Quantitative Prediction Model for Hydrate Formation, Deposition, and Blockage in Gas-Dominated Undulating Pipes

Summary To address the challenge of quantitatively predicting hydrate flow risks in undulating subsea pipelines during deepwater gasfield transportation, a coupled kinetic model was developed to describe hydrate formation, deposition, shedding, and blockage processes in a gas-dominated system. Laboratory tests using an undulating pipeline configuration demonstrated that the model achieves an average prediction error of 11.81%. The evolution of key flow parameters during hydrate blockage in both lifting and underlying pipes was analyzed. Results indicate that hydrate layer thickness exhibits a nonuniform distribution; as blockage approaches, gas velocity increases, pressure drop across the restriction rises, and temperature decreases by 6–8°C. In both lifting and underlying pipes, the upward-inclined segments show reduced droplet flow rate, increased liquid holdup, and greater subcooling—conditions corresponding to the highest hydrate formation rates and representing hydrate-blockage-prone zones. This study elucidates the evolution of hydrate-induced flow restrictions and the associated variations in multiphase flow parameters, bridging a critical gap in predictive modeling of hydrate risks in undulating subsea pipelines and providing a theoretical basis for subsea gathering system design and hydrate flow assurance.