Poroelastic Models for Fault Reactivation in Response to Injection and Production

Poroelastic stress changes in response to production can result in fault reactivation. The combined effects of production and injection on fault reactivation, especially for unconventional reservoirs where injection occurs in layers other than the produced interval, are not readily predicted based on flow models alone, requiring geomechanical models that account for coupled flow and poroelastic response. To investigate these effects, we conducted fully coupled poroelastic finite element simulations in Abaqus. Biot's theory of poroelasticity governs the poroelastic deformation, and the fault stability is governed by Terzaghi's effective stress via Coulomb failure stress. Using 3D models, we compared fault reactivation results under a normal-faulting stress regime for two scenarios: injection only, and concurrent injection and production in two different horizons. We used Coulomb failure stress on the fault to determine which scenario has a higher potential of fault reactivation. Our results demonstrate the effect of poroelastic stress changes in addition to changes in pore pressure on fault reactivation. Concurrent injection and production stabilizes the fault in the injection layer compared to the injection-only scenario. Also, production may increase the fault reactivation potential on the interface between the production reservoir and caprock. These simulations provide guidance toward optimizing injection strategies that minimize fault reactivation potential in fields with concurrent production and injection.