Abstract
Salt precipitation during CO2 injection into saline aquifers is a critical process that controls injectivity and long-term storage security. When brine evaporates into the injected CO2 phase, halite and other salts crystallize in pore constrictions, producing severe permeability reduction that is disproportionate to the corresponding porosity loss. Pore-scale observations have revealed that corner films and thin water layers act as preferential nucleation sites, leading to localized oversaturation and the initiation of precipitation. Coreflooding experiments confirm that salt deposition is not uniform but develops as irregular fronts near the injection face, governed by injection rate, CO2, phase state, and rock heterogeneity. Numerical modeling approaches, including continuum reactive transport simulators (e.g., TOUGH2, CMG-GEM), geochemical codes (e.g., PHREEQC), and pore-network frameworks, reproduce many of these dynamics and demonstrate the self-reinforcing feedback between salt growth and injectivity decline. Nevertheless, major challenges persist: thin-film transport is often neglected, multi-ion brine chemistry is oversimplified, and upscaling from laboratory to reservoir remains uncertain. This review synthesizes experimental and modeling evidence across scales. The results show that salt precipitation is nonlinear, localized, and strongly dependent on operational parameters. Future research should focus on integrating high-resolution imaging with reactive transport models and on developing mitigation strategies to ensure reliable long-term CO2 storage.