Nanohydrodynamic Model and Transport Mechanisms of Tight Oil Confined in Nanopores Considering Liquid–Solid Molecular Interaction Effect

Modeling oil flow confined in nanoscale pores is the preliminary and foundation of nonlinear seepage research of tight reservoirs. In this study, an analytical nanohydrodynamic model for the description of flow characteristics of confined oil in nanoscale pores with diameters greater than 2 nm is proposed coupling with viscosity distribution function and slip velocity model based on the liquid–solid intermolecular force mechanisms. This analytical model has been validated by experimental results. Analysis results of this model reveal the special flow characteristics of tight oil confined in nanopores: the velocity profile curve on the cross section is coupled parabolic with exponential line, and the maximum velocity in center is related to pore size and liquid–solid interaction strength. Furthermore, the thickness of the low-velocity region near the wall, which reflects the action scope of pore surface, could be quantified by this model. The critical radius of the nanopore to distinguish the confined flow and unconfined flow is determined by this model, which would increase with a decrease in the liquid–solid interaction strength. And the non-Darcy seepage mechanisms of tight reservoirs could be revealed by this model because of the consistent characteristics of flowrate curve and non-Darcy flow curve. Besides, increasing temperature could weaken the confinement effect and changing wettability is an effective method to enhance tight oil mobility. Finally, apparent permeability is derived for tight reservoirs from this nanohydrodynamic model.