Fractures and faults can modify bulk rock properties by orders of magnitude, impose strong anisotropy, and form primary conduits for fluid flow and transport. Their behaviour is inherently nonlinear and highly sensitive to fluid-rock interactions, which can change transmissibility over time. These dynamic processes influence reservoir productivity, containment performance, induced seismicity potential and operational risks in geoenergy and storage projects.
Representing and modelling these systems remains a challenging task due to their structural complexity, spatial variability in physical properties, and multi-scale deformation processes. Integrating field observations, monitoring data, laboratory measurements and numerical modelling is essential to capture fracture-network evolution and fluid-driven changes. We especially welcome contributions on faults and fractures addressing:
• Structural characterisation using deterministic or stochastic approaches
• Numerical methods for continuous, discontinuous (DFN), or hybrid media
• Simulation of coupled or individual (THMC) processes
• Deterministic and stochastic inversion techniques for model calibration and uncertainty reduction
• Interdisciplinary studies linking deformation processes, transmissibility changes and fluid-rock interactions
• Applications to geothermal, groundwater, petroleum, CO₂ storage, waste repositories and other low-carbon subsurface technologies
We encourage submissions spanning multiple scales from laboratory experiments to reservoir-scale analyses and studies that bridge the gap between observation, measurement and simulation. Research integrating diverse methods to improve predictive understanding of fault and fracture behaviour in subsurface energy systems is particularly welcome, and early-career scientists are warmly encouraged to contribute.
Highlights:
Keynote speeches by PETER EICHHUBL (University of Texas at Austin) and ANA PAULA BURGOA TANAKA (Université de Neuchâtel)
Orals: Tue, 5 May, 14:00–18:00 | Room -2.31
Fractures significantly control subsurface heat and fluid transport and the mechanical properties of rock formations. Natural and stimulated fracture growth processes are thus essential for production of oil and gas in conventional and unconventional reservoirs, caprock integrity, underground storage of carbon dioxide, hydrogen, or wastewater, and for geothermal energy production in systems that require fracture stimulation or that depend on natural fractures for heat extraction. While the formation of fractures is conventionally seen as a purely mechanical process, chemical processes can decrease or increase the propensity for fracture growth as a function of stress conditions, fluid chemical and physical environment, rock composition, and rate of change of fracture driving loading conditions. The influence of chemical reactions on rock fracture processes and their implications for subsurface energy resources is thus increasingly recognized.
In combination with field structural observations of fractures in a variety of natural settings, we conduct double torsion fracture mechanics tests for sandstone, shale, and polycrystalline halite to quantify effects of fluid chemical environment on fracture mechanical properties. Tests are conducted under a range of fluid compositional and environmental conditions that are relevant to subsurface hydrogen and CO2 storage and geothermal energy production. Double torsion fracture mechanics tests measure fracture toughness and subcritical fracture index. Fracture toughness quantifies the loading stress for critical fracture growth, and subcritical fracture index the rate of fracture propagation under subcritical loading conditions. Tests are conducted under ambient room conditions, in dry N2, CO2, or H2 gas environments, and partially or completely saturated aqueous conditions. Some materials are also reacted in an autoclave under elevated temperature and pressure conditions in the presence of H2 and N2 gas prior to fracture testing.
Both fracture toughness and subcritical fracture index are influenced by the chemical environment to varying degree dependent on rock mineral composition, fluid composition, and environmental conditions. For all rock types except polycrystalline halite, samples tested under dry conditions have higher toughness and subcritical index values compared to partially or fully water-saturated samples. This can be beneficial for caprock integrity of CO2 or H2 storage reservoirs where injected gas would dry out the formation reducing the tendency for fracture-controlled leakage of top seals. Aqueous chemical reactions triggered by H2 or CO2 gas injection in porous reservoirs can both impede and enhance mechanical fracture processes depending on the combined effects of mineral dissolution and concurrent precipitation of newly formed minerals. With increasing temperature, the effects of aqueous mineral reactions on fracture properties are generally more pronounced, demonstrating the significance of reactive fracture processes in conventional and enhanced geothermal reservoirs. It is envisioned that chemical effects of fracture growth can be utilized to reduce undesired fracture growth or to optimize stimulated fracture growth to obtain desired fracture geometries that benefit subsurface energy operations.
How to cite: Eichhubl, P. and Gajda, D.: Fracture growth under reactive subsurface conditions: Processes, Mechanisms, and Significance for Geoenergy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15090, https://doi.org/10.5194/egusphere-egu26-15090, 2026.
In contrast to convergent plate tectonics during subduction, collisional orogens in their late stages (e.g., Alps, Pyrenees, Himalayas) typically exhibit little to no magmatic activity. Consequently, these settings have historically received limited attention in exploration for geothermal energy. Nevertheless, such orogens do host active, amagmatic geothermal systems owing to the co-occurrence of several key features: (1) ongoing crustal-scale deformation within the brittle upper crust, which generates spatially dispersed, permeable fracture networks; (2) major, steep strike-slip and normal faults with permeable dilation zones that cut across the fracture networks; (3) geothermal gradients of 20–35 °C/km, which provide heat to circulating fluids; (4) pronounced topographic relief, which induces strong hydraulic head gradients between high surface elevations and valley floors.
The interaction of these features produces dynamic geothermal circulation systems: meteoric water infiltrates at high elevations into the dispersed fracture networks and is focused into the major faults, allowing the water to descend to depths up to 10 km and become heated to above 200 °C. Subvertical dilation zones within the major faults link the deep flow paths to the surface or relatively shallow depths, generally at lower elevations, allowing the topographically induced hydraulic gradients to drive the hot water up to discharge sites in the valley floors.
Unfortunately, in orogens where valleys are glacially over-deepened, outflow is commonly hidden under thick sequences of unconsolidated sediments. Therefore, the challenge in exploration in such settings is to locate these blind geothermal systems. To address this challenge, we examined the geothermal favorability of the mountainous Valais region in SW Switzerland, which is one of the most well-known areas of geothermal activity in the European Alps. Through collaboration among structural geologists, hydrogeochemists and seismologists, all available geological and hydrochemical data were compiled in a GIS database to conduct a Play Fairway Analysis. Each data layer was evaluated and rated for its ability to directly or indirectly indicate sites of deep thermal upflow. By weighting and combining these layers, we produced favorability maps displaying areas where active upflow of thermal water is most likely. A notable outcome is that most of the known thermal springs in the study area fall within the identified favorable areas. This success demonstrates the usefulness of the favorability maps in guiding more spatially-targeted exploration in the Valais region. Moreover, our methodology provides a transferable framework for exploration in similar geodynamic settings elsewhere.
How to cite: Herwegh, M., Schmid, T., van den Heuvel, D. B., Wanner, C., Diamond, L. W., Faulds, J., Berger, A., Diehl, T., and Madritsch, H.: Why late-stage collisional orogens are favorable for geothermal exploration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6253, https://doi.org/10.5194/egusphere-egu26-6253, 2026.
Understanding the development of fault zones in caprock shales and their impact on permeability is critical when considering underground CO2 storage in aquifers and depleted reservoirs. To enhance this knowledge, we characterize the paleofluid system in seismic-scale faults cutting through low-permeability shale formations, assesing whether fluids recorded in the fault core and damage zone record large-scale migration and enhanced effective permeability. The Somerset coast (UK), along the southern margin of the Bristol Channel Basin, exposes shale and marl dominated Mesozoic caprock successions dissected by seismic-scale normal and inverted faults, of which the timing of initial activity is well constrained by radiochronology and which exhibit well-preserved fault cores and damage zones as well. In this study, we present field-based structural analyses, petrographic investigations, stable isotope geochemistry (δ¹³C, δ¹⁸O) and clay mineralogy (XRD) from six selected outcrops. The vein-rich damage zones exhibit calcite and gypsum precipitation, recording transient fluid-flow episodes during reactivation. Stable isotope data, combined with fluid inclusion petrography, indicate that these episodes were dominated by meteoric fluids (δ¹⁸O<-10‰ VPDB) from which synkinematic calcite precipitated in faults at geothermal conditions (<60°C). When considering published radiogenic ages for the extensional development (150-120 Ma) and subsequent inversion (50-20 Ma) of the considered faults, the recharge of meteoric fluids in the fault at depth is consistent with regional paleogeographic reconstructions showing fluctuating emergence of landmasses in the area during the Late Triassic to Cretaceous. Within this framework of episodic fluid circulation, most fault cores are mechanically sealed rather than swelling-sealed, with permeability reduction controlled by grain-size reduction and the development of aligned clay fabric. Nevertheless, mineralized fault cores demonstrate that fault sealing is not static, during episodes of elevated fluid pressure or reactivation, permeability may be locally and temporarily enhanced along discrete slip surfaces. This behavior is strongly controlled by fault-zone architecture, with increasing displacement promoting gouge thickening and fabric development, ultimately leading to more effective long-term sealing. Beyond regional implications, our study reconstructs kilometer-scale downward fluid-flow along faults, supporting the significant impact of the damage zone on the long-term integrity of clay-rich caprocks.
How to cite: Aykut, T., Beaudoin, N., Wibberley, C., Dutilleul, J., Emmanuel, L., and Callot, J.-P.: Fault-controlled paleofluid flow in shale caprocks: Structural, geochemical, and mineralogical evidence from the Bristol Channel Basin (UK), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13705, https://doi.org/10.5194/egusphere-egu26-13705, 2026.
