A universal route to deciphering the internal mechanism of crude oil self–emulsification

Abstract

Crude oil emulsions generated during the life period of crude oil from production and separation comprise a fascinating interdisciplinary topic that is being actively studied in both chemical science and engineering. However, a comprehensive understanding of the emulsification mechanism based on a sound chemicophysical foundation for the natural emulsifiers of crude oil remains challenging and is not well established. In this study, we developed a framework that combines crude oil separation, molecular structure characterization and inference, self–assembly of natural emulsifiers at the oil–water interface, and phase behavior of natural emulsifier emulsions to decipher the self–emulsification of crude oil. Our results revealed that crude oil components have independent and synergistic effects on the formation and stabilization of crude oil emulsions. Asphaltene has the highest molecular weight and the strongest interfacial activity compared to other components, significantly contributing to the formation of crude oil emulsions. As the second highest molecular weight crude oil component, resin is the solvent for asphaltene. Aromatic and saturated hydrocarbons adsorbed at the oil–water interface form an interfacial viscoelastic film that mainly stabilizes the crude oil emulsion. The viscosity of crude oil emulsions is mostly affected by asphaltene and resin, while their phase inversion point is primarily determined by aromatic and saturated hydrocarbons. These results provide a universal insight into the internal emulsification mechanism of crude oil. We expect that these findings will also provide theoretical support for taking advantage of crude oil emulsions for the purpose of efficient oil recovery.