Experimental and molecular dynamic simulation assessment of H₂/brine/cement interfacial interactions during underground hydrogen storage

Cement is widely used as a structural and sealing material to ensure hydrogen containment in geological formations. However, the influence of H₂–brine–cement wettability and H₂–brine interfacial tension (IFT) on the integrity and sealing efficiency of cemented caprocks remains poorly understood. Furthermore, previous studies provide limited insights into hydrogen adsorption and sorption behavior under subsurface storage conditions. In this study, wettability and IFT of H₂–brine–cement systems were experimentally measured at pressures of 500–1000 psi and temperatures of 25–50 °C to evaluate hydrogen migration, trapping, and the performance of cemented seals. Molecular dynamics simulations were conducted at pressures of 500–3000 psi and temperatures of 25–100 °C to quantify hydrogen adsorption on cement surfaces and sorption within cement pores. The results show that variations in H₂–brine IFT did not exceed 6 mN/m, while maximum contact angles remained below 70°, indicating a predominantly water-wet system favouring residual hydrogen trapping in brine-saturated pores. Molecular simulations revealed hydrogen adsorption energies of −0.2 kcal/mol to −7.84 kcal/mol, consistent with moderate physisorption dominated by dispersive interactions, and sorption energies of 3.07 to 29.24 kcal/mol, indicating that hydrogen can be temporarily retained within pore networks, with retention strength increasing at low temperatures and high pressures. These findings suggest that the cement matrix maintains its chemical and structural stability, and that hydrogen migration is governed primarily by the physical microstructure rather than chemical interactions, supporting the effectiveness of cemented barriers for underground hydrogen storage.