Orals: Tue, 29 Apr | Room -2.43
Hydraulic fracturing is widely recognized as the most effective method for creating Enhanced Geothermal Systems (EGS). However, its application has been associated with induced seismicity, leading to the shutdown of several projects. As an alternative, low-viscosity fluids, such as CO2, may be used because they tend to generate complex fracture networks by inducing numerous small, isolated (remote) fractures without requiring high-pressure injection. Despite this potential, however, the mechanisms and conditions that govern the formation of such patterns remain poorly understood. This study identifies two critical factors through poroelastic analysis: (1) prolonged pressure diffusion facilitated by the low viscosity of the fluid, and (2) heterogeneity in Biot’s coefficient. To validate these findings, hydraulic fracturing experiments were performed on two types of marble: fine-grained marble, representing a homogeneous sample, and coarse-grained marble, representing a heterogeneous sample. Both water and CO2 were used as injection fluids. The results demonstrate that remote fractures only form in heterogeneous rocks when CO2 is used as injection fluid. These findings suggest the potential to develop a safe and innovative reservoir stimulation technique that effectively stimulates large surface areas by strategically alternating the viscosity of the injection fluid while maintaining low injection pressures.
How to cite: Yoshioka, K., You, T., Kanemaru, Y., Obata, N., Watanabe, N., and Sakaguchi, K.: Nucleation of remote hydraulic fractures, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3991, https://doi.org/10.5194/egusphere-egu25-3991, 2025.
Compaction band formation and permeability evolution in volcanic rocks are key to understanding fluid transport and the potential for pore fluid pressurisation, impacting volcano eruption dynamics and volcanic hazards, geothermal energy extraction, and CO₂ sequestration. Compaction banding and permeability evolution are influenced by the geometry and alignment of pores. Laboratory studies on volcanic rocks have provided valuable insights, yet the heterogeneity of volcanic rock microstructures—particularly in pore geometry and distribution—presents challenges in predicting deformation and permeability changes across varied geological settings. This study systematically investigates the role of pore geometry on compaction band formation and permeability evolution in a porous lava.
A porous lava, a trachyandesite from a quarry near Volvic, France, known as "Volvic Bulleuse" (VB), was studied to explore the factors influencing compaction band and permeability evolution. The pores in VB with an average aspect ratio of 0.44, exhibit elongation along a preferred orientation within a groundmass dominated by plagioclase microlites. To investigate the effects of pore geometry, cylindrical samples were drilled along two orientations—parallel (VBY) and perpendicular (VBZ) to the pore major axis—such that in VBY samples, the pore major axis aligns with the cylinder’s long axis, while in VBZ samples, the axes are perpendicular. Both VBY and VBZ exhibited porosities ranging from 23–27%, as determined by gas pycnometry. In terms of permeability, measured along the cylinder’s long axis, VBY samples showed a value of approximately 10⁻¹⁴ m², while VBZ samples exhibited a lower permeability of around 10⁻¹⁵ m².
Triaxial deformation experiments demonstrated that VBZ samples—featuring pores perpendicular to the cylinder axis—are approximately twice weaker than VBY samples deformed at the same pressure. Microstructural analysis of deformed samples revealed that pore geometry has minimal influence on compaction band orientation at lower effective pressures, where compaction bands typically formed sub-perpendicular to the major principal stress, as is commonly observed. However, at higher pressures, compaction bands preferentially formed at angles of 45–50° to the loading direction in VBY samples, a development that is closely linked to the preferred orientation of the pores.
Additionally, we measure permeability during triaxial deformation under an effective pressure in the ductile regime (75 MPa), revealing significant changes in permeability due to deformation and pore orientation. Our analysis emphasizes pore structure's role in deformation and permeability evolution, with applications ranging from geothermal energy extraction to various subsurface fluid transport processes.
How to cite: Bayramov, K., Heap, M., Baud, P., and Lazari, F.: The Impact of Pore Geometry and Orientation on Permeability Evolution and Compaction Band Formation in Volcanic Rocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-483, https://doi.org/10.5194/egusphere-egu25-483, 2025.
Understanding the impact of local stress states on computed permeability for fractured carbonates or any other lithotype is crucial to better assess the modalities of fluid flow in the subsurface. Considering Mesozoic fractured carbonates exposed along the flanks of the Viggiano Mt. of southern Italy, we investigate the control exerted by the local fracture networks on the output of DFN modelling of geocellular volumes whose dimensions are like those of the studied outcrops. Specifically, the following four sedimentary units are considered:
- Scarrone La Macchia II, (SLM II), well-layered, Sinemurian–Pleinsbachian carbonate succession of wackestone-packstones to grainstones arranged in discrete bed packages originally deposited in a low-energy, open lagoon environment.
- Scarrone la Macchia I, (SLM I), Toarcian oolithic carbonates characterized by bed amalgamation originally formed in a ramp setting rimmed by oolithic sand shoals.
- Piana del Buon Cuore (PBC), Lower Cretaceous - Upper Jurassic limestones whose clasts consist of oolites, oncolites and intraclasts deposited in a high-energy platform margin environment.
- The Il Monte (ILM), massive, amalgamated, Cretaceous carbonate rudstones and grainstones originally deposited along the paleo-slope of the carbonate platform.
By employing existing field data (Abdallah et al., 2023, 2024), we carried out Discrete Fracture Networks (DFN) modelling of 5 m-sided geocellular volumes including internal sub-volumes representative of single carbonate beds. This work was conducted by means of high-resolution computational meshes provided by the dfnWork ® code, which is capable of non-reactive solute transport simulation, and constrain of imposed depth-equivalent stresses to assessing effective horizontal permeability (effkxx, effkyy).
Focusing on the results achieved for the Viggiano Mt. aquifer, we simulated depth conditions of 500m coupled with principal stress axes of ~13MPa (sv), 10 MPa (shmax, NW-SE), and 7.58 MPa (shmin, NE-SW). The theoretical aperture data were hence modulated by the local stress state conditions. SLM I, exhibits an increase in permeability anisotropy ratio as a function of the stresses, hence, leading to flow channelling within the network. Lagrangian solute transport simulation supports the afore-mentioned results by marked changes in primary flow path, increase in path tortuosity, as a function of stress, and delay in breakthrough time. Similar results were achieved for PBC and ILM units. Differently, SLM II undergoes the opposite effect, where the permeability ratio seems to reduce drastically at a depth of 500m and stabilizes after that. We infer this behaviour as due to non-linear-fluid-flow behaviour as a function of aperture closure or dilation, as seen in highly connected systems of fractures including both stratabound and non-stratabound elements. Accordingly, SLM II is characterized by efficient mechanical units made up of bed interfaces, which were able to compartmentalize the vertical growth of high-angle fractures.
This research highlights the complex behaviour of permeability anisotropy in fractured carbonate rocks, in response to depth-equivalent stresses, and the importance of building realistic geomechanically coupled-DFN models to estimate fluid-flow and storage properties of fractured rocks at depth.
