Hydraulic Impacts of Salt Precipitation in CO 2 Storage: Roles of Wettability, Permeability, and Injection Rate

Salt precipitation during CO2 injection can alter injectivity and storage behavior, but its impact remains unclear because it is often evaluated based on salt presence rather than hydraulic consequences. This study examines when halite becomes flow-restrictive and how permeability, wettability, and injection rate jointly control salt-driven changes in trapping and plume migration. Fully compositional CMG–GEM simulations were performed across multiple permeability classes and wettability states (water-wet and weakly water-wet) under varying injection regimes. Permeability classes were defined based on formation transmissibility ranges, with low-permeability (0.8–2.6 mD), midpermeability (4–13 mD), and high-permeability (8–26 mD) systems representing tight to moderately conductive saline aquifers. Paired runs with and without water vaporization isolated the role of salt formation, and a plume-scale segregation index was introduced to link trapping partitioning with vertical migration. The results show that salt impact is governed by hydraulic restrictiveness. In low-permeability formations under high flow rates, restrictive salt banking increases capillary trapping by ∼18–23% and reduces plume segregation by up to ∼50%. Midpermeability systems exhibit partially restrictive behavior, where salt primarily redirects flow, enhancing dissolution by ∼3–4% while leaving residual trapping nearly unchanged (±1%). In high-permeability reservoirs, salt is largely nonrestrictive, producing subpercent trapping changes and minimal migration sensitivity. Wettability exerts a conditional influence, becoming important only when permeability and injection rate allow sustained dry-out with a continued brine supply, resolving previously inconsistent wettability trends. Overall, the study answers key questions on salt severity by showing that halite acts as a regime-dependent control on CO2 storage. The results provide a practical framework for identifying when salt precipitation alters trapping and migration, supporting more reliable screening and design of geological CO2 storage systems.