Impact of Rock Wettability and Mineralization on CO ₂ Storage Efficiency in Basalt Reservoirs

Basalt formations have emerged as highly promising targets for geological CO2 storage due to their abundance of reactive silicate minerals that can rapidly convert dissolved CO2 into stable carbonate minerals. The efficiency of CO2 trapping in basalts, however, depends not only on their geochemical reactivity but also on reservoir wettability, which governs how CO2 partitions among structural, residual, solubility, and mineral trapping mechanisms. However, wettability and mineral kinetics have largely been examined separately─wettability for plume migration and kinetics in terms of mineralization─leaving their coupled impact unquantified. Here, we systematically integrate these processes in a reservoir-scale reactive transport model to quantify the impact of three distinct wettability conditions (water-wet, mixed-wet, and CO2-wet) on plume migration, mineral precipitation, pore-scale blockage, and long-term immobilization. Results show that under ideal conditions (no mineralization), water-wet systems exhibited plume aspect ratios up to 28% higher than CO2-wet systems and promoted at least 60% greater residual trapping. When mineralization was incorporated, mineral trapping accounted for 57%, 53%, and 46% of the total immobilized CO2 in water-wet, mixed-wet, and CO2-wet systems, respectively. Dissolved CO2 contributed 43–46%, while residual trapping remained below 5%, and mobile CO2 was substantially reduced due to mineralization, demonstrating that, as the system becomes more water-wet, CO2 is more effectively converted into stable carbonate minerals, although extensive mineral precipitation may lead to pore clogging. A global Sobol-Morris sensitivity analysis further reveals that the kinetic parameters of reactive minerals are the most influential factor, followed by wettability, while salinity has only minor influence. These findings highlight that wettability is not merely a flow property but a fundamental control on CO2 mineralization in basalts, with direct implications for site selection in storage projects.