How to cite: Abdallah, I. B., Hollis, C., Healy, D., Hyman, J. D., Prosser, G., and Agosta, F.: Stress-induced permeability anisotropy and fluid flow dynamics in a Mesozoic fractured carbonate aquifer of southern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1131, https://doi.org/10.5194/egusphere-egu25-1131, 2025.
Assessing leakage mechanisms that compromise reservoir integrity is essential for effective geo-resource management and mitigating environmental risks. Reservoir leakages can occur via both anthropogenic pathways, such as active and inactive wells and pipelines, and natural pathways, including fractures and fault zones. Additionally, fault-valve action can temporarily disrupt sealing layers, allowing trapped fluids to migrate upward. Distinguishing between natural and human-induced causes of reservoir leakage is valuable but often challenging. To address this, we present an innovative approach that compares fluid circulation systems before and after the onset of reservoir exploitation. Present-day fluids are studied using standard groundwater sampling, modelling, and near-surface soil gas surveys. In contrast, paleo-fluids are analyzed using carbonate clumped isotope of fault-related calcite veins, along with fluid inclusion spectroscopy and microthermometry to determine parental fluid temperatures and compositions. We applied this approach to the giant Val d’Agri hydrocarbon reservoir in Southern Italy, a region characterized by: (i) high seismic hazard, with historical earthquakes up to magnitude 7; (ii) recent low-magnitude seismicity induced by oil extraction; and (iii) ongoing debate about industrial activities potentially triggering anthropogenic leakages. From our extensive dataset of fault-related calcite veins, we selected samples from Pleistocene-Holocene extensional-transtensional faults of the northeastern side of the valley, where productive oil wells are located. Carbonate clumped isotope analysis revealed precipitation temperatures of 160-180°C, while micro-Raman spectroscopy of fluid inclusions detected hydrocarbon phases matching those currently extracted from the reservoir. These findings suggest that past faulting, likely associated with strong earthquakes, temporarily breached the thick sealing layer, releasing trapped hydrocarbons. Considering present-day fluids, isotope analyses (carbon, boron, sulfate, and helium) from hydrogeochemical monitoring of nearby springs indicated long-term mixing between these hydrocarbons and shallow fluids. In summary, our multidisciplinary study demonstrates that natural leakage via fault-valve action occurred in the pre-exploitation period. Given the high seismic hazard in this region, we recommend incorporating these natural processes into future assessments to enhance environmental hazard mitigation and support sustainable hydrocarbon production management.
How to cite: Schirripa Spagnolo, G., Gori, F., Barberio, M. D., Boschetti, T., Marchesini, B., Ruggieri, G., Bernasconi, S., Caracausi, A., Sciarra, A., Paternoster, M., Novella, D., Barbieri, M., Petitta, M., Billi, A., and Carminati, E.: Fault leakages from the Val d’Agri hydrocarbon reservoir: a comparison between paleo- and present-day fluids, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1785, https://doi.org/10.5194/egusphere-egu25-1785, 2025.
We investigate seismic waveform changes in time-lapse along supercritical CO2-bearing faults from field data by analysing 4D seismic data from the Illinois Basin – Decatur Project. 1 million tonnes of CO2 was injected into the Lower Mt. Simon continuously over a three year period from 2011-2014. It has been established that the injected CO2 migrated vertically along faults at this site to reach the Middle and Upper Mt. Simon formations (Bukar et al., 2024). Time-lapse 3D vertical seismic profiles were acquired each year of injection in addition to a pre-injection baseline and a final survey two months post-injection. We study the time-lapse seismic waveforms in zones around previously interpreted faults. In post-stack, we observe waveform distortions in the monitor traces that manifest as phase changes when compared to the baseline traces. Interestingly, these distortions magnify with increasing injected CO2 volume, and decrease post-injection. To further investigate potential causes of these phase changes, we study the data in pre-stack. We also attempt to discriminate the contribution of CO2 saturation effects and pressure effects. This is crucial as pressure increase also causes a slowdown effect on seismic waves in fractured media due to positive physical strain (expansion) and an accompanied decrease in the rock bulk modulus. However, while CO2 injection is typically accompanied by pressure increases, the pressure would typically decline more quickly than CO2 would dissolve in brine; multiple pressure gauges at this site show a rapid decline in pressure once injection ceased. Therefore, time-lapse seismic acquired soon after stopping injection could offer insights. We also observe these distortions where faults have not been mapped – these could be CO2-filled fault zones with small throws that are below seismic resolution. This could potentially be used to illuminate unseen faults after CO2 injection.
References
Bukar, I., Bell, R., Muggeridge, A. H., & Krevor, S. (2024). Carbon dioxide migration along faults at the Illinois Basin – Decatur Project revealed using time shift analysis of seismic monitoring data. Geophysical Research Letters, 51, e2024GL110049. https://doi.org/10.1029/2024GL110049
How to cite: Bukar, I., Bell, R., Muggeridge, A., and Krevor, S.: Time-lapse seismic properties of CO2-filled fault zones: Field observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19549, https://doi.org/10.5194/egusphere-egu25-19549, 2025.
Modeling fluid behavior in fractured rock is essential for geo-resource exploration and geological storage. This study utilizes a Discrete Fracture Network (DFN) approach to evaluate the efficiency of fractured systems in storing supercritical CO₂ (scCO₂). Synthetic fracture networks, generated using the dfnWorks suite (LANL), based on outcrop data, represent a range of fracture densities. Key parameters such as fracture count, volume, porosity, and permeability are statistically analyzed, and their most frequent values are used to create representative DFN models for fluid flow simulations.
Results reveal a direct correlation between increased fracture density and storage capacity, with storage values consistently below 10% of the total injected mass. A Fracture Efficiency Factor (Efr) is introduced, quantifying CO₂ retained in fractures relative to the total injected CO₂. This efficiency reduces theoretical capacity estimates by approximately one order of magnitude, aligning with previous analytical and dynamic reservoir-scale studies (e.g., Nordbotten et al., 2005; Ringrose, 2020; Rutqvist et al., 1998).
This approach enhances CO₂ storage capacity estimates by explicitly accounting for fracture network contributions. While reservoir-scale scCO₂ flow simulations using DFN models remain challenging, this method provides critical insights into the storage potential of fractured media.
How to cite: Romano, V., Proietti, G., Pawar, R., and Bigi, S.: Advancing CO₂ Storage Analysis in Fractured Rocks with Discrete Fracture Network Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8886, https://doi.org/10.5194/egusphere-egu25-8886, 2025.
