Study on Decomposition Characteristics of Natural Gas Hydrate in Pipeline under the Condition of Thermodynamic...

Hydrate deposits in gathering pipelines for deep-sea oil and gas extraction can reduce the flow area of the pipeline and, in severe cases, cause pipeline blockage, resulting in huge economic losses. A high-pressure reactor and a semicircular pipe were used to simulate hydrate decomposition in a pipe wall environment. A steel plate of the same material was used to investigate the decomposition mechanism of thermodynamic inhibitors under microscopic conditions. The mechanism and model for hydrate decomposition in the pipe wall under thermodynamic inhibitor conditions were proposed. The decomposition mode of glycol solution is contact-induced decomposition. The hydrate decomposes from bottom to top, forming areas of different colors: decomposed, transitional, and undecomposed. The decomposition rate of hydrate accelerates with the increase of injection rate, but the decomposition efficiency decreases gradually. In the volume concentration range of 30-70%, increasing the concentration of glycol solution can significantly reduce the decomposition time of hydrates. It is demonstrated that high-concentration glycol solutions mainly accelerate the decomposition of hydrates away from the injection point, thereby increasing the decomposition rate. Decomposition efficiency peaks at 50% concentration and drops sharply when concentration rises from 50 to 70%.