielding exponential approximations of emissions rates (natural and plant), and reservoir CO2 content.
Calibration of this model to ten years of plant emissions and pressure decline data at Rotokawa and Ngā Tamariki geothermal fields (New Zealand), suggest that degassing trends are largely driven by CO2 dilution of the liquid reservoir. Furthermore, both depressurisation and dilution substantially lower the natural CO2 outflow, an effect not presently accounted for in greenhouse gas inventories. This means that measured plant emissions may exceed the true anthropogenic impact on geothermal emissions by up to a factor of three, which has substantial financial implications for geothermal plant operators.
How to cite: Dempsey, D.: Physics-based Accounting for Natural and Anthropogenic CO2 Emissions from Producing Geothermal Systems , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1510, https://doi.org/10.5194/egusphere-egu26-1510, 2026.
This contribution presents results from case studies on medium-depth hydrothermal geothermal projects in the North German Basin (NGB). Despite well-explored locations, these projects have not yet progressed to implementation. All cases were selected based on favourable geohydraulic conditions, and their geology is representative of that of the NGB. The selected sites differ intentionally in terms of their heat-offtake situations, such as the heating network, the size of the municipality, or the presence or absence of commercial heat consumers.
For each case study, technical concepts were developed that integrate geothermal heat for partial or full baseload coverage. A central element of all concepts is the use of one or more high capacity heat pumps to raise the production temperature to the required supply temperature of the district heating network.
One of the key aspects of this work is to evaluate the operational feasibility of the proposed technical concepts. To this end, the authors performed thermal-hydraulic coupled simulations of the hydrothermal system. These simulations provide insights into long‑term reservoir behaviour under different production and injection scenarios. They form the basis for an energy balance while maintaining reservoir integrity.
The results of the case studies will be generalised. Recommendations will be made to help the stakeholders of the heat transition to integrate medium-depth geothermal energy into the heat supply in a technically robust and economically viable way.
The presented work is part of the research project Warm‑Up, funded by the Federal Ministry for Economic Affairs and Energy (BMWE) and conducted at the Federal Institute for Geosciences and Natural Resources (BGR). Project partners include the Leibniz Institute for Applied Geophysics (LIAG), the ECOLOG Institute for Social‑Ecological Research and Education and the Institute for Ecological Economy Research (IÖW).
How to cite: Pechan, E., Krug, S., Röhling, S., Richter, S., Weber, J., Weiß, J., Holstenkamp, L., Jekel, J., and Spieß, M.: From Reservoir to District Heating: Success Factors and Challenges of Medium‑Depth Geothermal Energy in North German Municipalities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19874, https://doi.org/10.5194/egusphere-egu26-19874, 2026.
Abandoned mine infrastructures offer promising potential for subsurface thermal energy extraction and storage in urban environments. However, their integration into energy systems demands a thorough understanding of hydrogeological behavior and economic feasibility. In this study, we present a comprehensive investigation of a geothermal mine water system operating within an abandoned mine in Germany since 9 years. Our approach combines detailed field monitoring, advanced data-driven analysis, and techno-economic evaluation.
High-resolution, high-frequency measurements at the study site reveal dynamic interactions between mine water and surrounding groundwater. These data capture short-term fluctuations driven by recharge events and pressure propagation through interconnected voids and fractured rock. Combined with depth-resolved temperature profiles and in-situ video inspections of mine shafts using cameras and underwater rovers, we aim to gain a detailed understanding of hydraulic processes within the mine workings and their connection to the regional groundwater system.
To translate hydrogeological investigation into system planning and policy decisions, we analyze the sensitivity of the economic performance of the system to carbon pricing, integrating gained insights and operational experience with forward-looking economic modeling. Our results suggest that under the favorable geological and hydraulic conditions at the test site, mine-based geothermal systems can achieve levelized costs that are competitive with air-source heat pumps.
This integrated approach highlights the value of high-frequency field data, data-driven automated analysis, and economic modeling for assessing the viability of repurposing post-mining infrastructure for sustainable energy use.
How to cite: Heinze, T., Lam, F., and Gökpinar, T.: Hydrogeological Investigation and Techno-Economic Evaluation of a Geothermal Mine Water System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13444, https://doi.org/10.5194/egusphere-egu26-13444, 2026.