Geothermal energy represents a renewable energy source exploited for multiple purposes, including electricity, direct use, district heating and heat pumps. One of the most relevant problems in geothermal energy industry is the permeability of the reservoir, both for production and reinjection. Therefore, it is important to assess the fluid circulation in the reservoir and where deep fluids rise. Faults, fractures and active tectonics influence fluid behaviour and fluid-rock interactions in a geothermal context. It is necessary to estimate the role of faults and map as well as their distribution, as tectonic structures could act as barriers to fluid circulation or as preferential conduits. The Acque Albule Basin (AAB) is a case study representing one of the most important hydrothermal manifestations in central Italy. The AAB is a tectonically controlled basin, characterized by a huge hydrothermal manifestation (discharges in the order of m3/s). The deep hydrothermal activity is testified by the presence of a large and thick travertine deposits and several mineralized springs (Tmax at the surface up to 23°C) in which warm fluids rise from the geothermal reservoir. These hot fluids circulate through the Meso-Cenozoic carbonate reservoir, highly affected by dissolution and brittle deformation. In this framework, travertine deposition is mainly controlled by the faults activity. Several geophysical surveys were carried out to evaluate the cap-rock of the geothermal reservoir, beneath the travertine plateau. The exploration provided a clearer view of the stratigraphy of the AAB and revealed the carbonate roof at 300-400 m. The carbonate rocks are overlain by some alluvial sediments and a travertine plateau from 10 m to 90 m. Based on the geophysical investigations, the measurement of diffuse CO2 emissions from the soil was planned to ascertain the faults role in the hydrothermal circulation. Preliminary results show that the fault zone is characterised by an extremely low degassing (5/10 g m-2d-1). The low degassing could be related to the low-permeability of the alluvial and travertine deposits and/or by self-sealing processes through the main shear zone, which obstacle the upwelling of fluids and gases. The model will be improved with further regional CO2 surveys and δC13 analysis of CO2 of gaseous samples taken from the soil.
How to cite: Emili, S., Reitano, R., Ranaldi, M., Tarchini, L., Carapezza, M. L., Giordano, G., Picciallo, M., and Faccenna, C.: Investigation of geothermal fluid circulation through the study of CO2 soil flux: an application to the Tivoli quarry area (Rome, Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9882, https://doi.org/10.5194/egusphere-egu25-9882, 2025.
Deep geothermal energy is emerging as a key component of Switzerland’s Energy Strategy 2050. In the Canton of Vaud, projects target natural hydrothermal systems at depths of 800 to 1,000 meters, with temperatures ranging from 35 to 100°C, in Upper Malm limestone reservoirs. These limestones, with low matrix porosity and permeability, rely on well-connected fracture networks and karstic features to enhance fluid flow. However, subsurface data from seismic surveys and well data do not fully cover scale intervals that are relevant for reservoir characterization and modeling. To address this limitation, we use a virtual outcrop model (VOM) to characterize fractures in 3D, explore its potential to bridge the length-scale gap, and compare fracture patterns and kinematics between scales of observation.
At Creux-du-Van, a unique continuous, 3D exposure of fractured and gently folded Upper Malm limestones in the Central Internal Jura Fold and Thrust Belt provides an exceptional opportunity for fracture characterization at the decimeter to hundreds of meters scale, allowing comparisons with previous structural interpretations at the regional, 1:500,000 to 1:25,000 scale. Approximately 700 fractures were interpreted from high-resolution VOMs, i.e., point clouds (~110 points/m²), of Creux-du-Van, derived from terrestrial LiDAR scanning. These fractures were classified based on vertical persistence, which is a relative measure for the extent to which they propagate across mechano-stratigraphic boundaries. Geometric parameters such as orientation, dimensions (length, width, and aspect ratio), and spacing were also quantified. Field-based structural analysis complements the digital dataset by providing kinematic and chronological interpretations of brittle structures linked to the tectonic evolution of the fold and thrust belt.
The lengths of regional strike-slip fault traces span four orders of magnitude, ranging from tens of meters to tens of thousands of meters, with a median of 177 meters. Their orientation, kinematic, and length relationships align with the multi-scale Riedel shear model (Ruhland, 1973) forming the regional structural framework. Fractures in the VOM span scales from 0.1 to hundreds of meters, with a median length of 5 meters. Regional faults and VOM-derived fractures show an overlap in length distributions and consistency in fracture orientations and kinematics. Both align with the NW-SE compression inferred from field-based kinematic data and regional restorations associated with the Jura shortening event, demonstrating seamless characterization of brittle features across scales.
This study seeks to further investigate the role of mechanical boundaries (e.g., stratigraphic boundaries, regional structures) in controlling reservoir compartmentalization. It also showcases the potential of outcrop analogues such as Creux-du-Van to support 3D characterization and analyses of fracture properties such as length distributions, orientation, and vertical persistence, ultimately contributing to the advancement of structural modelling of subsurface reservoirs for sustainable energy solutions.
How to cite: Caldeira, J. and Samsu, A.: Seamless Fracture Characterization with Virtual Outcrop Models: Fracture Geometry and Vertical Persistence at Creux-du-Van, Swiss Jura Mountains , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11216, https://doi.org/10.5194/egusphere-egu25-11216, 2025.
Geothermal resources are renewable sources of energy and raw materials. A sustainable utilization for the long-term preservation of the resource requires a site-specific plan that needs to be based on geological and hydrogeological reconstructions. Northern Croatia is rich in geothermal resources that are generally hosted in carbonate rocks. The occurrence of thermal waters (temperatures of 38-50°C) in the town of Daruvar has been documented since the Roman age. In this research, the characterization of the Daruvar carbonate thermal aquifer was detailed using an integrated approach combining hydrogeological and structural investigations and discrete fracture network (DFN) modeling. Hydrogeological investigations consisted in the well logging and pumping tests of a 190 m deep well in Daruvar. Structural investigations were conducted NE of Daruvar where the carbonate rock complex of the aquifer is exposed at the surface. They included the measurement of the discontinuity sets and the photogrammetric reconstruction of the outcrop. The results were used to calibrate a DFN model at the scale of the aquifer explored by hydrogeological investigations (700x700x150 m).
The porosity distribution of the aquifer was obtained from the neutron log of the well ranging from 0.03 to 9.1% (average = 2.7%). The permeability was calculated using transmissivity values from the analysis of pumping tests and literature data resulting in a range from 7.4 to 122.8 D (average = 46 D). Structural analyses in the outcrop analog of the aquifer depicted two dominant systems of discontinuities (241/65 and 296/75). A highly fractured section of the outcrop was selected for the statistical analysis of the geometrical features of the discontinuity network to derive the input parameters for the DFN modeling. Discontinuity aperture was estimated based on the calibration of the DFN model. The results show a linear and power correlation of the aperture with porosity and permeability, respectively. Considering the average porosity of the aquifer, the calibrated aperture value was 3 mm obtaining a permeability of 1.5×105 D. Such high value was interpreted as connected to the porosity value used for the calibration, which was measured through the neutron log depicting the total porosity. On the other hand, the fluid flow and the aquifer permeability are influenced by the effective porosity, which is at least an order of magnitude lower than the total porosity in carbonate aquifers. This difference was accounted for by testing a “dual aperture” approach. Considering the experimental dataset, a porosity of 0.2% (10th percentile of the distribution) was tested. It resulted in a calibrated fracture aperture of 0.22 mm obtaining a permeability of 60.5 D, comparable with the experimental dataset.
The obtained results highlight the importance of integrating structural and hydrogeological approaches to investigate fractured aquifers. Structural data can be used to determine the architecture of the fracture network in the rock mass, while hydrogeological investigations supported by numerical modeling and structural results can provide a solid hydrogeological parametrization of the aquifer.
