The viscosifying behavior of W/O emulsion and its underlying mechanisms: Considering the interfacial adsorption of heavy components

Formation of water-in-oil (W/O) emulsion seriously limits heavy oil production, and the interfacial adsorption of heavy components of oil is the key to clarify the emulsification of crude oil and formation water. In this study, the viscosifying behavior of W/O emulsion was correlated with the interfacial adsorption of heavy components using two typical heavy oil samples, i.e., high-resins oil and high-asphaltenes oil. Results showed that the resins, instead of the asphaltenes, contributed to the pseudoplastic behavior of W/O emulsion. The interfacial adsorption of resins presented the lower interfacial tension (IFT), the higher interfacial viscosity and the stronger film stability. However, when more asphaltenes was adsorbed on the interface, the film of oil-water interface changed from viscous to brittle and breakable. According to the composition analysis, the interfacial activity of resins was much stronger than asphaltenes. Besides, the W/O emulsion formed using model oil with resins performed the better stability compared with that formed using model oil with asphaltenes. This study provided that the interfacial adsorption of resins enhanced the emulsifying ability of crude oil and the film stability of W/O emulsion, which heavily aggravated the viscosifying behavior.