Ground source heat pump (GSHP) systems are increasingly adopted as renewable energy contributing to global decarbonization efforts. Standing column wells (SCWs) circulate groundwater directly within a single borehole, thereby leveraging the advantages of both closed-loop and open-loop GSHP systems. Owing to their reduced installation area requirements and cost efficiency, SCWs have been widely implemented in urban environments. However, comprehensive studies on SCWs remain limited, particularly with respect to the environmental impact of SCW operation based on actual operational data. This study characterized the thermal behavior of an SCW system installed at a university library in South Korea. System loads were derived from the operational data and correlated with degree-days, an indicator of energy demand, to quantify their relationships. A numerical model was then developed incorporating this relationship to simulate the spatial and temporal distribution of thermal plumes under different operational conditions. Furthermore, thermal plume evolution was evaluated under future climate scenarios by applying projected degree-days that account for global warming effects. Through this approach, the environmental impacts of SCW operation were evaluated in a more realistic manner, providing insights from a representative case of SCW applications in public institutions. Collectively, these findings are expected to contribute to the enhanced efficiency and long-term sustainability of SCW systems.
Key words: Standing column well, Environmental impact, Numerical simulation
Acknowledgement: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2022R1A2C1006696).
How to cite: Oh, H.-R., Baek, J.-Y., Pasquier, P., Ha, S.-W., An, K.-M., and Lee, K.-K.: Subsurface Thermal Impacts of Standing Column Well Operation: Insights from Operational Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4674, https://doi.org/10.5194/egusphere-egu26-4674, 2026.
The utilization of geothermal energy through borehole heat exchangers (BHE) is growing in significance for a sustainable energy and heat supply in urban areas. Therefore, a comprehensive knowledge of the subsurface heat balance and the governing heat transport processes influenced by urban infrastructure is essential when operating multiple BHEs with a high spatial density in city districts.
The aim of this study is to investigate the long-term changes in the subsurface heat balance and subsurface temperatures due to the operation of an individual BHE and to determine the temporal evolution of the heat capture zone of the BHE depending on the presence of streets and buildings in the near surroundings. For this purpose, a numerical model for one plot of land with a standard single-family home from the 2000s and a 3-meter-deep basement next to a street was developed. A BHE is placed in the front yard between the street and the house in accordance to the required minimum distances. Operation of this BHE was simulated for 30 years using a standard load profile based on German guidelines. The model also includes seasonal temperature variations for the street and land surface as well as heat transfer from the building to the ground.
At the beginning of the simulation, the extracted heat originates from the plot subsurface itself. The street as well as the heated basement of the building transfer heat into the subsurface, which is partially extracted by the BHE since it is located in their immediate vicinity. During the 30-year simulation period, the heat capture zone of the BHE increases. After only two years, about 50 % of the extracted heat stem from the subsurface outside the plot. After five years this fraction increases above 65 %, after 30 years above 80 %. In simulations without accounting for heat transfer from the street or the building to the subsurface, this fraction increases to about 90 %. As a consequence, also subsurface temperatures near the BHE as well as BHE return temperatures are reduced by up to 0.87 K and 0.33 K, respectively, compared to the original scenario.
Overall, the results show that the major fraction of the heat extracted by BHEs originates from heat stored in the subsurface, and that after 30 years most of the extracted heat is replaced by heat from neighbouring plots. This indicates, that even if minimum distances to neighbouring BHEs are maintained, these might be significantly affected with consequences for subsurface and BHE return temperatures.
How to cite: Löschner, E., Beyer, C., Shakeri, A., and Bauer, S.: Analysis of long-term changes in temperature and heat flow rates caused by the operation of a BHE for a typical suburban setting, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3946, https://doi.org/10.5194/egusphere-egu26-3946, 2026.
Open-loop groundwater heat pump (GWHP) systems provide low-carbon heating and cooling by exchanging heat with pumped groundwater. In dense urban settings, however, this advantage can become a liability: overlapping thermal plumes and persistent warming may progressively elevate background groundwater temperatures, constrain resource availability, and reduce long-term system reliability. To address this, we introduce THERMAL (Shallow geoTHERmal energy MAnagement through hoListic optimization), a decision-support approach that integrates conventional performance metrics with aquifer-centred sustainability indicators to guide GWHP operation. THERMAL screens operating strategies designed to preserve the ambient thermal baseline while reducing thermal cross-interference between neighbouring installations.
