Abstract: Natural gas hydrate (NGH), a high quality, clean and efficient new energy, has received worldwide attention. Among the NGH dissociation methods, depressurization has been considered as an effective way. However, the result of depressurization dissociation is different for NGH with different saturations. A home-made one-dimensional experimental system is used for studying formation and dissociation behavior of NGH. At simulation marine geological conditions, NGH with different saturations is formed in the simulated porous media. Then they are dissociated by depressurizing slowly. Dissociation performance and saturation influence of NGH are analyzed. The results show that: the NGH dissociation by depressurization can be divided into three stages: free gas production in the early stage, gas release from hydrate dissociation in the second stage and surplus free gas release in the third stage. In the second stage, with NGH saturation increasing from 16% to 48%, the average rate of gas production increases first and then decreases. It shows that the effect of NGH saturation on gas production rate by NGH dissociation is of non-linear relation. Higher NGH saturation results in a large range of temperature decrease. Within the range of our experimental conditions, the dissociation rate of NGH with medium saturation (32%) is relatively larger, so depressurization is a appropriate method for NGH reservoirs with medium saturation.

Key words: hydrate, porous media, separation, depressurization, saturation

摘要： 天然气水合物作为一种新能源已得到世界各国的关注，降压是水合物藏的一种有效开采方式。采用自制的天然气水合物开采模拟实验装置，在多孔介质中生成不同饱和度的天然气水合物，之后进行缓慢降压开采实验。结果表明：降压开采可分为自由气产出、水合物降压分解产气和最后降压产出已分解气三个阶段。在降压分解阶段，当水合物饱和度从16%增加到48%时，平均产气速率先增加后减小，说明水合物饱和度对降压分解产气速率的影响是非线性的。降压分解时，水合物饱和度越大，温度下降幅度越大。实验研究范围内，中等饱和度（32%）的水合物藏降压分解产气速率比较大，降压开采效果较好。

关键词: 水合物, 多孔介质, 分离, 降压, 饱和度