Three-dimensional Lattice Boltzmann simulation of gas-water transport in tight sandstone porous media: Influence of microscopic surface forces

A three-dimensional two-phase Lattice Boltzmann model was developed and validated for the fundamental phenomena of gas-water transport in tight porous media considering microscopic forces, namely, the electrostatic and solid-liquid intermolecular forces. The thickness of the water film adhering to the porous media surface was calculated based on the principle of thermodynamic equilibrium and the gas-water electrostatic potential energy. The Lattice Boltzmann model simulations focused on the effects of the microscopic forces and water film thickness on the gas-water transport in tight porous media. The fluid flow in the porous media was simulated under different conditions for the characteristic length, interfacial tension, and displacement pressure gradient. The results confirmed that the gas-water transport is strongly affected by the microscopic forces in tight porous media and that the transport process is accompanied by a high seepage resistance. The seepage resistance is more pronounced in the case of smaller pores because the adhering water film is thicker and more stable. During the transport process, the water film may disintegrate under certain conditions, which would enhance the gas flow in the porous media. However, it is difficult to effectively improve the gas flow by increasing the displacement pressure gradient under microscopic forces; this can be attributed to the accumulation of water or increased seepage resistance dictated by the interfacial tension, which occurs more frequently with smaller pores. This paper provides a promising new perspective for efficiently improving the Lattice Boltzmann model for transport trends considering microscopic forces.