Electrochemical modulation of oil-water interfaces: Effects on interfacial tension and molecular composition

Abstract

The application of a direct current (DC) electric field can effectively reduce interfacial tension, thereby enhancing fluid permeability and improving the potential for oil reservoir exploitation. This study investigates the effects of varying DC voltages on oil-water interfacial tension, considering parameters such as the pH of the aqueous phase, ion concentration, the composition of the oil phase (including its four-component makeup), oxidation–reduction potential, and molecular composition from an electrochemical perspective. The results demonstrate that the introduction of a DC electric field significantly reduces interfacial tension, with the effect becoming more pronounced as the voltage increases. Notably, in NaHCO₃-based formation water, the reduction in interfacial tension is especially remarkable, from 12.63mN/m to 0.08mN/m. Additionally, the reduction in interfacial tension is positively correlated with an increase in the pH of the aqueous solution and is more responsive to sodium ions compared to calcium ions. Concerning the oil components, the application of a DC electric field results in an approximate increase of 2% in asphaltenes and 10% in resins. The increase in resin content is one of the key factors contributing to the reduction in interfacial tension. Enhanced oxidative conditions promote the formation of asphaltenes and resins, while concomitant reductive reactions lead to an increase in methylene content and its branched structures. Crucially, the increase in carboxylate ion content plays a decisive role in the reduction of interfacial tension. This study not only refines our understanding of the mechanisms by which DC electric fields reduce oil-water interfacial tension but also provides new insights into the principles and mechanisms behind the improvement of crude oil recovery. These findings contribute to the advancement and broader application of this technology.