Hydrate accident and prevention in Sebei-Xining-Lanzhou Gas Pipeline

Sebei-Xining-Lanzhou Pipeline passes through cold regions in the northwest plateaus of China. Due to gas with higher moisture and pipeline not being complete dried in the operation process, liquid water occurs in the pipeline, so that pipelines are vulnerable to frozen hydrate blockages. For the hydrate blockage accident which occurred at the Terminal Station in Lanzhou of Sebei-Xining-Lanzhou Gas Pipeline in winter of 2010, the dew point of gas and operating parameters of the pipeline were analyzed. The dew point value of natural gas was converted into water content value, and the water content value and process operating parameter scope obtained from the analysis were used to compare with hydrate formation condition parameters. Based on comparative results, operating parameters of the pipeline were controlled to prevent the formation of hydrate. The method to prevent hydrate formation by inhibitor injection and calculation method of the concentration were introduced. Practices in hydrate control technology in the pipeline hydrate accident indicated that compared with the inhibitor injection method, the method to detect gas parameters and monitor pipeline process operating parameters for preventing hydrate formation in the gas pipeline system can meet the requirements of operation and is more economic and safe.