Comparison of the characteristics for natural gas hydrate recovered from marine and terrestrial areas in China
Comparison of the characteristics for natural gas hydrate recovered from marine and terrestrial areas in China
复制标题
我国海洋与陆地天然气水合物特征比较
DOI：
10.1016/j.gexplo.2015.02.002
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发表时间：
2015-05-01
影响因子：
3.9
通讯作者：
Liang, Jinqiang
中科院分区：
文献类型：
--
作者：
Liu, Changling;Meng, Qingguo;Liang, Jinqiang
中国已在海洋和陆地开展了多次天然气水合物钻探，并成功获得了样品。2007年在南海深沪地区首次采集到海洋天然气水合物样品，2013年在南海珠江口盆地采集到海洋天然气水合物样品。分别于2009年和2013年在祁连山冻土中采集了天然气水合物样品。本文通过对这些天然气水合物样品的系统分析，比较了南海和青海湖天然气水合物的特征。结果表明，不同类型煤层的产状、构造特征和瓦斯成分特征有明显差异。南海海底天然气水合物具有不同的赋存状态，具有典型的I型结构，大笼和小笼中甲烷的笼占有率分别大于99%和90%，热力学计算对应的水合数约为6.0。客体分子主要是由CO2还原产生的生物来源的甲烷（>99%）。然而，QMP的陆地天然气水合物作为薄层出现在细粒砂岩、粉砂岩和泥岩的裂缝中，根据其拉曼光谱和气体成分，显示可能的结构II（sII）水合物。水合物束缚气体的分子组成表明，CH 4仅占客体的60%左右，其余为较重的碳氢化合物（如C2 H6、C3 H8和C4 H10），甲烷在小笼和大笼中的笼占有率（theta（S）/theta（L））约为7.5，表明大分子优先占据水合物的大笼.同位素分析表明，QMP中水合物束缚气为热成因气。(C)2015 Elsevier B. V.版权所有。
China has carried out several drilling campaigns for natural gas hydrate both in marine and terrestrial areas and successfully obtained the samples. The marine gas hydrate samples were firstly recovered from Shenhu area in 2007 and then from the Pearl River Mouth basin in 2013 in South China Sea (SCS). The terrestrial gas hydrate samples were recovered from Qilian Mountain permafrost (QMP) in 2009 and 2013, respectively. In this paper, systematic analyses have been carried out on these gas hydrate samples to compare the characteristics of gas hydrates from SCS with those from QMP. The results indicate that the characteristics of occurrence, structure and gas composition are obviously different. Marine gas hydrate from SCS shows different kinds of occurrence and demonstrates a typical structure I (sI), with cage occupancy of more than 99% methane in large cage and 90% in small cage, respectively, corresponding to hydration numbers of approximately 6.0 by thermodynamic calculation. The guest molecules are predominantly methane (>99%) from biogenic origin produced by CO2 reduction. However, the terrestrial gas hydrates from QMP occur as a thin layer within the cracks of fine-grained sandstones, siltstones and mudstones, showing a possible structure II (sII) hydrate based on its Raman spectra and gas composition. The molecular composition of hydrate-bound gas indicates that CH4 only accounts for similar to 60% of the guests while the others are heavier hydrocarbons (e.g. C2H6, C3H8 and C4H10).The cage occupancy ratio of methane in small and large cage (theta(S)/theta(L)) is around 7.5, suggesting that larger molecules preferentially occupy the large cage of the hydrate. The isotopic analysis shows that hydrate-bound gases in QMP are from thermogenic origin. (C) 2015 Elsevier B.V. All rights reserved.