Study on the relationship between viscosity reduction and energy density in electric treatment of crude oil and related mechanisms

Objective Electric treatment is a new method to improve the cold flowability of waxy crude oil. Previous studies on Jiudong crude oil have identified the input energy density of the electric field as a key factor in reducing the viscosity of waxy crude oil. When the input energy is sufficiently high, the electric treatment can achieve the maximum viscosity reduction at a given temperature. To guide the industrial application of electric treatment for crude oil, further verification of this conclusion’s applicability to other crude oils is essential.

Methods The relationship between input energy and viscosity reduction rate for Changqing crude oil and Daqing crude oil was investigated by examining the influence of varying electric field treatment conditions (field intensity: 0−3 kV/mm, treatment time: 0−1,200 s, treatment capacity: 1.0−2.5 mL) on the viscosity reduction effect.

Results The energy density threshold for the maximum viscosity reduction was defined for the first time, indicating the minimum energy density required for crude oil to achieve the maximum viscosity reduction through electric field treatment. The impact of treatment temperature (cumulative wax precipitation) on the maximum viscosity reduction and the corresponding energy density threshold was assessed. As treatment temperature decreased, the maximum viscosity reduction increased, while the corresponding energy density threshold decreased. The intrinsic reasons were analyzed through microscopic examination, focusing on the mechanisms of migration and adsorption of charged colloidal particles. At lower treatment temperatures, more wax particles were influenced by resin and asphaltene. The presence of more and larger wax particles increased surface charges under the electric field, promoting the migration of resin and asphaltene to the wax particle surface via dielectrophoresis, resulting in greater accumulation. Consequently, the maximum viscosity reduction increased, and the energy density threshold required became lower.

Conclusion The research results facilitate the understanding of the mechanism behind the electrorheological effect of crude oil, and the discovery of the energy density threshold offers a valuable reference for determining and optimizing processor power parameters.