Heating and cooling in both industry and households in Europe has become increasingly important but it is still heavily dependent on fossil fuels. Shifting to low-carbon alternatives cuts emissions, strengthens energy security, and enhances the efficiency for these energy systems in the future. These goals can be achieved with a combination of efficient energy storage and clean energy production. Two example solutions within this field are the Cavern Thermal Energy Storage (CTES) and Deep Geological Repositories (DGR), the first used to store thermal energy and the second to solve the waste issue in climate-neutral nuclear energy production. These two solutions have the common requirement of needing advanced structural geological studies. During the last decade research have focused, for example, on developing CTES, which rely on subsurface caverns in low-permeable rocks that are near surface and remain stable when injected with hot and cold water. Today, there is broad international scientific consensus that high-level nuclear waste should not be stored at the surface in the long term. DGR are considered the best solution as they enclose the radioactive waste in suitable host rock formations located several hundreds of meters below the surface. DGR has also been extensively researched and advanced in several countries, and Finland is a global leader in developing the concept for the storage of nuclear waste within crystalline bedrock.
These storage concepts in crystalline bedrock depend on selecting rock blocks that lack major deformation zones and contain few faults and fractures. Hence, the structural geological modelling is an important tool to mitigate uncertainties and to assess the applicability of the bedrock volume for storage. Several methods exist to assess the bedrock, such as non-intrusive geophysical surveys and intrusive drilling of boreholes into the bedrock. State-of-the-art research shows that best results are achieved by combining multiple research methods within a well-designed research framework to define a 3D geological model of the site.
Successful implementation of these energy storage projects requires the definition of parameters at early stages of the project to define the constrains for the structural geological 3D model. Detailed structural geological modelling enables evaluation of key aspects and mitigation of uncertainties, such as groundwater conditions, seismic risks, mechanical and thermal properties, as well as environmental factors for the project. This exploration approach can significantly reduce time constrains and costs during every step of these projects. In addition, these geological 3D models serve as an important tool for presenting and communicating projects, including their uncertainties, to policy makers, stakeholders and the public.
How to cite: Engström, J., Ahlqvist, K., Vallin, S., Ovaskainen, N., and Nordbäck, N.: The importance of structural geology in site characterisation of geoenergy and nuclear waste sites , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3852, https://doi.org/10.5194/egusphere-egu26-3852, 2026.
The Meuse/Haute-Marne Underground Research Laboratory hosts a large-scale hydraulic tomography experiment designed to characterize fracture networks induced around open and sealed galleries. The objective of this study is to reconstruct their hydraulic properties and fracture geometry to validate a conceptual model describing stress redistribution during tunnel excavation. In the first step, cross-hole responses from gas permeability tests conducted by Solexperts SA were analyzed using an equivalent porous media approach consisting of a 3D travel-time-based tomographic inversion. In the second step, a sequential inversion scheme was applied to reconstruct discrete fracture planes in 3D.
Gas injection tests were carried out across 11 boreholes, each equipped with a movable multi-packer system comprising six intervals for injection or observation. This configuration enabled the recording of 1168 pressure interference signals with a signal-to-noise ratio sufficient for inversion.
The applied 3D travel-time-based tomographic approach relies on transforming the transient groundwater flow equation into the eikonal equation using an asymptotic approximation. This inversion method allowed reconstruction of the 3D gas diffusivity distribution, capturing the key features of the conceptual model related to stress redistribution during excavation. The sequential inversion approach integrates the 3D travel-time inversion with multivariate statistics and basic geological constraints. This method enables significant mesh refinement within the model domain while avoiding a strong ill-posed inversion problem. It successfully reconstructed fracture traces of the induced network parallel to the tunnel surface, including both extension and shear fractures.
Combining results from both approaches enhanced understanding of the spatial geometry of the induced fracture network around galleries: the 3D travel-time tomography provided a comprehensive spatial representation of the conceptual model, while the sequential inversion delivered high-resolution 3D images of fracture traces associated with its main properties.
How to cite: Brauchler, R., Maqueda, A., de La Vaissière, R., Piedevache, M., and Laurent, A.: A massive hydraulic tomography experiment for the high-resolution characterization of the excavation induced fracture network using a travel-time based inversion scheme, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7692, https://doi.org/10.5194/egusphere-egu26-7692, 2026.
Self-potential (SP) monitoring was implemented at the Bedretto Underground Laboratory as part of the BEACH experiment to complement multi-parameter observations during fluid-injection tests. Continuous SP measurements have been conducted since the end of October 2025, with data acquired so far covering the period until mid-December, and monitoring planned to continue throughout the current year.
The SP setup consists of nine non-polarizable Pb/PbCl₂ electrodes installed along the tunnel wall and within one borehole in the Mesozoic Crystalline Fault Zone. Tunnel-wall electrodes were placed in shallow drill holes and embedded using conductive contact material to ensure stable long-term coupling to the rock. A single electrode was installed in a 50m borehole to provide additional depth sensitivity. All electrodes were connected to a CR6 data logger, recording continuous SP time series with a sampling interval of one value per minute.
The recorded data span different operational phases, including background conditions as well as cold and warm water injection cycles and associated shut-in periods. This contribution presents an initial overview of the acquired SP dataset.
Acknowledgements:
BEACH – Energie Speicherung und Zirkulation von Geothermischer Energie in Bedretto receives funding from the Swiss Federal Office of Energy (SFOE), Project number SI/502817.
"Geo-INQUIRE is funded by the European Commission under project number 101058518 within the HORIZON-INFRA-2021-SERV-01 call."
How to cite: Haaf, N., Azzola, J., Vargas Meleza, L., Hertrich, M., Gischig, V., Wimez, M., Rinaldi, A. P., Straub, F., Brehme, M., Giardini, D., Sorbeto, F., and Alcolea, A.: Electric Self-Potential Measurements during Fluid Injection at the Bedretto Underground Laboratory, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9512, https://doi.org/10.5194/egusphere-egu26-9512, 2026.
Heat transfer in fractured rocks is a key process for deep geothermal energy exploitation. Fractures represent the main pathways for fluid flow and advective heat transport, while diffusive thermal exchange occurs between the fluid within the fractures and the surrounding host rock. These two processes occur over very different spatial and temporal scales, and their variability is strongly influenced by fracture–rock heterogeneity, which ultimately controls geothermal performance.
In this work, we discuss two transient mechanical processes that can alter the geometry of fractured rocks during fluid circulation, thereby affecting heat transport and, consequently, the efficiency of geothermal plants. The first process involves flow channeling induced by shear slip activation in critically stressed fractures. We analyze this phenomenon at the single-fracture scale. Using analytical solutions and numerical simulations, we investigate the thermal response to the injection of a cold temperature pulse into a rough fracture, considering both synthetic and real heterogeneous aperture fields. The results reveal that fracture roughness has a significant influence on heat transport, with post-peak tailings of the breakthrough curves showing an anomalous transient decay rate in time before evolving toward the asymptotic regime with a -3/2 decay rate, which is characteristic of fracture-matrix diffusive heat exchange. This behavior is sensitive to variations in the fracture aperture field caused by the activation of relative sliding between fracture surfaces, with larger slips leading to earlier temperature peaks and delayed transitions to the asymptotic diffusive regime.
The second process focuses on cooling-induced thermal contraction of the rock surrounding the fractures, which tends to increase fracture aperture and directly affects fluid flow and advective heat transport. We analyze this phenomenon at the scale of the fractured rock mass. By means of a hybrid methodology that combines an analytical model with a particle tracking approach applied to Discrete Fracture Networks (DFNs), we numerically investigate the impact of cold fluid circulation in systems of fractures with different characteristics. Results show that rock contraction accelerates the advective transport resulting in a faster recovery of cold fluid at the outlet.
These analyses allow identifying the characteristics of fractured rocks that are most critical for heat transport under the occurrence of fracture slip and opening. This understanding is crucial to control the performance and lifetime of geothermal exploitations.
How to cite: De Simone, S., González-Fuentes, S., Andrés, S., and Vilarrasa, V.: Heat transport in deforming fractured rocks: the effects of fracture slip and opening, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3471, https://doi.org/10.5194/egusphere-egu26-3471, 2026.
Most existing fracture modeling workflows rely on the generation of discrete fracture networks (DFN), which simulate fracture patches based on stochastic distributions of geometric parameters and generally neglect topological constraints. To address the DFN constraints, we propose applying graph theory and deep learning to characterize and generate coherent fracture networks from real-world datasets. Our approach broadens the range of quantitative methods available for fracture modeling; it is non-gridded and accounts for both geometry and topology in the generation of new networks.
The generation of fracture networks based on a reference and/or analog network interpretation is useful for modeling subsurface uncertainties related to fracture positions and network intersections. This application is useful for sites where fracture interpretation is possible, but where full coverage of the study site is not available. For characterization, we integrate geometry, topology, kinematics, age relationships, and geomechanics to identify the most important connections within a network. For simulations, we combine a graph recurrent neural network (GraphRNN) for generating graph topology and graph denoising diffusion probabilistic models (DDPM) for generating node positions in space. Deep generative models learn distributions from the training fracture network data and generate new networks with a variable number of fracture lineaments, represented as edges, while intersections are represented as nodes.
