Abstract: In order to reveal leakage and migration mechanism of natural gas from marine hydrate decomposition, a prediction model of its migration behavior was established based on computational fluid dynamics. Then, considering the gradient change of current speed, environmental pressure and temperature along with water depth as well as variance of gas density and bubbles size, Lagrangian discrete phase model was employed to simulate movement of decomposition gas in marine environment, and its motion trajectory was tracked. Finally, critical parameters, e.g., rise time, dispersion distance and influence size on sea surface were predicted. The results show that under present produced quantity in engineering practice, release and movement of hydrate decomposition gas to sea level will not cause offshore fire and loss of stability. Rise time, dispersion distance and density of surface seawater are in inverse proportion to gas composition quantity, while influencing area increases first and then decreases along with the increase of it.

Key words: marine hydrate, decomposition gas leakage, migration consequence, dispersion distance, surface overflow area