Study on microstructure wax evolution behavior of waxy crude oil during cooling

Abstract

The microcosmic characteristics of wax evolution of waxy crude-oil directly affect the heat transfer process of crude-oil. A microscopic experiment was carried out on the wax deposit process of waxy crude-oil by polarized light microscopy. The phase change characteristics of wax crystals during wax deposit process were analyzed, and the process of wax crystal precipitation was quantitatively analyzed by the image analysis software ImageProPlus. The results show that the wax deposit process mainly includes wax crystal nucleation, growth and bonding, which together lead to the formation of wax crystal network. The sample oil particle number and the wax crystal area fraction curves have inflection points at 41 ? and 38?, respectively, which are caused by different carbon number alkane content and wax crystal bonding. By analyzing the particle size and particle area curves, it is known that nucleation precipitation and growth are alternately dominant in the early stage of wax crystal growth. Through the wax roundness study, it is found that the growth of wax crystals in the early stage is mainly in the longitudinal direction, and the growth in the late stage is not directional. According to the phase change process of wax crystal, it is proposed that the temperature of the crude-oil with porous media grid structure is coalescence point. By using the position point tracking of wax crystal and analysis of the variation characteristics of microscopic parameters, the coalescence point temperature of the sample crude-oil in this experiment is 38?.