Shale oil occurrence and slit medium coupling based on a molecular dynamics simulation

Abstract

Although the state of occurrence and characteristics of shale oil form the basis for studying the mobility of shale oil, studies on the state of occurrence and characteristics of shale oil, as well as factors affecting its mobility, are presently lacking. Molecular dynamics simulation is a very effective method for studying the state of occurrence of shale oil and the factors affecting its mobility. We used molecular dynamics (MD) simulation to study the adsorption behavior and distribution of shale oil within a nanoscale slit medium. Results show that fluid density is not uniform throughout the slit and that its oscillation from the solid wall surface to the central plane is attenuated, indicating distinct adsorbed layers and bulk-phase fluid. We studied the effects of slit aperture, temperature, pressure, oil composition, and slit medium on the volumes and densities of the adsorbed layers. We found that (a) there were multiple adsorbed layers of liquid hydrocarbons, (b) the number of adsorbed layers depended largely on the slit medium, slit size, and oil composition, (c) the adsorption propensity of heavier hydrocarbons were more pronounced, and (d) the adsorption capacity of the slit medium differed for different types of hydrocarbon molecules.