不同类型天然气水合物真空分解过程实验研究

在放置于恒温室内的真空装置内,对合成的冰粉-气体水合物(包括甲烷、乙烷、丙烷、正丁烷-氮气、异丁烷、混合气水合物)、冰粉-不同粒度多孔介质甲烷水合物和祁连山冻土区及南海神狐海域天然气水合物进行了分解实验研究,初步探讨了不同气体水合物分解动力学特征和分解规律。实验结果表明,合成的冰粉-气体水合物的分解过程相似,除丙烷水合物和异丁烷水合物外,分解压力基本呈单调增长,均未出现明显的自保护效应;不同粒度多孔介质中甲烷水合物分解过程,压力增长呈现"快→慢→快"的特点,主要原因可能是多孔介质中的水合物尺寸较大,分解时更易产生自保护效应;祁连山冻土区天然气水合物的分解压力曲线与不同粒度多孔介质中甲烷水合物的相似,总体呈现"快→慢→快"的特点,水合物自保护效应明显;南海神狐海域天然气水合物分解气体压力变化虽然总体与祁连山冻土区天然气水合物压力增长过程相似,但同时呈现"阶梯状"增长,这可能与两种不同水合物岩心的岩性和水合物在岩心中的分布模式和赋存状态有关。

Experimental Research on Dissociation Kinetics of Different Gas Hydrates

To improve our understanding of natural gas hydrates dissociation characteristics under vacuum pressure,preliminary experimental studies on the decomposition of synthetic hydrates including methane hydrates,ethane hydrates,propane hydrates,normal butane-nitrogen hydrates,iso-butane hydrates,mixed gas hydrates,methane hydrates in various size grained porous media,and natural hydrates recovered from Shenhu sea area in South China Sea and Qilian Mountain permafrost,were conducted in a vacuum device placed in a constant temperature room.The experimental results reveal that except propane hydrates and iso-butane hydrates,the decomposition processes of synthetic methane hydrates,ethane hydrates,normal butane-nitrogen hydrates and mixed gas hydrates are similar,and the pressures of the decomposing gases appear monotonically increasing at vacuum condition;however,during the dissociation processes of synthetic methane gas hydrates in porous media,the increasing rate of the decomposing gases pressures generally show "fast-slow-fast" feature and the peculiarity of gas hydrates self-preservation are obvious;similarly,natural hydrates recovered from Shenhu sea area in South China Sea and Qilian Mountain permafrost also reveal apparent self-preservation during the dissociation processes,but different from natural hydrates Qilian Mountain permafrost,the decomposing gases pressures of natural hydrates recovered from Shenhu sea area increase in a ladder form.The differences between both natural hydrates may be due to different distribution models and occurrences of hydrates in the cores.