Acknowledgment: This research was funded by the HyTheC project of the Croatian Science Foundation, grant number UIP-2019-04-1218.
How to cite: Pola, M., Kosović, I., Urumović, K., Borović, S., Frangen, T., Pavić, M., Matoš, B., Pavičić, I., Bistacchi, A., Mittempergher, S., Casiraghi, S., and Benedetti, G.: Hydrogeological parametrization of a carbonate thermal aquifer through integrated pumping test and virtual outcrop reconstruction (Daruvar, Croatia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15295, https://doi.org/10.5194/egusphere-egu25-15295, 2025.
Applied geoscience relies on robust structural models that are appropriately scaled and detailed to address specific challenges. However, the process of developing these models is influenced by human biases shaped by personal and professional experiences, area of expertise, cognition, and values. This diversity of approaches to geoscience interpretation, such as fracture characterisation, impacts the reliability of structural models, which are critical for geoenergy, resource and infrastructure applications. Ensuring robust interpretations is vital for improving safety, enhancing decision-making, and securing project success.
This study investigates the variability in fracture interpretations made by geoscientists analysing an aerial drone image of a fractured outcrop. We compare outputs such as fracture frequency, orientation & density, and network topology across participants to assess the variability in their observations and the uncertainty this develops.
Previous studies on 3D seismic data have shown that geoscientists’ experience and approach significantly impact structural models. Our research systematically assesses similar variability using remotely sensed outcrop data and shows that while our cohorts of geoscientists agree of the “big stuff”, there is less consensus when we examine the detail.
By illustrating these uncertainties, we can begin to inform improved interpretation workflows, team arrangements, assurance processes, and geoscience education and communication. Understanding biases in fracture interpretation is a critical step towards enhancing interpretational accuracy. Coupled with a clear idea of how “good” the structural model needs to be for the problem being solved and appropriate mitigation measures, (if necessary) this ensures better project outcomes and supports the development of reliable geoscience outputs across applications.
How to cite: Evans, L., Shipton, Z., Bond, C., Roberts, J., and Kim, N.: How Good is Your Fracture Model? Evaluating Human Biases and Uncertainty in Geoscientific Interpretations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16786, https://doi.org/10.5194/egusphere-egu25-16786, 2025.
Fracture network develops in response to deformation in competent rocks and are often related to fault related folding (Allmendinger, 1982; Watkins et al., 2018). The Baghewala structure in the Bikaner-Nagaur sub-basin is a fault related anti-form that encompasses the Marwar Supergroup. The structure has a spatial extent of ~12 km2 and is bounded by a major ENE-WSW trending reverse fault. The Upper carbonate (UC) Formation of Marwar supergroup here carries dominantly the dolomites and is traversed by extensive fractures that are visible in cores and image logs. This is a zone of severe mud loss and drilling complications.
We study the image logs from 6 wells to decipher the fracture orientation, understand the deformation mechanism and the implications for drilling and hydrocarbon production. The interpreted fractures from image logs are observed to be dominantly high-angle (60°-90°) extensional fractures oriented along ENE-WNW direction with respect to the sub-horizontal bedding. Additionally, it is seen that the fractures are confined to dolomitic part of UC Formation. Spatially the wells nearer to the fold crest and fault show higher fracture intensity compared to the peripheral wells. The transpressional tectonics after the deposition of the Marwar Super group induced ~NW-SE compression that led to the formation of fault related Baghewala fold. Consequently, the outer arc extension resulted in formation of the syn-post folding fracture network (Price 1966). The fractures thus can be inferred as late-stage high angle fractures due to its orientation (Basa et al., 2019; Ahmed and Bhattacharyya, 2021) and relative prominence (Ismat and Mitra, 2001). Dolomites accommodate deformation by forming fracture networks and fracture intensity is higher, proximal to the fault zone and fold structure (Ahmed and Bhattacharyya, 2021). Thus, lithology and structural position played a role in the partitioning of fractures vertically and spatially.
We see the horizontal wells that are oriented sub-parallel to the fracture network have significant history of mud loss within UC compared to the wells whose profile trends at high-angle to fracture orientation. The deviated wells oriented along the major fracture network will encounter weak planes leading to drilling complications compared to profiles that are oriented across. Therefore, understanding orientation of fracture networks has implications in designing deviation profile of the wells. In low permeability rocks like dolomite, fractures can affect fluid flow due to increase or decrease in permeability (Hanks et al., 2004). The extensional fractures developed in the Baghewala structure can lead to increase in permeability in the reservoir zone also i.e. the competent Jodhpur sandstone. We see enhanced production in one well that is closer to the fault zone which may be due to the increased permeability effected by the fractures, but the data is limited to conclusively prove this. This study will help to design the well position and trajectory not only to avoid mud loss and drilling complications but also to increase production by optimally placing the wells in proximity to the higher fracture intensity after arriving at a Discrete Fracture Network (DFN) model.
How to cite: Ahmed, F. and Rai, T.: Fracture network mapping using image logs from Baghewala structure, Bikaner Nagaur sub-basin: Implications for well profile and hydrocarbon production, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3144, https://doi.org/10.5194/egusphere-egu25-3144, 2025.
Faults are an important factor for geoenergy applications due to either their sealing or conducting properties or their mechanical behaviour. Consequently, (thermo-hydro-) mechanical numerical investigation of geoenergy applications often include faults in their modelled rock volume. It is often assumed, that faults can significantly alter the far-field stresses, impacting both magnitudes and the orientation. In contrast to the far-field, stress rotations in the vicinity of faults are clearly observed in numerous borehole stress analyses across the world.
While an impact of faults on the stress field is expected, the representation of faults in (thermo-hydro-) mechanical numerical models is technically highly diverse. We investigate different methods to incorporate faults in geomechanical-numerical models and the relationship between faults and the stress state on two different spatial scales.
(1) The impact of faults on the stress state at distances of several hundred meters to a few kilometres (far-field) is tested. Therefore, faults are modelled with different numerical representations, material properties, fault orientations w.r.t. the stress field, fault width, extent, and boundary conditions. The results show that the impact of faults on the far-field is negligible in terms of the principal stress magnitudes and orientations. Only in extreme cases, stress changes in the far-field (>1km) can be observed, but these are not significant considering the general uncertainties in stress field observations.
(2) Stress changes within the fault zone are investigated, too. Particularly, the material contrast between the intact rock and the damage zone and fault core is regarded. This contrast can be responsible for a dramatic change in the stress tensor, observed as a rotation of the principal stress axes. In general, the change in the stress field increases with increasing stiffness contrast. The orientation of the fault w.r.t. the background stress field and the relative stress magnitudes, particularly the differential stress, lead to further stress changes. A small angle between the fault and the maximum principal stress axis and a small differential stress promote stress changes.
The study indicates that the impact of faults on the stress field is mostly limited to the fault’s near-field. These models provide an upper limit of stress changes, as several factor which alter stress changes (joints, viscosity etc.) are not included. However, the stress changes depend on the acting processes and material properties. Furthermore, for models used for site investigation, the implementation method and the mesh resolution can play an important role. All these factors need to be considered when planning the setup of a model with faults and their implementation.
