Adsorption of Light Oil on Rock Surfaces: A Molecular Dynamics Study

Enhanced oil recovery techniques use extracting fluids such as brine, polymers, or surfactants to recover the residual oil from the reservoirs. A limited molecular-level understanding of oil−rock interactions hinders the development of novel injecting fluids for efficient crude oil extraction. In this study, we used molecular dynamics simulations to investigate the structure and energetics of light oil (dodecane) near the carbonate, clay-type, and sandstone reservoirs modeled using calcite, mica, and silica surfaces, respectively. We observed several layers of light oil adjacent to the rock surface with a strong bound layer on the calcite surface. We found epitaxial adsorption of light oil on the calcite surface, whereas less structured adsorption was observed on the mica and silica surfaces. Further, the distinctive adsorption pattern observed on each rock surface is governed by a specific surface atom (calcium on calcite, potassium on mica, and hydroxylated oxygen on silica). Hence, to delaminate the oil from the surface, the effect of such an influencing ion should be compensated with another ion or solvent that weakens the structuring.