Articles de revues : « Fault-zone hydraulics »

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Konstantinovskaya, Elena, Qiuguo Li, Alexey Zhmodik, Charles Ibelegbu, Ryan Schultz et Todd Shipman. « Lateral fluid propagation and strike slip fault reactivation related to hydraulic fracturing and induced seismicity in the Duvernay Formation, Fox Creek area, Alberta ». Geophysical Journal International 227, n^o 1 (16 juin 2021) : 518–43. http://dx.doi.org/10.1093/gji/ggab234.

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SUMMARY Fault shear slip potential is analysed in the area where induced earthquakes (up to 3.9 Mw) occurred in May–June 2015 approximately 30 km south of Fox Creek, Western Canada Sedimentary Basin, Canada. The induced earthquakes were generated by the hydraulic fracturing of the Upper Devonian Duvernay Formation. Interpretation of a 3-D seismic survey and analysis of the ant tracking attribute identifies a linear discontinuity that likely represents a subvertical fault with strike length of 1.4 km, which is aligned with the zone of induced earthquake hypocentres. 1-D–3-D geomechanical modelling is conducted to characterize mechanical rock properties, initial reservoir pressure and stress field. Hydraulic fracture propagation and reservoir pressure buildup simulations are run to analyse lateral fluid pressure diffusion during well treatment. The interaction of natural fractures introduced as Discrete Fracture Network and hydraulic fractures is tested. 3-D poroelastic reservoir geomechanical modelling is completed to simulate slip reactivation of the identified fault zone. The obtained results support that additional pressure buildup of 20 MPa in treatment wells can propagate laterally along hydraulic fractures (and potentially natural fracture network) for about 550 m and reach the fault zone. The increase of fluid pressure by 20 MPa in the fault zone results in dextral slip along the fault, mostly in the interval of the Duvernay and overlying Ireton Formations, corroborating prior focal mechanism results and hypocentral depths. The simulations indicate that lateral transmission of additional fluid pressure from the fracturing stimulation area to the fault zone could happen in a few days after the treatment of lateral wells that is supported by the observed induced earthquakes. This study helps to quantify changes in fluid pressure and stresses that may result in fault shear slip during hydraulic fracturing and predict the potential of induced seismicity connected to hydrocarbon production from the Duvernay Play.

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Liu, Weitao, Jiyuan Zhao, Ruiai Nie, Yuben Liu et Yanhui Du. « A Coupled Thermal-Hydraulic-Mechanical Nonlinear Model for Fault Water Inrush ». Processes 6, n^o 8 (7 août 2018) : 120. http://dx.doi.org/10.3390/pr6080120.

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A coupled thermal-nonlinear hydraulic-mechanical (THM) model for fault water inrush was carried out in this paper to study the water-rock-temperature interactions and predict the fault water inrush. First, the governing equations of the coupled THM model were established by coupling the particle transport equation, nonlinear flow equation, mechanical equation, and the heat transfer equation. Second, by setting different boundary conditions, the mechanical model, nonlinear hydraulic-mechanical (HM) coupling model, and the thermal-nonlinear hydraulic-mechanical (THM) coupling model were established, respectively. Finally, a numerical simulation of these models was established by using COMSOL Multiphysics. Results indicate that the nonlinear water flow equation could describe the nonlinear water flow process in the fractured zone of the fault. The mining stress and the water velocity had a great influence on the temperature of the fault zone. The temperature change of the fault zone can reflect the change of the seepage field in the fault and confined aquifer. This coupled THM model can provide a numerical simulation method to describe the coupled process of complex geological systems, which can be used to predict the fault water inrush induced by coal mining activities.

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Niu, Zhiyong, Shiquan Wang, Hongrui Ma, Hengjie Luan et Zhouyuyan Ding. « Study of Characteristics of Fault Slip and Induced Seismicity during Hydraulic Fracturing in HDR Geothermal Exploitation in the Yishu Fault Zone in China ». Geofluids 2021 (5 avril 2021) : 1–19. http://dx.doi.org/10.1155/2021/5515665.

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Hot dry rock (HDR) geothermal energy has become promising resources for relieving the energy crisis and global warming. The exploitation of HDR geothermal energy usually needs an enhanced geothermal system (EGS) with artificial fracture networks by hydraulic fracturing. Fault reactivation and seismicity induced by hydraulic fracturing raise a great challenge. In this paper, we investigated the characteristics of fault slip and seismicity by numerical simulation. The study was based on a hydraulic fracturing project in the geothermal field of Yishu fault zone in China. It revealed that fluid injection during hydraulic fracturing can cause the faults that exist beyond the fluid-pressurized region to slip and can even induce large seismic event. It was easier to cause felt earthquakes when hydraulic fracturing was carried out in different layers simultaneously. We also examined the effects of the location, permeability, and area of the fracturing region on fault slip and magnitude of the resulting events. The results of the study can provide some useful references for establishing HDR EGS in Yishu fault zone.

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Romano, Valentina, Sabina Bigi, Francesco Carnevale, Jeffrey De’Haven Hyman, Satish Karra, Albert J. Valocchi, Maria Chiara Tartarello et Maurizio Battaglia. « Hydraulic characterization of a fault zone from fracture distribution ». Journal of Structural Geology 135 (juin 2020) : 104036. http://dx.doi.org/10.1016/j.jsg.2020.104036.

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Jia, Ru, Caiwei Fan, Bo Liu, Xiaofei Fu et Yejun Jin. « Analysis of Natural Hydraulic Fracture Risk of Mudstone Cap Rocks in XD Block of Central Depression in Yinggehai Basin, South China Sea ». Energies 14, n^o 14 (6 juillet 2021) : 4085. http://dx.doi.org/10.3390/en14144085.

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The Yinggehai Basin is an important Cenozoic gas bearing basin in the South China Sea. With the gradual improvement of gas exploration and over-development in shallow layers, deep overpressured layers have become the main target for natural gas exploration. There are no large-scale faults in the strata above the Meishan Formation in the central depression, and hydraulic fracturing caused by overpressure in mudstone cap rocks is the key factor for the vertical differential distribution of gas. In this paper, based on the leak-off data, pore fluid pressure, and rock mechanics parameters, the Fault Analysis Seal Technology (FAST) method is used to analyze the hydraulic fracture risk of the main mudstones in the central depression. The results show that the blocks in the diapir zone have been subjected to hydraulic fracturing in the Huangliu cap rocks during the whole geological history, and the blocks in the slope zone which is a little distant from the diapirs has a lower overall risk of hydraulic fracture than the diapir zone. In geological history, the cap rocks in slope zone remained closed for a longer time than in diapir zone and being characterized by the hydraulic fracture risk decreases with the distance from the diapirs. These evaluation results are consistent with enrichment of natural gas, which accumulated in both the Yinggehai Formation and Huangliu Formation of the diapir zone, but it only accumulated in the the Huangliu Formations of the slope zone. The most reasonable explanation for the difference of the gas reservoir distribution is that the diapirs promote the development of hydraulic fractures: (1) diapirism transfers deep overpressure to shallow layers; (2) the small fault and fractures induced by diapir activities weakened the cap rock and reduced the critical condition for the natural hydraulic fractures. These effects make the diapir zone more prone to hydraulic fracturing, which are the fundamental reasons for the difference in gas enrichment between the diapir zone and the slope zone.

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Xue, Lian, Hai-Bing Li, Emily E. Brodsky, Zhi-Qing Xu, Yasuyuki Kano, Huan Wang, James J. Mori et al. « Continuous Permeability Measurements Record Healing Inside the Wenchuan Earthquake Fault Zone ». Science 340, n^o 6140 (27 juin 2013) : 1555–59. http://dx.doi.org/10.1126/science.1237237.

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Permeability controls fluid flow in fault zones and is a proxy for rock damage after an earthquake. We used the tidal response of water level in a deep borehole to track permeability for 18 months in the damage zone of the causative fault of the 2008 moment magnitude 7.9 Wenchuan earthquake. The unusually high measured hydraulic diffusivity of 2.4 × 10−2square meters per second implies a major role for water circulation in the fault zone. For most of the observation period, the permeability decreased rapidly as the fault healed. The trend was interrupted by abrupt permeability increases attributable to shaking from remote earthquakes. These direct measurements of the fault zone reveal a process of punctuated recovery as healing and damage interact in the aftermath of a major earthquake.

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Gao, Yanan, Peng Guo, Zetian Zhang, Minghui Li et Feng Gao. « Migration of the Industrial Wastewater in Fractured Rock Masses Based on the Thermal-Hydraulic-Mechanical Coupled Model ». Geofluids 2021 (16 octobre 2021) : 1–13. http://dx.doi.org/10.1155/2021/5473719.

