Multivariate screening analysis of water-in-oil emulsions in high externalelectric fields as studied by means of dielectric time domain spectroscopy- III - Model emulsions containing asphaltenes and resins

The effect of crude oil resins with various polar characters on the stabili ty of w/o model emulsions containing asphaltenes is investigated using a mi xture design. The resins were extracted using an adsorption-desorption tech nique. One asphaltene fraction and four different resin fractions from one European crude oil were used. The stabilities are measured using time-domai n dielectric spectrascopy in high external electric field. It is found that resins with different polar character have different effects on the emulsi on stability. At asphaltene/resin ratios of 1 and 5 :3 the resins in some c ases lead to an emulsion stability higher than that of a similar emulsion s tabilized by asphaltenes only, while at low asphaltene/resin ratios (simila r to 1:3) the emulsion stability is reduced by the resins. The effect on em ulsion stability of combining two different resin fractions depended on the resin types combined as well as the relative amount of resins and asphalte nes. Also, an increase in the stability of some of the emulsions containing resins and asphaltenes for a period of 50-300 min after the emulsification was observed. This time-dependence of emulsion stability is attributed to the mobility of resins at the oh-water interface and the slow buildup of a stabilizing interfacial film consisting of resins and asphaltenes. (C) 2000 Academic Press.