(201g) Electrical Treatment of Waxy Crude Oil to Address Wax-Related Flow Assurance Issues

Authors: 
Lu, Y., University of Tulsa
Ma, C., National Engineering Laboratory for Pipeline Safety/MOE Key Laboratory of Petroleum Engineering/Beijing Key Laboratory of Urban Oil & Gas Distribution Technology, China University of Petroleum, China
Zhang, J., National Engineering Laboratory for Pipeline Safety/Ministry of Education (MOE) Key Laboratory of Petroleum Engineering/Beijing Key Laboratory of Urban Oil & Gas Distribution Technology, China University of Petroleum (Beijing)
Chen, C., National Engineering Laboratory for Pipeline Safety/MOE Key Laboratory of Petroleum Engineering/Beijing Key Laboratory of Urban Oil & Gas Distribution Technology, China University of Petroleum
Wang, X., National Engineering Laboratory for Pipeline Safety/MOE Key Laboratory of Petroleum Engineering/Beijing Key Laboratory of Urban Oil & Gas Distribution Technology, China University of Petroleum, China
Waxy crude oils account for a significant portion of petroleum reserves. The wax precipitation from waxy crude oils caused by temperature reduction may manifest into several wax-related flow assurance issues including enhanced viscosity, wax deposition, or gelled pipeline. In the present work, we demonstrate a novel method of electrical treatment that shows great promises in addressing these issues. First, the low-temperature viscosity of waxy crude oil could be significantly reduced by treating it with high-voltage direct electric field. A highest viscosity reduction of 70% was obtained after the crude oil was electrically treated at 0.8 kV/mm for 90 s. The energy consumption of the electrical treatment was estimated to be less than 1% of that of the conventional heating method to achieve the same viscosity reduction performance. Interestingly, the heavy and polar components of crude oil such as asphaltenes and resins are found to undermine the performance of electrical treatment. Moreover, electrically treating waxy crude oil below the wax appearance temperature can also significantly reduce the overall strength of the formed waxy gel, which might facilitate the restart of a gelled pipeline. The results from microscopic observations indicated that the polarization and aggregation of wax crystals in the electric field might be responsible for the observed effects of electrical treatment. These findings suggest that electrical treatment may serve as a promising and energy-efficient technique to address wax-related flow assurance issues.
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