The work was partly funded by BGE SpannEnD 2.0 project, the Bavarian State Ministry of Education and Culture (Science and Arts) within the framework of the “Geothermal-Alliance Bavaria” (GAB), and the DFG (grant PHYSALIS 523456847).
How to cite: Ziegler, M., Reiter, K., Heidbach, O., Seithel, R., Rajabi, M., Niederhuber, T., Röckel, L., Müller, B., and Kohl, T.: Faults in geomechanical models – Necessary, nice, or nonsense?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8308, https://doi.org/10.5194/egusphere-egu25-8308, 2025.
Salt domes are considered as host rocks for long-term nuclear waste disposal. Groundwater flow in the near salt domes may lead to the transport of radionuclides into the biosphere. The following key factors that influence groundwater dynamics are the presence of brine as a result of salt dissolution, heat generation from radioactive waste and the "salt chimney effect"-a phenomenon in which the geothermal heat flux and high thermal conductivity of salt rock induce elevated temperatures around salt domes. The resulting temperature and salinity variations affect groundwater density (and viscosity), driving thermohaline convection in adjacent rock layers of the salt dome. Variable density and viscosity lead to coupled processes due to the highly nonlinear nature of the problem, which is challenging to model numerically. This study defines the fractured salt chimney problem and investigates for the first time the effect of fractures in the surrounding rock layers of a salt dome on thermohaline convection in these layers. Results show that the presence of fractures can have a strong impact on salt transport rates and the thermohaline convection patterns near salt domes.
How to cite: Suilmann, J. and Graf, T.: Numerical investigation of thermohaline convection in fractured-porous media near salt domes: the fractured salt chimney problem, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2742, https://doi.org/10.5194/egusphere-egu25-2742, 2025.
Safe and controlled exploration of deep geothermal resources in future decades is a key pillar for successfully transitioning to a carbon-neutral economy. A largely untouched source of deep hot source rocks can be found in crystalline basement formations in many European regions. Hydraulic stimulations are required to harness this thermal energy. Past geothermal projects were not always publicly accepted due to unintended induced seismicity that accompanied the projects. Faults and entire fault systems are jointly responsible for these seismic events and must therefore be thoroughly understood before they may be stimulated, to minimize tremors and unintentional shaking.
The Bedretto Underground Laboratory for Geosciences and Geoenergies in Ticino, Switzerland allows for decameter scale stimulation experiments and access to deeply (> 1km) buried crystalline faults. A complex fault zone is hydraulically and petrophysically described as part of the FEAR project, using various field and laboratory techniques. Two sub-parallel boreholes obliquely intersecting the target fault are analyzed using geophysical image and sonic logs. Hydraulic tests on predefined, packered intervals in the form of pulse-, constant rate- and step-rate injection tests are implemented on field scale, deducing parameters such as hydraulic conductivity and injectivity. In addition, laboratory petrophysical experiments on samples retrieved from varying parts along the fault zone are performed to determine permeability under certain effective stresses, porosity, and p-wave velocity, among other properties. This allows for a cross-scale hydraulic and petrophysical comparison. Prior, structural geologists described and analyzed the target fault using core logging, outcrop, and fracture data. Correlations between structural, hydraulic, and petrophysical observations can be drawn.
How to cite: Schaber, T., Jalali, M., Ceccato, A., Zappone, A. S., Pozzi, G., Selvadurai, P., Spagnuolo, E., Gischig, V., Meier, M.-A., Hertrich, M., and Amann, F. and the FEAR Team: Multidisciplinary characterization of a complex fault zone in crystalline basement rock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8404, https://doi.org/10.5194/egusphere-egu25-8404, 2025.
Understanding and predicting the hydro-mechanical (HM) behavior of subsurface porous and fractured formations is key to a number of engineering applications, including fluid injection/extraction, construction/excavation, geo-energy production and deep geological disposal. The interaction between fluid pressure, deformations and stresses is particularly affected by the subsurface heterogeneity, which may lead to non-intuitive responses, such as effective stress reduction and pressure increase during fluid extraction. While the impact of large-scale heterogeneities is acknowledged in most studies and modeling efforts, the presence of heterogeneities at smaller scales cannot be included in reservoir-scale models and it must be encompassed into equivalent properties assigned to uniform materials.
In this work, we focus on the Biot effective stress coefficient, a central property determining the HM behavior of fluid-saturated geological media. When not simply assumed as equal to 1, this coefficient is estimated experimentally at the laboratory sample-scale or analytically through expressions valid for isotropic homogeneous materials. However, these approaches are not able to estimate a representative equivalent coefficient for fractured rocks, which are strongly anisotropic and prone to sample-size effects, with fracture lengths spanning several orders of magnitudes from millimeters up to hundreds of meters. By employing a theoretical framework to quantify an equivalent Biot coefficient for a fractured rock mass from the properties of both the porous intact rock and the discrete fracture network (DFN), it is possible to analyze the variability of this coefficient with the DFN properties and highlight the implications for the rock upscaled HM behavior, in the context of natural processes and engineering applications.
How to cite: De Simone, S.: The equivalent Biot coefficient reveals the effects of heterogeneity on the Hydro-Mechanical behavior of fractured rocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11332, https://doi.org/10.5194/egusphere-egu25-11332, 2025.
Seismological observations show that earthquakes produce significant changes in the elastic and transport properties of active faults, with co-seismic drops in seismic wave velocities consistently followed by a slow post-seismic recovery, over months to few years. Such variations occur in volumes up to several hundred metres thick that correlate well with the dimensions of fault damage zones. This suggests the existence of a damage-recovery cycle within active fault zones, with the recovery phase possibly driven by a range of fluid-assisted re-strengthening “healing” mechanisms in the fractured medium and/or stress relaxation. Understanding how and how rapidly fractured rocks seal, regain their stiffness, and drive fluid flow in fault zones is fundamental to comprehend the mechanics of the brittle crust and for geo-engineering applications such as geothermal energy, ore deposits, the deep disposal of radioactive waste and CO2 sequestration.
At the Department of Geosciences of the University of Padua, a “percolation cell” apparatus has recently been installed to study long-term fluid-rock interaction under hydrostatic conditions with a maximum confining and pore pressure of 100 MPa and a maximum temperature of 250°C. Such apparatus is equipped with two syringe pumps and a back-pressure regulator that allow to monitor permeability evolution through time and a set of high-temperature P- and S- ultrasonic transducers to track changes of rock elastic properties in-situ. In addition, the pore fluid inlet circuit can flow into a stirred autoclave to pump solutions with controlled chemistry up to 20 MPa pore pressure and 200°C temperature through an externally heated pipe. Such an experimental apparatus allows to study both diffusion- and advection-dominated regimes within conditions representative for the upper crust.
