Water-in-Oil Emulsions: Formation and Prediction

摘要

The formation of water-in-oil emulsions was described. Research has shown that asphaltenes are the prime stabilizers of water-in-oil emulsions and that resins are necessary to. solvate the asphaltenes. It has also been shown that other factors play a role, including the amount of saturates and the oil viscosity and density. Essentially, water droplets injected into the oil by turbulence or wave action can be stabilized temporarily by the oil viscosity and on a longer-term basis by resins and then asphaltenes. Depending on the starting oil properties, four types of water-in-oil types are created: meso-stable and stable emulsions, entrained water-in-oil and unstable or those-that-do-not-form types. Each type with unique properties was described. For most oils, loss of lighter components by evaporation is necessary before the oils form a water-in-oil type. It was noted that variability in emulsion formation is, in part, due to the variation in types of compounds in the asphaltene and resins groups. Certain types of these compounds form more stable emulsions than others within the same asphaltene/resin groupings. A review of numerical modelling schemes for the formation of water-in-oil emulsions was given. A recent model was based on empirical data and the corresponding physical knowledge of emulsion formation. The density, viscosity, asphaltene and resin contents were correlated with a stability index.