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. Interfacial viscoelasticity of high-resins oil or high-asphaltenes oil and salinity water. Interfacial adsorption of heavy components heavily influenced the stability of W/O emulsion. The interfacial film was viscous when the adsorption of resins was dominated, while the film was elastic when the adsorption of asphaltenes was dominated. Therefore, compared with the high-asphaltenes oil-water emulsion, the viscous film enhanced the stability of high-resins oil-water emulsion, which caused the strong viscosifying behavior. [Display omitted] •Research was carried out to compare the viscosifying behavior of W/O emulsion.•The adsorption of resins increased the film viscosity and emulsion stability.•The interfacial film was elastic when the adsorption of asphaltenes was dominated.•The chain structure and the hydrogen bond enhanced the adsorption of resins.