Impacts of shear and thermal histories on the stability of waxy crude oil flowability improvement by electric treatments

Abstract

Recent studies have shown that the poor flowability of waxy crude oil can be obviously improved by the application of an external electric field. Available studies about this novel technique to treat waxy oils focus on the efficacy of this technique while the sustainability of the efficacy is not well understood. In this work, the impacts of shearing and thermal cycling on the stability of the electric treatment efficacy were investigated. A representative waxy crude treated by electric field was subjected to shearing at different conditions and reheating to an elevated temperature and cooling, then the viscosity and the yield stress were inspected and wax particle microscopic images were observed to examine the impacts of shear and thermal histories on the sustainability of waxy crude oil flowability improvement by electric treatment. The experimental results show that the electric treatment efficacy of waxy crude oil gradually diminishes after the removal of electric field. However, shearing at a high shear rate and for a prolonged duration partially preserves the efficacy of the electric treatment and intensively shearing the electric treated oil provides some additional flowability improvement. The flowability improvement by electric treatment is weakened by reheating the treated oil to an elevated temperature. When the treated oil is heated above the wax dissolution temperature, the efficacy of the electric treatment is eventually eliminated. The results presented in this work further the understanding of the flowability improvement of waxy crudes by electric treatment.