The Impact of Salinity on H2/brine Interfacial Tension at Natural Reservoir Conditions: Implications for Hydrogen Geo-Storage

Abstract The large-scale H2 economy may provide a solution to restrict carbon emissions and meet global energy demand. In this regard, underground H2 storage is of keen interest to researchers, which may contribute to the possibility of an H2 economy. The interfacial tension (IFT) and wettability of any liquid/gas system are crucial parameters that determine the gas storage capacities and control the fluid flow through the pore matrix and containment security. Therefore, we have measured the IFT of the H2/brine system at realistic reservoir pressure (10 to 100 bars) and temperature conditions (20 to 80 °C) and compared it to the H2/distilled water system to comprehend the salinity effect. The results show that IFT marginally decreases with the increase in temperature. This effect is the combined effect of temperature and brine. With temperatures where H2 density changes significantly, IFT should have increased (as happens in H2/distilled water systems); however, the presence of saline water supersedes the temperature effect, and IFT behaves oppositely. Similarly, IFT marginally decreases with the increase in pressure due to the marginal changes in H2 density irrespective of presence of salinity. The results of this study provide a fundamental understanding of the H2/brine/distilled water systems at higher pressure and temperature conditions and aid value for accurate calculations to determine the H2 structural and residual geo-storage capacities.