We apply THERMAL to three GWHP systems in Zaragoza’s urban alluvial aquifer, testing 27 alternative operating configurations against the current baseline. The scenario ensemble reveals substantial trade-offs: several configurations perform worse than present operation, whereas multiple options improve both environmental and economic outcomes. The best-ranked strategy achieves an emissions reduction of 14.94 t CO₂-eq yr⁻¹ and €7.53k yr⁻¹ in cost savings. However, the scenarios that maximize cost and CO₂ benefits do not systematically coincide with those that most effectively reduce the spatial footprint of strongly warmed groundwater (areas with ΔT > 4 °C). These results show why single-objective, “performance-only” optimization is insufficient in cities: robust planning requires multi-criteria decisions that explicitly protect the aquifer’s thermal integrity. THERMAL offers a practical route to align GWHP operation with the long-term conservation of urban groundwater thermal conditions.
How to cite: Martínez-León, J., Merino-Martínez, E., Marazuela, M. Á., Baquedano, C., Jiménez, J., Sariago, R., Gasco-Cavero, S., Escayola Calvo, O., and García-Gil, A.: Managing open-loop GWHP operation in urban aquifers to reduce thermal interference and background warming: the THERMAL approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13820, https://doi.org/10.5194/egusphere-egu26-13820, 2026.
Knowledge of subsurface thermal properties, particularly thermal conductivity, is essential for the effective design and operation of shallow geothermal energy systems. This study presents the results of a geological and thermal characterization conducted at a borehole heat exchanger field used for shallow geothermal heating and cooling of a non-residential building southwest of Leipzig, Germany. The subsurface is characterized by a pronounced heterogeneity, including lignite-rich layers. The presence of these units leads to a strong vertical variability in thermal conductivity, posing challenges for conventional geothermal site characterization.
To address this, different in situ and laboratory-based measurement techniques with differing spatial resolutions and support volumes were applied to assess the vertical distribution of thermal conductivity and subsurface heat transport properties. The results obtained from the various methods were systematically compared and evaluated. Additionally, laboratory analyses of lignite samples were performed to better quantify the influence of the organic-rich layers on thermal properties at the site.
How to cite: Hastreiter, N. and Vienken, T.: Characterization of a Lignite-rich Subsurface for Shallow Geothermal Applications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1935, https://doi.org/10.5194/egusphere-egu26-1935, 2026.
In need for alternative energy sources, deep borehole heat exchangers (DBHEs) are gaining increasing attention worldwide. Compared to deep open-loop geothermal systems, closed-loop systems generally provide low heat performance, while the advantage of DBHEs lies in their flexible installation (no reservoir needed), safer operation (low impact on the geological environment), and lower maintenance costs. Additionally, DBHEs may be installed in abandoned hydrocarbon wells or unsuccessful geothermal wells, significantly reducing installation costs. In DBHEs, the heat carrier fluid circulates inside the borehole, heated through heat conduction from the surrounding rock. The thermal conductivity and heat capacity of the geological environment therefore control system performance. In DBHE modelling studies, thermal properties of rocks are commonly averaged for lithological groups and the temperature- and pressure dependency of these properties are neglected. Bulk thermal properties are primarily controlled by porosity (i.e. pore fluid content) and the minerals constituting the rock matrix and can significantly change with increasing temperature and pressure conditions. Therefore, realistic estimates on in-situ thermal properties are key input for DBHE performance models. In this study we demonstrate and quantify the effect of depth- temperature- and pressure-dependent thermal properties on the performance of DBHEs in the siliciclastic sediments of the Pannonian Basin. Thermal conductivity and heat capacity profiles of typical lithotypes constituting the Neogene sedimentary succession of the Pannonian Basin, calculated using regional porosity-depth trends and literature-based correction formulas for temperature and pressure, are used as input for the numerical modelling. In addition to general thermal property profiles, we present DBHE models using well-log-based thermal conductivity estimates, showing the effect of local variations in thermal property profiles. DBHE models for an operational period of 1 year highlight significant differences in DBHE performance using constant vs. depth-dependent thermal properties. Models with well-log based thermal property profiles can improve DBHE performance estimates with 10 to 20 %. In general, models adopting temperature- and pressure-dependent thermal properties predict lower DBHE performance, governed by thermal conductivity decrease compared to non-dependent conductivity values. The effect of temperature- and pressure-dependent property variations on DBHE performance is dependent on lithotype and becomes relevant in the case of DBHE depth ~>2 km, further depending on local geothermal conditions. This study demonstrates that the adequate performance evaluation of DBHE projects requires modelling studies adopting carefully selected thermal properties representing the in-situ conditions of the geological environment.
