Predicting the emulsion phase inversion point during self-emulsification using an improved free energy model and determining the model applicability

Abstract

In-situ emulsification has recently shown promise for increasing oil production in water flooding reservoirs owing to its easy procedure and polymer and surfactant properties. The phase inversion point (PIP) plays a vital role in emulsification technology. However, the existing free energy models have limited accuracy in the calculation of the PIP, and the models’ areas of applicability are not specified. The free energy model was improved in this study by classifying crude oil to enhance the prediction accuracy and expand the free energy model’s range of calculation. The applicable range of the model was defined by analyzing and comparing the distribution characteristics of interfacial tension (IFT) and PIP. Firstly, the effects of temperature, shear rate, shear time, salinity, and pH on the PIP were discussed. The experimental results showed that, among these external factors, only the temperature could change the PIP. Generally, the PIP decreased with increasing temperature. Second, different parameters a and b were obtained using the differential aggregation characteristics of oil and water.Then, to further analyze and demonstrate the new model’s accuracy, the experimental data of three new oil samples (crude oil D, G, and J) were collected and compared with the results of other models. The results showed that the new model could successfully fit the data; its average absolute error was 4.47%, while that of the previous models was about 40%. The other models were particularly unsuitable for calculating the PIP of heavy oil, but the new model’s inaccuracy was only 1.48%. Finally, the IFT and PIP data were analyzed and compared. The results showed that, for conventional crude oil, the IFT and PIP decreased with the temperature increase. The applicable conditions of the model were also clarified. The model is suitable for crude oil whose IFT decreases with temperature increase. The results of this study can be used in the petroleum industry and other industries dealing with mixed immiscible fluid transport.