Pore-Scale Gas Transport in Shale: Effects of Water Distribution and Reservoir Conditions

Shale reservoirs commonly contain a certain level of water saturation, which affects gas transport and well productivity. This study developed a lattice Boltzmann method (LBM) framework for gas transport in water-bearing shale, incorporating a discrete Maxwell (DM) slip boundary condition for gas slippage and a Bosanquet effective viscosity correction for Knudsen layer effects. The model visualizes pore-scale gas flow in three-dimensional shale pore networks and quantifies the effects of water saturation, temperature, pressure, and geometric scale on shale gas transport. Results show that bound water in hydrophilic inorganic pores accumulates in small pores and narrow throats, whereas large pores contain thin water films, and organic pores are nearly water-free. Water saturation and geometric scale dominate the apparent permeability. At a water saturation of 44.68%, the apparent permeability decreased by 62.22% relative to that under dry conditions. Uniformly increasing the physical scale of the digital geometry markedly increased the apparent permeability. These results provide pore-scale insights into gas transport in water-bearing shale and highlight the importance of bound water in controlling the gas transport pathways.