Injection-induced poroelastic controls on the transient process of dynamic fault rupture in geo-energy engineering

Managing fluid-induced seismicity is one of the most crucial challenges in geo-energy engineering. A seismic event usually starts from initial fault slip, followed by a nucleation process, and finally propagates to dynamic rupture. Fault stability analysis based on the elastostatic Mohr-Coulomb failure criterion is limited to assess fault slip initiation only. In contrast, the interfacial slip model of cracks is well suited to describe the nucleation process and the initiation of dynamic rupture in addition to the initial slip. Moreover, it provides an opportunity to identify the distinguished slip regimes of dynamic fault rupture under various geomechanical conditions compared with other fully numerical approaches. Yet, existing studies following this model have not accounted for injection-induced poroelastic effects on the nucleation process and slip regimes. Here, we incorporate a well-established analytical solution of poroelastic stress instead of numerical reservoir tools into the interfacial slip model to simulate the earthquake nucleation process and slip regimes due to injecting fluid into a fault zone. Results highlight that the developed model is capable of capturing the failure transition from initial slip to dynamic rupture propagation. Including injection-induced poroelastic stress variations significantly impacts the specific evolution of crack growth, disclosing the poroelasticity-dominated nucleation in addition to that dominated by slip-weakening mechanism, which brings to light a wider range of slip regimes in nucleation process. Poroelasticity can stabilize faults by delaying the initiation of fault slip and its ultimate nucleation, which are beneficial for managing induced seismicity. However, it also leads to a potential risk of inducing damaging earthquakes, owing to the issue of long run-out distance, under certain conditions. These findings arise from a physics-based model and provide a better understanding of the transient rupture process, contributing to developing managing and forecasting tools of induced seismicity.