Opening versus shearing of a fluid-driven fault reactivation

Abstract

Geological injection of fluids plays a key role in addressing societal challenges such as renewable energy transition and climate crisis mitigation. However, frequent injection activities would disturb the stability of surrounding fault zones and furtherly induce seismicity. When fluid enters a fault, the competition among pressure front and slip front can play a role on the fault’s seismic behaviour. Fault’s stiffness as well as the rock’s Poisson’s ratio affects the shape of the slip and pressure front. In this study, the fault’s seismic behaviour has been extensively study through numerical modelling. The aim is to investigate the impact of deformable aperture and rock matrix’s Poisson’s ratio on the opening rupture and shear rupture of a pre-existing critically stressed fault. The parametric study shows that, with this initial stress state, the opening rupture grows slower than the shearing rupture, and the ratio between the front length is approximately 70%. A slip-weakening feature could boost this difference. Moreover, the variation between the front length along the y-direction and dip-direction of the fault increases with the increase of rock matrix’s Poisson’s ratio.