Influence Mechanism of Multicomponent Co-adsorption Behavior on the Stability of Oil–Water Interfaces in Shear Flow Fields: Insights from the Microscale

The co-adsorption of asphaltene, resin, surfactant, and polymer molecules at an oil–water interface forms a self-assembled structure that critically determines the stability of the interfacial film. A comprehensive understanding of the influence mechanism of this co-adsorption behavior on the interfacial film is of paramount importance for regulating emulsion stability during the processes of crude oil production and transportation. Therefore, models of water-in-oil emulsion droplets were established on the basis of the complex component characteristics of crude oil-produced fluids. A shear flow field was then generated by introducing two moving plates onto the upper and lower surfaces of the models. Utilizing a molecular dynamics simulation method, the influence mechanism of multicomponent co-adsorption affecting the stability of the oil–water interfacial film in the shear flow field is explained. The laws of shear velocity, pH, temperature, and pressure that influence this interfacial stability are revealed. The results indicate that increasing the shear velocity and temperature reduces the packing fraction of molecules in the interfacial adsorption layer and diminishes the hydration ability of surfactants, thereby resulting in a weakening interfacial film strength. As the pH is increased, influenced by the double-layer effect generated by the hydrolysis of partially hydrolyzed polyacrylamide (HPAM) molecules, the radius of gyration of the HPAM molecules initially increases and then decreases. Consequently, the stability of the oil–water interface does not increase linearly. As the pressure is increased from 0.1 to 4.0 MPa, the packing fraction of the interfacial adsorption layer molecules rises from 0.324 to 0.362. Concurrently, the hydrogen-bonding interactions between this layer and water molecules is strengthened, enhancing the stability of the oil–water interface film.