Numerical study of fluid injection-induced deformation and seismicity in a mature fault zone with a low-permeability fault core bounded by a densely fractured damage zone

Abstract

We apply a fully-coupled hydro-mechanical simulation tool to study fluid injection-induced pressure diffusion, poroelastic response, fracture slip, damage growth, and microseismicity occurrence in a complex fault zone. The fault zone has a low-permeability fault core bounded by a high-permeability damage zone, which is characterised by a fracture network with the fracture density exponentially decaying away from the fault core. We employ the discrete fracture network approach to explicitly represent the distribution and behaviour of these fractures in the fault zone. We use the finite element method to solve the coupled governing equations of fluid flow, solid deformation, and damage evolution in the fractured porous rock. We explore a number of scenarios with different orientations for the in-situ stress field and different locations for a constant rate fluid injection. We report an interactive control of fracture density, fracture orientations, in-situ stress state, and injection point position on the seismo-hydro-mechanical behaviour of the fault zone subject to fluid injection. Insight from our research findings may have important implications for injection-related geoengineering activities such as the development of enhanced geothermal systems and unconventional hydrocarbon reservoirs.