ALTERATION OF BIOTITE WETTABILITY BY SALINITY-INDUCED CHEMICAL REACTIONS UNDER CONDITIONS RELEVANT TO GEOLOGIC CO2 SEQUESTRATION

The wettability of rocks and minerals significantly impacts the efficiency and safety of geologic CO₂ sequestration. In this study, we investigated the effects of salinity-induced chemical reactions on biotite wettability changes under relevant operation conditions. Biotite was reacted with brine of different salinities (DI water, 0.1, 0.5, and 1.0 M NaCl) at 95 ^oC and 102 atm CO₂ for 70 h. Then, static and dynamic contact angles of the prereacted biotite with brine (0.1 M NaCl) and supercritical CO₂ were measured using the captive drop method at 102 atm CO₂ and 48 ^oC. We found that reaction with higher salinity solution resulted in more hydrophilic biotite surfaces. This increased hydrophilicity is due to increased surface roughness, increased surface negative charge and higher densities of hydroxyl groups. Additionally, CO₂ adhesion was observed during CO₂ receding process. Higher contact angle hysteresis was also observed for samples with a higher incidence of CO₂ adhesion, suggesting that CO₂ adhesion could have contributed to the hysteresis. For the first time, we experimentally related chemical reactions and the consequent wettability alterations of minerals under GCS relevant conditions. These findings can be beneficial in understanding CO₂ or other reactive fluids’ transport and their distribution in subsurface systems during energy-related operations.