Fault Reactivation and Seismicity Associated with Shale-Gas Fracturing and Geologic Carbon Storage—A Comparison from Recent Modeling Studies

Fault activation and induced seismicity associated with both geologic carbon storage (GCS) and shale-gas fracturing were simulated using a coupled multiphase flow and geomechanical numerical model with a strain-softening Mohr-Coulomb model for fault seismic rupture. The analysis shows that for the case representative of GCS, felt seismic events (e.g., moment magnitude 4) could be induced whereas in the case representing shale-gas fracturing, only unfelt, smaller magnitude events were calculated. In the GCS case, a fault, crossing or bounding the reservoir, could be uniformly pressurized over a much larger fault surface area that could then rupture in one instance. In the case of shale-gas fracturing, the analysis shows that the expected low permeability of faults intersecting gas saturated shales could be a limiting factor for the possible rupture size and seismic magnitude. In any case, the initial stress field as well as the rock properties, whether more ductile or brittle, are important factors that will determine whether larger seismic events could be induced.