Reason analysis for difficulties of restart after shutdown in Wei Jing pipeline

In recent years, oil transportation process with depressant has been adopted in Wei Jing pipeline. A-long with changing operating conditions over the pipeline, the original oil transporting condition can not be shifted simply to a new transporting process. In order to determine pipeline's safety shutdown time under new process condition, restart after shutdown test is carried out at Wei Jing pipeline site. The article discusses preparing works before restart after shutdown operation, shutdown condition and restart after shutdown process, and analyzes reasons of difficulties found in the period of restart after shutdown process: (1) uneven crude oil inside pipeline and great difference in oil quality; (2) serious pipe wall wax deposition and small equivalent pipe diameter; (3) large pipeline fluctuation forms mechanical admixture and deposition of wax. It also puts forward a number of proposals for future pipeline operation.