Pore-Scale Wettability Alteration in Green Surfactant Flooding: A Lattice Boltzmann Study on Contact Angle Dynamics

Green surfactants not only enhance crude oil recovery but also provide considerable environmental benefits. Nonetheless, the mechanisms of dynamic interfacial evolution at the mesoscopic scale remain inadequately understood. This study proposes a multicomponent multiphase pseudopotential MRT model based on the lattice Boltzmann method for three-dimensional contact angle simulation. The model accuracy was validated through Laplace tests for interfacial tension and static contact angle calibration. Results demonstrate that the model satisfies numerical accuracy requirements while effectively capturing the dynamic evolution of contact angles. Using this model, the dynamic wetting behavior on oil-wet and water-wet surfaces was systematically investigated, enabling visual tracking and quantitative analysis of contact angle evolution. Furthermore, by quantifying the correlation among the parameters G _c, G _ads,1, and G _ads,2, the regulatory mechanism of three-phase contact angles and the wettability alteration on rock surfaces at the mesoscopic scale were revealed. This work provides a theoretical foundation for understanding multiphase flow behavior and evaluating oil displacement efficiency in porous media.