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Methane hydrate investigations on sediment core samples obtained in the Sea of Okhotsk

对鄂霍次克海沉积物岩心样本进行甲烷水合物研究

基本信息

批准号：
14254003
负责人：
SHOJI Hitoshi
金额：
$ 21.63万
依托单位：
Kitami Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14254003/
关键词：
Methane Hydrate Clathrate Hydrate Sea Sediment Core Offsore Sakhalin, Okhotsk Sea Methane Seep Seepage Structure Gravity Corer Sea Bottom Survey ガスハイドレートオホーツク海サハリン沖海洋調査海底土壌バイカル湖チムニー結晶成長クラスレート構造1型

项目摘要

Side-scan-sonar survey with high-resolution seismo-acoustic profiling was performed offshore Sakhalin, Okhotsk Sea by the members of CHAOS (hydro-Carbon Hydrate Accumulations in the Sea of Okhotsk) Project lead by Kitami Institute of Technology in 2003. The survey results revealed characteristic distributions of gas hydrate accumulations with unique images of gas seepage structures and vertical fluid channel at/near sea bottom. More than 40 seepage structures were found within a 10 x 20 km survey area. The maximum size of seepage structure observed is about 600 m in diameter. Methane gas released from the seepage structures into the above water was detected as flare images by hydro-acoustic profiling. Gas hydrate and sediment core samples were obtained from those seepage structures and transported to Kitami Institute of Technology for laboratory studies by gas chromatography, liquid chromatography, oxygen/hydrogen/carbon isotopes, 13C-NMR, thermal analysis, physical analysis and other analytical techniques. Methane hydrates of massive forms, layers and/or small pieces were observed in silty-clay, sea sediment cores within a depth of 2-3 meter below the sea floor. Gas hydrates samples were stored in a liquid-nitrogen-temperature container immediately after core recovery, preventing hydrate samples from the dissociation. Main results obtained are summarized as below. Guest gases trapped in hydrates are mainly of methane and only small amount of ethane, propane and others. Crystal structure of hydrates is of clathrate hydrate structure I, and the hydration number is close to six, showing very high quality of gas hydrates. The results of carbon isotope and gas composition measurements show the methane gas in gas hydrates is of microbial origin. Latent heat of gas hydrate measured is found to be quite close to that of artificial, pure methane hydrate.

2003年，由北见工业大学牵头的“鄂霍次克海碳氢化合物累积”项目成员在鄂霍次克海萨哈林近海进行了侧扫声纳高分辨率地震-声学剖面测量。研究结果揭示了天然气水合物的分布特征，具有独特的天然气渗流结构和海底/近海底垂向流体通道图像。在一个10 x20公里的调查区域内发现了40多个渗漏结构。观测到的最大渗流结构直径约为600 m。从渗流结构释放到上述水体中的甲烷气体被检测为耀斑图像的水声剖面。从这些渗漏结构中获取了天然气水合物和沉积物岩心样品，并将其运到北见工业大学，以便利用气相色谱法、液相色谱法、氧/氢/碳同位素、13 C核磁共振、热分析、物理分析和其他分析技术进行实验室研究。在海底以下2-3米深处的粉质粘土、海洋沉积物岩心中观察到块状、层状和/或小块的甲烷水合物。在岩心回收后立即将天然气水合物样品储存在液氮温度容器中，防止水合物样品分解。所获得的主要结果总结如下。水合物中捕获的气体主要是甲烷，只有少量的乙烷、丙烷等。水合物的晶体结构为笼形水合物结构I，水化数接近6，显示出很高的天然气水合物质量。碳同位素和天然气成分分析结果表明，天然气水合物中的甲烷气是微生物成因的。所测得的天然气水合物的潜热与人工合成的纯甲烷水合物的潜热非常接近。