Reducing viscosity of waxy crude oil with electric field perpendicular to oil’s flow direction

Abstract

It has been reported that the application of a high-voltage electric field parallel to the oil flow direction or to a quiescent waxy crude oil can reduce the viscosity of the oil. In this work, an electric field perpendicular to the flow direction is applied to a flowing waxy crude oil in a rheometer equipped with in-situ electric field manipulation, and it is observed that viscosity reduction similar to that obtained with electric field parallel to the flow direction can also be achieved. This, therefore, confirms that the treatment efficacy is insensitive to the direction of the electric field compared to the oil flow direction. Moreover, the non-Newtonian characteristics of the treated crude oil become less significant, and more viscosity reduction is achieved at higher electric field strength and lower oil temperature. After the removal of the electric field, the reduced viscosity gradually recovers and the viscosity reduction disappears after about two days. Though it is found that the electric treatment causes an increase in wax crystal size and aggregation of particles to some extent, we think that weakened interaction between wax particles due to electric field exposure should be the primary reason of the viscosity reduction according to the knowledge of suspension rheology and the mechanism of waxy crude oil rheology.