Wax deposition laws and diffusion coefficient of oil-water emulsion

Wax deposition is one of the key problems that occur in waxy crude oil pipelines, but research has rarely been conducted on wax deposition of oil-water emulsion. In this paper, experiment samples are prepared with Daqing Crude Oil (water cut of 0) and its emulsions with water cut of 10%, 20% and 30%. Cold finger experiment facilities are used to analyze wax deposition laws of oil-water emulsion by changing the variants, including cold finger temperature, temperature difference between cold finger and tank wall, and water cut. It is shown by the experiment that at the same temperature difference, the volume of wax deposit rises with the decrease of oil tank temperature, but decreases with the rise of water cut. The calculation method of wax deposition diffusion coefficient is deduced and its distribution laws are obtained. Diffusion coefficient decreases with the decrease of average temperature and increase of water cut. The effect of water phase on diffusion coefficient is more in high-temperature interval than in low-temperature interval. The research findings are practically significant for understanding wax deposition laws of Daqing waxy crude oil pipelines and determining their pigging cycles.