Carbon capture and storage (CCS) has emerged as one of the key technologies for the abatement of CO2 emissions, and meeting the energy demands in a carbon-constrained world, especially in the context of negative-emissions technologies. Two issues, however, have emerged as critical to ensure safe and effective geologic CO2 storage:

Risk of felt seismicity caused by injection.

Risk of leakage through faults, given their potential to become preferential fluid pathways.

In view of these issues, several geologic, economic, and societal factors make the Gulf of Mexico (GoM) a prime candidate for CCS, such as: (1) the occurrence of very porous and permeable reservoirs with extensive laterally continuous caprocks; (2) the vanishingly low historic seismicity; (3) the widespread occurrence of extensional-growth faults of Miocene-age, such as the Clemente-Tomas growth fault zone, which have long been recognized as an important mechanism for trapping of large-volumes of hydrocarbons; (4) its long history of oil and gas exploration providing an unusually detailed knowledge of the subsurface; and (5) its proximity to large industrial sources of CO2.

Here, we investigate the impact of industrial-scale CO2 storage on the stability of, and potential leakage along, pre-existing faults in the GoM. We do so by performing 3D numerical simulations of coupled flow and geomechanics using high-fidelity geological models of the Miocene section of the GoM, both at the field scale (10s of km) and at the regional scale (100s of km). We pay particular attention to the frictional and hydraulic properties of unlithified sedimentary faults, and incorporate a detailed, physics-based, probabilistic representation of clay and sand smearing to populate the flow properties of normal faults. We then investigate different scenarios of injection-well location in relation with faults' geometry and architecture, representing geologic settings corresponding to "open" and "closed" reservoirs. The results of our flow-geomechanics simulations suggest that CO2 injection results in small fault destabilization, and vanishingly small probability of leakage along faults---supporting the notion that large-scale (100s of Mt) CO2 injection in the GoM is feasible, but that well placement is key for the success of individual CCS projects.