Prediction of the apparent viscosity of non-Newtonian water-in-crude oil emulsions

Abstract

On the basis of the effective medium theory and the classical viscosity prediction model proposed by Pal et al, the apparent viscosity and rheological properties of the water in crude oil emulsion with natural surface active components such as asphaltene and resin are predicted. The adsorption and entrainment of continuous phase by the surfactants molecular, which leads to the increment of effective water fraction, is the inducement of Non-Newtonian behavior in the bulk emulsion. The two actions of promoting and counteracting effects on the effective water fraction are considered separately and represented by Water Fraction Factor and Particle Reynolds Number Factor respectively. The Water Fraction Factor takes into account the positive effect of water fraction and drop size distribution in microscope, while the Particle Reynolds Number Factor reflects the negative effect of shear rate at different drop size. A new prediction model taking the influence of nearly all factors such as drop size distribution, shear rate, water fraction into consideration was built. Measured viscosity of emulsion of the crude oil and water from an oilfield was used to verify the predicted results of the model, which proves that the new model is high in accuracy with a maximum relative error of 11.44%. Key words: water-in-crude oil emulsion, non-Newtonian property, apparent viscosity, drop size distribution, prediction model