Multiwell CO₂ Injectivity: Impact of Boundary Conditions and Brine Extraction on Geologic CO₂ Storage Efficiency and Pressure Buildup

CO₂ storage efficiency is a metric that expresses the portion of the pore space of a subsurface geologic formation that is available to store CO₂. Estimates of storage efficiency for large-scale geologic CO₂ storage depend on a variety of factors including geologic properties and operational design. These factors govern estimates on CO₂ storage resources, the longevity of storage sites, and potential pressure buildup in storage reservoirs. This study employs numerical modeling to quantify CO₂ injection well numbers, well spacing, and storage efficiency as a function of geologic formation properties, open-versus-closed boundary conditions, and injection with or without brine extraction. The set of modeling runs is important as it allows the comparison of controlling factors on CO₂ storage efficiency. Brine extraction in closed domains can result in storage efficiencies that are similar to those of injection in open-boundary domains. Geomechanical constraints on downhole pressure at both injection and extraction wells lower CO₂ storage efficiency as compared to the idealized scenario in which the same volumes of CO₂ and brine are injected and extracted, respectively. Geomechanical constraints should be taken into account to avoid potential damage to the storage site