Computational fluid dynamics modeling of rock-liquid-H₂ contact angles: Implications for underground hydrogen storage

To achieve the net-zero target, hydrogen (H2) will emerge as an essential cornerstone within the energy supply chain of the future. To effectively attain such a target for an integrated and sustainable large-volume economy based on H2 on a global scale, proper H2 storage is imperative. This is where the significance of Underground H2 Storage comes to the fore. However, there are many concerns that should be addressed before using underground structures including the interactions between rock, H-2, and liquid within the pore spaces. In this study, we simulated the process of an H(2 )bubble hitting reservoir rock samples and measured the contact angles for rock-H-2-distilled water systems using the Navier-Stokes equations for mass and momentum conservation. The phase-field method was utilized for tracking the free surface. Since the phase-field method is essentially a coupling set of equations, we used the commercial finite element software COMSOL, which excels at solving Multiphysics coupling problems, to solve the Navier-Stokes equations and the phase-field method. The predicted contact angles were validated with the experimental results of basalt, shale, and calcite substrates. The simulated and experimental contact angles differed by <2 in most cases exhibiting favorable agreement. Additionally, the simulation was able to replicate the same behavior of the change in contact angle caused by variations in temperature and pressure during the experiments. It is noteworthy that the findings from this study are helpful to better understand and predict the wettability of different minerals during underground H2 storage.