How to cite: Békési, E., Porkoláb, K., and Lenkey, L.: The effect of depth, temperature and pressure dependency of rock thermal properties on the performance of deep borehole heat exchangers: example from the Pannonian Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6302, https://doi.org/10.5194/egusphere-egu26-6302, 2026.
The use of geothermal energy inevitably causes changes in pore fluid pressure in the subsurface due to the production of fluids at one location and their reinjection at another location. In turn, this local change in pore pressure influences the undisturbed effective stress state. Depending on the stress state and changes in pore pressure, the rock's stability can be compromised. A resulting failure of the rock is perceived as induced seismicity. Since this is undesirable, the thermo-hydro-mechanical response of the rock to operations is often studied with the aim of better understanding the underlying mechanisms that lead to induced seismicity and potentially identifying ways to constrain its impact. However, the availability of direct data on the relevant parameters is usually sparse, if available at all. Thus, it is of interest to understand the magnitude of impact of different parameters on the stability. The ultimate goal is to enhance understanding of the parameters that are most decisive.
Here, we present and quantify the influence of various relevant parameters on the stability of the rock mass. Specifically, we examine the effect of different initial stress states, varying hydraulic and mechanical fault properties, and different rock stiffnesses on the stability of the rock mass. For quantification and comparability, we use the slip tendency as a measure of how close a rock mass is to failure. Differences in slip tendency due to different parameter sets enable us to assess the impact of uncertain information for a specific parameter on the eventual uncertainty of stability prediction.
We illustrate this approach with a case study from the North Alpine Foreland Basin. The geothermal power plant in Unterhaching has operated for almost two decades. Currently, it is used solely for district heating, but it was previously employed for power generation. During its operation, it has experienced several hundred microseismic events around the reinjection well that are attributed to the operation.
We set up a 3D thermo-hydro-mechanical model around the reinjection well to model the response of the stress field to ongoing fluid reinjections. The model geometry is based on a 3D seismic survey that includes six lithological units, each populated with corresponding rock properties. Additionally, pore fluid overpressures, as observed locally in the North Alpine Foreland Basin, are incorporated. Different stress states based on data records and model results are calibrated. Furthermore, the hydraulic properties of the faults are assumed to be either sealing or conducting. Several model scenarios allow us to eventually identify those parameter sets that are in agreement with observations of induced seismicity and reject those that do not align with them. Essentially, this enhances the quality of model predictions and facilitates a more accurate assessment of future operations.
How to cite: Ziegler, M., Rettelbach, N., Drews, M., Cacace, M., Moeck, I., and Ziesch, J.: Thermo-Hydro-Mechanical modelling of a reinjection operation in the North Alpine Foreland Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10284, https://doi.org/10.5194/egusphere-egu26-10284, 2026.
The performance of geothermal reservoirs is fundamentally controlled by the evolution of porosity and permeability, which in turn is governed by diagenetic processes interacting with coupled thermal, hydraulic, mechanical, and chemical (THMC) processes. Diagenetic reactions may either enhance reservoir hydraulic performance - through mineral dissolution, secondary porosity generation, or dolomitization-related volume changes - or degrade it via mineral precipitation, compaction, and cementation, resulting in reduced hydraulic connectivity and geothermal productivity. A process-based understanding of these interactions and feedbacks is therefore essential for reliable geothermal resource assessment.
The Muschelkalk Formation in the Berlin–Brandenburg region of the North German Basin represents a promising geothermal target due to its favorable porosity, permeability due to brittle deformation, and temperature gradients at depth. However, its reservoir properties are strongly modified by diagenetic processes associated with halokinesis and fluid flow, including dolomitization, uplift-related deformation, and fluid-mixing corrosion. These processes generate pronounced spatial heterogeneity and uncertainty in reservoir performance, highlighting the need for a coupled, process-oriented modelling and analysis approach.
We developed a physics-based THMC-coupled modelling framework to investigate diagenetic controls on geothermal reservoir behavior from reservoir to basin scale using integrated geological and petrophysical data from the Muschelkalk Formation. The objectives of our study are (1) the analyses of THMC-coupled diagenetic processes in the Muschelkalk Formation and their effects on porosity–permeability evolution, (2) quantify the interaction between thermal, hydraulic, mechanical, and chemical processes and their influence on reservoir heterogeneity, and (3) assess the impact of these coupled processes on geothermal performance through reservoir- and basin-scale doublet simulations.
