Modification Effect of Asphaltene Subfractions with Different Polarities on Three kinds of Solid Nanoparticles and Their Costabilization of Crude Oil Emulsion

Fluids with complex components in oil field pipelines are mostly transported in the form of an emulsion. Asphaltene is an important natural surfactant in crude oil, and fine particles entrained in oil play a key role in Pickering stabilization. Therefore, it is necessary to study the synergistic impact of their coexistence on the stability of emulsions so as to develop an efficient demulsification scheme. In this work, the water contact angle and adsorption amount were first measured to evaluate the interaction between asphaltenes and three kinds of solid particles. Next, the bottle test and interfacial rheological experiment were carried out to verify the costabilization effect of the two substances. Further, the structural characteristics of the oil–water interfacial film were examined. It was confirmed that the concentration and polarity of asphaltenes affect their interactions with solid particles. At lower concentrations (500 ppm), the asphaltenes have a limited effect on altering the wettability of the solid particles, leading to a decrease in the interfacial film strength and weakening of the emulsion stability. Conversely, at a higher concentration (3000 ppm), the increased adsorption amount of the asphaltenes on the particle surface enhances the modification effect, and the asphaltenes can effectively fill the gaps between the particles at the interface, thus strengthening the interfacial film and ultimately improving the emulsion stability. In addition, the bottle test results reveal that the emulsions containing asphaltene subfraction ASP3 exhibit the smallest oil separation ratio. The water contact angle and adsorption amount show that the asphaltenes with weaker polarity have a better modification effect on the solid particles, while the emulsions containing ASP2 hold the strongest interfacial film. Therefore, it is concluded that under the combined influence of spatial hindrance, electrostatic repulsion, and the structural strength of the interfacial film, the particles modified with the asphaltene subfractions with appropriate polarity can best inhibit the creaming of emulsions.