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Industrial wastewater may have a long-time effect on the environment and human life as it goes underground and causes serious pollution continuously. To have a well understanding of the migration of such wastewater is a basic task for industrial wastewater treatment as well as industrial design. To study the migration mechanism of industrial wastewater in rock formations, the governing equations such as mechanics, seepage, heat, and mass transfer are reviewed, referenced, and proposed. The thermal (T)-hydraulic (H)-mechanical (M) coupled model of the multimedia of matrix-fault and matrix-fracture-fault is established. The influence of the fault and the fractures on the pressure distribution and contaminant migration is analyzed. The influence of fault length, width, dip angle, permeability, and temperature of wastewater on contaminant migration is parametrically studied. The following results can be obtained. (1) The fracture quantitively affects the concentration distribution, while the fault dominates the concentration distribution and contaminant migration. (2) The migration of the contaminants can be geometrically divided into 3 zones along the direction of the fault: the saturation zone, the rapid diffusion zone, and the concentration decrease zone. (3) There is a peak of the concentration along the bottom of the model. The position of the peak is the projection of the endpoint of the fault. (4) The fault length has the most significant effect on contaminant accumulation. The temperature of the wastewater has the minimum effect on the contaminant accumulation. (5) The accumulation of concentrations can be divided into 2 stages, the slow growth stage (before 20 years) and the rapid growth stage (after 20 years). The main channel of contaminant migration in the slow growth stage is a fault. During the rapid growth stage, the contaminants penetrate through the rock matrix as well as the fault.

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Lai, Jin Xing, Hao Bo Fan et Fei Zhou. « Fluid-Solid Coupling Numerical Simulation for Tunnel in Fracture Zone Based on 2D-FLAC Software ». Advanced Materials Research 503-504 (avril 2012) : 167–70. http://dx.doi.org/10.4028/www.scientific.net/amr.503-504.167.

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To understand the stressed characteristic of fault rupture zone under high hydraulic pressure, based on the F3 fault of Guanshan tunnel the software 2D-FLAC is adopted to found the fluid-solid coupling numerical model of ground water seepage and evolution in the process of tunnel structure in fault rupture zone under high hydraulic pressure and analyze the mechanical character of tunnel structure in three schemes of whole block, free discharge and limit discharge. The result shows that in the whole block condition, the partial seepage of ground water happened and the lining thickness should be more than 60cm; Regardless of water pressure, the rock is damaged at a large range, and the minimum safety factor of the lining structure meet the tunnel design standard; In the limit discharge condition, the grouting reinforced ring makes the effect of limiting drainage and keeping the tunnel’s stability in the construction. The tunnel drainage gets smaller with the increase of grouting ring’s thickness and the decrease of grouting ring’s penetration parameter; setting the drainage system can decrease the hydraulic pressure at the back of lining as well as grouting and water blocking.

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Donzé, Frédéric-Victor, Alexandra Tsopela, Yves Guglielmi, Pierre Henry et Claude Gout. « Pressurized fluid flow within the mechanical stability domain of fault zones in shale ». E3S Web of Conferences 98 (2019) : 01013. http://dx.doi.org/10.1051/e3sconf/20199801013.

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Fracture interaction mechanisms and reactivation of natural discontinuities under fluid pressurization conditions inside fault zone can represent critical issues in risk assessment of caprock integrity. A field injection test, carried out in a damage fault zone at the decameter scale i.e. mesoscale, has been studied using a Distinct Element Model. Considering the complex structural nature of a fault zone, the contribution of fracture sets on the bulk permeability has been investigated during a hydraulic injection. It has been shown that their orientation for a given in-situ stress field plays a major role. However, if homogeneous properties are assigned to the fracture planes in the model, the limited irreversible displacements cannot be reproduced. Despite these limited displacements (40 µm maximum), the transmissivity increased by a factor of 10-100. These results provide insights in fracture controlled permeability of fault zones depending on the geometrical properties of the fractures and their resulting hydro-mechanical behavior for a given in–situ stress field.

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Guo, Yanhui, Yi Yang, Zhijun Kong et Jin He. « Development of Similar Materials for Liquid-Solid Coupling and Its Application in Water Outburst and Mud Outburst Model Test of Deep Tunnel ». Geofluids 2022 (21 mai 2022) : 1–12. http://dx.doi.org/10.1155/2022/8784398.

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In order to explore the evolution mechanism of water and mud inrush, based on the fluid-solid coupling similarity theory and a large number of matching tests, fault similar materials with mountain sand, gravel, and red clay as raw materials and surrounding similar rock materials with mountain sand, red clay, cement, and water as raw materials are developed. Similar materials’ physical and mechanical properties and hydraulic properties with different ratios are tested and analyzed. The results show that the red clay content influences the mechanical properties of similar materials and their hydraulic properties, and the gravel substrate mainly influences the fault permeability coefficient. Similar material can be adjusted within a certain range of mechanical parameters. The material is simple and suitable for developing similar materials for different low and medium strength rock masses. Finally, a similar material was used in a model test of the tunnel fault fracture zone to reveal the mechanism of water and mud bursts in the tunnel. The study results can be used as a reference for the development of similar materials for tunnel fracture zone surrounding rocks.

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Lunn, Rebecca J., Zoe K. Shipton et Aileen M. Bright. « How can we improve estimates of bulk fault zone hydraulic properties ? » Geological Society, London, Special Publications 299, n^o 1 (2008) : 231–37. http://dx.doi.org/10.1144/sp299.14.

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Wei, Xiaochen, Jingxuan Zhang, Qi Li, Xiangjun Liu, Lixi Liang et Lili Ran. « Fault slippage and its permeability evolution during supercritical CO2 fracturing in layered formation ». Oil & ; Gas Science and Technology – Revue d’IFP Energies nouvelles 74 (2019) : 76. http://dx.doi.org/10.2516/ogst/2019051.

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Understanding the hydromechanical responses of faults during supercritical CO2 fracturing is important for reservoir management and the design of energy extraction systems. As small faults are widespread in Chang 7 member of the Yanchang Formation, Ordos Basin, China, supercritical CO2 fracturing operation has the potential to reactive these undetected small faults and leads to unfavorable fracking fluid migrate. In this work, we examined the role of fault slippage and permeability evolution along a small fault connecting the pay zone and the confining formation during the whole process of fracturing and production. A coupled hydromechanical model conceptualized from actual engineering results was introduced to address the main concerns of this work, including, (1) whether the existence of a undetected small fault would effectively constrain the hydraulic fracture height evolution, (2) what the magnitude of the induced microseismic events would be and (3) whether the permeability change along the fault plane would affect the vertical conductivity of the confining formation and thus increase the risk for the fracturing fluid to leak. Our results have shown that the initial hydrofracture formed at the perforation and propagated upward, once it merged with the fault surface, the existence of an undetected small fault would effectively constrain the hydraulic fracture height evolution. As fracturing continued, further slippage spread from the permeability increase zone of high permeability to shallower levels, and the extent of this zone was dependent on the magnitude of the fault slippage. At the end of extraction, the slip velocity decreases gradually to zero and the fault slippage finally reaches stabilization. In general, undetected small faults in targeted reservoir may not be the source of large earthquakes. The induced microseismic events could be considered as the sources of acoustic emission events detected while monitoring the fracturing fluid front. Due to the limited fault slippage and lower initial permeability, the CO2 fracturing operation near undetected small faults could not conduct preferential pathway for upward CO2 leakage or contaminate overlying shallower potable aquifers.

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Guerrero-Martínez, Lilia, Martín Hernández-Marín et Ángel Eduardo Muñoz-Zavala. « Hydraulic behavior of subsidence-induced surface discontinuities in the hydrogeology of the Aguascalientes valley ». Proceedings of the International Association of Hydrological Sciences 382 (22 avril 2020) : 589–94. http://dx.doi.org/10.5194/piahs-382-589-2020.

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Abstract. The impact of faults and fissures (discontinuities) on the groundwater flow has become important in several parts of the world because the heterogeneous and anisotropic distribution of permeability in fault zones is difficult to characterize. Based on this, we propose an analysis of patterns of parameters measured in groundwater, under the premise that the observed anomalies can be indicators of the hydraulic behavior of the flow in the direction perpendicular to the fault plane. In this context, if the discontinuities are sealed, they behave as hydraulic barriers, causing variation in the continuity of the parameters across the fault plane. Conversely, when faults are a conduit, they appear to have a small or null variation in the distribution of the parameter measurements. The impact of discontinuities in groundwater flow in a zone with a large number of faults and fissures such as that of the Aguascalientes valley is being studied using a graphical-correlation analysis with the revision of 230 wells, through the measurement of parameters such as temperature and static levels across discontinuities, in order to determine the hydraulic behavior of the faults. This investigation considered values over 4 ∘C for geothermal variations and 10 m for hydraulic-head changes to define fault behavior. Results show three zones through mapping analysis, where the fault presents barrier behavior and where the hanging block represents high values; these anomalies are much higher than the average across the valley and indicate the propensity for the fault to restrict horizontal flow. In conclusion, the Oriente fault presents complex behavior of a barrier–conduct system along the fault. This analysis gives a robust way to describe fault behavior without referring to elaborate and invasive hydrological investigations.

