Investigations on Water Imbibing into Oil-Saturated Nanoporous Media: Coupling Molecular Interactions, the Dynamic Contact Angle, and the Entrance Effect

Abstract

Spontaneous imbibition of hydraulic fracturing fluids into the water-wet inorganic media is a ubiquitous phenomenon, which has an important influence on tight/shale oil recovery and groundwater contamination. However, in nanoscale space, the fluid–solid (water–wall and oil-wall) molecular interactions, which can result in the nanoscale effects of the slip boundary and the varying interfacial fluid viscosity, will make the fluid flow behaviors be more complex and difficult to characterize. In this work, a new generalized imbibition model in inorganic nanopores and porous media is established by the theoretical analysis and a nanoscale Shan–Chen lattice Boltzmann method (LBM). The effects of pore dimensions and shapes in porous media, the nanoscale effects, the dynamic contact angle, and the entrance effect are considered and discussed. The results show that the proposed model can accurately characterize the oil/water imbibition mechanisms and be adapted to different nanoscale effects. Based on discussions, this study can provide microscopic basics of water imbibing into nanopores and provide guiding information and theoretical model for the oil recovery from tight/shale reservoirs by hydraulic fracturing, the groundwater remediation by restricting imbibition rate, and other relevant applications.