Effects of wettability and pore size on the transport dynamics of multiphase flow in porous media

Transport of multiphase flow in porous media is strongly influenced by surface wettability and pore-scale geometry. In the present study, the effects of wettability on gas-phase invasion dynamics in porous media with varying pore sizes are examined using a Lattice Boltzmann method. The numerical approach is validated against classical benchmark cases, including static droplet formation and the Young–Laplace bubble test. The simulation results clearly demonstrate that gas invasion behavior is highly dependent on both wettability and pore size. In porous media with relatively large pores (mean diameter greater than approximately 10 μm), increased wettability (i.e., more hydrophilic surfaces) suppresses lateral gas invasion, reducing gas saturation by 0.198 as the contact angle decreases from 87.1° to 30.6°, and accelerates gas breakthrough. In contrast, in fine-pore media (mean pore diameter below approximately 10 μm), decreased wettability (i.e., less hydrophilic surfaces) significantly enhances gas mobility by inducing bubble fragmentation mechanisms such as lamella division. This leads to a reduction in gas saturation by 0.572 as the contact angle increases from 30.6° to 87.1°, along with shorter breakthrough times. These findings highlight the coupled effects of wettability and pore structure in controlling multiphase fluid dynamics and provide fundamental insights into multiphase transport and bubble management in capillary-dominated porous media.