An evaluation method for the effect of DRA in a batch-transportation crude oil pipeline

For the field test of crude oil added with drag reduction agent (DRA) in a batch-transportation pipeline, the pressure difference between the initial station and the terminal station depends on the effect of DRA and the proportions of different crude oils in the pipeline, so the DRA effect can not be evaluated by the traditional method which is applicable to single crude oil pipeline. In this paper, considering the practical batch transportation of North Xinjiang crude oil and Kazakhstan crude oil via the Urumqi-Shanshan Crude Oil Pipeline, a new method was proposed to evaluate the effect of DRA in the process of batch transportation. If the crude oil with DRA injected at the initial station is of the same type as the one without DRA off-taken at the terminal station, and the proportions of different crude oils in the pipeline are constant, the drop of the pressure difference between the initial station and the terminal station is only attributable to the effect of DRA. Based on the length of the pipeline section transporting crude oil with DRA, the friction generated by the transportation of crude oil without DRA in this pipeline section was theoretically calculated. The ratio of the drop of pressure difference between the initial station and the terminal station to the friction is defined as the drag reduction ratio of DRA contributing to the crude oil in the pipeline. The field test results show that, when DRA-A is added, the drag reduction ratio for the transportation of Kazakhstan crude oil via the Urumqi-Shanshan Crude Oil Pipeline is 31.4%-34.7% if the flow rate is 410-600 m³/h; when DRA-B is added, the drag reduction ratio is 15.8%-17.2% if the flow rate is 550-933 m³/h.