Effects of salinity, temperature, and pressure on H₂–brine interfacial tension: Implications for underground hydrogen storage

Underground hydrogen (H₂) storage is a long-term, clean, and sustainable solution for a large-scale H₂ economy. Hydrogen geo-storage strategies in saline aquifers have gained considerable attention regarding meeting energy demand challenges. Rock-fluid interaction and interfacial tension (IFT) of any given gas determine the fluid flow, storage potential, and containment security. However, the literature lacks sufficient information on the IFT of H₂-brine systems at various thermophysical and salinity conditions. This study experimentally measures density using an Anton Paar DMA-HP densitometer and IFT with a Kruss drop shape analyzer (DSA-100). The density and IFT measurements of H₂-brine systems were evaluated at various pressures (0.1, 5, 10, 15, and 20 MPa), temperatures (25, 50, and 70 °C), and salinities, including deionized water, seawater (mixed brine), and individual brines (NaCl, KCl, MgCl₂, CaCl₂, and Na₂SO₄) at 1 and 3 M concentrations. The results indicate a significant decrease in H₂-brine IFT by the increasing temperature at a constant pressure and salinity. A slightly decreasing trend is observed when the H₂-brine IFT is plotted against pressure, maintaining a constant salinity and temperature. Increasing the salinity of the salt solutions (from 1 to 3 M), irrespective of the salt type, increases the H₂-brine IFT at a constant pressure and temperature. Due to the screening effect, the monovalent and divalent cations behave differently in H₂. To the best of our knowledge, this comprehensive dataset for H₂-brine IFT is presented for the first time. The provided data are crucial for reservoir simulations and determining the H₂ geo-storage potential under natural reservoir conditions.