We demonstrate that the cold flowability of the waxy crude oil can be significantly improved via electrical treatment. A novel apparatus was assembled to electrically treat the waxy crude oil while simultaneously measuring its rheological properties. A method was developed to calculate the oil’s viscosity by using non-Newtonian fluid mechanics and rheological principles. Lower treatment temperatures, higher electric field strengths, and lower shear rates provided greater viscosity reduction. Notably, a viscosity reduction of 70% was obtained when the oil was electrically treated near its pour point for 90 s. Microscopic examinations indicate that the broader size distribution of wax particles in the treated oil might be responsible for the observed viscosity reduction. Besides, 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.

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Impedance spectroscopy (IS) is a widely used nondestructive and high-throughput experimental technique for the characterization of electrical properties of materials. In the petroleum industry, IS is frequently employed to determine the electrical properties of asphaltenes and resins. The electrical properties of waxy crude oils, which correlate significantly with the flowability, however, have received little to no attention in the existing investigations. In this work, we inspected the influence of wax precipitation on IS of waxy crude oil for the first time. The investigation was carried out in a frequency range of 2 × 10–1 to 2 × 104 Hz and a temperature range of 5–60 °C. It was discovered that the Nyquist diagram representing the electrical response of waxy oil evolves from one semicircle to two semicircles as wax molecules precipitate at temperatures below the wax appearance temperature. IS of waxy crude oil can be reproduced by an equivalent circuit model composed of two serially connected constant phase element-ideal resistance combinations (R bulk|Q bulk – R wax|Q wax). It was found that the resistor-like contribution from wax in the equivalent circuit model, R wax, increases with the amount of precipitated wax, whereas the capacitor-like contribution in the equivalent circuit model, Q wax, decreases with the amount of precipitated wax. Furthermore, the flow property of waxy oil, such as viscosity, can be related to the conductivity according to the fractional Walden rule. The entire viscosity–conductivity relationship can be divided into three regions, and each segment of the relationship can be fitted by the fractional Walden rule.

In this study, a spiral groove liquid film vaporization model based on the viscosity–temperature equation, fluid internal friction, saturation temperature, and pressure relationship equation was established. Using a multiphase flow model based on the finite volume method, the influence of the change in the mass transfer coefficient on the vaporization of the liquid film was studied. Moreover, the influence law of structural parameter changes in liquid film vaporization characteristics and sealing performance was analyzed. The results indicate that, with an increase in the mass transfer coefficient, the average vapor phase volume fraction first increases and then gradually stabilizes. When calculating the average vapor phase volume fraction, it is necessary to consider the influence of the mass transfer coefficient, whereas its effect on the opening force and leakage can usually be neglected. Under the optimal mass transfer coefficient conditions, the average vapor phase volume fraction increases with an increase in the helix angle, groove-weir ratio, and groove depth. By comparison, with an increase in the groove-diameter ratio, the average vapor phase volume fraction first increases and then decreases. The opening force decreases with an increase in the helix angle, groove-to-weir ratio, and groove depth. On the other hand, it first decreases and then increases with an increase in the groove-diameter ratio. The leakage rate increases first and then stabilizes with an increase in the helix angle. Moreover, it increases continuously with an increase in the groove-diameter ratio, groove-weir ratio, and groove depth.