Effect of Naphthenic Acid and Metal Ions on Emulsification of Heavy Oil

The emulsification of heavy oil is universal in various stages of heavy oil extraction, processing, and transportation. In this study, molecular dynamics simulations were employed to reveal the emulsification of heavy oil from different regions. When the water mass fraction is low, metal ions in the Karamay emulsion exist at the oil-water interface and interact with naphthenic acid (NA), which results in strong emulsion stability. The dominant interactions between resin and water molecules cause weak emulsion stability for Liaohe and Canada heavy oils. On the basis of the thermodynamic analysis, we found that the interaction between the metal ion and NA in the Karamay emulsion is much stronger than the interaction between the asphaltene/resin molecules and water molecules in Liaohe and Canada emulsions, which is the main reason for stronger emulsion stability in the Karamay region. As the water concentration increases, the emulsion stability of Karamay heavy oil will have a significant change as a result of the lower metal ion concentration. The water-phase structures and emulsion viscosity were investigated, and the water aggregations present spherical, worm-like, stick, net, and honeycomb structures with the increase of the water concentration. The breakup of the emulsion structure leads to a sudden decrease in the viscosity of the Karamay heavy oil