A Modeling Study of Injection-Induced Rupture and Seismicity in Complex Faults

ABSTRACT: The potential for activating faults associated with geologic carbon sequestration is an issue of concern both related to induced seismicity and CO2 leakage. Faults are usually simplified (e.g., single, planar and homogeneous) in numerical simulations for the sake of computational efficiency. However, such simplifications might significantly impact the outcome of the analysis related to estimating the potential for fault activation and seismic magnitude. Thus, this paper focuses on the evaluation of injection-induced rupture and seismicity in faults of complex geometry. In this paper, we use a coupled multiphase fluid flow and geomechanical simulator (TOUGH-FLAC) to investigate the impact of complex fault geometries on fault rupture temporal and areal evolution and associated seismicity. Various meshing capabilities have been tested and adapted to allow us to discretize more complex and realistic fault geometries that might exist in subsurface formations. These fault geometries are taken as an input for the TOUGH-FLAC simulator to investigate fault reactivation induced by CO2 injection. The model demonstrates the importance of fault geometry on the spatial distribution and temporal evolution of rupture. 1. INTRODUCTION Fluid injection has the potential to induce fault reactivation during subsurface engineering activities, such as CO2 sequestration, enhanced geothermal systems, enhanced oil/gas recovery, and shale gas development (Cao et al., 2023; Cao and Sharma, 2023, 2022; Guglielmi et al., 2021; Park et al., 2020). The potential for activating faults associated with geologic carbon sequestration is an issue of concern both related to induced seismicity and CO2 leakage (Rutqvist et al., 2002; Rutqvist and Tsang, 2002). Faults are usually simplified (e.g., single, planar, and homogeneous) in numerical simulations for the sake of computational efficiency (Luu et al., 2022; Rinaldi et al., 2015, 2014; Rutqvist and Tsang, 2002). However, such simplifications might significantly impact the outcome of the analysis related to estimating the potential for fault activation and seismic magnitude. This paper focuses on the evaluation of injection-induced rupture and seismicity in non-planar faults.