Microscopic Numerical Study on the Entry Pressure of CO2 Hydrate-Bearing Sand Layers

Abstract Carbon capture and storage (CCS) is attracting attention as a measure against global warming. In recent years, a subsea storage method utilizing gas hydrate has been proposed. Evaluating the barrier performance of gas hydrate against CO2 leakage within porous media is crucial for determining the feasibility of this type of CCS. Capillary pressure is one of the key properties to consider when assessing the safety of CO2 hydrate storage within geological formations. In this study, we measured the contact angle between CO2 gas and water on the surface of CO2 hydrate. Using the obtained contact angle, we calculated the entry pressure through three-dimensional microscopic numerical simulations to investigate the effects of hydrate saturation and contact angles on the sand surface. The results of the numerical method demonstrated its validity comparable to the values derived from a theoretical formula. It was also revealed that the entry pressure increases with rising hydrate saturation and that the ratio of this increase is independent of the contact angle. This may be attributed to the negligible influence of the curvature of the pore area.