Effects of surfactant with different injection times on asphaltene adsorption behaviors on the kaolinite surfaces: A molecular simulation study

Abstract

The adsorption behavior of asphaltenes on the mineral surfaces seriously reduces oil recovery, which is dependent on the molecular structure, surface properties of the inorganic minerals, and the injection time of chemicals. In the present study, the molecular dynamics (MD) simulation is performed to construct the asphaltene-kaolinite adsorption systems and the 3-(N,N-Dimethyloctadecylammonio) propane sulfonate (DOPS) surfactant flooding systems to explore the effect of DOPS injection times on the detachment of asphaltene aggregates with discrepant adsorption characteristics. The number density distribution and the interaction analysis between asphaltene and kaolinite are employed to evaluate the adsorption behaviors of asphaltene on the kaolinite-liquid interfaces. The radial distribution function (RDF) describes the relative positions of the surfactants and asphaltene aggregates. The effective free energy and the independent gradient model based on Hirshfeld partition (IGMH) method further illustrate the microscopic mechanism of asphaltene detaching by the surfactant. The simulation results indicate that intensely polar carboxylate groups and polyaromatic rings with π-conjugated structures dominate the adsorption behavior of asphaltenes. The DOPS surfactants injected after the water flooding are difficult to produce effective ways of detaching asphaltenes, while the introduced DOPS surfactants during water flooding can generate DOPS-ASPn combinations to detach asphaltene from the kaolinite surfaces. This work first investigates the effects of surfactants with different injection times on the oil detachment efficiency at a molecular scale, further deepening the understanding of oil detachment process via surfactant flooding.