A Mathematical Model for Predicting the Viscosity of Oil Emulsions as a Function of Water Cut

The formation of oil–water emulsions following reservoir-water breakthrough is widely observed during oil production. The viscosity of these polydisperse systems may increase sharply with increasing water cut, creating substantial operational difficulties in well-gathering systems and increasing hydraulic pressure losses. The rheological behaviour of oil emulsions is influenced by the phase ratio, flow velocity, degree of dispersion, temperature and several other parameters. However, no generally applicable model is currently available for describing the rheological behaviour and predicting the properties of oil emulsions, which are anomalous and rheologically complex systems. Therefore, developing a reliable method for estimating the viscosity of stable emulsions while accounting for increasing water content is of considerable practical importance. This study evaluates existing empirical correlations used to characterise the rheological properties of oil emulsions. The analysis shows that their application under oilfield conditions is associated with several limitations and that, in many cases, they are unsuitable for solving practical engineering problems. Accordingly, a mathematical model was developed and validated for estimating and predicting the viscosity of structurally stable oil emulsions as a function of water cut. The proposed model demonstrated good agreement with the experimental data and may be used for engineering calculations related to the production and transportation of water-cut oil.