In situ Raman spectroscopy study of synthetic gas hydrate formed by cold seep flow in the South China Sea
In situ Raman spectroscopy study of synthetic gas hydrate formed by cold seep flow in the South China Sea
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DOI：
10.1016/j.jseaes.2018.02.003
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发表时间：
2018-12-01
影响因子：
3
通讯作者：
Yan, Jun
中科院分区：
文献类型：
--
作者：
Du, Zengfeng;Zhang, Xin;Yan, Jun
天然气水合物的性质研究通常采用模拟实验或从冻土和海洋沉积物中采集的水合物样品。南海福尔摩沙海岭活跃冷泉喷出的流体和气泡首次快速形成了合成气水合物。利用Faxian遥控潜水器上的气体水合物拉曼探针（RiP-Gh）对SGH样品进行了原位探测。通过对合成气水合物样品的原位拉曼光谱的时空分析，确定了合成气水合物的结构和演化过程。首次在SGH样品的原位拉曼谱中发现了自生碳酸盐碎屑或其他碎屑作为成核粒子，这可能是促进合成气水合物形成的因素之一。观测结果表明，气水界面也有助于SGH样品的快速形成，这与前人的研究结果一致。采集了3个SGH样品在海底放置0 h、4 h和21 h后的原位拉曼光谱。实验室拉曼光谱的一个样品，已令人惊讶地发现和回收后9840小时（410天），因为形成在海底也被收购。4个SGH样品的拉曼光谱表明，水合物中甲烷大笼与小笼的占有率从1.01变化到1.39，甲烷大笼与气体的比例从0.53增加到1.55。与实验室模拟结果相比，本文的工作对天然气水合物快速生成的机理提出了新的解释，揭示了合成气水合物快速生成后的演化规律，为天然气水合物的研究提供了新的思路。
Properties of gas hydrate are commonly investigated in laboratory by simulators or studied using the hydrate samples recovered from permafrost and marine sediments. Here synthetic gas hydrate (SGH) is quickly formed for the first time by fluids and bubbles erupted from the active cold seeps at the Formosa Ridge in the South China Sea (SCS). SGH samples are in situ detected by a Raman insertion probe for gas hydrate (RiP-Gh) which is deployed by the remotely operated vehicle (ROV) Faxian. Both spatial and temporal in situ Raman spectra of the SGH samples are acquired in order to determine the structure and the evolution of the synthetic gas hydrate. Authigenic carbonate debris or other debris serving as nucleation particles, which is found in the in situ Raman spectra of SGH samples for the first time, may be one factor that can promote the formation of synthetic gas hydrate. The gas-water interface demonstrated by the observation results, also contributes to the quick formation of SGH samples, which agrees well with the previous study. In situ Raman spectra of three SGH samples which have been placed on the seafloor for 0 h, 4 h and 21 h respectively are acquired. Laboratory Raman spectra of one sample which has been surprisingly found and recovered after 9840 h (410 days) since formed on the seafloor are also acquired. The Raman spectra of the four SGH samples indicate that the methane large-to-small cage occupancy ratios of the hydrates vary from 1.01 to 1.39, and the ratios of methane large-to-gas of the hydrates increase from 0.53 to 1.55. Overall, our work suggests a new explanation for the quick formation of gas hydrate compared to that in laboratory simulation work, and reveals the evolution of synthetic gas hydrate after quick formation, which provides a new insight for the study of natural gas hydrate.