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Riegel, Hannah, Miller Zambrano, Fabrizio Balsamo, Luca Mattioni et Emanuele Tondi. « Petrophysical Properties and Microstructural Analysis of Faulted Heterolithic Packages : A Case Study from Miocene Turbidite Successions, Italy ». Geofluids 2019 (2 juin 2019) : 1–23. http://dx.doi.org/10.1155/2019/9582359.

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Geofluid reservoirs located in heterolithic successions (e.g., turbidites) can be affected by vertical and lateral compartmentalization due to interbedded fine-grained facies (i.e., shale, siltstones) and the presence of faults, respectively. A fault can behave as a conduit or barrier to fluid flow depending on its architecture and the individual hydraulic behavior of its components (i.e., fault core, damage zone). The fault core, normally composed by fault rock or smeared clay material, commonly acts as a flow inhibitor across the fault. Fault-related fractures (macro- and microscopic) in the damage zone generally increase the permeability parallel to the fault, except when they are cemented or filled with gouge material. Although macrofractures (which define the fracture porosity) dominate fluid flow, the matrix porosity (including microfractures) begins to have a more important role in fluid flow as the aperture of macrofractures is occluded, particularly at greater depth. This study investigates the variation in matrix permeability in fault zones hosted in heterolithic successions due to fault architecture and stratigraphy of host rock (i.e., sand-rich turbidites). Two key areas of well-exposed, faulted Miocene turbidites located in central and southern Italy were selected. For this study, six separate fault zones of varying offset were chosen. Each impacts heterolithic successions that formed under similar tectonic conditions and burial depths. Across the selected fault zones, an extensive petrophysical analysis was done in the field and laboratory, through air permeameter measurements, thin section, and synchrotron analysis in both host rock, damage zone, and fault core. Results suggest that the amount and distribution of clay layers in a heterolithic sequence affects fluid flow across the fault, regardless of fault offset.

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Eyre, Thomas S., David W. Eaton, Dmitry I. Garagash, Megan Zecevic, Marco Venieri, Ronald Weir et Donald C. Lawton. « The role of aseismic slip in hydraulic fracturing–induced seismicity ». Science Advances 5, n^o 8 (août 2019) : eaav7172. http://dx.doi.org/10.1126/sciadv.aav7172.

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Models for hydraulic fracturing–induced earthquakes in shales typically ascribe fault activation to elevated pore pressure or increased shear stress; however, these mechanisms are incompatible with experiments and rate-state frictional models, which predict stable sliding (aseismic slip) on faults that penetrate rocks with high clay or total organic carbon. Recent studies further indicate that the earthquakes tend to nucleate over relatively short injection time scales and sufficiently far from the injection zone that triggering by either poroelastic stress changes or pore pressure diffusion is unlikely. Here, we invoke an alternative model based on recent laboratory and in situ experiments, wherein distal, unstable regions of a fault are progressively loaded by aseismic slip on proximal, stable regions stimulated by hydraulic fracturing. This model predicts that dynamic rupture initiates when the creep front impinges on a fault region where rock composition favors dynamic and slip rate weakening behavior.

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Putra, Ahmad Dedi, Norasiah Sulaiman, Norsyafina Roslan, Habibah Jamil et Khairunnisa Alias. « Fault Zone Identification for Groundwater Flow Assessment Based On Seismic Reflection Survey Data at the Area of Felda Lepar Utara, Pahang, Malaysia ». Journal of Physics : Conference Series 2309, n^o 1 (1 juillet 2022) : 012037. http://dx.doi.org/10.1088/1742-6596/2309/1/012037.

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Abstract Geological structures such as faults and fractures have an important influence in the process of fluid movement below the surface. The hydraulic behavior in aquifers can be determined by proper characterization of fractures, fault zones and their connectivity. In this study, we concern on detection and identification of fault zones in the groundwater basin to verify whether faults in the basin area connect to the surface, and whether the fault zones occurring serve as conduits or barriers for groundwater to flow. The seismic reflection method with Common Depth Point (CDP) profiling technique has been applied in this study. Through this study, we have identified that several large and small-scale faults were found in the study area. Generally, these large-scale faults cut the bedrock (granodiorite) up to impermeable layer. This large-scale fault group can be a barrier that block the groundwater flow. The fault zone is connected to the surface as evidenced by the presence of normal fault that is clearly observed at the surface. This seismic method is good to apply in this study because it can be used to record deeper subsurface conditions, especially for fault zone detection purposes.

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Yan, Rui, Guangcai Wang et Zheming Shi. « Sensitivity of hydraulic properties to dynamic strain within a fault damage zone ». Journal of Hydrology 543 (décembre 2016) : 721–28. http://dx.doi.org/10.1016/j.jhydrol.2016.10.043.

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Wei, Xiaochen, Qi Li, Xiaying Li, Zhiyong Niu, Xiangjun Liu et Lixi Liang. « Effects of Different Penetration Patterns on a Fault during Underground Fluid Injection ». Geofluids 2019 (8 avril 2019) : 1–15. http://dx.doi.org/10.1155/2019/2027510.

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At underground fluid injection sites with natural faults, understanding how to avoid the subsequent fault reactivation and induced seismicity plays a crucial role in the success of subsurface anthropogenic activities. In this work, with the objective of avoiding risky faults in site selection in the Shengli Oilfield, we investigated the faults that are usually encountered in the target demonstration zone; based on the geophysical observations of fault structures, we designed different fault tectonic scenarios to investigate the different penetration patterns of faults. We used the finite element-based numerical method to assess the influence of the effective lateral and vertical reservoir transmissivity in each fault penetration pattern. Our results indicate that when a permeable fault intersects into the target reservoir, it presents both barrier effect to reservoir transmissivity within the target reservoir and hydraulic connection between reservoirs. The effective lateral reservoir transmissivity is dominated by the barrier effect of the fault, and the effective vertical reservoir transmissivity is dominated by the hydraulic connection between reservoirs. Relatively impermeable faults with less contact with the target aquifer make higher effective lateral reservoir transmissivity and lower effective vertical reservoir transmissivity, which would mitigate the risk of caprock failure and the magnitude of the induced seismicity.

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Cooke, Andy P., Quentin J. Fisher, Emma A. H. Michie et Graham Yielding. « Permeability of carbonate fault rocks : a case study from Malta ». Petroleum Geoscience 26, n^o 3 (12 août 2019) : 418–33. http://dx.doi.org/10.1144/petgeo2019-055.

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The inherent heterogeneity of carbonate rocks suggests that carbonate-hosted fault zones are also likely to be heterogeneous. Coupled with a lack of host–fault petrophysical relationships, this makes the hydraulic behaviour of carbonate-hosted fault zones difficult to predict. Here we investigate the link between host rock and fault rock porosity, permeability and texture, by presenting data from series of host rock, damage zone and fault rock samples from normally faulted, shallowly buried limestones from Malta. Core plug X-ray tomography indicates that texturally heterogeneous host rocks lead to greater variability in the porosity and permeability of fault rocks. Fault rocks derived from moderate- to high-porosity (>20%) formations experience permeability reductions of up to six orders of magnitude relative to the host; >30% of these fault rocks could act as baffles or barriers to fluid flow over production timescales. Fault rocks derived from lower-porosity (<20%) algal packstones have permeabilities that are lower than their hosts by up to three orders of magnitude, which is unlikely to impact fluid flow on production timescales. The variability of fault rock permeability is controlled by a number of factors, including the initial host rock texture and porosity, the magnitude of strain localization, and the extent of post-deformation diagenetic alteration. Fault displacement has no obvious control over fault rock permeability. The results enable better predictions of fault rock permeability in similar lithotypes and tectonic regimes. This may enable predictions of across-fault fluid flow potential when combined with data on fault zone architecture.

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Zhang, Wen Quan, Wei Li, Guang Peng Zhang et Gui Bin Zhang. « Water Controlling Research of Complex Fault Structures in Wugou Mine ». Advanced Materials Research 616-618 (décembre 2012) : 499–504. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.499.

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Once the lead abutment pressure influence the fault structure, its internal rock mass is damaged easily while the fault structures are the most vulnerable of mining influence weak link. If the fault structures conduct the aquifer, the mine water inrush will occur. This paper researchs water level of Taiyuan limestone aquifer with three-dimensional form simulation and analyzes mine water movement characteristics and the change of water level and hydraulic contact of each aquifer combining with complex geological conditions of Wugou mine, aiming at tectonic evolution and tectonic combination characteristic of the mine, according to the long observation hole material. Combining with water pressure test results and drilling and geophysical prospecting achievement, using daubing coefficient method to analyze sealing of fault structure, we conclude that faults are pressure-torsional normal faults which their fault zone is compact and has high strength so we can narrow even do not leave set fault waterproof pillar in Wugou mine.

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Jeanne, P., Y. Guglielmi et F. Cappa. « Structural and hydraulic properties of a small fault zone in a layered reservoir ». E3S Web of Conferences 4 (2014) : 03001. http://dx.doi.org/10.1051/e3sconf/20140403001.

