An energy perspective on the mechanism of crude oil electrorheological effect

Abstract

Exposing a waxy crude oil to an electric field represents an emerging environmentally sound strategy for improving the cold flowability of oil. However, a substantial knowledge gap still exists regarding the quantitative relationship between the viscosity reduction and treatment parameters (field strength, treatment time, the volume of treated oil, etc.). This study endeavors to investigate the physical essence of the effect of these treatment parameters on the viscosity reduction and its duration. It was found when subjected to electric fields of varying strengths (0.5–5 kV/mm) for sufficient time, a same maximum viscosity reduction of approximately 40% can be achieved regardless of the applied field strength. Further research has elucidated that the factor determining the viscosity reduction is energy input, rather than the field strength as was reported previously, and the inputted energy may work in three stages: first, it works for initiating a decrease in viscosity. Subsequently, the continued energy input further reduces the oil viscosity and ultimately achieves a maximum reduction at that temperature. Then further inputted energy enhances the duration of the viscosity reduction. Fundamentally, the inputted energy density, i.e., the inputted energy per unit volume/mass of the oil, is the essential factor. These new findings facilitate further understanding of the negative electrorheological effect and its mechanism of crude oil and may help for the development of electric treaters for reducing crude oil viscosity.