Salt precipitation near injection wells critically influences both the efficiency and integrity of CO₂ geological storage in saline aquifers, especially under high-salinity conditions. To clarify the dominant mechanisms of supercritical CO₂ (ScCO₂)-induced salt crystallization and inform mitigation strategies, we conducted static high-temperature, high-pressure soaking experiments. Results demonstrate a coupled mechanism whereby ScCO₂-induced interfacial dehydration and acid-driven water–rock interactions jointly alter pore structures and surface wettability. A CO₂–brine–rock tri-phase reaction system was established using nuclear magnetic resonance (NMR), low-temperature nitrogen adsorption, SEM/EDS, XRD, ion chromatography, and contact angle measurements. These analyses revealed a cascade of physicochemical processes, including mineral dissolution, ion accumulation, crystal nucleation, pore blockage, and wettability shift. Compared to N₂ controls, supercritical CO₂ (ScCO₂) significantly accelerates salt crystallization, forming NaCl, KCl, CaSO₄, and MgCO₃ phases. These precipitates reduce total pore volume by 15%–20% and cause a leftward NMR T₂ shift, indicating 30% macropore signal attenuation. Mesopore fraction increases from 47% to 60%, while micropore content decreases to 34%. Surface wettability shifts from hydrophilic (41.6°) to hydrophobic (58.0°). Based on these findings, we propose a multi-dimensional mitigation framework encompassing aqueous-phase regulation, injection protocol optimization, pore structure preconditioning, and real-time in situ monitoring. These insights support improved injection stability, long-term CO₂ storage security, and risk control in saline reservoirs.

Article link: https://doi.org/10.1029/2025WR041172