Our method is applied to a real case study from the Western Helvetic Alps domain in Switzerland. The model is trained on graphs derived from the fracture network interpretation of a Cretaceous limestone aquifer. The generation of new fracture networks as graphs yields coherent topologies with statistical distributions similar to those of the training data for node degree and relative node positions (i.e., edge length and azimuth). Furthermore, the training dataset and the generated networks are compared using node centrality measures (betweenness and percolation), which help describe the network's connectivity and highlight preferential flow paths, thereby emphasizing the role of fracture connectivity in enhancing permeability and controlling flow anisotropy. The method is promising for the generation of fracture networks as an alternative approach that can be used to identify preferential fluid flow paths and to build scenarios for later flow simulation for hydrogeology, reservoir management, geothermal energy, nuclear waste disposal, and geologic sequestration.
How to cite: Burgoa Tanaka, A. P., Renard, P., Liang, X. X., Straubhaar, J., and Lauzon, D.: Fracture network modeling with graph deep learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11471, https://doi.org/10.5194/egusphere-egu26-11471, 2026.
Fluid circulation in ductile rocks controls the deposition of critical resources such as copper and molybdenum, as well as the potential for deep, supercritical geothermal systems. However, the mechanisms that allow or hinder such circulation under high temperature and pressure conditions remain poorly understood.
In this study, we conducted two sets of healing experiments on thermally cracked Lanhelin granite, both water-saturated and dry, under high confining pressure and temperature. The first set of experiments was carried out under hydrostatic conditions (Peff = 85 MPa) with increasing temperature (21–400 °C). The second set was conducted under triaxial conditions, in which specimens were deformed at Peff = 85 MPa, temperatures ranging from 200 to 600 °C, and a strain rate of 10⁻⁶ s⁻¹. In both cases, permeability was continuously recorded throughout.
Under hydrostatic conditions, permeability remained roughly constant at room temperature and in dry samples, but decreased by up to an order of magnitude over 8 hours at 400 °C. Under triaxial deformation, water-saturated specimens were weaker and exhibited more ductile behavior compared to dry samples. Moreover, the more ductile the sample, the greater the increase in permeability observed leading up to failure.
Microstructural evidence supports chemical crack self-healing as the dominant healing mechanism in the hydrostatic experiments. In the deformed samples, post-mortem analysis revealed that the observed increase in permeability is associated with pervasive cracking throughout the bulk of the rock.
Overall, our study demonstrates the necessity of deformation to generate permeability in ductile rocks, while also highlighting the transient nature of this permeability.
How to cite: Meyer, G., Lazari, F., and Violay, M.: Transient permeability in ductile rocks: the competition between deformation and healing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13002, https://doi.org/10.5194/egusphere-egu26-13002, 2026.
Development of large-scale rock friction apparatus started around 2010 at National Research Institute for Earth Science and Disaster Resilience (NIED) in Japan (Fukuyama et al., 2014, NIED Rep.). Until now, three generations of the apparatus have already been developed, whose sliding area ranges from 1.5 m to 6.0 m in length. The purpose of this project was to investigate the rock frictional properties and earthquake rupture process at various sliding scales. There are two important characteristics in these apparatuses. One is that the nucleation zone size can be generated within the sliding fault area. The other is that the nucleation process can be spatially monitored by local strain measurement array installed close to the sliding surfaces. When nucleation zone is confined to the experimental fault surfaces, the whole rupture process from initiation to termination could be able to be observed in the experiments (Yamashita et al., 2026, EGU). Using these apparatuses, many kinds of large-scale rock friction experiments have been conducted. Through such experimental research, the following results have been reported. 1) The spatial distribution of strength on the fault surface is heterogeneous, which had not been properly considered by small-scale experiments (Yamashita et al., 2015, Nature). 2) Such spatial heterogeneity of strength on the fault surface could contribute to the fault-size dependence of macroscopic rock friction as well as the rich spectrum of rupture behaviors, which are quite important for the modeling of earthquake generation process (Xu et al., 2023, Nat. Geosci.). Especially, due to high-speed loading (~1 mm/s) and long-distance sliding (~40 cm), ten-decimeter-scale heterogeneity on the fault surface could be generated, which is found to play an important role in large-scale friction experiments (Yamashita et al., 2018, Tectonophys.). In addition to these spatially heterogeneous fault friction experiments, rupture propagation has been investigated in detail to investigate the fracture energy (Okubo et al., 2026, EGU; Matsumoto et al., 2026, EGU). In the near future, we expect that such large-scale rock friction experiments would contribute significantly to seismology, especially, physics of earthquake generation process, by establishing new constitutive law(s) of the rock friction through the usage of dense arrays of near-fault observations.
How to cite: Fukuyama, E., Yamashita, F., Xu, S., Mizoguchi, K., Kawakata, H., Okubo, K., Matsumoto, Y., and Maeda, S.: Development of Large-scale Rock Friction Apparatuses at NIED, Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8504, https://doi.org/10.5194/egusphere-egu26-8504, 2026.
Fractured crystalline rocks are widely regarded as suitable host formations for waste isolation applications, including deep geological repositories for spent nuclear fuel. Fluid flow in these systems is predominantly controlled by networks of fractures whose hydraulic properties are governed by internal heterogeneity, contact area distribution, and stress-dependent aperture evolution. These properties are strongly influenced by in situ stress conditions, which may evolve over geological to engineering time scales due to processes such as glacial loading, stress redistribution, and excavation-induced damage. Robust representation of fracture-scale flow behaviour is therefore critical for the development and calibration of large-scale discrete fracture network models.
In this study, we investigate the coupled hydro-mechanical behaviour of a natural single fracture using a laboratory-scale flow experiment under increasing normal load. The fracture aperture field was reconstructed using high-resolution 3D scanning of the opposing fracture surfaces, with vertical alignment refined using pressure-sensitive film measurements. A systematic sensitivity analysis of 27 alignment cases, incorporating translational uncertainties along the x-, y- and z-directions was performed to quantify their influence on flow behaviour. Measured flow rates were compared against predictions from the local cubic law under varying normal stress. Results demonstrate that flow is highly sensitive to fracture surface alignment, with misalignment along the flow direction and normal direction exerting the dominant influence. The local cubic law systematically overestimates flow by at least two orders of magnitude for all loading cases. Furthermore, the application of a constant correction factor to convert mechanical to hydraulic aperture, calibrated under unloaded conditions, fails to reproduce experimental flow rates as normal load increases. We propose a stress-dependent correction factor linked explicitly to the evolution of fracture contact area. Incorporating this relationship yields close agreement with experimental observations across all loading and alignment cases.
How to cite: Stock, B., Frampton, A., and Mas Ivars, D.: Hydro-mechanical loading effects on flow through a single natural fracture, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11476, https://doi.org/10.5194/egusphere-egu26-11476, 2026.
Mudrocks are a crucial resource for subsurface storage of gases or radioactive waste, both as host rock and caprock. They are characterised by low primary permeability and high creep rates, limiting the lifespan of fractures, both decreasing the chance of leakage. Large faults pose a significant risk to this, as they act as coupled hydro-mechanical weak points, with potential for increased flow up-dip and along-strike. Gouge generation is well established as a process which limits this permeability increase, however cementation of void space in faults is less well studied.
We studied faults hosted in the Mercia Mudrock Group in the Bristol Channel (southwest UK). We find that gouge and cementation work cyclically with more than one mineral phase, indicating the hydro-mechanical development of a fault through its lifespan. In the fault core, veins tend to be redirected parallel to the mechanical discontinuity between damage zone and gouge, indicating the location of preferential flow. In the damage zone, veins are not always planar in the soft mudrocks and are often part of an anastomosing network which is influenced by other non-fault related structures, such as older veins, sand dyking, and mechanical stratigraphy. The elongated, fibrous gypsum and calcite crystals observed emphasise the importance of high fluid pressures to open and maintain these fractures.
We interpret episodic overpressures that build up layers of gypsum veining in the gouge core of a number of faults; however, the limited special extent of these veins suggests patch-style dilation and slip that may not pose a significant leakage risk. Gypsum veining appears to destroy most remaining evidence of a damage zone in these instances.
This is in contrast to brittle calcite, associated with rifting and inversion, which shows more fluid movement up-and-down-dip and appears to preserve the damage zone. This results in structures that can be reactivated, both by more calcite-bearing fluid but also overpressure caused by rehydration of anhydrite to. This reactivation causes brecciation of the calcite that is not seen in the gypsum despite the overprinting of stress events.
In summary, tectonic environments which open large fault patches potentially pose a higher risk to leakage through mudrock-hosted faults, than fluid overpressure events. However, cementation of these faults, while providing mechanical discontinuities for later dilation events, do appear to seal voids generated by fault activity.
How to cite: Page, G., Forbes Inskip, N., Cartwright-Taylor, A., Kampman, N., and Busch, A.: The fault in our clay: Variation in fault cementation in evaporite-bearing mudrocks and implications for sealing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4557, https://doi.org/10.5194/egusphere-egu26-4557, 2026.
Heating water using waste heat and excess renewable energy in Cavern Thermal Energy Storage (CTES) systems provides a sustainable solution for large-scale thermal energy storage. In addition to challenging economics of CTES, unexpectedly high thermal losses have been a major concern in many cases in the past. In crystalline bedrock, fractured brittle deformation zones can act as fluid pathways, potentially causing thermal losses and compromising cavern stability. Therefore, detailed modelling of these zones is essential for the safe and efficient operation of CTES facilities.
