Analysis of heat transfer effects on gas production from methane hydrate by depressurization

摘要

The dissociation of natural gas hydrates is an endothermic process. This dissociation process requires the continuous absorption of heat energy from the sediment and pore fluid. This heat transfer governs the dissociation rate and affects gas production. In this study, a two-dimensional axisymmetric simulator is developed to model the effects of heat transfer on the process of hydrate dissociation in porous media by depressurization. A series of simulations are performed to study sensible heat effects on the sediment, heat flow transfer in the cap- and base-sediment, and the effects of conductive and convective heat transfer on gas production from methane hydrate depressurization. The results show that the porous media material and the water content are two significant factors that affect the sensible heat in gas hydrate dissociation: the porous media material can increase methane hydrate dissociation, but water inhibits the dissociation process by affecting the pressure on the inner sediment. A high thermal conductivity of the sediment can initially positively affect hydrate dissociation but may later partially inhibit the process. Convective heat transfer in the gas flow increases hydrate dissociation markedly compared to that in water flow.