Hydrate Deposition and Blockage Mechanism in Undulating Pipes of Deepwater Gas Transmission Pipelines

Due to the uneven terrain of the seabed, there are numerous undulating sections in deepwater gas transmission pipelines. Compared with straight pipes, the gas–liquid distribution and flow characteristics in undulating pipe sections are more complex, and the mechanisms of hydrate deposition and blockage in undulating pipe sections are still unclear. This study clarified the mechanism of hydrate deposition and blockage in concave and convex pipe sections based on the hydrate deposition and blockage experiment and further investigated the rules of hydrate deposition and blockage in concave and convex pipe sections with different curvatures. Under the experimental conditions of this study, as curvature increases, hydrate blockage time in concave pipe sections is significantly shortened, while hydrate blockage time in convex pipe sections is significantly increased. The risk of hydrate deposition and blockage is highest in the concave pipe section with large curvature. Under the conditions of undercooling of 6 °C and curvature of 0.8, the average hydrate blockage time in the concave pipe section is 7.4 and 20.5 min earlier than that in the straight pipe and convex pipe sections, respectively. This study provides references for predicting and preventing the risk of hydrate deposition and blockage in undulating pipes of deepwater gas transmission pipelines.