Rheological properties of coarse oil-water emulsions

Compared with stabilized oil-water emulsion, coarse oil-water emulsion tends to separate into two phases after setting aside, similar to the dispersion of two-phase flow. The existing superficial viscosity theory for emulsion is not suitable for coarse crude oil-water emulsion. In this paper, Haake RS6000 rheometer is used to measure flow curves at different oil content of coarse oil-water emulsion, and the effect of temperature on the coarse oil-water emulsion viscosity is observed at the same time. The results show that coarse oil-water emulsion shows different types of non-Newtonian fluid characteristics at different oil content. When water is the continuous phase, the emulsion shows the features of expansion fluid, when crude oil is the continuous phase, the emulsion shows features of pseudoplastic fluid. The emulsion viscosity increases gradually with the increase of oil content and reaches the maximum at 60% oil content. As oil content continues to raise, the viscosity start to decrease to pure oil's level. At different temperatures, the viscosity of the emulsion of the same oil content decreases exponentially as the temperature increases. In addition, based on the experimental data, the existing oil-water emulsion viscosity calculation model is evaluated, and the viscosity model for coarse oil-water emulsion with low oil content is corrected, resulting in improvement in its prediction accuracy. The study results of rheological properties of coarse oil-water emulsion will enhance the prediction accuracy of pressure drop in the pipeline of crude oil exploitation and transportation, and provide a reliable physical parameters to the design of pipeline transportation system.