Experimental study on the wax deposit properties in the crude oil pipeline: Crystal morphology, yield stress

Radial properties of wax deposits in crude oil pipeline are of great significance for the selection of wax removal process. Herein, the wax deposits were obtained in a flow loop device and the important characteristics of wax crystal morphology and yield stress were quantitatively analyzed. The polarizing microscopic observations revealed that the amount and size of wax crystals increased in the radial from deposit surface to bottom, while the aspect ratio and boundary fractal dimension varied little, ranging from 1.68–1.80 and 1.61–1.75, respectively. In addition, the yield stress of wax deposit was found to increase with the rise of wax content and deposition duration, ranging from 5310–16,400 Pa in the cold flow experiments and 7550–24,500 Pa in the hot flow experiments. Furthermore, the bottom deposit was stronger in structure and presented higher yield stress than the surface deposit. This work provides a whole understanding on the wax deposit properties in different radial positions and is of great help to the analysis of pig force and pig selection.