Abstract: The gas hydrate in permafrost regions could be an important energy source for future. In this paper，we studied methane hydrate dissociation in a one-dimensional experiment apparatus by depressurization and hot water injection in porous sediments under simulated conditions of 1.24 ℃ to 1.35 ℃ and 2.83 MPa to 2.89 MPa for permafrost regions. The changes of pressure，temperature，gas production，water production and energy efficiency with time were investigated. The results revealed three stages in the gas production process：free gas release，hydrate dissociation and production of remaining gas. In the first stage，there was no water presented in the depressurization or hot water injection process. In the process of the hot water injection，water production rate was equal to water injection rate. The energy efficiency in the hot water injection process increased before it came to a decrease. Lower energy efficiencies associated with higher rates of the water injection.

Key words: methane hydrate, porous sediment, depressurization, thermal stimulation, energy efficiency

摘要： 冻土区天然气水合物是未来能源的重要补充，然而冻土区天然气水合物的开采研究还处于初级阶段。本文利用一维水合物分解实验装置，在1.24～1.35 ℃以及2.83～2.89 MPa温度压力条件下，模拟冻土区天然气水合物降压定压分解以及注热水定压分解实验研究，分析降压分解及注热水分解过程中温度、压力、产水以及产气随时间变化特性及能量效率。研究结果表明，分解过程产气可分为自由气释放、水合物分解以及残余气体产出3个阶段，实验过程中温度先降后升，降压分解过程与注热水分解自由气产出阶段基本没有水产出，而在水合物分解阶段，产水速率与注水速率相等。注热分解过程中能量效率先升后降，注热量越大，能量效率越低。

关键词: 甲烷水合物, 多孔介质, 降压分解, 注热分解, 能量效率