Molecular simulations of oil adsorption and transport behavior in inorganic shale

Oil production from shale has grown dramatically in North America, and has the potential to do so globally. Understanding the adsorption and transport of liquid hydrocarbon through nanopores of inorganic minerals is crucial not only to develop liquid-rich shale reservoirs, but also to grasp oil migration from deeply buried extremely low permeability source rocks. In this work, the adsorption and transport behavior of n-octane (pentane, dodecane) confined in nanoscale dolomite slit pores have been investigated by grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The adsorbed phase density, molecular-scale structures at the interface, self-diffusion are then calculated and analyzed by equilibrium molecular dynamics (EMD). The number of adsorption layers is related to the size of pore. Increasing temperature will decrease the amount adsorbed, while pressures have little effect on amount adsorbed. Near the dolomite surface, the n-octane molecules adopt a preferential alignment parallel to the substrate, better packed and diffuse more slowly. Consider three alkanes, the long alkanes (octane, dodecane) are more easily to be adsorbed on dolomite surface. Lastly, the nonequilibrium molecular dynamics (NEMD) have been used to study the pressure-driven flow of n-octane in dolomite slits, flow characterization, viscosity, and slip length are analyzed. A larger driving force will increase slip length, while having only a negligible impact on the effective viscosity of the n-octane.