Abstract
Hydrogen is well known as a medium for clean energy storage. However, storing large amounts of hydrogen in tanks at the surface has many technical, environmental, safety, and economical challenges. Meanwhile, under-ground formations are good candidates for large-scale storage, but not all subsurface formations are suitable, and the selection of a good subsurface formation is vital. In this respect, the storage capacity and injection/pro-duction rate of hydrogen gas are significantly influenced by interfacial characteristics such as the rock-water interfacial tension (gamma rock-water) and rock-gas interfacial tension (gamma rock-gas) in the rock/H2/water system. Because these factors cannot be experimentally measured, they are characterized via theoretical methods. Therefore, in the present work, the interfacial properties are calculated by using Young's equation and Neumann's equations of state for various lithologies, including calcite, dolomite, quartz, shale, anhydrite, gypsum, granite, and basalt. The results indicate that gamma rock-water and gamma rock-gas are significantly affected by the rock composition and tend to increase with increasing temperature, but are unaffected by changes in pressure. Furthermore, the gamma rock-water value is found to decrease with increasing salinity for lithologies such as calcite, dolomite, and quartz, but in-creases with salinity for lithologies such as basalt, granite, and gypsum. Meanwhile, the gamma rock-gas is found to decrease with increasing pressure, but increase with increasing salinity. However, the variation of gamma rock-gas with temperature is not straightforward. For example, the interfacial tension in the rock-hydrogen system is shown to increase with increasing temperature for certain minerals in distilled water, but decreases for other samples, such as anhydrite, granite, and shale, especially in brine. The data presented herein is expected to assist in under-standing the suitable subsurface formations and reducing the level of uncertainty for the successful feasibility of underground hydrogen storage projects.