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Andrews, Billy James, Zoe Kai Shipton, Richard Lord et Lucy McKay. « The growth of faults and fracture networks in a mechanically evolving, mechanically stratified rock mass : a case study from Spireslack Surface Coal Mine, Scotland ». Solid Earth 11, n^o 6 (18 novembre 2020) : 2119–40. http://dx.doi.org/10.5194/se-11-2119-2020.

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Abstract. Fault architecture and fracture network evolution (and resulting bulk hydraulic properties) are highly dependent on the mechanical properties of the rocks at the time the structures developed. This paper investigates the role of mechanical layering and pre-existing structures on the evolution of strike–slip faults and fracture networks. Detailed mapping of exceptionally well exposed fluvial–deltaic lithologies at Spireslack Surface Coal Mine, Scotland, reveals two phases of faulting with an initial sinistral and later dextral sense of shear with ongoing pre-faulting, syn-faulting, and post-faulting joint sets. We find fault zone internal structure depends on whether the fault is self-juxtaposing or cuts multiple lithologies, the presence of shale layers that promote bed-rotation and fault-core lens formation, and the orientation of joints and coal cleats at the time of faulting. During ongoing deformation, cementation of fractures is concentrated where the fracture network is most connected. This leads to the counter-intuitive result that the highest-fracture-density part of the network often has the lowest open fracture connectivity. To evaluate the final bulk hydraulic properties of a deformed rock mass, it is crucial to appreciate the relative timing of deformation events, concurrent or subsequent cementation, and the interlinked effects on overall network connectivity.

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Guo, Yanhui, Zhijun Kong, Jin He et Ming Yan. « Development and Application of the 3D Model Test System for Water and Mud Inrush of Water-Rich Fault Fracture Zone in Deep Tunnels ». Mathematical Problems in Engineering 2021 (4 octobre 2021) : 1–16. http://dx.doi.org/10.1155/2021/8549094.

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In order to study the evolution process, damage characteristics, and occurrence mechanism of water and mud inrush disaster in deep tunnel fault zone with infiltration instability under complex conditions, a set of the three-dimensional physical model test systems of water and mud inrush flow-solid coupling in tunnel fault zones is developed. The system mainly comprises a rigid test frame, ground stress loading system, hydraulic loading system, multiple information monitoring and acquisition system, and mud and water protrusion recovery system. The system’s main features are that it can meet the model’s simulation of the ground stress field, water pressure, and other complex environments subjected to ground stress, and water pressure gradients can be controlled. The system is characterized by high rigidity, high-pressure strength, visualization, good sealing, and expandability. Taking the water fault zone of a well in the Dazhu Mountain Tunnel of the Darui Railway as the research object, the new fault zone and surrounding rock similar materials applicable to the flow-solid coupling model test are designed using the self-developed flow-solid coupling similar materials. The system is used for model tests to reveal the spatial and temporal changes of the surrounding rock stress field and seepage field during the tunnel excavation process. The test results show that the system is stable and reliable, and the research method and results are of guiding significance to the research of the same type of underground engineering.

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Ma, Yuchuan, Guangcai Wang, Rui Yan, Bo Wang, Huaizhong Yu, Chen Yu, Chong Yue et Yali Wang. « Relationship between Earthquake-Induced Hydrologic Changes and Faults ». Water 13, n^o 19 (8 octobre 2021) : 2795. http://dx.doi.org/10.3390/w13192795.

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Hydraulic properties of fault zones are important to understanding the pore pressure development and fault stability. In this work, we examined the relationship between water level changes caused by the 2008 Wenchuan Mw 7.9 earthquake and faults using four wells with the same lithology around the Three Gorges Dam, China. Two of the wells penetrating the fault damage zones recorded sustained water level changes, while the other two wells that are not penetrating any fault damage zones recorded transient water level changes. The phase shift and tidal factor calculated from water level, a proxy of permeability and storage coefficient, revealed that both the permeability and storage coefficient changed in the two wells penetrating the fault damage zones, while the other two wells not penetrating the fault damage zone did not show any change in permeability and storage coefficient. Thus, we tentatively suggest that faults may play an important controlling role on earthquake-induced hydrologic changes because the detrital or clogging components in the fractures may be more easily removed by seismic waves.

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Taillefer, Audrey, Roger Soliva, Laurent Guillou-Frottier, Elisabeth Le Goff, Guillaume Martin et Michel Seranne. « Fault-Related Controls on Upward Hydrothermal Flow : An Integrated Geological Study of the Têt Fault System, Eastern Pyrénées (France) ». Geofluids 2017 (2017) : 1–19. http://dx.doi.org/10.1155/2017/8190109.

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The way faults control upward fluid flow in nonmagmatic hydrothermal systems in extensional context is still unclear. In the Eastern Pyrénées, an alignment of twenty-nine hot springs (29°C to 73°C), along the normal Têt fault, offers the opportunity to study this process. Using an integrated multiscale geological approach including mapping, remote sensing, and macro- and microscopic analyses of fault zones, we show that emergence is always located in crystalline rocks at gneiss-metasediments contacts, mostly in the Têt fault footwall. The hot springs distribution is related to high topographic reliefs, which are associated with fault throw and segmentation. In more detail, emergence localizes either (1) in brittle fault damage zones at the intersection between the Têt fault and subsidiary faults or (2) in ductile faults where dissolution cavities are observed along foliations, allowing juxtaposition of metasediments. Using these observations and 2D simple numerical simulation, we propose a hydrogeological model of upward hydrothermal flow. Meteoric fluids, infiltrated at high elevation in the fault footwall relief, get warmer at depth because of the geothermal gradient. Topography-related hydraulic gradient and buoyancy forces cause hot fluid rise along permeability anisotropies associated with lithological juxtapositions, fracture, and fault zone compositions.

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Zappone, Alba, Antonio Pio Rinaldi, Melchior Grab, Quinn C. Wenning, Clément Roques, Claudio Madonna, Anne C. Obermann et al. « Fault sealing and caprock integrity for CO2 ; storage : an in situ injection experiment ». Solid Earth 12, n^o 2 (5 février 2021) : 319–43. http://dx.doi.org/10.5194/se-12-319-2021.

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Abstract. The success of geological carbon storage depends on the assurance of permanent containment for injected carbon dioxide (CO2) in the storage formation at depth. One of the critical elements of the safekeeping of CO2 is the sealing capacity of the caprock overlying the storage formation despite faults and/or fractures, which may occur in it. In this work, we present an ongoing injection experiment performed in a fault hosted in clay at the Mont Terri underground rock laboratory (NW Switzerland). The experiment aims to improve our understanding of the main physical and chemical mechanisms controlling (i) the migration of CO2 through a fault damage zone, (ii) the interaction of the CO2 with the neighboring intact rock, and (iii) the impact of the injection on the transmissivity in the fault. To this end, we inject CO2-saturated saline water in the top of a 3 m thick fault in the Opalinus Clay, a clay formation that is a good analog of common caprock for CO2 storage at depth. The mobility of the CO2 within the fault is studied at the decameter scale by using a comprehensive monitoring system. Our experiment aims to close the knowledge gap between laboratory and reservoir scales. Therefore, an important aspect of the experiment is the decameter scale and the prolonged duration of observations over many months. We collect observations and data from a wide range of monitoring systems, such as a seismic network, pressure temperature and electrical conductivity sensors, fiber optics, extensometers, and an in situ mass spectrometer for dissolved gas monitoring. The observations are complemented by laboratory data on collected fluids and rock samples. Here we show the details of the experimental concept and installed instrumentation, as well as the first results of the preliminary characterization. An analysis of borehole logging allows for identifying potential hydraulic transmissive structures within the fault zone. A preliminary analysis of the injection tests helped estimate the transmissivity of such structures within the fault zone and the pressure required to mechanically open such features. The preliminary tests did not record any induced microseismic events. Active seismic tomography enabled sharp imaging the fault zone.

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Du, Yanhui, Weitao Liu, Xiangxi Meng, Lifu Pang et Mengke Han. « Effect of Crack Propagation on Mining-Induced Delayer Water Inrush Hazard of Hidden Fault ». Geofluids 2021 (11 août 2021) : 1–12. http://dx.doi.org/10.1155/2021/6557578.

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Hidden faults in deep coal seam floor threaten the exploitation of coal resources. Under the influence of mining and water confined in the floor, the cemented filler in the hidden fault will be eroded by water flow, in order to investigate the fracture characteristics and water inrush risk of hidden faults in floors above confined aquifer. Using the 27305 working face as geological background, the influence of the seepage scouring filler on the mechanism of water inrush from hidden faults was assessed by developing a stress-seepage coupling model and employing the finite difference method to simulate the seepage process of hidden faults under the combined action of high ground stress and high confined water. The evolution of seepage, shear stress, and plastic zone was also assessed. The influence of the hydraulic pressure of the aquifer and the thickness of a waterproof rock floor on the formation of the water inrush pathway was analyzed. Results indicate that (1) under the influence of mining, the hidden fault experienced the change process of stress stability, stress concentration, and stress release. The shear stress increases first and then decreases. The compressive stress decreases gradually due to stress release. (2) Water inrush disaster will not occur immediately when the working face is above the hidden fault. The delayed water inrush occurs in the mined-out area when the working face advances to 160 m, the floor failure zone is connected with the hidden fault failure zone, and the delayed water inrush channel is formed. (3) With the mining advances, the water pressure of aquifer is the same. The larger-angle fault leads to the thinner thickness of floor aquifer. The greater the influence of hidden fault on coal seam mining, the higher the danger of water inrush.

