Investigation of Wax-Deposit Thickness in Oil and Water Emulsions: Facing the Development Trend of Intelligent Pipeline Operation

Abstract

In recent years, the concept of pipeline intelligence, or smart pipelines, has emerged as a promising approach to address various pipeline transmission issues. Intelligent control system requires the variation and thickness of wax deposition inside the crude oil transmission pipeline to make decisions to minimize wax deposition. This study aimed to investigate wax deposition in both polyethylene (PE) and stainless steel (SS) pipes under different water contents, utilizing a custom-designed flow loop apparatus. It was found that the wax-deposit thickness on the surface of the PE test section was thicker (water content lower than 50 vol. %) and then thinner (water content higher than 50 vol. %) than that on the surface of the SS test section. The radial diffusivity and wax mass flux were calculated and proved to be responsible for the behavior variation of wax deposition. The contact angles of oil and water on the PE surface were both larger than those on the SS surface. Experimental investigation was conducted to determine the phase inversion point of oil and water emulsions, which was found to be around 50 vol.%. The results indicated that when water was the bulk phase, greater water adherence to the steel pipe wall resulted in reduced wax deposition on the SS test section. As a result, distinct deposition behaviors were observed both before and after the phase inversion point.