Progress on Emulsification, Viscosity, Phase Inversion Characteristics, and Prediction Methods of Crude Oil–Water Mixed System

This paper provides the research progress on emulsification, viscosity, phase inversion characteristics, and prediction methods of crude oil-water mixed systems. In the development of onshore and offshore oilfields, oil and water are often transported through pipelines in a mixed state, and the shear strength within the pipelines promotes the formation of emulsions. Such emulsions significantly increase the effective viscosity of the mixture, thereby altering the flow characteristics and pressure drop of the pipelines. In-depth studies have revealed that the properties of this system are determined by the combined action of internal and external factors. Among the internal factors, the physical properties of crude oil and natural surface-active substances (such as asphaltenes) are core elements. They directly affect the stability of emulsions by influencing the interfacial tension, interfacial film strength, solid particle distribution, and electric double-layer status. External factors, represented by shear force, water content, and temperature, continuously regulate the degree of emulsification and the viscosity characteristics of the mixture. It is worth noting that the phase inversion point of crude oil emulsions, as a key parameter, holds significant guiding significance for oilfield production and pipeline oil-water mixed transportation processes. Based on this, future research should focus on three aspects: exploring the influence of aqueous phase properties on emulsification characteristics, establishing a unified viscosity prediction model that can integrate stable and unstable systems, and introducing big data technology to enhance the universality and applicability of research results. These efforts will provide strong support for optimizing process calculations in oilfield development and promote the in-depth integration of theoretical research and engineering practice.