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Eyinla, Dorcas S. « Analysis of the influence of joint direction on production optimization in enhanced geothermal systems ». Journal of Petroleum Exploration and Production Technology 11, n^o 9 (9 août 2021) : 3437–49. http://dx.doi.org/10.1007/s13202-021-01254-7.

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AbstractHeat extraction from geothermal reservoir by circulating cold water into a hot rock requires an amount of fluid pressure, which is capable of inducing fault opening. Although stress change promotes the potential of fault failure and reactivation, the rate at which fluid pressurization within the fault zone generates variations in pore pressure as fault geometry changes during geothermal energy production have not been thoroughly addressed to include the effects of joint orientation. This study examines how different fault/joint models result in different tendency of injection-induced shear failure, and how this could influence the production rate. Here, a numerical simulation method is adopted to investigate the thermo-hydro-mechanical (THM) response of the various fault/joint models during production in a geothermal reservoir. The results indicate that pore pressure evolution has a direct relationship with the evolution of production rate for the three joint models examined, and the stress sensitivity of the individual fault/joint model also produced an effect on the production rate. Changing the position of the injection well revealed that the magnitude of shear failure on the fault plane could be controlled by the hydraulic diffusivity of fluid pressure, and the production rate is also influenced by the magnitude of stress change at the injection and production wells. Overall, the location of the injection well along with the fault damage zone significantly influenced the resulting production rate, but a more dominating factor is the joint orientation with respect to the maximum principal stress direction. Thus, the rate of thermal drawdown is affected by pore pressure elevation and stress change while the fault permeability and the production rate are enhanced when the joint’s frictional resistance is low.

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Chen, Tao, Yaowei Liu et Guomeng Zhang. « Numerical Simulation of Fluid Pore Pressure Diffusion and Its Mechanical Effects during Wenchuan Aftershocks ». Water 14, n^o 6 (18 mars 2022) : 952. http://dx.doi.org/10.3390/w14060952.

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The Ms 8.0 Wenchuan earthquake occurred on 12 May 2008, in the Sichuan Province of China, and it was accompanied by a series of strong aftershocks. The mechanisms contributing to the triggering of the Wenchuan aftershocks have attracted international attention. In this paper, based on previous analysis of spatiotemporal distribution of aftershocks regarding pore pressure diffusion of deep fluid, we established a three-dimensional hydraulic–mechanical coupling model and investigated the influence of fluid migration and its mechanical effects in the Longmenshan fault zone by using FLAC3D software. We obtained the characteristics of the pore pressure diffusion and fault reactivation within 70 days in an area NA. The results show that the pore pressure significantly increases up to 80 MPa during fluid intrusion into the fault plane. The pore pressure increase along the fault dip is greater than that along the fault strike, with a maximum difference of 3.18 MPa. The increase in pore pressure along the fault reduces the effective stress and leads to fault reactivation. The evolution of the fault reactivation area calculated in the model is compared with the spatiotemporal characteristics of the aftershocks. This study is meaningful for furthering the understanding of the role of deep fluids in fault dynamics and aftershocks triggering.

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Shi, Guangcheng, Yifeng Wang, Yingkui Wang, Zhigang Tao, Liangpeng Wan et Lanyun Xi. « Numerical Analysis and Deformation Mechanism Study on an Excavated High-Steep Slope of a Hydropower Station ». Advances in Civil Engineering 2020 (25 juillet 2020) : 1–17. http://dx.doi.org/10.1155/2020/3402762.

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The high-steep rock slope stability is one of the key technologies in the construction of water conservancy and hydropower projects, which affects and restricts the development of hydraulic resources and the construction of hydropower projects. In this paper, a three-dimensional numerical model was built incorporating stratigraphy, geological structures, and the inverted rock mechanical parameters to perform displacement, stress, and plastic zone analyses for an excavated slope in China using the FLAC3D software. The numerical simulation results after slope excavation show that the deformation near the fault fracture zone is the largest, ranging from 350 mm to 380 mm. The compressive stress is concentrated on the slope foot and the connecting part, the stress value is 2 MPa∼5 MPa, there is a large tensile stress area in the slope, and the tensile stress value is 0 MPa∼0.4 MPa. The plastic zone of the slope is concentrated near the fault F6 and the structural influence zone, and the rock mass of the slope basically enters the plastic state. On this basis, the deformation mechanism of slope was analyzed, while the internal and external factors affecting the slope deformation were described in detail. This work would provide an effective reference basis for slope stability evaluation and treatment of similar hydropower stations.

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ROSSETTI, FEDERICO, LUCA ALDEGA, FRANCESCA TECCE, FABRIZIO BALSAMO, ANDREA BILLI et MAURO BRILLI. « Fluid flow within the damage zone of the Boccheggiano extensional fault (Larderello–Travale geothermal field, central Italy) : structures, alteration and implications for hydrothermal mineralization in extensional settings ». Geological Magazine 148, n^o 4 (22 décembre 2010) : 558–79. http://dx.doi.org/10.1017/s001675681000097x.

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AbstractThe Neogene extensional province of southern Tuscany in central Italy provides an outstanding example of fossil and active structurally controlled fluid flow and epithermal ore mineralization associated with post-orogenic silicic magmatism. Characterization of the hydrodynamic regime leading to the genesis of the polysulphide deposit (known as Filone di Boccheggiano) hosted within the damage zone of the Boccheggiano Fault is a key target to assess modes of fossil hydrothermal fluid circulation in the region and, more generally, to provide inferences on fault-controlled hydrothermal fluid flow in extensional settings. We provide a detailed description of the fault zone architecture and alteration/mineralization associated with the Boccheggiano ore deposit and report the results of fluid inclusion and stable oxygen isotope studies. This investigation shows that the Boccheggiano ore consists of an adularia/illite-type epithermal deposit and that sulphide ore deposition was controlled by channelling of hydrothermal fluids of dominantly meteoric origin within the highly anisotropic permeability structure of the Boccheggiano Fault. The low permeability structure of the fault core compartmentalized the fluid outflow preventing substantial cross-fault flow, with focused fluid flow occurring at the hangingwall of the fault controlled by fracture permeability. Fluid inclusion characteristics indicate that ore minerals were deposited between 280° and 350°C in the upper levels of the brittle extending crust (lithostatic pressure in the order of 0.1 GPa). Abundant vapour-rich inclusions in ore-stage quartz are consistent with fluid immiscibility and boiling, and quartz ore vein textures suggest that mineralization in the Boccheggiano ore deposit occurred during cyclic fluid flow in a deformation regime regulated by transient and fluctuating fluid pressure conditions. Results from this study (i) predict a strongly anisotropic permeability structure of the fault damage zone during crustal extension, and (ii) indicate the rate of secondary (structural) permeability creation and maintenance by active deformation in the hangingwall of extensional faults as the major factor leading to effective hydraulic transmissivity in extensional terranes. These features intimately link ore-grade mineralization in extensional settings to telescoping of hydrothermal flow along the hangingwall block(s) of major extensional fault zones.

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Pampillón, Pedro, David Santillán, Juan Carlos Mosquera et Luis Cueto-Felgueroso. « Geomechanical Constraints on Hydro-Seismicity : Tidal Forcing and Reservoir Operation ». Water 12, n^o 10 (29 septembre 2020) : 2724. http://dx.doi.org/10.3390/w12102724.

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Understanding the risk associated with anthropogenic earthquakes is essential in the development and management of engineering processes and hydraulic infrastructure that may alter pore pressures and stresses at depth. The possibility of earthquakes triggered by reservoir impoundment, ocean tides, and hydrological events at the Earth surface (hydro-seismicity) has been extensively debated. The link between induced seismicity and hydrological events is currently based on statistical correlations rather than on physical mechanisms. Here, we explore the geomechanical conditions that could allow for small pore pressure changes due to reservoir management and sea level changes to propagate to depths that are compatible with earthquake triggering at critically-stressed faults (several kilometers). We consider a damaged fault zone that is embedded in a poroelastic rock matrix, and conduct fully coupled hydromechanical simulations of pressure diffusion and rock deformation. We characterize the hydraulic and geomechanical properties of fault zones that could allow for small pressure and loading changes at the ground surface (in the order of tens or hundreds of kPa) to propagate with relatively small attenuation to seismogenic depths (up to 10 km). We find that pressure diffusion to such depths is only possible for highly permeable fault zones and/or strong poroelastic coupling.

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Mahmoodpour, Saeed, Mrityunjay Singh, Christian Obaje, Sri Kalyan Tangirala, John Reinecker, Kristian Bär et Ingo Sass. « Hydrothermal Numerical Simulation of Injection Operations at United Downs, Cornwall, UK ». Geosciences 12, n^o 8 (29 juillet 2022) : 296. http://dx.doi.org/10.3390/geosciences12080296.

