原油电场改性机理研究进展与展望

Advance in investigation on mechanism of electric field treatment for improving the cold flowability of crude oil and its prospect

高压电场处理是一种新兴的原油改性方法,其物理原理既非电加热,也并非电场脱水,而是原油的负电流变效应。基于电流变学已有研究成果,总结了负电流变效应的几种机理;分析了以颗粒聚集成链、蜡晶颗粒变大及多分散性增强作为原油电场改性机理存在的问题。阐释了蜡晶界面极化机理的依据,蜡晶颗粒、胶质、沥青质共存是电场发挥改性效果的必要条件。在高压电场作用下,原油中的带电颗粒(胶质、沥青质)聚集于蜡晶表面,即界面极化,静电斥力削弱蜡晶之间的引力,宏观上体现为原油低温流动性改善。胶质、沥青质的行为是认识原油负电流变效应机理的关键,其主要包括3个过程,即电场作用下从体相向蜡晶颗粒运移、在蜡晶颗粒表面积聚、撤消电场后向体相扩散。未来,需要针对此3个过程进行深入、量化研究,以全面揭示原油电流变效应的科学机制。

High-voltage electric field treatment is an emerging approach to improve the cold flowability of crude oil, of which the physical principle is the negative electrorheological effect of crude oil other than electric heating and electric field dehydration. Based on the review of literatures on electrorheology, several mechanisms of negative electrorheological effect were summarized, and the problems in the electric field treatment mechanisms of crude oil, such as particle aggregation into chains, increasing the particle size of wax crystal, and enhancing the polydispersity, were analyzed. Besides, the basis of wax particle interface polarization was explained. Generally, the co-existence of wax particles, resins and asphaltenes is the necessary condition to realize the treatment effect of electric field. When a high-voltage electric field is applied, the charged particles(i.e. the resins and asphaltenes) in the crude oil would aggregate on the surface of wax crystal, which is the interface polarization. During the process, the electrostatic repulsion between wax particles is increased while their attraction is weakened, resulting in improved cold flowability of the crude oil. Therefore, the behavior of resins and asphaltenes in the oil is the key to understand the mechanism of the negative electrorheological effect of crude oil, which mainly includes three processes: the migration of resins and asphaltenes from the bulk phase to wax particles upon the application of electric field,accumulation of resins and asphaltenes on the surface of wax particles, and their diffusion back to the bulk phase after the removal of electric field. In the future, further in-depth and quantitative research should be focused on these three processes to fully reveal the scientific mechanism of the electrorheological effect of crude oil.