The transportation technology of waxy crude oil treated with pour point depressant was investigated in laboratory. Several pour point depressants were evaluated and the optimal treating conditions were determined. Furthermore, the influences of the sudden temperature drop when mixing with cold oil and the high-speed shearing exerted by centrifugal pump were analyzed. In addition, the treating effect in the whole pipeline was verified by reproducing the cooling rate and shear rate of the pipe flow with in-door experiment. The blend oil could be transported safely with the treatment technology of pour point depressant in winter.
When the temperature of waxy crude oil drops below its wax appearance temperature (WAT), wax components will precipitate forming wax crystals. These crystals can gradually develop into a three-dimensional network structure, which deteriorates the flow ability of crude oil. If the oil temperature was below its pour point, oil will totally lose its flow ability and show up solid-like properties, as described by Visintin et al. (2008) and Fan et al. (2022). As to long-distance oil pipelines exposed to cold surroundings, oil temperature will drop significantly during transportation. Crudes with high wax fraction tend to gel at a comparatively high temperature. Once there was oil gelation incident in a certain pipeline section, oil transportation would be interrupted and the pipeline might even rupture because of overpressure.
In waxy crude oil pipelines, heating transport technology is commonly used to guarantee operating safety. However, as being reported by Zhang et al. (2013), the application of this technology spends a huge amount of energy, as well as the invested capital and manpower of heat stations. For some waxy oils with high pour point or low flow rate, it would be impossible to maintain oil temperature at a safe level even with heating in some cold regions with low soil temperature.
