Variation of yield stress of Daqing crude oil with pipelining history

Abstract

The yield stress of waxy crude oil is a fundamental parameter in the calculation of pipelining technique and analysis of flow safety for the heated oil transported through pipeline. Daqing crude oil was studied and the variation of yield stress with shear history was explored through simulation experiment of pipelining. It is found that the effect of throughput variation or shear rate on yield stress is not obvious. With the decrease of final dynamic cooling temperature, the yield stress of waxy crude oil decreases, but there exists a little increase at the beginning. The prediction model of yield stress for waxy crude oil under the condition of shutdown is developed and it can be used to predict the yield stress of Daqing crude oil at certain heating temperature, final dynamic cooling temperature and measurement temperature. For the 139 groups of yield stress data of Daqing crude oil from the simulation experiment of pipelining, the result of prediction with this model shows that the average relative deviation between the yield stress measured and predicted is 30.27%, and the coefficient of correlation is 0.962 3.