Hydrogen wettability of Saudi Arabian Basalt: Implications for H2 geo-storage

[Display omitted] •Wettability of rock-H2-brine system is crucial in determining the H2 geo-storage capacities.•At all tested reservoir conditions, the pure Saudi Arabian (SA) basalt is strongly water-wet.•The wettability of SA basalt turn into hydrophobic due to the presence of organic acids.•The organic-aged SA basalt depicts lower H2 column heights than pure SA basalt.•The remedies should be taken into consideration to reverse the organic effect. The large-scale subsurface storage of hydrogen is a crucial element of the hydrogen economy value chain and is an essential process for achieving the successful replacement of carbon-based fuels. The wettability of the rock-H2-brine system, as quantified by contact angle measurement, has been the focus of most recent research due to its impacts on fluid flow, H2 migration and recovery efficiency during underground hydrogen storage (UHS). However, the reported contact angle data sets are quite inconsistent, and there are relatively few literature reports regarding the contact angles of H2/brine on Saudi Arabian basalt (SAB) compared to the contact angle data for quartz, shale, mica, and calcite. Hence, the advancing and receding contact angles θaandθr of the SAB-H2-brine system are measured herein via the sessile drop method at various temperatures (308 and 323 K) and pressures (0.1–20 MPa) to ascertain the appropriateness of SAB for UHS. The results indicate that the H2 wettability of SAB generally increases with pressure and temperature, but the pure SAB remains strongly water wet, having θa and θr