Migration of oil/methane mixture in shale inorganic nano-pore throat: A molecular dynamics simulation study

In shale reservoirs, crude oil always involves a varying percentage of methane gas that may greatly affect the properties and the migration behavior of crude oil. In this work, to evaluate the effect of methane gas and to clarify the molecular mechanisms, the migration of oil/gas mixture in shale channels was characterized using molecular dynamics (MD) simulations. Specifically, the transport of oil with different methane fractions in a shale inorganic nano-pore throat was simulated. With analyzing the force that the oil undergoes when going across the nano-pore, the oil dynamic transport feature for different methane fractions was clarified. Then, the interfacial tension, the diffusion coefficient, and the interaction energy were calculated to give insights into the methane effects on oil transport. In addition, other oil-associated gases (ethane and propane) and the effect of temperature were studied and discussed. This work expands our knowledge of the oil and gas transport in nanopore throat at the molecular level, and it is expected to facilitate future studies on the migration of fluids through space-confined channels.