Abstract
The Shunbei crude oil pipeline is prepared to use the unheated transportation process to transport waxy crudes. However, the wax formation in the pipeline is unknown. In order to predict the wax deposition of the pipeline, the physical property experiment of Shunbei crude oil was carried out through field sampling. The density, freezing point, hydrocarbon composition, and viscosity–temperature characteristics of crude oil are obtained. The cloud point and wax precipitation characteristics of the crude oil were obtained using the differential scanning calorimetry (DSC) thermal analysis method. Then, the wax deposition rate of the pipeline was predicted by two methods: OLGA software and wax deposition kinetic model. Finally, the optimal pigging cycle of the pipeline was calculated on this basis. The results show that: Shunbei crude oil is a light crude oil with low wax content, a low freezing point, and a high cloud point. Comparing the OLGA simulation results with the calculation results of the Huang Qiyu model, the development trend of wax deposition along the pipeline was the same under different working conditions. The relative error of the maximum wax layer thickness was 6%, proving that it is feasible for OLGA to simulate wax deposition in long-distance crude oil pipelines. Affected by the wax precipitation characteristics of Shunbei crude oil, there was a peak of wax precipitation between the pipeline section where crude oil temperature was 9.31–13.31 °C and the recommended pigging cycle at the lowest throughput was 34 days in winter and 51 days in spring and autumn.
Highlights
Safety is essential for the normal operation of pipelines [1,2,3,4,5]
In the process of crude oil pipeline transportation, when the pipeline temperature is lower than the cloud point of crude oil, the wax or paraffin of crude oil begins to precipitate and deposit on the pipe wall
The cloud point of the Shunbei crude oil is higher than the ground temperature at The cloud point of the Shunbei crude oil is higher than the ground temperature at the buried depth of the pipeline, and wax deposition occurs in the pipeline
Summary
Safety is essential for the normal operation of pipelines [1,2,3,4,5]. Among safety issues, wax deposition is a problem that cannot be ignored. The study of wax deposition management is significant in determining pipeline transportation process formulation and realizing an economical and safe operation. Most scholars believe that molecular diffusion is the management is significant in determining pipeline transportation process formulation and most realizing important of wax deposition. Molecular diffusion, aging, and shear peeling are considered the peeling, and aging, considering the hydraulic and thermal effects of wax deposition on most significant mechanisms influencing the formation of wax deposits [14,15]. The predicting state of wax is unknown It is necessary crude oil pipeline transportsand waxy crude bythe an unheated transportation to predictThe theShunbei wax deposition in the pipeline calculate optimal pigging cycle to process. To predict the wax deposition in the pipeline and calculate the optimal pigging cycle to ensure the economic benefits of pipeline operation
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