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The United Downs Deep Geothermal Project (UDDGP) is designed to utilize a presumably permeable steep dipping fault damage zone (constituting the hydrothermal reservoir in a very low permeability granitic host rock) for fluid circulation and heat extraction between an injection well at 2.2 km depth (UD−2) and a production well at 5 km depth (UD−1). Soft hydraulic stimulation was performed to increase the permeability of the reservoir. Numerical simulations are performed to analyze the hydraulic stimulation results and evaluate the increase in permeability of the reservoir. Experimental and field data are used to characterize the initial reservoir static model. The reservoir is highly fractured, and two distinct fracture networks constitute the equivalent porous matrix and fault zone, respectively. Based on experimental and field data, stochastic discrete fracture networks (DFN) are developed to mimic the reservoir permeability behavior. Due to the large number of fractures involved in the stochastic model, equivalent permeability fields are calculated to create a model which is computationally feasible. Hydraulic test and stimulation data from UD−1 are used to modify the equivalent permeability field based on the observed difference between the real fractured reservoir and the stochastic DFN model. Additional hydraulic test and stimulation data from UD−2 are used to validate this modified permeability. Results reveal that the equivalent permeability field model derived from observations made in UD−1 is a good representation of the actual overall reservoir permeability, and it is useful for future studies. The numerical simulation results show the amount of permeability changes due to the soft hydraulic stimulation operation. Based on the validated permeability field, different flow rate scenarios of the petrothermal doublet and their respective pressure evolution are examined. Higher flow rates have a strong impact on the pressure evolution. Simulations are performed in the acidized enhanced permeability region to make a connection between the ongoing laboratory works on the acid injection and field response to the possible acidizing stimulation.

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Zhou, Jun, Tingxue Jiang, Haijun Mou, Shanhong Jiang et Linbo Zhou. « Effect of fault zone and natural fracture on hydraulic fracture propagation in deep carbonate reservoirs ». IOP Conference Series : Earth and Environmental Science 861, n^o 6 (1 octobre 2021) : 062057. http://dx.doi.org/10.1088/1755-1315/861/6/062057.

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Labaume, P., S. Sheppard et I. Moretti. « Structure and hydraulic behaviour of cataclastic thrust fault zones in sandstones, Sub-Andean Zone, Bolivia ». Journal of Geochemical Exploration 69-70 (juin 2000) : 487–92. http://dx.doi.org/10.1016/s0375-6742(00)00097-2.

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Zhang, Xiang Wen, Tao Wang et Sheng Gao Cheng. « Application of Tracer Test in Survey of Hydraulic Connection between Water Gushing and Fracture Water in Karst Tunnel – Taking Zhongjiashan as an Example ». Advanced Materials Research 1006-1007 (août 2014) : 115–20. http://dx.doi.org/10.4028/www.scientific.net/amr.1006-1007.115.

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The field tracer test is dropping quantitative tracer materials in the entrance of ponor upstream and to monitor online concentration of tracer materials in the main export of underground river downstream, and then deduce the type of groundwater pipe and the source of supply according to the concentration. This thesis takes the landslide areas in highways across form Quanzhou to Nanning and in tunnels connecting Ji’an with Zhongjiashan in Lianhua (a town in Pingxiang) as the research object, explores the supply source of tunnel water, meanwhile uses three tracer materials of different nature, namely the fluorescein sodium, fluorescent whitening agent and rhodamine, to place 4 drop points and 3 receiving points within 20 square meters of the surveyed area, to conduct groundwater tracer test. The test shows that there is no obvious connection between tunnel water gushing and F5 fracture main ditch surface water as well as F5 tectonic fracture zone; Fault F2 has good conductivity, and the gushing water in the right hole in the import and export of tunnel is related with F2 fault tectonic fracture zone.

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BEACOM, L. E., T. B. ANDERSON et R. E. HOLDSWORTH. « Using basement-hosted clastic dykes as syn-rifting palaeostress indicators : an example from the basal Stoer Group, northwest Scotland ». Geological Magazine 136, n^o 3 (mai 1999) : 301–10. http://dx.doi.org/10.1017/s0016756899002605.

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Clastic infills of fractures (here termed clastic veins) in basement rocks immediately underlying sedimentary cover sequences can be used to date fault movements if these demonstrably occurred at the time of infilling or prior to the lithification of the entrained clastic material. This allows reconstruction of the syn-rifting palaeostress system using stress inversion techniques. During Riphean intracontinential rifting of Laurentia, the Torridonian Stoer Group sediments of northwest Scotland were deposited in half-graben basins controlled by faults, e.g. the Coigach and Clachtoll faults. At Clachtoll, northeast–southwest oblique sinistral normal faulting in the underlying basement is associated with extensive development of shear, hybrid and tensile clastic veins filled with Stoer Group sediment, infilled and deformed prior to sediment lithification. Clastic veins initially formed by gravitational infilling of sediment from above, followed by tectonically-driven, forceful hydraulic injection of fluidized sand into new fractures and reactivated pre-existing basement faults. Palaeostress axes, determined from fault lineation data and tensile fracture extension directions in the Clachtoll Fault zone, indicate west-northwest–east-southeast directed extension during rifting. On a regional scale, this implies oblique-dextral extension on the north- to north-northeast-trending Coigach Fault during Stoer Group deposition. Similar orientations, age relationships and kinematics have been obtained from pre-Torridon Group fault arrays developed in the Lewisian basement near Gairloch and Loch Maree. Overall, the faulting patterns reflect a three-dimensional strain (k≠1) formed by east-southeast–west-northwest-directed extension during deposition of the Stoer Group. More speculatitively, asymmetric density patterns of sinistral and dextral faults may indicate that rifting occurred in a regional zone of broadly north–south-oriented dextral transtension.

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Cherubini, Y., M. Cacace, M. Scheck-Wenderoth et V. Noack. « Influence of major fault zones on 3-D coupled fluid and heat transport for the Brandenburg region (NE German Basin) ». Geothermal Energy Science 2, n^o 1 (4 avril 2014) : 1–20. http://dx.doi.org/10.5194/gtes-2-1-2014.

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Abstract. To quantify the influence of major fault zones on the groundwater and thermal field, 3-D finite-element simulations are carried out. Two fault zones – the Gardelegen and Lausitz escarpments – have been integrated into an existing 3-D structure of the Brandenburg region in northeastern Germany. Different geological scenarios in terms of modelled fault permeability have been considered, of which two end-member models are discussed in detail. In addition, results from these end-member simulations are compared to a reference case in which no faults are considered. The study provides interesting results with respect to the interaction between faults and surrounding sediments and how it affects the regional groundwater circulation system and thermal field. Impermeable fault zones seem to induce no remarkable effects on the temperature distribution; that is, the thermal field is similar to the no-fault model. In addition, tight faults have only a local impact on the fluid circulation within a domain of limited spatial extent centred on the fault zone. Fluid flow from the surrounding aquifers is deviated in close proximity of the fault zones acting as hydraulic barriers that prevent lateral fluid inflow into the fault zones. Permeable fault zones induce a pronounced thermal signature with alternating up- and downward flow along the same structures. Fluid flow along the plane of the faults is principally driven by existing hydraulic head gradients, but may be further enhanced by buoyancy forces. Within recharge domains, fluid advection induces a strong cooling in the fault zones. Discharge domains at shallow depth levels (~<−450 m) are instead characterized by the presence of rising warm fluids, which results in a local increase of temperatures which are up to 15 °C higher than in the no-fault case. This study is the first attempt to investigate the impact of major fault zones on a 3-D basin scale for the coupled fluid and heat transport in the Brandenburg region. The approach enables a quantification of mechanisms controlling fluid flow and temperature distribution both within surrounding sediments and fault zones as well as how they dynamically interact. Therefore, the results from the modelling provide useful indications for geothermal energy exploration.

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Rutqvist, Jonny, Antonio P. Rinaldi, Frédéric Cappa et George J. Moridis. « Modeling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale-gas reservoirs ». Journal of Petroleum Science and Engineering 127 (mars 2015) : 377–86. http://dx.doi.org/10.1016/j.petrol.2015.01.019.

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Hernàndez-Diaz, Rebeca, Emma Petrella, Antonio Bucci, Gino Naclerio, Alessandra Feo, Gabriella Sferra, Alessandro Chelli, Andrea Zanini, Patricia Gonzalez-Hernandez et Fulvio Celico. « Integrating Hydrogeological and Microbiological Data and Modelling to Characterize the Hydraulic Features and Behaviour of Coastal Carbonate Aquifers : A Case in Western Cuba ». Water 11, n^o 10 (24 septembre 2019) : 1989. http://dx.doi.org/10.3390/w11101989.

