Jul 2026· Deep Underground Science And Engineering· 0 citations· 115 references
Abstract
Subsurface fluid injection, widely employed in enhanced geothermal systems, CO₂ geological storage, and unconventional hydrocarbon extraction, can reactivate pre‐existing faults and induce seismicity. We present a physics‐based numerical framework that integrates fluid pressure diffusion, poroelastic stressing, and rate‐and‐state friction to evaluate fault stability in homogeneous poroelastic reservoirs. Compared with traditional Coulomb failure stress (
CFS
) approaches, which rely on quasi‐static stress changes, the model captures a broad spectrum of slip behaviors, ranging from aseismic creep to dynamic rupture, and quantifies systematic controls exerted by injection rate, tectonic loading rate, fault orientation, and reservoir permeability. Our numerical simulations reveal that poroelastic stressing plays a dominant role in triggering fault slip, particularly at large distances from injection sources and during the early stage of injection. We demonstrate that elevated injection rates and tectonic loading rates produce similar effects on induced seismicity patterns. Favorably oriented faults experience early slip events that precede the arrival of the fluid pressure diffusion front, whereas unfavorably oriented faults exhibit delayed slip that occurs only after the pressure front passage. In low‐permeability formations, fault slip onset is delayed but characterized by higher slip velocities. We additionally examine the post‐injection (shut‐in) stage, during which pore pressure continues to accumulate before eventual dissipation. The results indicate that shut‐in can either mitigate or accelerate slip depending on fault orientation, stress regime, and pre‐shut‐in injection history. Importantly, once slip nucleation has initiated, shut‐in may fail to prevent induced seismicity, underscoring the critical importance of timing in operational mitigation.
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Fluid injection in deep reservoirs can induce fault reactivation and seismicity, posing challenges for geothermal and subsurface energy development. This study investigates the mechanical interaction between two adjacent non-intersecting faults under fluid injection using a pseudo-three-dimensional thermo-hydro-mechanical (THM)-coupled numerical model. The results show that injection first triggers slip on F2, which then redistributes stress onto F1. The response of F1 is strongly heterogeneous: some segments are stabilized due to a decrease in Coulomb failure stress, whereas other segments are destabilized due to an increase in Coulomb failure stress. Stress-path analysis indicates that the immediate response of F1 to F2 slip is mainly governed by changes in effective normal stress and shear stress, rather than abrupt pore pressure changes on F1. These findings demonstrate that fault slip can act as a mechanical stress source that either promotes or inhibits adjacent fault reactivation. Therefore, slip-induced stress transfer should be explicitly considered when assessing fault stability in reservoirs containing multiple closely spaced faults.
A unified constitutive model for friction is developed using a generalised power‐law framework that captures rate, load, temperature and state dependencies across granular, cohesive, soft‐material interfaces and geological faults. Grounded in an energy‐balance derivation and state‐evolution tribology, the model defines the interface velocity (strain‐rate) as the fundamental constitutive property. The inverted kinetic friction formulation utilises a power‐law representation, successfully reproducing static‐to‐dynamic transitions, direct velocity‐strengthening effects and evolutionary velocity‐weakening behaviours. Representative systems: rock penetration, cohesive soil sliding, high‐speed machining and fault friction are systematically mapped. The explicit incorporation of Arrhenius temperature kinetics corrected to couple the activation energy with the rate‐and‐state exponent () proves that the model captures macroscopic thermal weakening. Furthermore, numerical sensitivity analyses of the real area of contact evolution confirm sublinear growth under confining pressure, successfully predicting pressure‐induced friction drops. This robust formulation bridges classical empirical laws with modern rate‐and‐state mechanics. The framework is parsimonious, physically coherent and demonstrates powerful predictive capabilities across tribological and Earth science contexts.
Deep and ultra-deep hydrocarbon resources are of strategic importance for energy security. The pronounced ductility of deep reservoirs and faults makes hydraulic fracture propagation and induced seismicity mechanisms fundamentally different from those in conventional brittle reservoirs. This review systematically synthesizes recent theoretical, experimental, and numerical advances in hydraulic-fracturing-induced seismicity, covering triggering mechanisms, fault reactivation risk evaluation, and perspectives. A core distinction is identified: brittle faults exhibit instantaneous stick-slip rupture with high seismic frequency and significant magnitude, whereas ductile faults undergo stable aseismic creep and progressive slip, with long-term deformation prone to delayed large earthquakes—their nucleation shows unique mechanical responses including high stress drop, low rupture velocity, and low seismic radiation efficiency. Subsequently, four major challenges are distilled for risk evaluation systems: insufficient dynamic characterization of mechanical parameters in ductile reservoirs, lack of fracturing-control strategies adapted to ductile behavior, poor understanding of multi-scale slip transition mechanisms, and inadequacy of multi-field coupling models in capturing long-term delayed evolution. Traditional brittle-based risk frameworks cannot characterize the time-dependent slip and progressive reactivation of ductile faults, limiting their applicability to deep reservoirs. Future works are proposed, including refined characterization of mechanical parameters under high temperature and pressure, intelligent full-cycle hydrofracturing control, quantitative criteria for slip activation, and optimization of long-term multi-field coupling models. This study elucidates recent progress in hydrofracturing-induced seismicity mechanisms and quantitative risk assessment in ductile reservoirs, filling a gap in the conventional brittle-dominant research. It also provides theoretical support for seismic risk evaluation and early warning in deep fracturing operations, with significant implications for improving induced seismicity management and ensuring safe, efficient, and sustainable deep-resource development.
