Interfacial Hydration Improves Transport Capacity of Shale Oil within Montmorillonite Nanoconfinements

Fluid transport within clay nanopores is governed by nanoscale interfacial interactions and can deviate from continuum flow theory because of strong adsorption and mineral-fluid friction. Here, nonequilibrium molecular dynamics simulations probe shale oil transport in Na-montmorillonite nanopores. Pure n-octane simulations quantify the effects of slit aperture, temperature, pressure, and driving pressure gradient, followed by a multicomponent mixture of methane, n-octane, toluene, pyridine, and asphaltene to characterize component fractionation. Interfacial water films are then introduced to evaluate hydration effects. Confined oil develops pronounced density layering near montmorillonite surfaces, while pore-center velocity profiles remain Poiseuille-like. Larger apertures expand the mobile region and substantially increase volumetric flow rate, although the relative contribution of interfacial slip decreases. Higher temperature weakens near-wall adsorption, lowers apparent viscosity, and enhances slip, whereas higher pressure compresses confined oil molecules, strengthens interfacial resistance, and reduces mobility. Flow rate increases approximately linearly with the driving pressure gradient, indicating quasi-Newtonian behavior over the simulated range. In multicomponent systems, pyridine, asphaltene, and toluene preferentially adsorb on montmorillonite, forming an immobile boundary layer that causes negative slip and increases apparent viscosity. This boundary-layer reconstruction reduces the effective hydraulic aperture and markedly increases the overall resistance compared with pure n-octane. Interfacial water films passivate active mineral adsorption sites, redistribute polar and heavy components toward the pore center, restore positive slip, and enhance multicomponent oil transport. These findings reveal the coupled effects of nanoconfinement, oil composition, and surface hydration governing shale oil transport in clay nanopores.