Studies of water-in-oil emulsions : formation of water-in-oil states from heavy oils

The formation of water-in-oil states from heavy oils was examined. Previous studies have demonstrated that viscosity is a significant factor affecting the formation and stability of water-in-oil emulsions. It was suggested that a viscosity window is a necessary requirement for the formation of stable emulsions. Highly viscous oils produce an entrained water state. A stable or meso-stable emulsion is rarely produced by heavy oils. In most cases, heavy oils result in an entrained water-in-oil state that lasts days longer than the entrained water-on-oil state of lighter oils. This can be explained by the lower migration rate of water droplets from a heavy oil compared to that of a light oil. These results were used to conduct an evaluation of the basis for using the stability index. This index provides a quantitative characterization of the stability of an emulsion, under varying formation regimes. The stability factor has been previously defined as the complex modulus of the water-in-oil state after emulsion formation, divided by the starting oil viscosity. It was shown that this stability factor remains a robust indicator, despite being less predictive in the case of heavy oils. The use of the newly developed stability scale produced values that were similar for water-in-oil states of both light and heavy oils. It was concluded that this new stability scale is complex, but the discriminating power over the old stability scale is not better. 6 refs., 6 tabs., 2 figs