This study presents a workflow for geological characterization and deformation zone modeling at the planned site of the world’s largest CTES facility, VARANTO, in Vantaa, southern Finland. The dataset includes drill core samples totaling over 4 km, acoustic and optical borehole imaging, outcrop observations, and a photogrammetric model. We delineated deformation zone intersections from core samples and classified them into core and damage zones, defining zone dimensions for altered and fractured bedrock. We clustered orientation data from borehole imaging and core logs to determine mean fracture orientations, which, together with zone dimensions, were integrated into a 3D geological model to construct a volumetric representation of deformation zones. Additionally, we parameterized these zones based on properties such as core fracturing, fracture infill, and alteration to characterize and evaluate their structural significance in terms of stability and potential hydraulic conductivity.
The resulting 3D model improves understanding of potential fracture zones and thus pathways for groundwater flow and their impact for thermal and mechanical behaviour, supporting system simulations, monitoring, and maintenance. Representing deformation zones as volumes rather than surfaces enhances integration with groundwater flow models, reduces uncertainty, and enables more accurate prediction of hydraulic connectivity and thermal losses, thereby optimizing system performance. This workflow also provides a transferable methodology for other underground energy storage projects, facilitating risk assessment and design optimization in crystalline bedrock environments.
How to cite: Ahlqvist, K. M., Engström, J., Vallin, S., and Hagström, M.: Geological 3D modeling in crystalline bedrock for a cavern thermal energy storage site in S Finland - defining properties and parameters for deformation zones, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4833, https://doi.org/10.5194/egusphere-egu26-4833, 2026.
Ensuring the safe disposal of high-level radioactive waste in a suitable host rock requires compliance with several legally defined criteria. In Germany, these criteria are established by Repository Site Selection Act (Standortauswahlgesetz – StandAG). One of the key hydrogeological criteria constrains the hydraulic conductivity of the host rock to values below 10-10 m/s. In crystalline rocks, hydraulic conductivity is governed by contributions from both the rock matrix and the fracture network, with transport typically dominated by fractures.
Fractures are characterized by multiple parameters, including orientation (strike and dip angles), fracture size (strike and dip lengths), volumetric fracture density (number of fractures per unit volume), and hydraulic aperture. The main objectives of this study are to (i) evaluate the sensitivity of effective hydraulic conductivity to individual fracture parameters and their correlations, (ii) test a DFN-based workflow for hydraulic upscaling at the representative elementary volume (REV) scale, and (iii) identify parameter combinations that satisfy the hydraulic safety criterion defined by StandAG for nuclear waste repositories.
Parameter correlations represent dependent relationships between fracture properties. Semi-correlated DFN models account for relationships between fracture aperture, strike length, and fracture density while incorporating a stochastic term to capture natural variability, whereas uncorrelated DFN models assume full parameter independence.
Both semi-correlated and uncorrelated DFN models were considered to investigate the influence of correlations between fracture length, aperture, and volumetric fracture density on hydraulic behavior. The proposed workflow integrates DFN generation using the software Frackit, the upscale of fracture-scale properties to an equivalent porous medium (EPM) based on Oda’s method assuming cubic-law fracture-scale flow, and flow simulations performed with FEFLOW 10 to derive effective hydraulic conductivity.
The DFNs were generated within a cubic volume of 50×50×50 m³. Fracture lengths range from a few to several tens of meters, volumetric fracture densities vary between approximately 10-4 and 10-2 m-3, strike and dip angles span 0–180° and 0–90°, respectively, and fracture apertures extend from 10-7 to 10-2 m.
The results show that (1) fracture aperture was consistently found to be the strongest parameter controlling hydraulic conductivity in both semi-correlated and uncorrelated models. In semi-correlated models, volumetric fracture density and fracture dimensions such as strike and dip lengths also significantly affect the effective hydraulic conductivity. Strike and dip angles exhibited low sensitivity. In uncorrelated models, the aperture alone dominates flow, while other parameters show negligible influence. (2) Effective hydraulic conductivity compatible with the StandAG limit is typically found when fracture apertures are small, i.e., smaller than 10-4 m, strike lengths are short, i.e., shorter than 10 m, and fracture density is moderate to high, i.e., higher than 1 × 10-3 m-3, in semi-correlated models. In uncorrelated models, hydraulic conductivity below the standard limit is primarily controlled by small apertures, i.e., smaller than 10-4 m, independent of fracture density.
How to cite: Jimenez, V. and Renz, A.: Sensitivity analysis of fracture parameters in discrete fracture network (DFN) models for effective hydraulic conductivity under StandAG, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12023, https://doi.org/10.5194/egusphere-egu26-12023, 2026.
Discrete Fracture Network (DFN) models are widely used for predicting the hydraulic properties of heterogeneous fractured rock masses through the implementation of diverse numerical and semi-analytical methods. However, recent advancements in the parametrization of fracture networks by statistical analyses of field and geophysical data are not yet fully integrated into the capabilities of standard DFN simulators. Available 3D stochastic DFN generators (i) lack the ability to produce realistic topological relationships, and (ii) are limited to random spatial distributions of fracture seeds based on Poisson processes, thereby excluding clustered or regular patterns common in real fracture systems. In the case of heterogeneous rock masses with multiple clustered fracture sets, this leads to an inaccurate representation of connectivity, which significantly impacts the accuracy of hydraulic property estimates and flow modeling results. In addition, the simplified shape of fractures in DFN codes – either rectangular or elliptical, is very different from what observed in our natural sample, where due to mutual abutting relationships the fractures tend to have a triangular or trapezoidal shape, with a strong impact on the evaluation of P32 (i.e. the volumetric fracture intensity), that is a critical parameter in DFN generation. We present a comparative experiment in which a 3D deterministic fracture network was reconstructed from high resolution micro-CT scans of Miocene diatomitic marls (equivalent to the Tripoli Fm., Palena, Central Italy) using a combination of open-source and commercial software, including Move, Petrel, and PZero. This deterministic model was then compared with multiple stochastic DFN realizations sharing the same statistical parameters, generated with DFNWorks, Move and Petrel. Finally, the hydraulic properties of resulting fracture networks and their impacts on flow simulations were assessed using the flow-based model (Petrel), the semi-analytical Oda approach (Petrel and Move) and fully numerical simulations (finite volume in DFNWorks).
Our results indicate that advanced numerical methods, where flow is really simulated along interconnecting fractures, exhibit a greater sensitivity to input data quality than semi-analytical approaches. This discrepancy arises because methods such as the Oda approach rely on idealized assumptions and spatially averaged parameters, disregarding critical parameters such as network topology, connectivity, and fracture aspect ratios. In absence of experiments conducted under controlled lab conditions, we tend to trust the more advanced numerical results (e.g. DFNWorks finite volume) with respect to simplified semi analytical approaches (e.g. Oda).
How to cite: Facci, M., Favaro, S., Casiraghi, S., Agliardi, F., Mittempergher, S., Hussain, W., Hyman, J., Gainov, R., Slipeniuk, O., Fogazzi, M., and Bistacchi, A.: A Comparative Study of Deterministic and Stochastic DFN Models for Rock Mass Hydraulic Property Estimation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18678, https://doi.org/10.5194/egusphere-egu26-18678, 2026.
Posters on site: Tue, 5 May, 08:30–10:15 | Hall X1
Understanding hydraulic properties in fractured crystalline bedrock is essential for predicting groundwater flow and heat transport in deep geological settings. This study focuses on the Kopparnäs Test Site in southern Finland, where the bedrock mainly consists of granites, granodiorites, and, commonly migmatitic mica gneiss.
Fracture orientation and aperture were characterized using acoustic (ABI) and optical borehole imaging (OBI), combined with hydraulic conductivity measurements obtained from zone-based slug tests in a borehole drilled to a depth of 233 m. Seven test zones at depths ranging from 18 m to 132 m were selected for integrated hydraulic conductivity and fracture analysis. The borehole intersects a nearly vertical east–west striking fault zone at approximately 100 m depth, where three core zones were targeted for hydraulic conductivity measurements. Each zone was analysed in terms of fracture frequency, orientation, and infilling to achieve an integrated understanding of hydraulic behaviour.
Structural analysis indicates that most fractures are steeply dipping, with dominant NNE-SSW orientations and dips towards the SSE. Sub-horizontal fractures mainly occur at shallow depths within the upper 100 m, which is typical of Finnish crystalline bedrock due to glacial unloading after the latest glaciation. Between 100-130 m, the borehole intersects a sub-vertical fault zone that significantly increases fracture frequency. Below this zone fracture frequency decreases markedly with only sporadic fractures observed.
Hydraulic conductivity remains within the same order of magnitude (10-7 m/s) but varies between zones reflecting differences in fracture characteristics rather than fracture density alone. Higher hydraulic conductivity is observed at shallow depths where fractures are predominantly sub-horizontal and partially open. In contrast, deeper sections are dominated by steeply dipping, mineral-filled fractures associated with reduced conductivity. Intermediate conductivities reflect mixed orientations and aperture conditions. Overall, fracture orientation and infilling exert a stronger control on hydraulic conductivity than fracture frequency, the role of fracture connectivity, aperture and mineral filling in governing fluid flow.
