Numerical Simulation Study on Flow Aggregation Characteristics of Hydrate Slurry in Z-Shaped Pipeline

Abstract The distribution and deposition of natural gas hydrates in deepwater subsea pipelines are critical to flow assurance safety. The primary approach to mitigate hydrate blockage risks involves controlling hydrates to flow in a slurry form. Currently, hydrate flow simulations based on the Population Balance Model (PBM) primarily focus on long, straight pipelines, with limited studies addressing the nucleation, aggregation, and deposition dynamics of hydrates in special pipeline structures. To address this gap, a hydrate flow model was developed for Z-shaped pipelines in an oil-water system by considering the collision, fragmentation, and aggregation dynamics of hydrate particles. The model was solved using the Eulerian multiphase flow method coupled with the PBM model to investigate the effects of flow velocity, hydrate particle size, and hydrate volume fraction on the flow characteristics of hydrate slurries in the pipeline. The results indicate that the velocity distribution of hydrate particles along the transverse direction at the pipeline outlet exhibits an approximately symmetric pattern. The particle size distribution of hydrate particles in the hydrate slurry flow field within the pipeline follows a log-normal distribution. Increasing the hydrate volume fraction accelerates the aggregation process. A concentrated hydrate particle aggregation zone forms at the bottom of the downstream section of the Z-shaped pipeline’s outlet bend, posing a significant risk of hydrate blockage. These findings not only provide a theoretical basis for understanding the flow behavior of hydrate slurries in complex pipeline systems but also hold significant practical value for optimizing hydrate slurry transportation processes. font.