Abstract: Viscosity of water-oil emulsion is an important parameter for oilfield development, which should be measured in condition of high temperature and high pressure using rheometer, when matching the formation conditions of an oilfield. The study shows that the point of reverse phase of water-oil emulsion occurs at water cut from 40% to 60%, by which the mathematical model for the emulsion viscosity prediction is developed. The viscosity variation is accordant with Gaussian and Lorentzian functions. That is, the viscosity of water-oil emulsion will be decreased with increase of gas-oil ratio, similar to the law of gas-free emulsion viscosity at normal temperature and pressure. These results provide the theoretical bases for oilfield development.

Key words: emulsion, water cut, viscosity, rheology, characteristic, law