Together with the experimental setup, here we present some preliminary long-term percolation tests in which de-ionized water was flowed at 25°C through rock cylinders of micritic limestones with mated and non-mated single fractures under 20 MPa confining pressure and 5 MPa pore pressure. The temporal evolution of permeability and elastic properties were monitored together with the fluid-chemistry at the outlet. Mechano-chemical processes along the fractures were also investigated through X-ray microtomography and SEM analyses.
How to cite: Fondriest, M. and Akker, I. V.: An experimental apparatus to investigate fluid-assisted long-term recovery of fractured rocks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12950, https://doi.org/10.5194/egusphere-egu25-12950, 2025.
Permeability in crystalline rocks, considered for use as geothermal reservoirs or deep geological repositories, is controlled by networks of well-connected fractures. Fracture connectivity depends on fracture orientation and density, which are influenced by tectonic and non-tectonic stresses, pre-existing foliations, and fracture zones. This study investigates fracture variability in the Devonian Wilsons Promontory granitic batholith of southeast Australia, which intruded Devonian metasediments that are unconformably overlain by Cretaceous rift-related sedimentary rocks.
Outcrop analogues allow 2D and 3D observation of fracture networks at scales from centimeters to hundreds of meters, complementing sub-meter-scale borehole data and regional lineament mapping. Additionally, digital outcrop models from uncrewed aerial vehicle (UAV) surveys enable fracture characterization in outcrops that are difficult to physically access, such as the granites in the study area. In this study, over 2,500 fractures were mapped and characterized from a UAV-derived point cloud. Most fractures strike NNW-SSE to N-S; they are are interpreted as extensional and to have formed coevally with NNW-SSE striking joints in outcropping Cretaceous rocks during regional uplift under NNW-SSE horizontal compression. Domains characterized by distinct fracture patterns are separated by meter-scale fracture zones, suggesting structural segmentation within the granite.
Future work will investigate the geometry and origin of these domain-bounding fracture zones and their links to mechanical heterogeneities in the granite. These insights will inform discrete fracture network (DFN) and hydrological models of granite reservoirs and repositories for spent nuclear waste. They will also support comparisons of brittle deformation in granitic versus siliciclastic rocks under shared tectonic regimes, relevant to energy projects involving multi-level, multi-lithology reservoirs.
How to cite: Samsu, A., Gasche, G., and Cruden, A. R.: Fracture Network Variability in Granite: Insights from Wilsons Promontory, Southeast Australia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13175, https://doi.org/10.5194/egusphere-egu25-13175, 2025.
Discrete Fracture Network (DFN) models have a widespread use when predicting hydraulic properties of fractured rock masses with different numerical and (semi-)analytical methods. However, recent advances in the way fracture network parameters are characterized in the field or in geophysical datasets are not completely reflected in input options of DFN simulators. For instance, to our knowledge no 3D DFN stochastic simulator is able to generate fracture networks with realistic topological relationships, and fracture spatial distributions different from a completely random Poisson distribution cannot be generated (so clustered or regular distributions cannot be modelled). This means that stochastic fracture networks cannot show realistic connectivity, with a strong impact on our possibility to model hydraulic properties.
Here we report on a comparative experiment where we have (i) reconstructed a 3D deterministic fracture network, based on rich outcrop data (Cretaceous platform limestones from Cava Pontrelli, Puglia, Italy), and stochastic DFNs with the same statistical parameters, and then (ii) we have modelled hydraulic properties with different semi-analytical (e.g. Oda method) and numerical methods (e.g. finite volumes implemented in DFNWorks).
Our preliminary results suggest that more advanced numerical methods are more sensitive to the quality of input data than simple semi-analytical methods. This is explained by the fact that for instance the Oda method simply ignores topology, connectivity, fracture height/length ratio and other important parameters.
How to cite: Favaro, S., Facci, M., Casiraghi, S., Mittempergher, S., and Bistacchi, A.: Comparing the impact of deterministic and stochastic fracture networks on modelling hydraulic properties, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16743, https://doi.org/10.5194/egusphere-egu25-16743, 2025.
Switzerland aims to reach net-zero CO2 emissions by 2050 (BAFU, 2021). Implementation of geological storage of CO2 and geothermal heat mining to help achieve this aim requires reservoir properties to be assessed. The structural and permeability architectures of the target reservoirs are essential input for numerical models used to assess storage and production potential, minimize fluid injection and extraction uncertainties, and reduce exploration risks. The so-called Muschelkalk aquifer (Triassic) including the Schinznach Formation is regarded as one of the key potential aquifers for gas storage and hydrothermal geothermal systems in Switzerland (Chevalier et al., 2010). While the matrix permeability of the Schinznach Formation is relatively well known (Diamond et al., 2019), magnitude and distribution of its fracture permeability and structural controls on these fractures are poorly understood.
This study aims to assess the style and intensity of natural fracture networks in the Muschelkalk aquifer at sub-seismic scale and explain their regional variability. Outcrop analogues in the Wutach Gorge of southern Germany are used to improve understanding of lateral and vertical variability of fracture networks, including how they are influenced by regional structures. The Wutach Gorge is within the Tabular Jura and provides cliff exposures along 5–12 km-long E–W and N–S transects, aligning with and crossing fault strands of the Freiburg–Bonndorf–Bodensee Fault zone.
Insights from field observations contribute to ongoing work that supports the proposed pilot CO2 injection test into the Schinznach Formation via an existing exploration borehole at Trüllikon in northern canton Zurich. A feasibility study (Diamond et al., 2023) assessed the reservoir properties at Trüllikon by building discrete fracture network models and computing their permeabilities from a combination of rock-matrix properties, vertical drill hole fracture logs, a horizontal fracture log from another nearby drill hole, and results from hydraulic tests. This multidisciplinary approach should provide a more robust basis for exploration for CO2 storage sites and geothermal energy.
REFERENCES
Chevalier, G., Diamond, L. W., & Leu, W. (2010). Potential for deep geological sequestration of CO2 in Switzerland: a first appraisal. Swiss Journal of Geosciences, 103, 427-455.
Diamond, L. W., Alt-Epping, P., Brett, A.C., Aschwanden, L. and Wanner, C. (2023) Geochemical–hydrogeological study of a proposed CO2 injection pilot at Trüllikon, Switzerland. Report 2023-7 submitted to the Swiss Geological Survey (swisstopo). Rock Water Interaction, University of Bern, 87 pp. https://doi.org/10.5281/zenodo.10938102
Diamond L.W., Aschwanden, L., Adams, A., and Egli, D. (2019) Revised potential of the Upper Muschelkalk Formation (Central Swiss Plateau) for CO2 storage and geothermal electricity. Slides of an oral presentation at the SCCER-SoE Annual Conference at EPFL-Lausanne, 4th Sept. 2019. 13 pp. http://static.seismo.ethz.ch/sccer-soe/Annual_Conference_2019/AC19_S3a_08_Diamond.pdf
BAFU (2021) Switzerland Long-Term Climate Strategy. 4 pp. https://www.bafu.admin.ch/dam/bafu/en/dokumente/klima/fachinfo-daten/langfristige-klimastrategie-der-schweiz.pdf.download.pdf/Switzerland's%20Long-Term%20Climate%20Strategy.pdf
How to cite: Brett, A. C., Caldeira, J., Samsu, A., Diamond, L. W., and Madritsch, H.: Fracture networks in the Muschelkalk aquifer of the external northen foreland of the Central Alps (CH/DE); implications for permeability, CO2 storage and geothermal potential, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8885, https://doi.org/10.5194/egusphere-egu25-8885, 2025.
