Fluid Migration Along Faults: Implications for CCUS

Abstract The capture and geological storage of CO2 is a safe, proven, and immediately deployable technology that can decarbonize heavy industry and manufacturing. Worldwide, there are several projects that currently store CO2 in depleted hydrocarbon fields and saline aquifers. In the United States, there has been significant progress in CCS project development in such formations subject to Underground Injection Control (UIC) Class VI guidance. Concern for contamination of underground source of drinking water (USDW) zones is regulated by limiting CO2 injection near faults. This represents a loss of potential pore space for CO2 storage. This work examines fluid migration along faults using a model based on a potential storage site in the Gulf of Mexico (GOM). The feasibility of brine and CO2 migration from the storage zone into the upper layers of the formation and USDW zones via faults is investigated through numerical simulation. A fault plane is simulated through local grid refinement (LGR) with varying properties to imitate different fault transmissibilities. Additional sensitivity studies on various operating parameters and fault characteristics were performed to determine conditions that could lead to USDW contamination. The simulation followed an injection schedule of 30 years injection at 1.6 MTA followed by 1000 years of shut-in observation. Fluid tracers were implemented to track the migration of brine to and from varying zones within the model. A range of fault characteristics, ranging from an open conduit to a fully sealing fault, were studied to observe the behavior and migration of fluids over the course of the simulation to get a sense of what average fault permeability is necessary to get a material amount of fluid migration. More realistic variations of fault characteristics will result in more conservative cases of CO2 migration upwards toward the USDW zone. Future work will involve extending this work to additional assets and using more sophisticated fault permeability descriptions.