Experimental and Theoretical Investigation of the Bound Water Film Thickness in Porous Media

The existence of a bound water film on rock surfaces profoundly affects the effective flow radius in porous media featuring micro- and nanoscale pores. The variations in bound water film thickness directly impact recovery efficiency and pose extraction challenges in tight oil reservoirs. The impact of different mediums introduced into water was investigated to understand their effect on the bound water film thickness. Based on its adsorption capacity and ability to strip water at the oil–water–solid interface, this study explores the mechanism influencing the bound water film thickness within porous media at the molecular level. When water contained surfactant-based mediums, the bound water film thickness ranged from 13.11 to 23.56 nm, whereas with alcohol-based mediums, it ranged from 47.51 to 61.33 nm. When the introduced mediums occupied a smaller area within the water, they demonstrate enhanced water-stripping capability, adhere to water molecules on the surface in a neat manner, and bind more tightly to the rock surface, resulting in the formation of a relatively thin, bound water film. The mechanism governing the influence of bound water film thickness establishes a research foundation for altering effective flow radii under micro- and nanoscale pore size conditions. Future research will concentrate on controlling the bound water film thickness to enhance the tight oil recovery more effectively.