Abstract:

Hydrate surface morphology was affected by hydrate growth patterns, as well as can reflect distribution in sediments and the spatial relationship with sediments, thereby affecting the physical properties of hydrate-bearing sediments. Methane hydrate was synthesized in the device by using the actual drilled marine mud in the Shenhu sea of South China Sea at a depth of 2713m as sediment. Cryo-scanning electron microscopy (Cryo-SEM) and energy spectrometry (EDS) were used to characterize the microscopic morphology and elemental composition of the synthesized hydrates. The results showed that the methane hydrate in the pure water system was homogeneous and easily decomposed compared to ice. The hydrates formed in the pure water system and in the marine mud were similar in morphology, both of which were in the form of granular colloid, with trace amounts of nanoscale particle ice distributed on the surface. The element analysis showed that the content of carbon element in marine mud was higher than that in pure water, and hence the hydrate cage occupancy was higher. The content of carbon element in marine mud was negligible, and the cement structure on the surface of the marine mud was proved to be hydrate by the increase of the content of carbon element and the ratio of carbon to silicon elements. The research provided a new idea to identify hydrate from sediments and an important way to investigate the surface morphology and occurrence of hydrate in sediments.

Key words: marine mud, methane, hydrate, surface morphology, scanning electron microscopy and energy dispersive spectrometer

摘要：

水合物表观形貌受水合物的生长方式影响，能够反映水合物在沉积物中的分布以及与沉积物的空间关系，进而对含水合物沉积物的物理特性产生影响。本文通过在实际钻采的南海神狐海域水深2713m的海泥中生成甲烷水合物，利用冷冻扫描电子显微镜（Cryo-SEM）和能谱仪（EDS）对合成水合物的微观形貌、元素组成进行表征。结果表明，与冰相比，纯水体系下的甲烷水合物形貌单一且容易分解。纯水体系生成的水合物与海泥体系生成的水合物形貌相似，均呈颗粒胶结状，微量纳米级别的颗粒冰分布在表面。元素分析表明相较于纯水体系，海泥中生成的水合物C元素含量更高，水合物笼子占有率也越高。海泥中含有微量的C元素，通过C元素含量增加及C、Si比提高确定了表面颗粒胶结状为水合物。本研究为辨别沉积物中的水合物提供了新思路，为研究水合物的表观形貌及赋存提供了重要方法。

关键词: 海泥, 甲烷, 水合物, 表面形貌, 扫描电镜和能谱仪