Optimization of Methane Hydrate Recovery System from Ocean Floor: Basic Study on Hydrate Decomposition Rate

A system for recovery of methane hydrate from the deep ocean floor has not been established. As one possible recovery system, a gas-lift system was investigating. Methane gas, which was generated from decomposition of methane hydrate in the recovery pipe, reduce the power consumption of gas-lift system. In the present paper, gas hydrate decomposition rate was measured by using HCFC141b hydrate. Methane hydrate decomposition phenomenon was simulated by gas hydrate decomposition model applied from lattice gas automata method. From the results of experiment and simulation, the formula which expressed the heat transfer around the lump of methane hydrate, was obtained as the relationship between Reynolds number and Nusselt number. Furthermore, methane hydrate decomposition quantity under recovery pipe condition was calculated from this formula. It was indicated that gas-lift effect generated from decomposition methane gas reduce the gas lift system for recovery of methane hydrate.