Core analysis revealed porosity values of about 30% at 140 m depth within heavily altered zones. A similar pattern is observed at the Kivetty site in central Finland, where increased alteration intensity correlates with higher total porosity, improved pore connectivity, and enhanced permeability. Future work will extend hydraulic testing to intervals with high porosity and include fracture aperture and spacing measurements to assess their combined influence. This integrated approach provides a robust framework for distinguishing hydraulically significant fractures from inactive ones, improving site characterization for groundwater resource management, geothermal energy exploration and deep geological repository safety assessments.
How to cite: Okutan, H., Engström, J., Carbajal-Martinez, D., Markovaara-Koivisto, M., Salmi, R., Reijonen, H., and Kortunov, E.: Integrated Characterization of Fracture Orientations and Hydraulic Properties in Crystalline Bedrock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3278, https://doi.org/10.5194/egusphere-egu26-3278, 2026.
Stable intraplate cratonic blocks usually have less structural deformation and fewer earthquakes than other locations on Earth, but with strong compressional deformation around their periphery. Investigating how and why this different deformation occurred is beneficial for understanding why the cratonic block is so stable and how the intraplate in-plane stress is transmitted. In this work, we first investigated the structural deformation changes from the margin to the interior of the western Ordos Block (OB; one of the most tectonically stable area in China) via seismic data. The results show abrupt structural deformation changes from the margin to the interior of the OB in terms of the deformation strength (from strong to weak), structural orientation (high angle oblique relationships), and kinematics (from compression to wrenching). Our investigation also shows that such phenomena are widespread in cratonic blocks worldwide. The abrupt changes are probably induced by special in-plane stress transfer inside the cratonic block: when far-field stress is transmitted into continental interiors from active plate margins, the weak belt around the cratonic block filters and accommodates the in-plane stress. Consequently, this decreases the stress, changes the stress direction, and transmits the in-plane stress along a shallower layer (probably less than 1500 m). Furthermore, the compression stress from the plate margin is converted into shear stress within the cratonic block. This stress transmission manner makes reactivation of the deep preexisting faults difficult under far-field horizontal plate-boundary stresses in the cratonic block without vertical forces from the mantle, guaranteeing long-term stability and low seismicity. This understanding can provide a new perspective for the interpretation of earthquakes in stable continental regions. It can also be applied to appraise the long-term stability of sites for the storage of CO2.
How to cite: Huang, L., Wang, Z., Zhang, Y., Li, X., and Liu, C.: Abrupt structural deformation changes from the boundary to the interior of the Craton Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-124, https://doi.org/10.5194/egusphere-egu26-124, 2026.
Abstract: Accurate construction of multi-scale fracture models is essential for optimizing hydraulic fracturing design, predicting sweet-spot distribution, and improving shale gas recovery in deep, structurally complex reservoirs. The Wufeng–Longmaxi shale in the northern Luzhou area is characterized by strong tectonic deformation, lithological heterogeneity, and fracture development across multiple scales. To address these challenges, this study proposes an integrated multi-scale fracture modeling framework that couples reservoir geomechanics, multi-attribute seismic analysis, and microstructural characterization. First, pre-stack seismic inversion was performed to derive elastic parameters, including P-impedance, Vp/Vs ratio, and density, which were further used to construct 3D mechanical property volumes such as brittleness index, Young’s modulus, and Poisson’s ratio. Curvature attributes and ant-tracking analysis were applied to delineate zones of enhanced structural deformation and large-scale fracture corridors. Second, triaxial rock mechanics experiments and CT-based digital core analysis were conducted to calibrate lithology-dependent failure criteria and layer-parallel anisotropic mechanical parameters for siliceous and calcareous shales, forming the basis of a heterogeneous geomechanical model. Finite-element simulations were then used to resolve the present-day in-situ stress field and quantify fracture openness, density, and orientation under mechanical–stratigraphic constraints. Results show that: (1) a NW–SE trending high-curvature anticline dominates the northeastern study area, where brittle siliceous shale (brittleness index > 0.65) accounts for 58%, and the maximum horizontal stress (NW 130°–150°) provides favorable conditions for fracture development; (2) large-scale fractures (>10 m) are controlled by curvature ridges and fault transfer zones, while mesoscale fractures (1–10 m) correlate positively with the product of brittleness index and bedding density, and (3) microscale fractures (<1 mm) exhibit strong coupling with TOC-rich domains (TOC > 3.5%). Integrating curvature volumes, ant-tracking results, geomechanical simulations, and microfracture fractal parameters yields a hierarchical workflow linking macroscopic structural guidance, mesoscale mechanical response, and microscale pore–fracture attributes. Field validation shows that the predicted fracture-rich zones match production performance with an accuracy of 82%. The L202 well, deployed using this workflow, achieved a post-fracturing daily gas rate of 2.3×10⁵ m³, 37% higher than adjacent wells. This integrated methodology overcomes the limitations of single-scale modeling and provides a robust framework for 3D shale gas reservoir evaluation and development in complex structural domains.
Keywords: Multi-scale fracture modeling; reservoir geomechanics; seismic attribute integration; in-situ stress; Luzhou area
How to cite: Ren, Q.: A Multi-Scale Fracture Modeling Framework Driven by Integrated Reservoir Geomechanics and Seismic Attribute Analysis: A Case Study from the Northern Luzhou Shale Gas Play, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1485, https://doi.org/10.5194/egusphere-egu26-1485, 2026.
Many renewable subsurface energy systems rely on understanding fracture networks. In geothermal systems, fractures often provide the primary pathways for fluid flow, while in underground hydrogen storage (UHS) and carbon capture and storage (CCS), fracture networks can strongly influence pressure communication, injectivity or caprock integrity. Similarly, in nuclear waste repositories, fractures can compromise barrier integrity and limit containment. This study investigates the representativity of discrete fracture networks (DFNs) generated from high-resolution photogrammetric outcrop data to support robust models and simulations.
Observed data such as fracture orientations, lengths, intensities, and topological node classifications (X-, Y-, and I-nodes) are used to construct synthetic DFNs via (1) geometric modelling, (2) fracture-growth algorithms, and (3) tracemap extrusion. These DFNs are then meshed and integrated into single-phase flow simulations. Pressure gradients are applied to quantify the influence of fracture intensity and topology on flow behaviour across above fracture generation methods.
Results show systematic topological deviations between natural and synthetic networks. Geometric and growth-based methods overestimate X- and I-nodes while underrepresenting Y-nodes, affecting connectivity and predicted flow paths. Tracemap extrusion reproduces geometry more accurately but requires significantly higher computational resources. Flow simulations reveal that fracture intensity and node topology strongly influence pressure evolution and steady-state attainment. Both parameters are central to injectivity forecasting, (thermal) breakthrough prediction, and storage containment assessment.
Overall, the results demonstrate that current DFN generation methods reproduce fracture geometry reasonably well but struggle to match natural network topology, introducing systematic biases into models and simulations. Improving the representation of Y-node-dominated branching structures is therefore essential for developing more reliable models and simulations of fractured reservoirs and repositories.
How to cite: Weihmann, S., Gärtner, C., Mullins, J., Charlier, F., and Fischer-Appelt, K.: Capturing natural fracture topology in DFNs for energy and storage applications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4021, https://doi.org/10.5194/egusphere-egu26-4021, 2026.
The performance of enhanced geothermal systems (EGS) depends critically on effective water–rock heat exchange. This often requires creation of new fractures, however, for certain scenarios, occluding short-circuiting high flow fractures is needed. Here we introduce an approach for reducing the permeability of large fractures using heat-activated epoxy resin foam. The resin is transported as discrete droplets that become thermally activates (foam, expand and cure) in-situ at a prescribed temperature range. We present modelling and experiments for the transport and adhesion characteristics of resin droplets that result in gradual permeability reduction in large aperture fractures (mm-cm scale). The coupled transport and adhesion of resin droplets is represented in a 2-D numerical model enabling quantification of changes in pressure distribution, flow pathways, and effective permeability. Droplet adhesion considers velocity perturbations coupled with Hertz–Mindlin contact mechanics for thermally activated chemical reaction kinetics. Model predictions show good agreement with laboratory-scale fracture experiments, demonstrating the capability of the proposed approach to capture key mechanisms governing resin sticking and permeability alteration in fractured rock.
How to cite: Cui, Y., Parashar, R., Ying, Y., Bishwokarma, M., and Or, D.: Permeability reduction in fractured geothermal field using heat-activated epoxy resin droplets: resolving droplet transport and adhesion dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4053, https://doi.org/10.5194/egusphere-egu26-4053, 2026.
