Analysis of Molecular Dynamics of CO₂/Oil DissolutionPhenomena in Enhanced Oil Recovery

Abstract

Carbon dioxide enhanced oil recovery (CO₂-EOR) is a technique to recover the residual oil from oil reservoirs by injection of CO₂. CO₂ dissolution causes changes in the physical-chemical properties of oil, resulting in improvement in the oil recovery efficiency. However, the fundamental dissolution mechanism is not clear. To clarify it, we have investigated CO₂ dissolution phenomena in cyclohexane (C₆H₁₂) using molecular dynamics simulations. The results show that CO₂ dissolves in C₆H₁₂ by forming a cluster structure. The dissolution state of CO₂ in C₆H₁₂ is discussed by comparing with the dissolution state of H₂O in C₆H₁₂, and the electric fields around CO₂, H₂O, and C₆H₁₂ are analyzed from the viewpoint of molecular polarity and coulomb interactions. As a result, the CO₂ dissolution state with cluster formation is considered to be strongly dominated by the similarity of the shape and size of the electric fields around CO₂ and C₆H₁₂.