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Carbonate aquifers are the primary source of freshwater in Cuba. Unfortunately, coastal groundwater is often contaminated by seawater intrusion. The main aim of the present study was to test the efficacy of an experimental modelling approach, ranging from hydrogeology/geomorphology to microbiology, to better characterise both the hydraulic features and behaviour of a coastal carbonate aquifer and acquire useful information to prevent groundwater salinization. The interdisciplinary approach was an effective tool in order to understand (i) the hydraulic role played by some fault zones; (ii) the influence of discontinuous heterogeneities on groundwater flow and saltwater wedge shape; (iii) mixing processes between different water bodies (groundwater, surface water, seawater); (iv) the role of karst conduits in influencing the step-like halocline within the mixing zone between fresh groundwater and seawater.

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Huang, Zhen, Wei Zeng et Kui Zhao. « Experimental investigation of the variations in hydraulic properties of a fault zone in Western Shandong, China ». Journal of Hydrology 574 (juillet 2019) : 822–35. http://dx.doi.org/10.1016/j.jhydrol.2019.04.063.

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Ribeiro, Priscila M., et Roland N. Horne. « Detecting Fracture Growth Out of Zone by Use of Temperature Analysis ». SPE Journal 21, n^o 04 (15 août 2016) : 1263–78. http://dx.doi.org/10.2118/170746-pa.

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Summary Hydraulic fracturing is a widely applied well-stimulation technique. Recently, the application of multiple hydraulic fractures along horizontal wells has made possible the exploitation of unconventional reservoirs, such as shale gas and shale oil. However, the process of horizontal-well fracturing is uncertain and it is not fully understood yet. There exist many questions about the number and position of created fractures and whether the fracture stays contained within the main reservoir thickness. This work presents the modeling and analysis of temperature data during and after the creation of multiple fractures along a horizontal well. Our model accounts for fracture growth and closure, the well effects, and interaction between multiple fractures. The interference between multiple fractures growing simultaneously and the presence of reservoir-permeability heterogeneity were investigated. Capabilities and limitations of information carried by temperature data are presented through different geometry analyses. A special consideration of fracture growth out of zone was addressed. For this case, it was considered that one of the hydraulic fractures activates a pre-existing fault and interconnects the reservoir with other zones hundreds of feet away. Our work shows the advantage of the use of continuous-distributed-temperature data in comparison with the traditional single-point-pressure analysis. The local characteristic of temperature allows us to identify not only which of the created hydraulic fractures has interconnected the main reservoir with a different zone, but also the location of this zone. We also account for the effect of the interconnection on the growth of the other hydraulic fractures along the horizontal wellbore. The simultaneous multiple fracture growth shows that falloff-distributed-temperature data can predict the number of created fractures. More than that, in the presence of heterogeneity, the interaction between the contained fractures can be captured by the temperature analysis. Different from the pressure analysis, distributed-temperature data can differentiate between heterogeneity locations along the wellbore. Throughout this study, we present a series of examples in which the temperature can provide information that would not be obtained from the traditional pressure analysis.

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De Souza, Stéphane, Benoît Dubé, Patrick Mercier-Langevin, Vicki McNicoll, Céline Dupuis et Ingrid Kjarsgaard. « Hydrothermal Alteration Mineralogy and Geochemistry of the Archean World-Class Canadian Malartic Disseminated-Stockwork Gold Deposit, Southern Abitibi Greenstone Belt, Quebec, Canada ». Economic Geology 114, n^o 6 (1 septembre 2019) : 1057–94. http://dx.doi.org/10.5382/econgeo.4674.

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Abstract The Canadian Malartic stockwork-disseminated gold deposit is an Archean world-class deposit located in the southern Abitibi greenstone belt. It contains over 332.8 tonnes (t; 10.7 Moz) of Au at a grade of 0.97 ppm, in addition to 160 t (5.14 Moz) of past production (1935–1981). Although the deposit is partly situated within the Larder Lake-Cadillac fault zone, most of the ore occurs up to ~1.5 km to the south of the fault zone. The main hosts of the mineralized zones are greenschist facies turbiditic graywacke and mudstone of the Pontiac Group (~2685–2682 Ma) and predominantly subalkaline ~2678 Ma porphyritic quartz monzodiorite and granodiorite. These intrusions were emplaced during an episode of clastic sedimentation and alkaline to subalkaline magmatism known as the Timiskaming assemblage (<2680–2670 Ma in the southern Abitibi). The orebodies define two main mineralized trends, which are oriented subparallel to the NW-striking S2 cleavage and the E-striking, S-dipping Sladen fault zone. This syn- to post-D2 ductile-brittle to brittle Sladen fault zone is mineralized for more than 3 km along strike. The ore mainly consists of disseminated pyrite in stockworks and replacement zones, with subordinate auriferous quartz veins and breccia. Gold is associated with pyrite and traces of tellurides defining an Au-Te-W ± Ag-Bi-Mo-Pb signature. The orebodies are zoned outward, and most of the higher-grade (>1 ppm Au) ore was deposited as a result of iron sulfidation from silicates and oxides and Na-K metasomatism in carbonatized rocks. The alteration footprint comprises a proximal alteration envelope (K- or Na-feldspar-dolomite-calcite-pyrite ± phlogopite). This proximal alteration zone transitions to an outer shell of altered rocks (biotite-calcite-phengitic white mica), which hosts sub-ppm gold grades and reflects decreasing carbonatization, sulfidation, and aNa+/aH+ or aK+/aH+ of the ore fluid. Gold mineralization, with an inferred age of ~2664 Ma (Re-Os molybdenite), was contemporaneous with syn- to late-D2 peak metamorphism in the Pontiac Group; it postdates sedimentation of the Timiskaming assemblage along the Larder Lake-Cadillac fault zone (~2680–2669 Ma) and crystallization of the quartz monzodiorite. These chronological relationships agree with a model of CO2-rich auriferous fluid generation in amphibolite facies rocks of the Pontiac Group and gold deposition in syn- to late-D2 structures in the upper greenschist to amphibolite facies. The variable geometry, rheology, and composition of the various intrusive and sedimentary rocks have provided strain heterogeneities and chemical gradients for the formation of structural and chemical traps that host the gold. The Canadian Malartic deposit corresponds to a mesozonal stockwork-disseminated replacement-type deposit formed within an orogenic setting. The predominance of disseminated replacement ore over fault-fill and extensional quartz-carbonate vein systems suggests that the mineralized fracture networks remained relatively permeable and that fluids circulated at a near-constant hydraulic gradient during the main phase of auriferous hydrothermal alteration.

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Gao, Qian, Yueming Cheng, Ebrahim Fathi et Samuel Ameri. « Analysis of Stress-Field Variations Expected on Subsurface Faults and Discontinuities in the Vicinity of Hydraulic Fracturing ». SPE Reservoir Evaluation & ; Engineering 19, n^o 01 (22 décembre 2015) : 054–69. http://dx.doi.org/10.2118/168761-pa.

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Summary In this study, a local stability evaluation method, slip-tendency analysis, is proposed on the basis of the Coulomb criterion to investigate the effects of hydraulic fracturing on stress-field variations and possibility of fault reactivation. The effects of net pressure and in-situ stress fields on the stability of faults are investigated in two typical faulting environments (i.e., normal and strike-slip faults). A 3D numerical model developed on the basis of the finite-element method (FEM) is also adopted to better understand the stability states around pressurized hydraulic fractures. The orientation and relative magnitudes of in-situ stress fields differ under different faulting environments, which, in turn, control the direction of fracture propagation and its geometry. It is found that the general patterns of slip-tendency distributions around pressurized hydraulic fractures are similar under different in-situ stress fields. Providing the normal and strike-slip faults with a same initial slip-tendency, the normal faulting environment demonstrates larger variations in slip-tendency than the strike-slip faulting environment. The comparison between analytical and numerical solutions indicates an excellent agreement was achieved, which certifies the validity of the proposed numerical models in complex situations. Numerical models and analytical solutions confirm the presence of both unstable and stable regions around the pressurized fractures. Fault stability during hydraulic operation depends on the position of faults with respect to the hydraulic fractures. The critical angle and distance between fault and hydraulic fracture in analytical solutions are identified when a region transits from stable to unstable status. For faults and discontinuities with an angle larger than 40° (i.e., with respect to horizontal direction) and distances less than 2.5 times the height of the fracture (i.e., from the center of pressurized fracture), the slip-tendency is greater than the initial value, indicating that the discontinuities within this zone are unstable and have the potential to slip. The developed model predicts that the unstable regions extend from fracture tips in both lateral and vertical directions. This generates relatively planar-distributed microseismic events, which are well-demonstrated in monitored field events. It was shown that the slippage of underground faults and other discontinuities could improve the fluid flow and transport by increasing the apparent permeability of the reservoir, such that the unstable regions could be recognized as permeability-improved zones.

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Müller, Axel, Morgan Ganerød, Michael Wiedenbeck, Skule Svendsen Spjelkavik et Rune Selbekk. « The Hydrothermal Breccia of Berglia-Glassberget, Trøndelag, Norway : Snapshot of a Triassic Earthquake ». Minerals 8, n^o 5 (23 avril 2018) : 175. http://dx.doi.org/10.3390/min8050175.

