Distribution and flow of methane and water in kaolinite nanoslits

Inorganic mineral pores in coal are highly effective conduits for the transport of methane and water but are primary sites for water blocking. Current research on methane/water two-phase flow in coal focuses on pores in organic matter, and few studies have been performed on inorganic mineral pores. Inorganic materials are typically hydrophilic, making it essential to investigate the distribution and transport of two-phase flow in inorganic mineral nanofluidic channels. In this study, a nanoscale kaolinite slit model was constructed using results from scanning electron microscopy and energy dispersive spectroscopy Molecular dynamics simulations were conducted on methane and water in the model. The influence of water saturation, pressure differential, and pore size on two-phase flow was systematically analyzed. Water molecules preferentially adsorb onto the surface of kaolinite channels. With increasing water saturation, the water molecules order into various structures, such as films, bridges, and locks. The presence of water substantially reduces the space available for methane flow. As the water saturation increases, for methane, the peak density near the channel walls decreases, the distribution gradually becomes parabolic, and the flow rate decreases considerably (particularly for 0–45% water saturation). At 45% water saturation, the methane flow rate is 69.46% lower than that for single-phase methane flow. Both the water and methane flow rates increase with the pore size, but the effect is stronger for water than for methane. These findings provide valuable insights into the underlying mechanisms of water blockage and could make production performance prediction more accurate.