Wax deposition and aging of waxy crude oil with high pour point and high viscosity

Cold finger experimental device was used for wax deposition experiment on three kinds of crude oil with high pour point and high viscosity with wax content of 20.95%, 27.5% and 35.0% respectively. Moreover, the high temperature gas chromatograph was adopted to analyze the changes of sediment composition, in order to study the aging phenomenon of wax deposition layer and identify the influence of temperature on aging phenomenon. The results show that, over the time, the deposition rate increases, especially to larger extent for the crude oil with larger wax content. As time goes further, the wax molecules with high carbon number diffuse to the deposition layer constantly and the wax molecules with low carbon number back-diffuse from deposition layer to oil flow, presenting the aging process. This process results in the increasing content of wax molecules with high carbon number and decreasing proportion of wax molecules with low carbon number in deposition layer. In the high temperature interval, the diffusion and back-diffusion are stronger and the relative changes of carbon number are more obvious. As temperature lowers, the maximum of waxy content in deposition layer occurs earlier.