Effect of shear on durability of viscosity reduction of electrically-treated waxy crude oils

Abstract

Applying a high-voltage electric field to waxy oil can significantly reduce its viscosity near the pour point, and the viscosity recovers gradually after the removal of the electric field. The impact of shear, which is an inevitable occurrence during oil pipeline transportation, on the durability of viscosity reduction remains inadequately explored. In this study, four waxy crude oils were subjected to electric fields with various strengths, and the effect of shear on the viscosity and impedance of treated oils was evaluated. The results revealed that a higher field strength promotes the accumulation of more colloidal particles (asphaltenes and resins) on wax particle surfaces, resulting in longer maintenance of viscosity reduction. Shear exhibited a contrasting impact on electrically-treated oils’ viscosity: it hastened the disappearance of the modification effect of oils with low liquid phase viscosity and small colloidal particle size, but preserved the viscosity reduction of oils with high liquid phase viscosity and large colloidal particle size. Further investigation revealed that shear disrupted the interconnection between colloidal particles and wax particles, and promoted the collision and adhesion of free-moving colloidal particles with wax particles. The competition between these two effects determined the effect of shear on the viscosity of treated oils.