Considerable hydrate deposits are proved to exist by drilling in-situ in the Shenhu Area of South China Sea in China, and the survey and evaluation as a potential energy resource has been carried out. In May, 2007, gas hydrate samples have been collected in the Shenhu Area, which will become a strategical area of gas hydrate exploitation in China. TOUGH＋HYDRATE is employed to simulate the hydrate dissociation and water/gas production process with the single depressurization and the depressurized＋thermal stimulation, based on the geological data of the SH2, SH3 and SH7 site in the Shenhu Area in South China Sea. The simulation results indicate that the hydrate dissociate at the area surrounding the production well, the boundary area of the bottom and top of the hydrate bearing layer (HBL). There is an inversion of the geothermal gradient at the interface between the overburden (OB) and the HBL because of hydrate dissociation-induced cooling in the HBL. Practically impermeable secondary hydrate barrier evolves around the wellbore, which sealed the hydrate body and prevented communication with the evolving upper dissociating interface at the end of the depressurization process. With the hot water injected from the top of the HBL, the secondary hydrate can be eliminated during the depressurization＋thermal stimulation process.

Key words: natural gas hydrate, depressurization, thermal stimulation, TOUGH＋HYDRATE, Shenhu Area, South China Sea