Two suggested systems of oil in the porosity of the reservoir rock after water flooding were built with an oil cylinder inside a silica nanopore. A series of MD simulations were performed to obtain the aggregation structure of oil phase. The results revealed that heavy oil components showed different distribution position inside silica nanopore in the two oil systems. Heavy oil molecules in heptane can precipitate and adsorbed on silica surface. Steered MD simulation was used to study the oil displacement. By analyzing solvent accessible surface area (SASA), we demonstrated the migration of heavy oil components at molecular level. (C) 2017 Elsevier B.V. All rights reserved.