11. Displaced Fluid Management—the Key to Commercial-Scale Geologic CO₂ Storage

The most critical problem with commercial scale geological CO₂ sequestration is management of displaced fluids. All of the high quality numerical simulations of carbon capture, utilization, and storage (CCUS) on the Rock Springs Uplift (RSU), utilizing realistic 3-D reservoir models, demonstrate that commercial-scale geological CO₂ storage will require the removal of formation brines in approximately 1:1 ratio of injected CO₂ to displaced fluid. Without the production of formation brines the simulations suggest that very quickly injected CO₂ will cause pressures in the storage domain to exceed fracture pressures. To solve this problem, Carbon Management Institute (CMI) proposed a strategy that includes integration of fluid production/treatment with injection of CO₂. The treatment of the brines involved three important steps: (1) use of the temperature of the produced brines (~100 °C) to produce electricity via a heat exchanger to power the treatment facility, (2) to separate fresh water from the brines via nanofiltration and reverse osmosis, and (3) to recover metals, notably lithium, from the residual brines after partial evaporation. The impact of this approach; production of electricity, fresh water, and metals such as lithium from produced brines transform an anticipated carbon storage penalty into a revenue center.