A systematic review of salt ion-regulated interfacial behavior in shale oil reservoirs for CO2-EOR and carbon storage

Brine-bearing shale reservoirs feature low porosity, low permeability, strong heterogeneity, and highly mineralized formation water. Multiscale coupling of minerals, oil, and CO 2 in saline environments affects oil occurrence, fluid behavior, and CO 2 storage potential. This review systematically summarizes key issues: chemical composition and evolution of formation water; regulation of mineral surface properties and wettability by salt ions; oil–water distribution and migration under nanopore confinement; and mechanisms of CO 2 flooding and geological storage. Highly saline formation water can regulate oil–water distribution via electrical double-layer compression and ion adsorption, but may also induce salting-out blockage, mineral dissolution–precipitation, and pore-structure evolution, constraining CO 2 flooding efficiency and storage safety. Clarifying the multiscale coupling mechanisms among salt ions, minerals, fluids, and CO 2 is critical. Future work should integrate molecular simulation, microscale visualization, and multiscale characterization. These efforts will deepen mechanistic understanding and improve predictive models for efficient development and coordinated CO 2 storage.