南海神狐海域天然气水合物样品的基本特征

Characteristics of gas hydrate samples recovered from Shenhu Area in the South China Sea

我国于2007年在南海神狐海域成功地钻获了天然气水合物样品。为了深入了解这些样品的结构、气体组成及饱和度等基本特征,在实验室内采用不同的技术手段对其进行了系列的分析测试研究,主要包括水合物结构鉴定、气体组分分析、含气量及饱和度计算等。结果表明,南海神狐海域水合物是典型的I型结构,主要组成气体是甲烷,占99.3%以上;甲烷分子在大笼的占有率99%以上,在小笼中86%左右,水合指数5.99。沉积物中水合物的饱和度为21%左右,低于野外观测的数值,主要是由于沉积物岩心样品中存在部分自由水,使测定结果偏低。

Natural gas hydrate samples were successfully recovered from Shenhu area on the northern margin of the South China Sea in 2007. A series of research projects were carried out in the laboratory to investigate the basic characteristics （i.e., the structure, gas composition, gas content and saturation） of the hydrate samples using various analytical techniques. The results show that the gas hydrates are a typical structure I （sI） hydrate, with occupancy rates of methane being more than 99% in large cage and -86% in small cage, corresponding to a hydration number of 5.99. The guest molecules in hydrate cages are predominantly methane （〉 99.3%）. The saturation of gas hydrate in the sediments is found to be around 21%, which is lower than that observed in the field. The relatively low percentage is due to free water in the sediment, which affects the measurement of the ratio of gas to water