Quantification of fault leakage dynamics based on leakage magnitude and dip angle

Abstract Subsurface leakage of fluids, such as CO, along faults is a key quantity to estimate when modeling underground fluid storage. Using our coupled multiphase flow‐geomechanics‐fault slip simulator, we quantify leakage dynamics using the fault dip angle and leakage magnitude, a proposed metric of gas leakage. We present novel leakage dynamics of faults to show that leakage is non‐trivially coupled to induced seismicity and multiphase flow along faults due to the effect of fault dip. The onset time of induced fault slip, controlled by the initial shear‐to‐effective normal stress ratio on the fault, is a non‐monotonic function of the fault dip. The leakage directions of gas and liquid phases are determined by the directions of slip propagation and the buoyancy vector, both of which depend on the dip. A consequence is that leakage evolution is non‐monotonic in time for hanging wall injection‐induced seismicity on a normal fault because of the competition between up‐dip oriented buoyancy and down‐dip oriented induced slip. With respect to monitoring, we note that subsidence at the location of an injection well could be indicative of leakage.