Wettability of Caprock–H<sub>2</sub>–Water: Insights from Molecular Dynamic Simulations and Sessile-Drop Experiment
Safwat Abdel‐Azeim, Ahmed Al‐Yaseri, Kion Norrman, Pramod Patil, Abdulaziz Qasim, Ali Yousef
Abstract
Structural trapping is the most critical geostorage mechanism utilized in H 2 subsurface storage projects due to the substantial gravity segregation of H 2 and reservoir fluids. Hence, it is crucial to comprehend the wettability of caprocks under H 2 gas storage conditions. Several studies have investigated the wettability of H 2 using the sessile water-drop method on caprocks at various pressures and temperatures; nevertheless, the reported data display significant variability. In this study, molecular dynamic simulation has been coupled with a sessile-drop experiment to estimate the water–H 2 –mica, water–H 2 –anhydrite, water–H 2 –gypsum, and water–H 2 –halite wettability under various conditions of pressure, temperature, and salinities. We observed that the clean mica, anhydrite, gypsum, and halite minerals are strongly water-wet under all tested conditions. The analysis of molecular interactions has revealed that the caprock surfaces have high hydration energies, which makes it difficult for H 2 to displace water and alter the wettability of the rock. Consequently, this research suggests that caprocks are strongly water-wet, H 2 does not show wetting phase characteristics, and the considered caprocks have a high sealing efficiency.