Mesoscale fractures, with lengths between meters and hundreds of meters, cannot be effectively characterized in the subsurface, due to limitations of borehole and geophysical datasets. However, large quantitative structural datasets can be collected by combining field and remote sensing techniques in digital outcrop models (DOMs). These data can be then used to constrain stochastic models of subsurface fracture networks with the outcrop analogue approach. However, to date a methodology optimized to characterize all parameters of a fracture network remains elusive. In this contribution we present a workflow that leverages digital outcrop models including both pavement and wall exposures, allowing for a three-dimensional analysis. Different parameters are calculated starting from different types of support, so we collect orientation data on point cloud DOMs (PC-DOMs) of vertical outcrops with semi-automatic methods. These data are classified based on field observations and segmented using a k-medoid approach. The goodness-of-fit to orientation distributions is tested with a proper statistical treatment. Topological parameters are measured on the fracture network digitalized from textured surface DOMs (TS-DOM). Standard topological analysis only provides averaged information on the whole fracture network. In this contribution a novel approach called directional topology is presented, in which every node retains information about the branches that generated it. This not only provides a more comprehensive understanding of the network's connectivity but also allows for the extraction of quantitative parameters about the degree of abutting of a specific fracture set on another (on horizontal outcrops) and on the extent to which a set is stratabound (on vertical outcrops). The trace length, height and spacing distributions are measured with a robust innovative approach, accounting for the censoring bias with survival/reliability analysis. P21 data are collected distributing several grids of scan area with increasing edge length, and the representative elementary area is qualitatively defined. A particular focus will be placed on the calculation of the H/L ratio, often overlooked but of fundamental importance, as it is responsible of the jump in dimensionality in 3D stochastic models.
How to cite: Casiraghi, S., Benedetti, G., Bertacchi, D., Agliardi, F., Mittempergher, S., and Bistacchi, A.: Integrated Workflow for Parametrization of Fracture Networks in Digital Outcrop Models: Focus on Directional Topology and H/L ratio calculation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18626, https://doi.org/10.5194/egusphere-egu25-18626, 2025.
Fault-related karst systems and silicification processes are important factors in controlling permeability heterogeneities in shallow crusts. In recent years, the interest in these processes has become more important since they significantly modify the texture, mineralogy, and petrophysical properties of carbonate reservoirs.
The hypogenic Morro Vermelho Cave, in the Irecê Basin, Bahia (Brazil), is a key study area for understanding the development of fault-related silicification and subsequent karstification along fault networks in dolomitized carbonate rocks of the Neoproterozoic Salitre Formation.
This contribution focuses on a tridimensional digital cave model analysis and a detailed outcrop and cave investigation to constrain fracture attitude, type, geometry, and kinematics. Field data show the presence of regional-scale E-W thrust data.
The Morro Vermelho cave is developed in the proximity of one of these thrusts and is mostly developed along silicified carbonates with bedding dipping 40° toward SE.
The analysis of the lidar model reveals that the cave has an irregular morphology with several branching passages controlled by major N-S to NNE-SSW thoroughgoing fractures.
Both 3D model and high-resolution structural mapping in the cave highlight the presence of high-angle N-S-oriented normal faults and the following fracture sets: E-W-striking sheared veins and joints, bed-parallel NE-SW-striking veins, fault-parallel N-S-striking veins and joints, and bed-perpendicular NW-SE-striking veins and joints.
The obtained results indicate that the silicification process was mostly controlled by regional-scale E-W-striking thrust, associated with the N-S shortening of the Brasiliano orogeny, whereas the Morro Vermelho cave developed mostly along bedding layers and small-scale N-S-oriented normal faults, system and related fractures. The fractures also controlled the occurrence of late-stage silica crusts that post-date the cave development.
We propose a preliminary conceptual model that includes different stages of silicification events and karstification related to fault systems and fracture networks, in alignment with the structural regional-scale evolution of the study area.
The findings might be highly significant for understanding the permeability characteristics of deeply buried pre-salt fractured carbonate reservoirs in offshore Brazil and other similar settings.
How to cite: Porta, F., Morandi, C., La Bruna, V., Auler, A., Bezerra, F. H. R., and Balsamo, F.: Structural control on silicification and hypogenic karst: insights from Morro Vermelho cave, Irecê Basin, Brazil , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17127, https://doi.org/10.5194/egusphere-egu25-17127, 2025.
Abstract: Fracture propagation dynamics in complex geological formations is crucial for understanding cracking mechanism of deep rock and facilitating subsurface reconstruction and resource extraction. However, predominant mechanism-driven numerical model exist several inherent limitations: 1) Over-reliance on empirical formulas and simplified hydraulic fracture propagation model with multi-assumptions restrict its capacity for effectively characterizing the multi-physics coupling in 3-D space, thereby reducing the accuracy of fracture morphology. 2) Computational schemes such as finite element method (FEM) or discrete element method (DEM) involving extensive repetitive calculations, are resource-intensive and exhibit poor temporal efficiency, posing a challenge to engineering requirements. Therefore, a data-model-interactive neural proxy model combining the prior-knowledge from mechanism models and fitting efficiency of deep neural networks, is put forward to depict the fracture propagation dynamics in complex geological formation. Initially, a numerical model for fracture propagation is developed by implementing the 3-D discrete lattice method alongside the elastic-plastic constitutive equation. The coupling of rock deformation and fluid flow is iteratively processed in a stepwise manner to generate a sequence of fracture morphology evolution over time. These mechanism data will provide training samples for the subsequent neural proxy model. Secondly, the efficacy of the neural proxy model is contingent upon the richness and diversity of features presented in the training dataset, necessitating a close approximation of all conceivable scenarios. In light of the irregular spatial distribution of data resulting from the complex geological formation with strong heterogeneity, the Latin Hypercube sampling method is employed to ensure a uniform selection of all conditions, mitigating the potential data imbalance. Furthermore, the integration of numerical results with empirical measurements is employed to train the developed deep-neural networks, fitting high-dimensional mapping relationships among formation physical parameters, engineering parameters, and fracture morphology. Finally, the efficiency and the accuracy of the proposed method are verified by multi-level comparison experiments between real data and simulation results. Our research provides reliable technical support for rapid evaluation of formation fracturing potential in field and guidance of development process.
Keywords: Fracture propagation, Neural proxy model, Deep learning, Numerical simulation, Deep-formation
How to cite: Zhang, F., Tang, J., Fan, Y., Yang, J., Li, J., Chen, W., Wang, H., and Jia, Y.: Fracture Propagation Dynamics Predicted by Data-model-interactive Neural Proxy Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14719, https://doi.org/10.5194/egusphere-egu25-14719, 2025.
