Roles of fault structures and regional formations on CO2 migration and distribution in shallow saline aquifer in Green River, Utah

Understanding CO2 migration and distribution in fault systems is essential to evaluate long-term secure CO2 storage and prevent hazardous effects caused by CO2 leakage. To elucidate the role of the fault system on subsurface CO2 migration and leakage processes, a two-dimensional multi-phase transport model was constructed to represent Little Grand Wash (LGW) and Salt Wash (SW) faults, where naturally originating CO2 is being leaked to the surface. According to simulation results, buoyant CO2 leaked through various pathways including the faults themselves, fault offsets, and damaged caprock. Because of both fault systems and caprocks serving as barriers, multiple trapped CO2 plumes were developed in this region. Presence of trapped CO2 plumes in the subsurface is supported by multiple field-observations (e.g., elevated soil CO2 fluxes, travertines, and CO2-driven cold-water geysers/CO2 springs) adjacent to both LGW and SW faults. Sensitivity studies were conducted with different permeabilities for faults and caprock, various CO2 source locations, and differing fault parameters (e.g., fault throw and cutoff angle), which affected subsurface CO2 distribution including size, shape, and location of trapped CO2 plumes. Finally, such trapped CO2 plumes have played a key role in the development of CO2-driven cold-water geysers in these regions.