The Research of Yield Stress of Waxy Crude Oil

Yield stress is an important rheological property of waxy crude oil. It can represent the gel strength of waxy crude oil and the extent of difficulty of restart of pipeline in shut-down. The research advances in yield stress are reviewed. The influence factors of yield stress of waxy crude oil are analyzed. They mainly include the heat history, shear history, the composition and the holding time. There are mainly two groups of measurement methods of yield stress, i. e. the direct method and indirect method. All kinds of measure ment methods are summarized and analyzed. Some factors such as the geometry dimensions of measurement system, wall property and time influence the measurement result of the yield stress. According to the problems in the cogitation and research, some suggestions are proposed.