The modelling workflow is implemented using the GOLEM application (based on MOOSE framework) for coupled thermal–hydraulic–mechanical (THM) processes, which is coupled with PHREEQC to represent key geochemical reactions, enabling fully THMC-coupled model development and simulations. Despite the high computational demand of large-scale coupled modelling, this approach enables a comprehensive assessment of temperature, fluid flow, stress state, geochemistry, and petrophysical evolution. Overall, the study aims to provide a quantitative and process-based foundation for improving geothermal resource evaluation and long-term reservoir management in sedimentary basins.
How to cite: Tian, D., Blöcher, G., Maerz, S., Winterleitner, G., Niederau, J., Meier, N., Siever-Wenzlaff, C., Meeder, A., Frigo, S., Cacace, M., and Bruhn, D.: THMC-Coupled Simulation of Diagenetic Processes in Carbonate Geothermal Systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10847, https://doi.org/10.5194/egusphere-egu26-10847, 2026.
Renewable energy sources have been recognized over the past years as a key solution for mitigating emissions of CO₂ gas into the atmosphere. Meanwhile, the rapid expansion of the artificial intelligence (AI) industry and the growing demand for large-scale data centers have placed unprecedented pressure on the energy sectors and making a significant contribution to greenhouse gas emissions [1]. Consequently, attention is directed toward geothermal energy due to its ability to operate continuously and efficiently, providing a reliable source of energy for both electricity and heat generation [2].
Western Lithuania has many subsurface reservoirs with temperatures suitable for geothermal applications. Previous studies have analyzed the heat and electricity generation potential of these reservoirs, highlighting promising opportunities for geothermal development in the region [3, 4]. Consequently, the implementation of enhanced geothermal methods could significantly improve the feasibility and efficiency of these geothermal reservoirs.
The Baltic Basin reaches its maximum depths beneath Lithuania, where the subsurface reservoirs in western Lithuania exhibit favorable temperature and pressure conditions and rock properties for CO₂ storage [5]. Several past studies have demonstrated significant storage potential in these subsurface reservoirs of Lithuania [5]. Therefore, opportunity exists to utilize CO₂ , as a fluid for geothermal applications, such as brine displacement for heat extraction. Additionally, CO₂ exhibits advantageous thermophysical properties compared to brine which can enhance heat extraction, electricity generation, and geothermal energy storage efficiency.
This research aims to investigate pore-scale CO₂–brine physical interactions under Lithuanian geothermal reservoir conditions (e.g., temperature, pressure, and salinity). The objective is to evaluate the influence of CO₂ on brine displacement and local temperature distribution. In addition, pore-scale scenarios of CO₂ storage for geothermal energy storage are analytically examined to assess CO₂–brine–rock interactions, identify suitable operating conditions, and estimate viable storage durations. Numerical simulations of flow dynamics and heat transfer are conducted using reservoir simulation tools. A homogeneous and a heterogeneous pore-network models are developed for the simulations.
References
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R. Jha, R. Jha and M. Islam, "Forecasting US data center CO2 emissions using AI models: emissions reduction strategies and policy recommendations," Frontiers in Sustainability, 2025. |
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G. J. N. J. J. P. Ashok A. Kaniyal, "The potential role of data-centres in enabling investment in geothermal energy," Applied Energy, pp. 458-466, 2012. |
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M. Pijus, I. Kaminskaite-Baranauskiene, A. Rashid Abdul Nabi Memon and M. Pal, "Assessing Geothermal Energy Production Potential of Cambrian Geothermal Complexes in Lithuania," Energy, 2024. |
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A. Rashid Memon, P. Makauskas, I. Kaminskaitė-Baranauskienė and M. Pal, "Repurposing depleted hydrocarbon reservoirs for geothermal energy: A case study of the Vilkyčiai Cambrian sandstone in Lithuania," Energy Reports, pp. 243-253, 2025. |
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S. Malik, P. Makauskas, R. Sharma and M. Pal, "Evaluating Petrophysical Properties Using Digital Rock Physics Analysis: A CO2 Storage Feasibility Study of Lithuanian Reservoirs," Applied Sciences, 2024. |
How to cite: Alimohammadiardakani, P., Horbenko, A., and Pal, M.: Enhancing Geothermal Performance of Lithuanian Reservoir Using CO2: A Pore-Scale Study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17797, https://doi.org/10.5194/egusphere-egu26-17797, 2026.
