Laboratory study on the transformation of oil-water interface properties under direct current electric field

Interface tension is one of the important mechanisms that affect crude oil recovery and plays an important role in the development of tight oil reservoirs. Electrical-enhanced oil recovery can be used as a technology to reduce interfacial tension and improve crude oil recovery. In the previous research process of Electrical-enhanced oil recovery, the focus was more on the influence of electric field on wettability, and the understanding of the changes in interfacial tension under electric field action is not yet comprehensive. This article designs an orthogonal experiment to study the effect of electric field on oil-water properties. The degree of influence of three factors, namely sodium chloride solution concentration (C), direct current voltage (V), and voltage action time (t), on interfacial tension is studied. Gas chromatography, four component analysis, and Fourier transform infrared spectroscopy are combined to discuss the mechanism of the influence of changes in solution pH, crude oil components, and oil phase functional groups on interfacial tension. The results show that an external electric field can effectively reduce the interfacial tension between oil and water, and the maximum change in interfacial tension after the experiment can be reduced from 23.21 mN/m to 0.37 mN/m; Through range analysis, it can be concluded that the concentration of sodium chloride solution has the greatest impact on interfacial tension, followed by DC voltage and voltage action time. The optimal experimental conditions are 0.5 mol/L sodium chloride solution, 10 V DC voltage, and a voltage action time of 18 h, and the change in interfacial tension is related to the increase in pH value. The change in crude oil composition is also an important reason for the decrease in interfacial tension under external electric fields. Finally, Fourier transform infrared spectroscopy was used to determine that under the action of an electric field, the increase in pH of the sodium chloride solution resulted in the formation of carboxylate salts through chemical reactions between alkaline substances of solution and acidic substances of the oil, which were the key factors in reducing interfacial tension. This study helps to understand and explore the principles and mechanisms of Electrical-enhanced oil recovery in improving oil recovery, with the aim of contributing to the development and promotion of Electrical-enhanced oil recovery technology.