Performance and mechanism of a novel electro-magnetic treatment for improving the cold flowability of waxy crude oil

Abstract

Under the framework of achieving carbon neutrality, the transformation of pipeline transportation modes, coupled with the poor flowability of crude oil, has raised the standards for ensuring the flow assurance of oil pipelines. Improving the cold flowability of waxy crude oil is crucial for flow assurance. Previous studies have demonstrated that electric or magnetic treatment could have such efficacy. However, the combined treatment of electric and magnetic fields has never been investigated. This paper introduces such a novel exploration, revealing a quite encouraging synergistic effect on cold flowability improvement. Specifically, the crude oil was first exposed to a magnetic field above its WAT, followed by an electric field below the WAT. For the studied crude oil, the synergistic treatment achieved a 50 % reduction in viscosity, compared to 24 % and 30 % reductions for magnetic and electric treatment alone, respectively. Although magnetic treatment showed limited effect on weakening the structural strength of the oil gel, it significantly enhanced the effectiveness of the electric field, increasing the yield stress reduction from 77 % to 84 %. Attention must be paid to the non-monotonic influences of magnetic field strength, treatment duration, and temperature. Mechanistically, magnetic treatment reduced the crude oil’s impedance, indicating an enhanced dispersion of resins and asphaltenes. This improved dispersion allowed for greater adsorption of resins and asphaltenes onto wax particles during subsequent electric treatment, thus making the electric treatment much more effective. These new findings reveal the electro-magnetorheological effects of crude oil, guiding advanced flowability improvement technologies.