Faults critically control hydrocarbon migration and accumulation, especially in deep to ultra-deep environments where reservoir quality is generally poor. However, current understanding of fault-controlled hydrocarbon accumulation remains largely qualitative, relying on geological interpretation and conceptual models. A quantitative reconstruction of episodic hydrocarbon expulsion, migration, and accumulation during fault activity under in-situ temperature, pressure, and stress conditions remains lacking, thereby constraining a mechanistic understanding of fault-controlled petroleum systems. In western China, thrust-fault-controlled hydrocarbon reservoirs are widely developed in superimposed basins. This study establishes a geological conceptual model based on typical deep reservoirs, incorporating multiple reservoir–seal assemblages and fault systems. Numerical simulations of hydrocarbon migration and accumulation under fully coupled thermo‑hydro‑mechanical (THM) conditions were conducted using COMSOL Multiphysics. The research quantitatively evaluates the effects of fault geometry, reservoir–seal configurations, and fluid properties on accumulation dynamics. The high-resolution simulations of the fully coupled THM processes reveal that during active faulting periods, hydrocarbons preferentially migrate vertically along the high-permeability damage zone on the fault zone, and are blocked by the seal rock, showing a top-down charging into the reservoirs. During transitional periods, diminished vertical conductivity leads to hydrocarbon accumulation preferentially in proximal, bottom reservoirs. Hydrocarbon enrichment is jointly controlled by fault type (reverse faults being more favorable than normal faults), fault activity sequence, and the relationship between strata and fault tendency. Notably, a “seal-before-break” fault activity pattern can lead to instantaneous release of overpressure-driven hydrocarbons, facilitating highly efficient hydrocarbon accumulation. This study provides a quantitative reconstruction method for fault‑controlled hydrocarbon migration and accumulation under realistic subsurface conditions. It advances the mechanistic understanding of fault‑controlled petroleum systems and offers theoretical support for exploring deep fault‑related reservoirs.
How to cite: Jia, K., Liu, J., and Liu, K.: Hydrocarbon migration and accumulation in a thrust fault-controlled deep reservoir: Insight from the THM coupling numerical modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4203, https://doi.org/10.5194/egusphere-egu26-4203, 2026.
Cavern thermal energy storage (CTES) is increasingly recognized as a key technology for integrating renewable energy sources and balancing seasonal heat supply and demand. The implementation of CTES in crystalline bedrock settings requires detailed characterization of brittle deformation zones and fracture networks that both control heat transfer and cavern stability. Site-scale zones of localized brittle deformation, ranging from tens of centimetres to several metres in thickness and tens to hundreds of metres in length, can often be identified from drillcore interpretations and represented deterministically in structural geological models. In contrast, fracture networks are commonly constrained by sparse observations of individual fractures with small apertures, necessitating stochastic approaches to account for limited sampling and uncertainty within poorly constrained subsurface volumes. Consequently, detailed fracture mapping and classification, together with the identification of volumes of bedrock constrained by the deformation zones, i.e. bedrock domains, are essential prerequisites for fracture network modelling that utilize, for example, Discrete Fracture Network (DFN) approaches.
In this study, we evaluate the usability of the conventionally acquired and subsequently classified fracture data for generating fracture sets for 3D DFN models in crystalline bedrock deformed by multiple tectonic events and comprising variably altered granites and gneisses. We also evaluate brittle deformation zones as constraints for determining structurally homogeneous bedrock domains. The study focuses on the planned largest CTES site in the world, VARANTO, located in Vantaa, southern Finland, with an approximate storage volume of 1 million m³ and a heat capacity of 90 GWh. The dataset comprises optical or acoustic borehole images (OBI and ABI) from 36 boreholes, fracture observations from oriented drillcores and field observations, and 3D deformation zone models available from earlier work.
The results indicate that classification of discontinuities from the OBI and ABI images based on filling type can present challenges in distinguishing between brittle fractures and other structures such as dikes without a brittle interface. In addition, variations in the OBI and ABI image quality may lead to intervals with limited or less distinct observations. These findings highlight the value of integrating supplemental data sources, such as the fractures mapped from oriented drill cores and field observations, to enhance interpretation and overall representativity of the fracture data. Moreover, using the deformation zone models to constrain the bedrock domains results in a domain pattern that is challenging in terms of drillhole fracture data availability for DFN modeling. Therefore, we briefly discuss filtering of the domains based on available data.
How to cite: Lindqvist, T., Ahlqvist, K., Engström, J., and Hagström, M.: Preparation of fracture data and delineation of bedrock domains for 3D DFN modeling of a cavern thermal energy storage site in Southern Finland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4886, https://doi.org/10.5194/egusphere-egu26-4886, 2026.
Abstract: Early-term inactive faults can be reopened as hydrocarbon migration channels under overpressure. Clarifying their opening mechanism during the hydrocarbon accumulation period is the foundation of hydrocarbon exploration. In view of the problem that early-term inactive faults in the Junggar Basin have the potential for cross-layer migration but the overpressure-driven opening mechanism is unclear, this study constructs a mechanical model coupled with strong and weak layer combinations and pore fluid pressure. Combined with the Mohr-Coulomb fracture criterion, the mechanical response characteristics of the faults under two boundary conditions of lateral confinement and unconfined confinement are analyzed, thereby revealing the opening mechanism of early-term inactive faults. The study shows that: (1) Under lateral confinement conditions, the overpressure evolution is in two stages: "Mohr circle translation - radius enlargement". Due to stress distribution, the Mohr circle is preferentially tangent to the original fracture line, which promotes the local opening of the fault. (2) Under lateral unconfined confinement conditions, the effective stress change is concentrated on the fracture surface, driving the Mohr circle to the left and reducing the critical stress value for opening early-term inactive faults. (3) Both laterally restricted and laterally unrestricted states exhibit the characteristics of "priority of overpressure zone, dominance of lower fault, and initial opening of overpressure segment", and can further extend along the original fault. (4) The study area as a whole shows that the critical opening pressure of the western fault is higher than that of the eastern fault, and this pressure has shown an evolution trend of "increasing-decreasing-increasing" since the end of the Triassic. Areas closer to the overpressure center of the source rock and with a smaller angle between the fault strike and the maximum principal stress have better opening properties. In the late hydrocarbon accumulation stage, some early-decaying faults open due to the overpressure reaching the critical condition, and can serve as effective hydrocarbon migration channels.
How to cite: Zhang, W. and Liu, H.: Research on the Opening Mechanism of Early-Term Inactive Faults: A Case Study of the Junggar Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9318, https://doi.org/10.5194/egusphere-egu26-9318, 2026.
Unlike classical positive and negative flower structures, antiformal negative flower structures represent a unique structural type developed under strike-slip tectonic inversion regimes. Rarely reported in previous studies, the genesic mechanism of such structures remains poorly understood, particularly the mechanical reasons that inhibit the inversion of pre-existing normal faults under compressional conditions. Based on detailed interpretation of high-resolution seismic data, this study systematically investigates the tectonic setting, structural characteristics, and formation mechanism of antiformal negative flower structures in the Doseo Basin of the Central–West African Rift System, and discusses their implications for the structural evolution of strike-slip inversion basins and the development of hydrocarbon traps.
The Doseo Basin is located within the basin-controlling domain of the Central-West African Rift System and experienced two major tectonic episodes: transtension during the Early Cretaceous and intense tectonic inversion during the Eocene. These tectonic events resulted in the development of multiple types of inversion-related structures, including fault-associated, thrust-related, fold-dominated, and antiformal negative flower structures. Antiformal negative flower structures are mainly developed within the central low-relief uplift belt of the basin. In planar view, these structures are arranged in en echelon with a NWW-SEE trend, whereas in cross-section they are characterized by an antiformal uplift controlled by a set of normal faults. During the inversion stage, the pre-existing normal faults were not reactivated to reverse faults; instead, the strata experienced pronounced compressional arching. Notably, the spatial extent of the anticlinal uplift closely coincides with the distribution of the normal faults. Genetic analysis indicates that under the Early Cretaceous transtensional stress field, basement weak zones were reactivated, leading to the formation of normal faults and the initial development of negative flower structures. During this stage, the scale, vertical extent, and activity intensity of the normal faults were established. During the Eocene tectonic inversion, regional transpressional stress was superimposed on the negative flower structure system. However, constrained by two key factors, the relatively high mechanical stability of the early transtensional structures (related to fault cementation and lithological properties of surrounding rocks) and high dipping of the normal faults, the inversion-stage stress failed to reach the critical threshold required for fault polarity reversal. Instead, it was only sufficient to induce compressional arching of the strata, ultimately resulting in antiformal negative flower structures characterized by the preservation of pre-existing normal faults combined with an antiformal uplift.
This study demonstrates that the preservation of normal faults is jointly controlled by insufficient inversion-stage stress and the mechanical stability of pre-existing transtensional fault systems. These findings expand current genetic models of structural styles in strike-slip inversion basins and provide new geological constraints for structural interpretation and hydrocarbon trap prediction in the Doseo Basin and other analogous basins.
How to cite: Yang, Y., Song, Y., Xiao, K., Du, Y., Zhang, X., Wang, L., Ou, Y., and Hu, Y.: Structural Characteristics and Genesic Mechanism of Antiformal Negative Flower Structures: Insights from the Doseo Basin, Central-West African Rift System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10407, https://doi.org/10.5194/egusphere-egu26-10407, 2026.
