A new method for calculating the viscosity of W/O and O/W emulsion

The viscosity of water-in-oil and oil-in-water emulsions is a key parameter to understand during oil exploitation and transportation. Water content increases with the extraction of crude oil, especially in the middle and late periods of exploitation. Apparent viscosity increases as formation water content increases. However, apparent viscosity decreases when the water cut is beyond the phase transition point, after which, the water-in-oil emulsion becomes an oil-in-water emulsion. Many models for calculating the viscosity of W/O emulsions has been proposed, but methods for predicting the viscosity of O/W emulsions are rare. In this article, a method to calculate viscosity of W/O and O/W emulsions based on the Richardson and Taylor equations is introduced. Contrary to the existing correlations, the method presented here takes into account more factors, including water cut, temperature, shear rate, viscosity of oil and formation water. Additionally, whereas conventional correlations have been able to only calculate the viscosity of water-in-oil emulsions, the proposed method can also calculate the viscosity of oil-in-water emulsions. The accuracy and reliability of 5 conventional correlations and of this new method are assessed using the experimental data. The proposed model better fits the data when predicting the viscosity of W/O and O/W emulsions, with average absolute error of 12.71-16.43%.