The rapid increase in greenhouse gas (GHG) emissions due to industrialization, urban
development, and extensive use of cooling and heating devices and appliances such as air
conditioners, refrigerators, and water heaters has become a major environmental concern
worldwide. These systems release harmful GHGs that significantly contribute to global warming
and environmental degradation. To mitigate these impacts, geothermal energy stands out as a
reliable and environmentally friendly source of heat, with the potential to provide long-term
energy security and reduced carbon emissions. Despite its environmental advantages, the
development of geothermal energy projects has been limited due to issues of sporadic
distributions, involvement of high initial investment and operational costs, etc. Therefore,
accurate pre-assessment of reservoir performance is critical to determine whether a geothermal
project can meet the required energy demand and remain economically viable. Numerical
modelling plays a crucial role in this assessment by predicting fluid flow and heat transport
behaviour within geothermal reservoirs. Traditionally, most geothermal reservoir models assume
linear Darcy flow to be valid for both the porous rock matrix and the fracture networks.
However, this assumption may lead to inaccurate predictions when fractures exhibit high
roughness. In such cases, fluid flow within fractures deviates from linear Darcy behaviour and
becomes nonlinear due to inertial effects, which are better described by the Forchheimer flow
regime. Neglecting this nonlinear flow behaviour can result in significant errors in estimating
pressure losses, flow distribution, and ultimately the production temperature over time.
In this study, a numerical model of a fractured geothermal reservoir is developed that
incorporates nonlinear flow behaviour within rough fractures while retaining Darcy flow in the
surrounding porous matrix. The model is applied to a fractured geothermal system, and the
results are systematically compared with those obtained using the conventional Darcy flow
assumption for fractures. The comparison demonstrates that Darcy-based fracture models tend
to overestimate fluid mobility, leading to an underestimation of pressure losses and premature
thermal breakthrough. Consequently, Darcy flow models overestimate the magnitude of the
production temperature decline and underestimate the production temperature. The findings
highlight the importance of considering nonlinear fracture flow in geothermal reservoir
simulations, particularly for systems with highly rough fractures. Incorporating realistic flow
physics improves the reliability of production forecasts and provides a more accurate basis for
decision-making in geothermal project development.
Keywords: Geothermal energy, fractured reservoirs, nonlinear flow, Forchheimer equation, heat
transport.
How to cite: Kumar Sonkar, A., Ganguly, S., and Das, R.: Numerical Investigation of Non-Darcy Flow Characteristics in Rough Fractures for Geothermal Reservoir Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10256, https://doi.org/10.5194/egusphere-egu26-10256, 2026.
In the context of geothermal energy development, accurate characterization of the subsurface thermal field is critical for successful exploration, resource assessment, and validation of numerical models. The temperature distribution in the subsurface is strongly influenced by the distribution of heterogeneous material properties, which are often poorly constrained, leading to significant uncertainties in model predictions. A key challenge lies in designing or improving sensor networks that effectively capture the spatial and temporal evolution of the thermal field, while considering related sources of uncertainty. Maximizing the expected information that can be acquired with an improved sensor network would enable a reliable calibration and validation of subsurface models during the exploration phase of geothermal projects. We approach this challenge by using a Bayesian optimal experimental design strategy, which allows an optimization of the sensor placement considering uncertainties in, for the case discussed in this contribution, bulk material properties. Bayesian optimal design has the disadvantage of requiring numerous forward solves, which are often prohibitive for high-fidelity numerical simulations. We address this computational burden through the construction of interpretable physics-based machine learning surrogate models. They allow faster evaluations of coupled thermal numerical models, by combining model-order reduction methods with data-driven techniques, enabling rapid and accurate predictions across large parameter spaces, while retaining interpretability grounded in the underlying physical laws. As an application of the method we address the problem of thermal sensor placement to monitor the subsurface response for (sedimentary) basin-wide applications. Our results aim at identifying optimal locations for a regional observation network that maximizes sensitivity to key subsurface characteristics.
How to cite: Siegel, C., Degen, D., and Cacace, M.: Hybrid ML assisted Bayesian Optimal Experimental Design for Thermal Field Monitoring, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11172, https://doi.org/10.5194/egusphere-egu26-11172, 2026.
