沉积物中天然气水合物减压分解实验

基于自行研发的天然气水合物开采实验装置,进行了沉积物中甲烷水合物减压分解实验研究,并用时域反射技术(TDR)实时监测水合物分解过程中其饱和度的变化。实验采用粒径为0.18~0.35 mm的干砂,0.03%的十二烷基硫酸钠(SDS)水溶液和高纯甲烷气体。实验结果表明:水合物减压分解过程中不同层位的温度与水合物饱和度存在差异,体现了一定沉积环境下水合物的分解规律,位于沉积物上层与外侧的水合物先分解;TDR技术测量水合物饱和度时,压力迅速降低不会对TDR波形产生影响,TDR曲线变化仅由水合物分解引起;水合物分解时TDR技术测得其饱和度变化规律与根据分解气体总量计算的结果一致,说明该技术可以准确实时监测水合物饱和度变化。

Experimental Research of Gas Hydrate Dissociation in Sediments by Depressurization Method

Experimental investigation of methane hydrate dissociation process in sediments using depressurization method was carried out based on an self-developed experimental setup for gas hydrate exploitation.The TDR(time-domain reflectometry) technique was applied to measure hydrate saturation during gas hydrate dissociation.The materials used in this study are natural sand(0.18-0.35 mm),0.03% sodium dodecyl sulfate(SDS) solution and high-purity methane.The results show that during gas hydrate dissociation,the temperature and hydrate saturation vary in different parts of sediments,suggesting that hydrates dissociate earlier on the surface and in outer layer of the sediments than those in inner layer.The TDR waveforms aren't affected by rapid depressurization.The changes of TDR curve is just due to gas hydrate dissociation so that the measured hydrate saturations aren't affected by pressure changes.Moreover,the cumulative volume of dissociation gas is also used to calculate the hydrate saturation for comparison,and the result is well consistent with that of TDR method.It indicates that TDR method can be used to measure the variation of hydrate saturation and exactly demonstrate the hydrate dissociation process.