Significant Reduction of the Viscosity of Waxy Oils by Electrical Treatment

Abstract

Abstract Wax crystallization at low temperatures sharply increases the viscosity of waxy oils, posing difficulties to their pipeline transportation. Conventional methods of lowering the viscosity of waxy oils include adding chemicals or externally heating the pipeline, both of which are energy costly and carbon intensive. In light of the need for low-carbon and sustainable energy production, we present an environmentally benign concept that lowers the viscosity of waxy oils by electric fields generated from renewable sources. The viscosity of model waxy oils (mineral oil + decane + paraffin wax) before and after electrical treatment was characterized by a rheometer equipped with an Electro-Rheology accessory. We monitored the oil's viscosity changes in three consecutive 10-minute stages: before, during, and after the application of DC electrical fields ranging from 0 to 3.5 kV/mm. The results show that the viscosity of waxy oils can be significantly reduced upon the application of electric fields and the highest viscosity reduction achieved is 82%. The magnitude of viscosity reduction strongly depends on the treatment temperature and the strength of the applied electric fields. Notably, the model oil systems used in this work contain no asphaltenes and resins, which challenges the widely agreed theories in the literature that the presence of charged colloidal particles like asphaltene and resin in waxy crude oils are the prerequisites for electrical treatment of waxy oils to be effective. The observed viscosity reduction is speculated to be caused by a combination of electrophoresis, Quincke rotation, and electrohydrodynamics. Overall, this technology of electrical treatment presents new opportunities to remediate wax-related flow assurance issues in a low-carbon and more sustainable manner.