Impact of wettability on immiscible displacement in water saturated thin porous media

Abstract

The characterization of immiscible displacement processes at the pore scale is crucial in order to understand macroscopic behaviors of fluids for efficient use of multiphase transport in various applications. In this study, the impact of porous material wetting properties on gas invasion behavior at various gas injection rates was investigated for thin hydrophilic porous media. An experimentally validated two-phase computational fluid dynamics model was employed to simulate the dynamic fluid–fluid displacement process of oxygen gas injection into liquid water saturated thin porous media. A phase diagram was developed through a parametric characterization of the thin porous media in terms of the material hydrophobicity and gas flow rates. In addition to calculating the saturation of the invading gas, gas pressure variations were calculated and used to identify the locations of phase diagram boundaries. Non-wetting phase streamlines resolved at the microscale were visualized and presented as a novel indicator for identifying displacement regimes and phase diagram boundaries. It was observed that the crossover from the capillary fingering regime to the stable displacement regime occurred between contact angles of 60° and 80°. By increasing the gas injection rate, due to viscous instabilities, flow patterns transitioned from the capillary fingering and stable displacement regimes to viscous fingering regime.