MODELING FLUID PRESSURE PROPAGATION INTO DEEP BASEMENT ROCKS FROM MANAGED AQUIFER RECHARGE: A CASE STUDY OF THE VIRGINIA SWIFT PROJECT

The Sustainable Water Initiative for Tomorrow (SWIFT) is a managed aquifer recharge project designed to enhance long-term groundwater resource sustainability in the Virginia Coastal Plain Aquifer System, while offsetting coastal land subsidence and saltwater intrusion. The SWIFT project is targeting recharge rates of ~378,000 m³/day (100M gal/day) into the Potomac Aquifer through a network of seven recharge facilities. Research shows that this cumulative injection volume may result in sufficient pore fluid pressure to offset land subsidence caused by groundwater withdrawals; however, fluid pressure changes from large-scale injection operations are also known to cause seismicity in regions where earthquakes are uncommon. Here, we simulate aquifer recharge at the James River Facility, which is planned to operate at ~61,000 m³/day (16M gal/day). The 3-D geologic model reproduces the Coastal Plain Aquifer system and underlying basement within a ~150 × 150 km region in southeast Virginia. Prior to injection modeling, groundwater production is simulated from 1982 to 2019. Recharge injections are then simulated for 15 years (2020 – 2035) while maintaining the 2019 groundwater production levels. Results from this study provide first-order constraints on the spatiotemporal characteristic of fluid pressure propagation from recharge injections into the underlying crystalline basement. These results will be utilized to optimize seismic monitoring stations throughout the Coastal Plain Aquifer system prior to large-scale fluid injection operations.