The vast amount of hydrocarbon gas encaged in gas hydrates is regarded as a kind of future potential energy supply due to its wide deposition and cleanness. How to exploit gas hydrate with safe, effective and economical methods is being pursued. In this paper, a mathematical model is developed to simulate the hydrate dissociation by depressurization in hydrate-bearing porous medium. The model can be used to analyze the effects of the flow of multiphase fluids, the intrinsic kinetic process of hydrate dissociation, the endothermic process of hydrate dissociation, ice-water phase equilibrium, the variation of permeability, the convection and conduction on the hydrate dissociation and gas and water production. The numerical results agreed well with the 1-D and 2-D experiments. The numerical results for 3-D hydrate reservoir show that in the first stage of depressurization gas can be produced effectively from hydrate reservoir. With the depletion of reservoir energy because of endothermic process of hydrate dissociation the gas rate decreases rapidly. Then, methods such as thermal stimulation and inhibitor injection should be considered to replace depressurization