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The quartz-K-feldspar-cemented breccia of Berglia-Glassberget in the Lierne municipality in central Norway forms an ellipsoid structure 250 m × 500 m in size. The hydrothermal breccia is barren in terms of economic commodities but famous among mineral collectors for being a large and rich site of crystal quartz of various colours and habits. Despite being a famous collector site, the mineralization is rather unique in respect to its geological setting. It occurs within Late Palaeoproterozoic metarhyolites of the Lower Allochthon of the Norwegian Caledonides regionally isolated from any other contemporaneous hydrothermal or magmatic event. In order to understand better the formation of the Berglia-Glassberget breccia, the chemistry, fluid inclusion petrography and age of the breccia cement were determined. Structural features indicate that the Berglia-Glassberget is a fault-related, fluid-assisted, hydraulic breccia which formed by single pulse stress released by a seismic event. 40Ar-39Ar dating of K-feldspar cement revealed a middle Triassic age (240.3 ± 0.4 Ma) for this event. The influx into the fault zone of an aqueous CO2-bearing fluid triggered the sudden fault movement. The high percentage of open space in the breccia fractures with cavities up 3 m × 3 m × 4 m in size, fluid inclusion microthermometry, and trace element chemistry of quartz suggests that the breccia was formed at depths between 4 and 0.5 km (1.1 to 0.1 kbar). The origin of the breccia-cementing, CO2-bearing Na-HCO3-SO4 fluid may have been predominantly of metamorphic origin due to decarbonation reactions (T > 200 °C) of limestones of the underlying Olden Nappe. The decarbonation reactions were initiated by deeply derived, hot fluids channelled to sub-surface levels by a major fault zone, implying that the breccia is situated on a deep-seated structure. Regionally, the Berglia-Glassberget occurs at a supposed triple junction of long-lived fault zones belonging to the Møre-Trøndelag, Lærdal-Gjende and the Kollstraumen fault complexes. These fault systems and the associated Berglia-Glassberget earthquake are the expression of rifting and faulting in northern Europe during the middle/late Triassic.

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Han, Kaihang, Lin Wang, Dong Su, Chengyu Hong, Xiangsheng Chen et Xing-Tao Lin. « An analytical model for face stability of tunnels traversing the fault fracture zone with high hydraulic pressure ». Computers and Geotechnics 140 (décembre 2021) : 104467. http://dx.doi.org/10.1016/j.compgeo.2021.104467.

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Yoon, Jeoung Seok, Amir Hakimhashemi, Arno Zang et Gunter Zimmermann. « Particle Based Discrete Element Modeling of Hydraulic Stimulation of Geothermal Reservoirs, Induced Seismicity and Fault Zone Deformation ». Journal of Korean Society For Rock Mechanics 23, n^o 6 (31 décembre 2013) : 493–505. http://dx.doi.org/10.7474/tus.2013.23.6.493.

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Caspari, Eva, Andrew Greenwood, Ludovic Baron, Daniel Egli, Enea Toschini, Kaiyan Hu et Klaus Holliger. « Characteristics of a fracture network surrounding a hydrothermally altered shear zone from geophysical borehole logs ». Solid Earth 11, n^o 3 (7 mai 2020) : 829–54. http://dx.doi.org/10.5194/se-11-829-2020.

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Abstract. Hydrothermally active and altered fault/shear zones in crystalline rocks are of practical importance because of their potential similarities with petrothermal reservoirs and exploitable natural hydrothermal systems. The petrophysical and hydraulic characterization of such structures is therefore of significant interest. Here, we report the results of corresponding investigations on a prominent shear zone of this type located in the crystalline Aar massif of the central Swiss Alps. A shallow borehole was drilled, which acutely intersects the core of the shear zone and is entirely situated in its surrounding damage zone. The focus of this study is a detailed characterization of this damage zone based on geophysical borehole measurements. For this purpose, a comprehensive suite of borehole logs, comprising passive and active nuclear, full-waveform sonic, resistivity, self-potential, optical televiewer, and borehole radar data, was collected. The migrated images of the borehole radar reflection data together with the optical televiewer data reveal a complicated network of intersecting fractures in the damage zone. Consequently, the associated petrophysical properties, notably the sonic velocities and porosities, are distinctly different from intact granitic formations. Cluster analyses of the borehole logs in combination with the structural interpretations of the optical televiewer data illustrate that the variations in the petrophysical properties are predominantly governed by the intense brittle deformation. The imaged fracture network and the high-porosity zones associated with brittle deformation represent the main flow pathways. This interpretation is consistent with the available geophysical measurements as well as the analyses of the retrieved core material. Furthermore, the interpretation of the self-potential and fluid resistivity log data suggests a compartmentalized hydraulic behavior, as evidenced by inflows of water into the borehole from different sources, which is likely to be governed by the steeply dipping structures.

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Grauch, V. J. S., Mark R. Hudson et Scott A. Minor. « Aeromagnetic expression of faults that offset basin fill, Albuquerque basin, New Mexico ». GEOPHYSICS 66, n^o 3 (mai 2001) : 707–20. http://dx.doi.org/10.1190/1.1444961.

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High‐resolution aeromagnetic data acquired over the Albuquerque basin show widespread expression of faults that offset basin fill and demonstrate that the aeromagnetic method can be an important hydrogeologic and surficial mapping tool in sediment‐filled basins. Aeromagnetic expression of faults is recognized by the common correspondence of linear anomalies to surficial evidence of faulting across the area. In map view, linear anomalies show patterns typical of extensional faulting, such as anastomosing and en echelon segments. Depths to the tops of faulted magnetic layers showing the most prominent aeromagnetic expression range from 0 to 100 m. Sources related to subtler fault expressions range in depths from 200 to 500 m. We estimate that sources of the magnetic expressions of the near‐surface faults likely reside within the upper 500–600 m of the subsurface. The linear anomalies in profile form show a range of shapes, but all of them can be explained by the juxtaposition of layers having different magnetic properties. One typical anomaly differs from the expected symmetric fault anomaly by exhibiting an apparent low over the fault zone and more than one inflection point. Although the apparent low could easily be misinterpreted as representing multiple faults or an anomalous fault zone, geophysical analysis, magnetic‐property measurements, and geologic considerations lead instead to a “thin‐thick model” in which magnetic layers of different thickness are juxtaposed. The general geometry of this model is a thin magnetic layer on the upthrown block and a thick magnetic layer on the downthrown block. The thin‐thick model can be represented geologically by growth faulting and syntectonic sedimentation, where relatively coarse‐grained sediment (which is more magnetic than fine‐grained material) has accumulated in the hanging wall. This implies that the aeromagnetic data have potential for mapping growth faults and locating concentrations of coarse‐grained material that may have high hydraulic transmissivity. Although cementation along fault zones is common in portions of the area, we found no evidence that this secondary process results in measurable aeromagnetic anomalies. This observation differs from the findings in other sedimentary basins suggesting that magnetic anomalies arise from secondary magnetization along fault planes.

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Ma, Bin, Menggui Jin, Xing Liang et Jing Li. « Application of environmental tracers for investigation of groundwater mean residence time and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers ». Hydrology and Earth System Sciences 23, n^o 1 (24 janvier 2019) : 427–46. http://dx.doi.org/10.5194/hess-23-427-2019.

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Abstract. Investigating groundwater residence time and recharge sources is crucial for water resource management in the alluvium aquifers of arid basins. Environmental tracers (chlorofluorocarbons, 3H, 14C, δ2H, δ18O) and groundwater hydrochemical components are used for assessing groundwater mean residence times (MRTs) and aquifer recharge in fault-influenced hydraulic drop alluvium aquifers in the Manas River basin (China). Aquifers under the Manas River upstream (south of the fault) contains very high 3H activity (41.1–60 TU), implying water recharge affected by the nuclear bomb tests of the 1960s. Carbon-14 groundwater age correlates positively with distance from mountain area (3000–5000 years in the midstream to > 7000 years in the downstream) and groundwater depth, but correlates negatively to a decrease in 3H activity (1.1 TU) and more negative δ18O values. This phenomenon reveals that the source of the deeper groundwater in the semi-confined aquifer is paleo-meteoric recharge. Special attention has been paid to the estimation of MRTs using CFCs and 3H by an exponential piston flow model. The results show that MRTs vary from 19 to 101 years by CFCs and from 19 to 158 years by 3H. MRTs estimated from 3H are much longer than those from CFCs, probably due to the different time lag of liquid (3H) and gas-phase CFCs through the unsaturated zone. The MRTs estimated by CFCs show good correlations with pH and the concentrations of SiO2 and SO42-, which can provide a possible approach to estimate first-order proxies of MRTs for groundwater age. The young water fractions are investigated by the CFC binary mixing method in the south and north of the fault. Relatively modern recharge is found in the south of the fault with young (post-1940) water fractions of 87 %–100 %, whereas in the north of the fault the young water fractions vary from 12 % to 91 %. This study shows that the combination of CFCs and 3H residence time tracers can help in analysing the groundwater MRTs and the recharge sources for the different mixing end-members.

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