With renewed interest in the Bristol Channel and Celtic Sea Basins for geoenergy, South Wales offers the opportunity to study exposed basement rocks at the basin margins. Field relationships show NW-SE and NE-SW trending faults, joints, and fissure fills in South Wales underwent multiple episodes of deformation. Previous studies assume deformation initiated during the Late Variscan, with extensional reactivation during the Mesozoic (e.g. Wright et al., 2009). Recent studies demonstrate the importance of Cenozoic reactivation of Mesozoic structures in the Wessex Basin (Parrish et al., 2018), Bristol Channel Basin (Connolly et al., 2024), and Ireland (Monchal et al., 2023). Due to challenges dating fault rocks associated with low-temperature deformation, the timing of reactivation of Variscan structures is poorly constrained - only one previous study in Gower dates Cretaceous hematite (Ault et al., 2016). New data using the U-Pb carbonate geochronometer at Limeslade Bay, Gower, yields multiple U-Pb ages spanning the Mesozoic to the Cenozoic. A N-S oriented, blocky calcite vein yields a Triassic 206Pb/238U intercept age of 245 ± 11 Ma (MSWD = 2.3, n = 31), and alteration-seam recrystallised host rock yields a Jurassic 206Pb/238U intercept age of 186 ± 19 Ma (MSWD = 2.3, n = 37). Six samples associated with strike-slip deformation yield Eocene-Oligocene (39 - 24 Ma) ages. NW-SE dextral and NE-SW sinistral fault systems displace calcite veins of 27.0 ± 3.4 Ma (MSWD = 1, n = 62) and 24.53 ± 1.28 Ma (MSWD = 1.7, n = 37), respectively. Additionally, an Oligocene (28.6 ± 2.5 Ma, MSWD = 1.2, n = 55) vein is disrupted by Miocene deformation, where a 206Pb/238U intercept age of 13.6 ± 5 Ma (MSWD = 1.4, n = 41) was obtained for recrystallised calcite cross-cutting earlier Oligocene vein fabrics. Cenozoic fault reactivation occurred during N-S compression, resulting from far-field stress during the late Oligocene to Miocene Pyrenean-Alpine orogenies. Fluid circulation is significant in reactivating basin margin structures during basin inversion, which poses a hazard to many geoenergy applications.
References:
AULT, A. K., FRENZEL, M., REINERS, P. W., WOODCOCK, N. H. & THOMSON, S. N. 2016. Record of paleofluid circulation in faults revealed by hematite (U-Th)/He and apatite fission-track dating: An example from Gower Peninsula fault fissures, Wales. Lithosphere, 8, 379-385.
CONNOLLY, J., ANDERSON, M., MOTTRAM, C., PRICE, G. & SANDERSON, D. 2024. Using U-Pb carbonate dating to constrain the timing of structural development and reactivation within the Bristol Channel Basin, SW England. Journal of the Geological Society.
MONCHAL, V., DROST, K. & CHEW, D. 2023. Precise U-Pb dating of incremental calcite slickenfiber growth: Evidence for far-field Eocene fold reactivation in Ireland. Geology, 51, 611-615.
PARRISH, R. R., PARRISH, C. M. & LASALLE, S. 2018. Vein calcite dating reveals Pyrenean orogen as cause of Paleogene deformation in southern England. Journal of the Geological Society, 175, 425-442.
WRIGHT, V., WOODCOCK, N. H. & DICKSON, J. A. D. 2009. Fissure fills along faults: Variscan examples from Gower, South Wales. Geological Magazine, 146, 890-902.
How to cite: Dawe, N., Mottram, C., Anderson, M., Andrews, B., and Watkinson, M.: Dating faulting and fluid circulation using the U-Pb carbonate geochronometer reveals Cenozoic reactivation in Gower, Wales, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19033, https://doi.org/10.5194/egusphere-egu26-19033, 2026.
Abstract: Natural fractures exert a first-order control on permeability, sealing capacity, and stress sensitivity of carbonate reservoirs, yet quantitative links between measured fracture-surface roughness and evolving transport properties remain poorly constrained across scales. We present a workflow that combines high-resolution optical surface profilometry with numerical closure and flow modelling to evaluate fracture hydraulic behaviour under effective stress, with implications for CO₂ storage efficiency and containment in fractured carbonates. A 4 × 4 cm fractured carbonate sample is split along the fracture plane to expose complementary surfaces, which are imaged using 3D optical microscopy in the metrology laboratory. Surface height grids are processed in Vision64 and exported for analysis. We computed roughness statistics and constructed aperture fields by digitally pairing the two surfaces, thereby enabling progressive mechanical closure to be simulated as either a prescribed displacement (closure) or field-stress-controlled loading.
Using closure-dependent aperture maps, we quantified transport anisotropy by solving pressure-driven flow through the fracture for orthogonal directions. Conductivity/permeability proxies are calculated using both cubic-law scaling and a spatially variable conductivity formulation (k ∝ b³) solved on the aperture grid. In parallel, capillary entry pressure is estimated from aperture distributions to evaluate stress-dependent sealing. Results show a nonlinear reduction in connected aperture with increasing closure, producing rapid declines in fracture conductivity and increases in capillary entry pressures as contact patches expand and percolating pathways collapse. Directional differences in flow and sealing metrics reveal pronounced anisotropy inherited from the surface topography, with dominant flow aligned with the most persistent connected channels.
Finally, stress-path sweeps (injection/depletion and shear ramp scenarios) demonstrate how effective normal stress and shear-related dilation can produce contrasting permeability–capillary responses, highlighting the potential for hysteresis and path dependence during CO₂ injection and pressure cycling. This integrated approach provides a quantitative bridge between laboratory-scale roughness measurements and stress-sensitive fracture transport, supporting improved parameterisation of fractured carbonate reservoirs in CO₂ storage models and risk assessment for leakage versus immobilisation.
Keywords: capillary entry pressure, fracture roughness, CO₂ storage integrity, anisotropy.
How to cite: Elattar, H., Glover, P. W. J., Collier, R., and Botter, C.: Stress-controlled fracture closure and anisotropic flow in carbonate reservoirs: implications for CO₂ storage, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20086, https://doi.org/10.5194/egusphere-egu26-20086, 2026.
Placing constraints on the geometry and growth of faults has significant implications for the management of resources in the subsurface; faults are widespread structures and can either compartmentalise subsurface reservoirs or provide favourable fluid migration pathways.
There are two widely accepted models of fault growth: the isolated fault growth model and the constant length fault growth model. These models, largely derived from field, seismic, and analogue modelling data, both describe three stages in fault growth: (1) propagation of fault segments, (2) slip accumulation on fault segments, and (3) segment interaction and linkage. However, they differ in how the initial fault segments interact, whether they are kinematically dependent, and how rapidly their full length is established. The debate is currently still open on which model best describes natural faults, and what geological controls favor one model over the other.
To further address the topic of fault growth, we investigate the different stages of growth through two sets of experiments. First, loading experiments are performed on intact samples of a rock analogue material to track both the propagation of the fracture and the displacement accumulation to test which of the two fault growth models most accurately describes the initial stages of fault propagation. Second, loading experiments are performed on samples with pre-cuts to replicate realistic fault segment geometries, to track fault tip migration and displacement partitioning during the linkage stage of fault growth, to test geometrical controls on the process of fault linkage.
The samples are made of a rock analogue material capable of accommodating displacement gradients through ductile processes, similar to those observed in natural rocks over geological timescales. This material is cohesive and allows the creation of pre-cuts to replicate fault segment geometries. Loading experiments are conducted in a biaxial apparatus at low strain rates, coupled with an interferometric technique using an optical bench to obtain speckle patterns. These speckles are employed to track in high resolution the increase in the length of the fault using Diffusive Wave Spectroscopy (DWS). In addition, we concurrently use the same speckle patterns to track displacement along the fault using Digital Image Correlation.
How to cite: Yadav, S., Amon, A., Camanni, G., Russo, G., Vitale, E., and Iacopini, D.: An experimental study of fault growth in a 2D Biaxial apparatus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20517, https://doi.org/10.5194/egusphere-egu26-20517, 2026.
The Upper Rhine Graben (URG) is a tectonically active area that has been extensively investigated for its geothermal energy potential. However, modification of fluid pressures in subsurface reservoir for geothermal energy production can affect the regional stress field inducing seismicity that causes high public and social concern as well as economic losses, e.g., in Landau, Insheim, Soultz-sous-Fôrets, Rittershofen, Strasbourg, and Basel. The effective frictional strength and stability of faults depend on the nature of stimulation, the reservoir conditions, and subsurface fault rock characteristics. It is crucial that we explore the complex relationships between these factors and the frictional stability of faults for safe geothermal energy operations. In this study, to understand the seismic potential of faults in geothermal reservoir rocks, we investigated how the frictional behaviour of fault gouges from the URG area varies when stimulated with fluids at different temperatures and pressures using hydrothermal rotary shear friction experiments.
Our data are fit by rate-and-state friction laws (RSF) and the mechanical results are supplemented with microstructural observations to identify the active deformation mechanisms. We also analyzed porosity, grain size, shape, and mineralogy of fault gouges employing scanning electron microscopy and energy-dispersive spectroscopy. Simulated fault gouges were prepared from Muschelkalk, Buntsandstein, Rotliegend, and crystalline basement rocks (granite and gneiss), and velocity-stepping tests were conducted at temperatures from 20 to 250 ºC, effective normal stresses of 60 and 75 MPa, pore fluid pressures of 40 and 50 MPa, and slip velocities 0.3 to 100 µm/s, depending on the fault gouge type. Moreover, X-ray diffraction (XRD) was performed on the fault gouge samples to determine their mineralogical composition, which significantly influences the mechanical behavior of the gouges.
