Determination of critical scour stripping conditions for tank bottom deposits during pipeline transportation

Abstract

Waxy crude oil stored in the tank for a long time will form tank bottom sediment. The settling of tank bottom deposits in oil flow during the pipeline transportation of waxy crude oil will reduce the pipeline transportation capacity, and even block the pipeline in severe cases. Herein, the settling and scour transport law of tank bottom deposits during transportation were explored through numerical simulation and the laboratory loop experiment. As indicated by the simulation results, the suspended tank bottom deposits in the low-velocity oil flow are apt to accumulate at pipeline bottom because of the weak carry-over capacity of the oil flow. Besides, the laboratory loop scour experiment shows that the scour stripping effect of oil flow to the pipeline bottom deposits depends on the balance of oil flow scour stress against the shear strength of tank bottom deposit. Hence, the laboratory experiment results were adopted to establish a calculation relation between the critical scour stress and the shear strength of the deposits. The results predicted by this relation are further verified by the experimental results and the results of field scouring operation. Therefore, it is recognized that the study is of great popularization and application value in the field of tank bottom deposit treatment technology for crude oil pipeline.

Keywords

• waxy crude oil pipeline
• tank bottom deposit
• settling
• scour transport
• critical scour stress