Experimental study on hydrate blockage formation and decomposition in gas-dominated Fluctuating pipes

Current research pertaining to hydrate flow assurance in the transportation of deep-sea natural gas through undulating pipelines remains sparse. Employing a novel undulating pipeline equipped with multipointdistributed sensors, we delve to the processes of hydrate generation, migration, deposition, blockage, and decomposition. Our findings reveal that the upward inclination sections of both lifting and underlying pipes are particularly vulnerable to hydrate blockage. The lifting pipe is not conducive to hydrate deposition and blockage, whereas the underlying pipe poses a heightened risk for hydrate formation. Increasing subcooling leads to a reduction in blockage duration and sloughing frequency, alongside an extension in decomposition time. Furthermore, increasing the water injection rate and pipeline curvature prolongs the blockage of the lifting pipe. However, the impact of the water injection rate on the underlying pipe is negligible. Increasing pipeline curvature promotes the blockage of the underlying pipe. We propose models that encapsulate hydrate blockage and decomposition based on varying gas-liquid distributions. This research fills the gap in the study of hydrate blockage and decomposition in undulating pipelines and provides a reference for monitoring hydrate risks in natural-gas transmission pipelines.