Introduction: As a new type of clean energy strongly supported by the state, the efficient development of hot dry rock (HDR) relies on hydraulic fracturing technology to create an effective reservoir fracture network. However, the dynamic propagation of fractures and fluid migration during the fracturing process are difficult to observe directly. The Time-Frequency Electromagnetic (TFEM) method, as an artificial source electromagnetic technique with high excitation energy, high precision, broad frequency band, and strong anti-interference capability, provides a powerful geophysical means for real-time monitoring of the fracturing process. This is based on the significant resistivity contrast between the fracturing fluid and the HDR rock mass (e.g., granite).
Method: This study applied the TFEM method to monitor HDR fracturing. The monitoring network was deployed along the direction of the principal crustal stress (i.e., the main direction of fracturing stimulation and the most probable direction of fracture development) to maximize the capture of resistivity change signals induced by fluid injection. After field data acquisition, the raw data and corresponding source data were processed through organization and validation, followed by Fourier transform. Subsequent processing steps included current normalization, editing, filtering, etc. Finally, amplitude anomalies were extracted from the frequencies showing the highest anomalous response to characterize the relative changes in subsurface resistivity.
Results: The basement of the study area consists of high-resistivity granite (buried at approximately 1500 m depth, resistivity 2000~100,000 Ω·m), overlain by medium-to-low resistivity sedimentary strata. The target HDR stimulation depth was 3500-4000 m. Through continuous monitoring of the entire fracturing cycle (including multiple stages such as test fracturing, high-pressure stimulation, stable high-pressure stimulation, pressure-maintained sustained stimulation, pressure-maintained flowback, and enhanced stimulation), amplitude anomaly maps for each stage were obtained (Figure 1a-f). The monitoring results indicate that the resistivity decrease caused by fracturing is clearly reflected in the amplitude anomalies of the surface-collected data. The anomaly maps can intuitively display the spatial distribution of fluid migration and accumulation during different fracturing stages and effectively indicate the preferential migration pathways of the fluid.
Figure1 Plan View of Abnormal Amplitude of Fracturing Monitoring in Each Stage
Discussion and Conclusion: This case study demonstrates that the TFEM method can effectively monitor the resistivity changes induced by fluid injection during HDR fracturing, successfully imaging the dynamic development of the fracture network and fluid migration pathways. This method highlights the advantage of utilizing the physical property differences between the rock mass and fluids to address engineering geological problems, providing crucial technical support for the real-time evaluation and optimization of HDR reservoir fracturing stimulation effectiveness.
How to cite: cheng, Z., lian, S., zhang, H., and wei, Q.: Application of Time-Frequency Electromagnetic Method in Monitoring Hydraulic Fracturing in Hot Dry Rock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2473, https://doi.org/10.5194/egusphere-egu26-2473, 2026.
Flooded, abandoned coal mines represent a reliable, low-enthalpy geothermal resource, providing significant subsurface stores of water, which heat can be extracted from or rejected to. Understanding the hydraulic processes not just within the mine, but of the local groundwater regime is key for accurate characterisation and modelling of the heat extraction and storage potential of Minewater Geothermal (MWG) systems. Here, we investigate the interaction between the local groundwater regime and MWG system, their influences on each other, and how ambient flow is diverted, with the mine representing a preferential pathway. Using MODFLOW and Python, we have developed a 3D groundwater model, to assess the rate of groundwater flow through flooded coal mines.
During active mining, continual pumping of water was necessary to maintain dry working conditions. Once closed, pumps were shut off and the mines were left to flood through groundwater rebound. The UK Mining Remediation Authority are responsible for the monitoring of regional coalfield groundwater resources, investigating the impact on individual MWG sites, however, requires an understanding of the local regime.
Post-mining hydrogeology is very uncertain, with increased fracturing and hydraulic conductivity of surrounding strata producing irregular flow paths into the open mine galleries, the extent of which at individual mine sites is not known. To deal with this level of hydrogeological uncertainty, a broad modelling approach has been taken. We have completed sensitivity analysis of a conceptual model to gain a first-order view of how the distribution of hydraulic conductivity values alters the amount of water flowing through the mines, and the determination of a scaling relationship. We have also carried out transient pumping tests to calibrate the conceptual model.
