Experimental insights into surface wettability alterations and solvent adsorption effects on porous sandstone and carbonate rocks in H₂-brine systems: Implications for underground hydrogen storage

The hydrogen (H₂) economy promises a transformative shift toward clean energy and environmental sustainability. However, its large-scale implementation relies on efficient, safe, and economical storage systems. While underground hydrogen storage (UHS) in porous media presents a viable solution, the H₂ wettability behavior of rocks under various geological conditions remains poorly understood, particularly regarding surface roughness and solvent-induced wettability alterations upon adsorption. Therefore, the present study investigates the wettability and adsorption effects of various solvents on porous sandstone and carbonate rocks in H₂/brine systems under various pressure (0.1–20 MPa) and temperature (293–343 K) conditions. Experiments are conducted using the tilted plate method to measure the advancing (θ_a) and receding (θ_r) contact angles both before and after exposing the substrates to organic solvents mixed with stearic acid. The results reveal that the wettability of sandstone increases with rising pressure and temperature, thereby enhancing the H₂ wettability under reservoir conditions. By contrast, the wettability of carbonate increases with pressure but decreases with the increase in temperature. Hence, these results highlight the importance of mineralogical composition along with the influence of temperature, pressure, surface roughness, and organic acids on solvent adsorption. Moreover, these findings highlight the critical role of H₂ wettability and rock-fluid interactions for optimizing the fluid flow, capillary trapping, and efficiency of the UHS system. This study presents significant implications for H₂ storage potential and containment strategies, and supports the industrial-scale deployment of UHS in sandstone and carbonate formations.