Effect of Asphaltenes and Resins to the Stabilization of Water-in-Oil Emulsions

The formation of water in oil emulsions is a problem that can arise during the recovery, treatment, and transportation of oil. In refineries, water-in-oil emulsions are deliberately created and then broken to wash-out contaminants that are present in the produced water emulsified in the oil. Fine solids, asphaltenes, and resins all play a significant role in the stabilization of water-in-hydrocarbon emulsions. Asphaltenes and native solids act as emulsion stabilizers while resins destabilize emulsions. The asphaltenes appear to absorb as a monolayer with interfacial configurations that depend on asphaltenes concentration. The highest packing density occurred at high concentrations but led to less stable emulsions. The most likely explanationis that there fewer points of attachments to the interface per moleculeat at higher packing density and the interface is more fluid and the emulsions less stable. The interfacial composition was determined from a combination of emulsion surface area measurements of both the continous and the emulsion phases. The concentration was found from gravimetric analysis. The stability of model emulsions was assessed from the amount of the water resolved after heating and periodic contrifugation of the emulsions. Asphaltene surface coverage was found to increase with an increase in asphaltene bulk concentration until a limiting surface coverage was achieved. While asphaltenes tend to stabilize these emulsions, the stability of emulsions decreased as asphaltene surface coverage increased.