Pore-scale investigation on the flow behavior and oil displacement of ultralow IFT surfactant flooding based on CFD simulation

In order to investigate the flow behavior and oil displacement of ultralow interfacial tension (IFT) surfactant flooding, the experimentally validated computational fluid dynamics simulation model is constructed by coupling the Navier-Stokes equations and the Cahn-Hilliard equation. The mixed surfactant solution is prepared using the ionic liquid surfactant and the nonionic surfactant, and the fluid parameters are measured experimentally. Due to the reduced oil-water IFT, the low pressure drop in porous medium and the decreased oil viscosity, ultralow IFT surfactant contributes to increasing the mobility ability of the fluid front in pores, and its optimal injection velocity is 0.01 m/s. In addition, the sweep area of surfactant flooding in oil-wet porous medium is significantly larger than that of brine flooding because of wettability alteration. Finally, for different porosity models, the residual oil content and the pressure drop of surfactant flooding show a 66.7% and 71.4% decrease than those of brine flooding, respectively, proving its better displacement performance.