Adsorption–flow coupling model for quantifying the transport mechanism of shale oil under nanoconfinement effects

Fluid transport under nanoconfinement effects governs essential processes in separation, energy conversion, bioengineering, and subsurface energy extraction, where interfacial interactions critically influence flow behavior. Despite its significance, the physics of nanoscale hydrocarbon transport, particularly in shale oil recovery, remains inadequately understood, especially with respect to adsorption-induced flow suppression and its impact on permeance. In this study, molecular dynamics simulations are employed to investigate the effects of nanoconfinement on n-alkane adsorption and pressure-driven flow within quartz nanopores and an adsorption–flow coupling model is developed to unravel its nanoscale transport mechanism. We demonstrate that Darcy's law fails to describe n-alkane transport in these nanopores, as permeability decreases with pressure and carbon chain length. This deviation is attributed to adsorption within the nanopores, which reduces the available space for molecular motion and impedes n-alkane mobility. By linking the free volume of n-alkanes in nanopores to adsorption and permeance, we establish a mechanistic model that predicts permeability based on fluid density and carbon chain length. This work advances the understanding of fluid transport in shale nanopores and provides a theoretical framework for flow behavior in nanopore materials, with implications for resource recovery and fluid engineering.