Posters virtual: Mon, 28 Apr, 14:00–15:45 | vPoster spot 4
EGU25-4960 | ECS | Posters virtual | VPS16
Study on the Vertical Transport Capacity of Prematurely Failed Faults in Deep Oil and Gas Enriched Areas: A Case Study of Lufeng 13 Sag in the Pearl River Mouth BasinMon, 28 Apr, 14:00–15:45 (CEST) | vP4.11
With the continuous development of deep oil and gas exploration, the phenomenon of oil and gas enrichment near prematurely failed source faults in deep formations has been revealed. However, the mechanism of how these prematurely failed faults open to transport hydrocarbon is not yet clearly understood, and there is a lack of quantitative evaluation of their transport capacity. This study takes the Lufeng 13 Sag in the Pearl River Mouth Basin as an example. Based on 3D seismic data, software simulation, and mudstone plastic deformation experiments, it analyzes the reactivation mechanism of prematurely failed faults and evaluates their vertical transport capacity, revealing the role of these faults in deep hydrocarbon enrichment. The study shows that the transport capacity of prematurely failed faults is negatively correlated with the normal stress on the fault plane during the reservoir-forming period and positively correlated with the ultimate pressure for mudstone plastic deformation. When the normal stress on the fault plane during the reservoir-forming period is less than 13.9 MPa, the buoyancy of hydrocarbon can overcome the normal stress on the fault plane at the upper interface of the source rock, allowing hydrocarbon to migrate upward along the fault. When the ultimate pressure for mudstone plastic deformation is greater than 18.5 MPa, the pressure on the fault plane is less than the ultimate pressure for mudstone plastic deformation, and the argillaceous components in the fault zone do not undergo plastic deformation and flow. The leakage spaces left in the fault zone are not blocked, and no seal is formed vertically. Based on the normal stress on the fault plane during the reservoir-forming period and the ultimate pressure for mudstone plastic deformation, a vertical transport coefficient (K) for prematurely failed faults is established. When K is less than 1.1, the prematurely failed fault has vertical transport capacity during the reservoir-forming period.
How to cite: Cao, X., Liu, H., Peng, G., and Long, Z.: Study on the Vertical Transport Capacity of Prematurely Failed Faults in Deep Oil and Gas Enriched Areas: A Case Study of Lufeng 13 Sag in the Pearl River Mouth Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4960, https://doi.org/10.5194/egusphere-egu25-4960, 2025.
EGU25-16619 | ECS | Posters virtual | VPS16
3D Fault Identification Based on Improved U-Net with Multi-Scale Feature FusionMon, 28 Apr, 14:00–15:45 (CEST) | vP4.12
In the fields of geological research and engineering applications, fault identification is of great significance for understanding geological structure evolution, predicting geological disasters, and guiding resource exploration and development. Traditional fault identification methods based on manual interpretation and seismic attributes struggle to meet the requirements in terms of efficiency and accuracy when faced with complex geological conditions and massive amounts of data. With the development of deep learning technology, convolutional neural networks have demonstrated excellent performance in image recognition and segmentation tasks. However, the multi-scale characteristics of faults, that is, the fault structures in seismic images are diverse in size, shape, and complexity, pose severe challenges to image recognition. This paper innovatively proposes a fault identification method based on an improved U-Net neural network. Focusing on the multi-scale characteristics of faults, it aims to enhance the accuracy and robustness of fault identification. The model introduces a multi-scale feature fusion mechanism, skillfully integrating encoder feature maps with different spatial resolutions, which significantly improves the ability to express fault features. In addition, in view of the insufficient representativeness of synthetic datasets, this study adopts data augmentation techniques, performing operations such as rotation, flipping, and scaling on the training data to effectively expand data diversity and enhance the generalization ability of the model. Experimental results show that when the improved U-Net model is tested on the publicly available F3 seismic data of the Dutch North Sea and the data of an oilfield in the Junggar Basin, China, compared with the traditional U-Net model, it has achieved significant improvements in key evaluation indicators such as recognition accuracy, recall rate, IOU, and PR curve. Especially in complex geological backgrounds, the improved model can more accurately identify the location and shape of faults, providing a more reliable and efficient fault identification technical means for fields such as geological structure research, oil exploration, and underground engineering construction. It has important theoretical significance and practical application value.
How to cite: Huang, Y., Cui, L., Niu, Y., Tao, Y., Liu, Y., and Chen, Y.: 3D Fault Identification Based on Improved U-Net with Multi-Scale Feature Fusion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16619, https://doi.org/10.5194/egusphere-egu25-16619, 2025.
EGU25-10984 | ECS | Posters virtual | VPS16
Impact of Pre-Mesozoic Strike-Slip Faults on Dolomite Gas Reservoir in the Central Sichuan Basin and Its Exploration PotentialMon, 28 Apr, 14:00–15:45 (CEST) | vP4.13
Abstract: A large strike-slip fault system has been found in the central Sichuan Basin, although its effects on the pre-Mesozoic tight dolomite gas reservoirs in the deep (>4500 m) subsurface are uncertain. By integrating 3D seismic fault mapping, detailed fracture characterization, and well production data, this study demonstrates that strike-slip faults are extensively developed as vertically stratified arrays within the Ediacaran, Cambrian, and Permian dolomite intervals. These faults connect Lower Cambrian source rocks to multiple reservoir horizons, thereby establishing both lateral and vertical hydrocarbon migration pathways. A defining element of this system is the spatiotemporal coupling of “source-fault-reservoir,” which underpins the formation of a large-scale, pre-Mesozoic fault-controlled gas accumulation. Seismic evidence shows that many of these faults exhibit near-vertical geometries, en echelon arrangements, and step-over structures, all of which foster intense fracturing in the adjacent dolomites. Such fracturing substantially enhances porosity and permeability, yielding localized “sweet spots” with improved storage capacity and fluid flow properties, particularly within slope areas where structural conditions favor gas trapping. Production data strongly corroborate the geological and seismic observations, with wells that intersect or closely adjoin these fault zones typically exhibiting higher flow rates and more stable production profiles. This phenomenon highlights the pivotal role of fault-induced fractures in reservoir performance and underscores the need for detailed fault mapping and fracture network analysis in deep, tight carbonate plays. Furthermore, the recognition of this large-scale, strike-slip fault-controlled dolomite reservoir in a deep intracratonic setting underscores its considerable exploitation potential and points to broader implications for petroleum geology. Consequently, this study provides a robust framework for understanding the interplay between fault architecture and reservoir quality, offering valuable insights for guiding future exploration and development in analogous deep carbonate basins worldwide.
Key words: Strike-slip fault; Deep tight dolomite reservoir; Strike-slip fault-related petroleum system; Migration and accumulation; Exploration; Sichuan Basin
How to cite: Tian, W., Jiang, T., and Wu, G.: Impact of Pre-Mesozoic Strike-Slip Faults on Dolomite Gas Reservoir in the Central Sichuan Basin and Its Exploration Potential, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10984, https://doi.org/10.5194/egusphere-egu25-10984, 2025.