Here, we present the results of i) conceptual modelling, ii) sensitivity analysis and iii) transient pumping tests, aiming to assess how varying hydrogeology of mined strata influences the rates of groundwater flow through the mine. These initial findings suggest that local groundwater flow has a significant role in the hydraulic conditions of MWG schemes and should be a key consideration when selecting sites for new schemes. Significant flow through the mines could be positive or negative, depending the on the use. For extraction schemes, a regular supply of warm water would be beneficial to the longevity of the scheme. Whereas, for storage purposes, a strong flow through the mine would carry the warm water away from the site leaving it unusable. This becomes a complex issue for seasonal storage/extraction schemes, such as the ICHS project at Durham University.
How to cite: Thomas, C., van Hunen, J., and Knapp, J.: Minewater Geothermal: Mine-groundwater interactions and the effects on Geothermal Resource feasibility, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11577, https://doi.org/10.5194/egusphere-egu26-11577, 2026.
The role of geothermal energy in the energy transition is rapidly gaining recognition. Its storage technologies provide flexible solutions to address the intermittent nature of other renewable resources. Abandoned mines and other underground caverns have recently attracted particular attention as valuable geothermal reservoirs.
In this context, a pilot project was recently initiated in the flooded abandoned underground slate exploitation area of Martelange (Belgium & Luxembourg). This area, with its long industrial history, represents a significant opportunity for future geothermal applications. The large volume of water stored within these underground caverns, in combination with heat-pumps, is sufficient to provide heating and cooling for a quite large number of buildings.
Where natural regeneration, depending on groundwater flows and the thermal conductivity of the surrounding soil, proves insufficient and where water temperature changes exceed 5 °C, active regeneration may be implemented. This involves the installation of (un)glazed solar thermal absorbers to collect low-cost solar heat during summer and cold during winter, transforming the system into a form of solar district heating. In such a scenario, the flooded slate caverns would function as a seasonal energy storage body.
The objective of the project is to develop a modern, highly energy-efficient urbanized area with a commercial zone, based on a low-temperature urban heat and cold network fed by heat-pumps. Achieving this requires a detailed assessment of the local geological and hydrogeological conditions, especially the structure and connections of the slate caverns, to ensure optimal and sustainable use of the available water resources. The first results from this study will be presented.
How to cite: Kuhlmann, N., Colbach, R., Thein, J., and Maas, S.: Groundwater of a former underground slate exploitation in Martelange-Rombach (Luxembourg) and its renewable energy potential , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17546, https://doi.org/10.5194/egusphere-egu26-17546, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 4
EGU26-20884 | ECS | Posters virtual | VPS19
Integrated Approach for Low-Enthalpy Geothermal Resource Appraisal and Assessment in Nigeria: Implications for Net-Zero TargetTue, 05 May, 15:09–15:12 (CEST) vPoster spot 4
The global energy transition is accelerating due to the climate crisis, with nations aiming for net-zero emissions as outlined in the “UAE Consensus” from the 28th United Nations Climate Change Conference (COP28). Sub-Saharan Africa must balance climate resilience and economic growth. Geothermal energy, a low-carbon, under-explored alternative to fossil fuels, can help Nigeria meet expanding energy needs. The study which aims to aims to develop an integrated, multi-scale approach for assessing geothermal resource potential employed a multi-criteria decision-making framework combining Fuzzy AHP and TOPSIS to assess geothermal potential across Nigeria’s 37 states. Fuzzy AHP provided weighted criteria, while TOPSIS calculated performance scores based on each state’s proximity to the ideal solution. Initial findings suggest that most of the highest-ranked states for geothermal potential align within regions influenced by the most recent magmatic activities in Nigeria, which occurred during the Tertiary period The analysis showed a wide spread of results, reflecting significant regional variability in geothermal conditions. Nasarawa, Bauchi, and Benue ranked highest, indicating strong geothermal suitability. Lagos, Gombe, and Ogun ranked lowest, while states such as Rivers, Katsina, and Niger showed moderate potential. Meanwhile, we will undertake targeted fieldwork in high-prospect states to map structural features at outcrop scale and conduct geochemical analysis.
How to cite: Yohanna, O.: Integrated Approach for Low-Enthalpy Geothermal Resource Appraisal and Assessment in Nigeria: Implications for Net-Zero Target , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20884, https://doi.org/10.5194/egusphere-egu26-20884, 2026.