We observed differences in gouge sliding strength and frictional character as a function of both sliding velocity and temperature. Preliminary mechanical results show a strong temperature dependent steady-state strength during initial sliding, with friction coefficients in the range of 0.38 – 0.9. All the fault gouges exhibit stable velocity-strengthening (aseismic) behavior, except those derived from Rotliegend and granite, which show a transition from velocity strengthening to velocity weakening with increasing sliding velocity at T>200 ºC. The rate-and-state parameters (a, b, and Dc) for Rotliegend and granite show a transition from a velocity-neutral to velocity- and strain-weakening behavior at temperatures between 200 and 250 ºC. This transition enhances mechanical instability and creates conditions more favorable for earthquake nucleation. In contrast, the Muschelkalk and Buntsandstein samples revealed velocity-strengthening and strain-hardening behavior, favouring aseismic creep over dynamic rupture, which we interpret to be mainly due to the presence of small amounts of weak hydrous minerals and amorphous content. These results indicate that the Rotliegend and crystalline basement rocks (granite) are more prone to induced seismicity than Muschelkalk and Buntsandstein. Our findings provide vital insights into the understanding of fault behavior at regional scales, allowing constraint input for seismic models, and strengthen the connection to numerical models.
How to cite: Mebrahtu, T. K., Rudolf, M., Niemeijer, A., Toy, V., Warr, L., and Henk, A.: Velocity-dependent frictional properties of fault gouges in the Upper Rhine Graben under hydrothermal conditions: Implications for induced seismicity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21242, https://doi.org/10.5194/egusphere-egu26-21242, 2026.
To study the effect of hydraulically induced damage in a caprock (argillite from Tournemire), hydraulic fracturing tests were conducted in a hollow cylinder triaxial cell on core samples with inner borehole, oriented parallel to the bedding plans. Acoustic Emission (AE) monitoring and strain measurements during hydraulic fracturing tests, as well as post-mortem X-ray CT analysis were carried out. Samples were subjected to stresses representative of the in-situ stress state, and different injection rates of low-viscosity fluid (water) were tested.
Overall, the breakdown pressure is higher and AE activity due to microcracking damage (which increases almost simultaneously with the pressure drop) appears earlier when the injection flow rate increases. During the second injection phase, peak pressures are lower, pressurization rates are higher and stress-strain behaviour is stiffer. The analysis of values of Rise Angle (RA) and Average Frequency (A-FR) indicates that increasing the injection flow rate generates more tensile cracks and increases the severity of damage. The cumulative damage variable, calculated from AE activity, increases significantly just before the first pressure drop and this increase is stiffer when the injection flow rate increases. This confirms that the use of a low-viscosity fluid (water) induces the propagation of unstable cracks, which initiate almost simultaneously with the pressure drop in the borehole, and that this propagation is faster for higher injection rates.
The breakdown pressure and the crack orientation are analysed thanks to the elastic theory for transverse isotropic materials and chemo-hydro-mechanical coupled processes at the borehole wall. The analysis of core samples deformations and X-ray images, and post-mortem visual observation of samples surface indicate that cracks are primarily oriented parallel to the bedding planes and the core sample axis.
How to cite: Grgic, D., Giraud, A., Gbewade, C., Walter, B., and Moumni, M.: Hydraulic fracturing of the transverse isotropic argillite from Tournemire in a hollow cylinder triaxial cell: experimental study and analytical modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14875, https://doi.org/10.5194/egusphere-egu26-14875, 2026.
China currently possesses a substantial number of coal seams characterized by thick hard roofs and steep inclinations. With continuous advancements in mining mechanization, increasing mining height and working face length, as well as intensified extraction intensity, the fracture of thick hard roofs induces high-intensity dynamic disturbances and extensive impacts. During weighting periods, intense strata behaviors—such as support crushing, rib spalling, roof collapse, and coal wall spalling—occur frequently. Moreover, the inclination angle of the working face leads to recurrent accidents, including support biting and overturning, severely compromising safe and efficient mining operations. Conventional beam or thin-plate theories are inadequate for analyzing thick hard roofs, as they neglect shear effects induced by roof thickening. The post-fracture structure of thick hard roofs differs significantly from that of thin roofs, resulting in variations in support–surrounding rock interactions and overburden spatial fracture behavior, thereby exacerbating ground control challenges. To elucidate the disaster mechanisms associated with thick hard roof fracturing and to develop corresponding stability control strategies, this study focuses on the 140502 working face of Kouzidong Coal Mine and the 0448 working face of Chunyi Coal Mine, employing a comprehensive approach that integrates theoretical analysis, numerical modeling, platform development, similar material simulation experiments, rock mechanics testing, and in-situ measurements. The research addresses five key aspects: (1) the law of mine pressure manifestation under thick hard roofs; (2) theoretical analysis of medium-thick plate deformation and failure in roof strata; (3) inclination-thickness coupling effects on roof fracturing; (4) spatial fracture patterns of overburden strata; and (5) support–surrounding rock interactions.
How to cite: Cui, X., Yang, S., and Zhou, H.: Study on mechanism and control of space fracture instability of thick and hard roof under dip angle effect in coal mines, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20002, https://doi.org/10.5194/egusphere-egu26-20002, 2026.
Fluid injection into fractured crystalline rock enhances permeability by opening new fractures and reactivating natural ones, yet the relative roles of fluid pressure and elastic stress transfer remain insufficiently constrained. In this study, we develop a fully coupled hydro-mechanical Particle Flow Code in 3 Dimensions (PFC3D) model calibrated against two mini-frac tests in Rotondo Granite at the Bedretto Underground Laboratory. Applied to intact and naturally fractured intervals, the model reproduces the observed pressure evolution and enables quantitative analysis of fracture slip and stress redistribution, thereby revealing two distinct reactivation mechanisms. The first mechanism arises from effective stress reduction. Elevated pore pressure lowers the effective normal stress and weakens frictional resistance, leading to localized and directionally consistent shear within the high-pressure core. Weaker and more diffuse slip develops outward following the pattern of elastic stress perturbation, and minor shear failure appears at the far edge of the fluid-affected region due to shear stress transfer acting on the compressed faces of the opening fracture. This spatially hierarchical slip structure reflects a transition from deformation dominated by effective stress reduction to deformation dominated by elastic stress transfer. The second mechanism is governed by elastic stress transfer. Deformation of pressurized fractures redistributes surrounding stresses and induces weak, remote shear on neighboring fractures that remain disconnected from the fluid. The resulting stress perturbation resembles that generated by localized volumetric expansion and promotes slip on nearby fractures. An analytical estimate indicates that the radial extent of stress perturbation exceeds the fluid-pressurized region and increases with injected volume while decreasing with rock stiffness. These results establish a unified, field-calibrated framework linking fluid pressure, fracture deformation, and stress redistribution during hydraulic stimulation.
How to cite: Shen, H., Hofmann, H., Zang, A., Zhang, S., Zhou, J., and Yoon, J. S.: Reactivation of Natural Fractures Driven by Fluid Pressure and Stress Transfer During Hydraulic Stimulation: A Three-Dimensional Discrete Element Modeling Study of the Bedretto Underground Laboratory, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14876, https://doi.org/10.5194/egusphere-egu26-14876, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 4
EGU26-2105 | ECS | Posters virtual | VPS19
Fracture modeling of the hydrocarbon reservoir using geostatistical and neural network methods in the SW Iran OilfieldTue, 05 May, 15:12–15:15 (CEST) vPoster spot 4
Abstract
Fracture characterization and modeling are essential for hydrocarbon exploration and enhanced production. To model the fracture network in the Asmari reservoir of the Rag-e-Sefid Oilfield (SW Iran), this research characterizes fracture intensity using well, fracture driver, and fracture controller data. First, these data are analyzed to estimate fracture intensity. Then, fracture intensity is modeled using geostatistical methods. The geostatistical outputs are compared and calibrated based on the structural setting of the study area and the fracture indicator. Finally, selected fracture intensity data are integrated into a single model using an artificial neural network, resulting in a comprehensive fracture intensity model for the Asmari reservoir of the Rag-e-Sefid Oilfield. The results show that fracture intensity increases near the Rag-e-Sefid and Nourooz-Hendijan-Izeh Faults and in the fold forelimb and crest. The highest fracture intensity in the Asmari reservoir is observed at the intersection of structures with the N-S Arabian trend and the NW-SE Zagros trend, where the fold axis has rotated. Generally, the northwestern part of the Rag-e-Sefid anticline has higher fracture intensity than the southeastern part. The high fracture intensity in the northwest part of the Rag-e-Sefid Oilfield is related to inversion tectonics, multi-stage reactivation along pre-existing basement structures, and an older deformation history in this area compared to its southeastern part. The Asmari reservoir in the NW part of the Rag-e-Sefid anticline contains a greater share of oil and gas in its hydrocarbon traps than the SE part. Moreover, the results of this study indicate that the simultaneous use of different data and the integration of geostatistical and artificial neural network methods can effectively predict fracture distribution in hydrocarbon reservoirs and be used as a suitable technique for fracture modeling in natural oil and gas fields. This research suggests that artificial intelligence and quantum computing techniques provide efficient solutions for characterizing and modeling the entire scale of geological fractures in hydrocarbon reservoirs.
Keywords: Fracture modeling, Geostatistical and neural network methods, Asmari reservoir, Rag-e-Sefid Oilfield, SW Iran
How to cite: Tajmir Riahi, Z., Faghih, A., Soleimany, B., Sarkarinejad, K., and Payrovian, G. R.: Fracture modeling of the hydrocarbon reservoir using geostatistical and neural network methods in the SW Iran Oilfield , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2105, https://doi.org/10.5194/egusphere-egu26-2105, 2026.
