Benchmarking Analytical and Numerical Simulation of Induced Fault Slip

Abstract Pore pressure fluctuation in subsurface reservoirs and its resulting mechanical response can cause fault reactivation. Numerical simulation of such induced seismicity is important to develop reliable seismic hazard and risk assessments. However, modeling of fault reactivation is quite challenging, especially in the case of displaced faults, i.e., faults with non-zero offset. In this paper, we perform a systematic benchmarking study to validate two recently developed numerical methods for fault slip simulation. Reference solutions are based on a semi-analytical approach that makes use of inclusion theory and Cauchy-type singular integral equations. The two numerical schemes considered are both finite volume (FV) methods which consider discrete faults in different manners. One of them employs a conformal discrete fault model (DFM) while the other uses an embedded (non-conformal) fault model. The latter allows for flexible fault and rock matrix grids and is computationally attractive. It was found that both numerical methods accurately represent pre-slip stress fields caused by pore pressure changes. Moreover, they also successfully coped with the vertical frictionless fault. However, for the case with an inclined displaced fault with constant friction coefficient, the embedded method did not converge for the post-slip phase, whereas the DFM results did converge for both constant and slip-weakening friction coefficients. In its current implementation, the DFM is therefore the model of choice when accurate simulation of local faulted systems is required.