Assessment of rock-hydrogen and rock-water interfacial tension in shale, evaporite and basaltic rocks

Underground hydrogen storage (UHS) is a distinguished method for reducing anthropogenic greenhouse gases (GHGs) and meeting global energy demand. One of the important parameters for subsurface storage of gas is rock-fluid interfacial tension (γrock-fluid) as gas injection and production rate, spread and flow in porous media, storage capacity, and containment security can be derived by this parameter. However, it is impossible to experimentally measure γrock-fluid. Moreover, γrock-fluid data for rock/H2/water systems in various shales, evaporite, and basaltic formations at geo-storage conditions are scarce in the literature. Thus, advancing and receding contact angles data were used to theoretically compute it at various pressures, temperatures, and shale-TOC by the combination of Young's equation and Neumann's equation of state. For all the rocks evaluated in this study, it was found that γrock-gas decreased with pressure, temperature, and shale-TOC. Also, γrock-water decreased with temperature but increased with shale-TOC, assuming that it remained constant with pressure. Thus, this work provides a deep understanding of wetting characteristics at various rock/H2/water systems, leading to a better investigation of hydrogen storage beneath shales, evaporite, and basaltic formations.