The Impact of Natural Gas Hydrate Phase Transition on Deepwater Hydrocarbon Leakage

Deepwater oil and gas leakage is a critical risk source in marine ecological environment protection and oil-gas development safety. In the low-temperature, high-pressure conditions of the deep water, natural gas hydrate (NGH) is prone to formation and decomposition. This phase transition critically influences the migration pathways and overall plume evolution of a subsea leak, presenting a major challenge for accurate risk prediction and mitigation. This study establishes a comprehensive simulation model for deepwater hydrocarbon leakage that incorporates the effects of NGH phase transition. The model is developed using a Computational Fluid Dynamics (CFD) framework, further enhanced by integrating phase equilibrium thermodynamics and reaction kinetics to describe the formation and decomposition of NGH during the leakage process, thereby obtaining the spatiotemporal distribution of the hydrocarbon plume. Further, a sensitivity analysis is carried out to quantify the influence of key factors—such as leakage rate, ocean current, and deep-water temperature gradient—on NGH distribution and hydrocarbon plume behavior. The research results show that NGH formation inhibits the vertical ascent of the hydrocarbon plume, thereby altering its dispersion dynamics. Conversely, hydrate dissociation can lead to the re-mobilization of trapped hydrocarbons, potentially exacerbating environmental exposure risks.