Guangjie Wu, Qing Qiao, Hongyu Li et al.· Sustainability· 0 citations
Reservoir-triggered seismicity (RTS) is commonly associated with stress perturbations induced by reservoir loading and pore-pressure diffusion within fractured rock masses. Shortly after the initial impoundment of the Irapé Hydropower Plant (Minas Gerais, Brazil), a sequence of induced earthquakes was recorded, providing an opportunity to investigate the compatibility between reservoir loading and the observed seismic response. This study presents a first-order hydromechanical assessment integrating finite element modelling, analytical elasticity solutions, and pore-pressure diffusion theory to evaluate the spatial distribution of stress perturbations and the characteristic diffusion times associated with reservoir impoundment. A two-dimensional elastic model was developed to simulate stress redistribution induced by the maximum reservoir load, while a parametric diffusion analysis was performed for representative hydraulic diffusivities and hypocentral depth scenarios between 1 and 6 km. Numerical results showed excellent agreement with the analytical elasticity solution (RMSE = 14.36 kPa, MAE = 11.08 kPa, mean relative error = 1.38%, and R2 = 0.999), supporting the reliability of the numerical model. The simulations indicate that vertical stress perturbations decrease from approximately 1.8–2.0 MPa immediately beneath the reservoir to about 0.01–0.1 MPa at kilometer-scale depths, where the recorded seismicity is presumed to occur. The diffusion analysis indicates that pore-pressure propagation to these depths generally requires substantially longer times than the interval between reservoir filling and the onset of seismic activity. Nevertheless, owing to uncertainties in hydraulic diffusivity, fracture connectivity, and hypocentral depth estimates, the diffusion results are interpreted as a first-order sensitivity analysis rather than a site-specific prediction. Overall, the results support the temporal compatibility and physical plausibility of rapid elastic stress redistribution as a potential triggering mechanism, while recognizing that the available geological and seismological data are insufficient to establish a direct causal relationship or demonstrate fault reactivation.
Iarly Vanderlei da Silveira, Gilberto Gomes· Géosciences· 1 citation
Induced seismicity associated with subsurface fluid injection poses significant challenges for geothermal reservoir management. While quasi-static models capture long-term pressure, temperature, and stress evolution, dynamic rupture codes resolve transient earthquake mechanics. In this study, we develop a fully coupled framework that integrates both approaches to simulate fault reactivation and induced seismicity in a synthetic geothermal system. Unlike previous one-way coupled frameworks, our approach implements a closed-loop feedback, where stress redistribution from dynamically simulated seismic events is fed back into the quasi-static THM reservoir model. A 3D thermo-hydro-mechanical model tracks stress build-up during injection until a failure criterion is met, triggering a transition to a dynamic rupture solver that computes spontaneous 3D rupture propagation and seismic wave radiation. An automated coupling protocol ensures seamless data exchange between solvers. We demonstrate the framework by simulating two injection-induced events on a single-fault reservoir model. Results show that event-driven fault displacements and dynamic stress transfers significantly alter reservoir stress states. Simulated Coulomb stress changes, focal mechanisms, and slip distributions align with the ambient stress field and fault geometry. This closed-loop approach provides a robust tool for assessing seismic risk and optimizing injection strategies in geothermal environments.
R. Habibi, T. Ulrich, A. Gabriel et al.· Rock Mechanics and Rock Engi...· 0 citations
Enhanced geothermal systems rely on increasing permeability and pore surface area in rock. Cyclic thermal shocking can achieve both by inducing thermal cracks through repeated rapid cooling. Laboratory experiments subjected micritic limestone, granodiorite, and trachybasalt to up to 10 thermal shock cycles, while tracking crack evolution qualitatively using time‐lapse electron microscopy and quantifying pressure‐dependent permeability and elastic wave velocities. This work advances prior efforts focused primarily on crack initiation by demonstrating how lithology‐specific microstructures govern the cyclic evolution, persistence, and efficiency of pressure‐dependent permeability enhancement during cyclic thermal shocking. This reframes microstructure as a key design variable controlling permeability enhancement and monitoring during geothermal stimulation. Contrasting mineral thermal properties, large mineral grains, and irregular vugs promote the greatest permeability enhancement. Velocity reductions were most pronounced <10 MPa effective pressure (Peff) and diminished with increasing cycle number, indicating that velocity‐based monitoring in geothermal systems must account for Peff and cycle number.
M. Malenda, T. Vanorio· Geophysical Research Letters· 0 citations