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Pressure-induced structural changes of methane hydrate and their application to developing techniques on gas hydrates reservoir.

压力引起的甲烷水合物结构变化及其在天然气水合物储层开发技术中的应用

基本信息

批准号：
14550871
负责人：
YAGI Hisako
金额：
$ 2.3万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

Methane hydrate, called as "fiery ice", is expected to be a fruitful natural resource, at the same time, methane is rather effective greenhouse gas than carbon dioxide. In order to develop the techniques for practical using methane hydrate, understanding on basic properties such as stability and structural changes under high pressure of methane hydrate are indispensable. In this research, high-pressure experiments were performed in the pressure range from 0.1 MPa to 86 GPa using diamond anvil cell, to clarify the changes in structure and hydration number of methane hydrate and also to provide the knowledge to developing new technique for gas hydrate reservoir. The in-situ X-ray difrractmetry (XRD), Raman spectroscopy, and optical microscopy revealed several structural changes. The initial structure of methane hydrate (MH-sI) became a hexagonal structure (MH-sH) at approximately 1.0 GPa and was further transformed into an orthorhombic filled ice I_h, structure (MH-ice I_hi,) at 2.0 GPa, as has previously been observed. The MH-ice I_h, survived up to 42 GPa. On the other hand, the other gas hydrates decomposed into ice VII and solid phases of guest gas components below 5 to 6 GPa. The main reason for the characteristic stability of methane hydrate was examined to be due to attractive interaction between methane molecules and between methane molecules and water molecules of the framework. Above 42 GPa, MH-ice I_h changed to further high-pressure structure, however the detail structural analysis could not made because of broadness of the XED pattern.

甲烷水合物被称为“炽热的冰”，是一种很有潜力的天然资源，同时甲烷也是一种比二氧化碳更有效的温室气体。为了开发甲烷水合物的实用化技术，必须了解甲烷水合物的基本性质，如稳定性和高压下的结构变化。本研究利用金刚石压砧在0.1 ~ 86 GPa的压力范围内进行了甲烷水合物的高压实验，旨在阐明甲烷水合物结构和水化数的变化规律，为开发天然气水合物储层新技术提供依据。原位X射线衍射（XRD），拉曼光谱，和光学显微镜揭示了几个结构的变化。甲烷水合物（MH-sI）的初始结构在约1.0 GPa时变为六方结构（MH-sH），并在2.0 GPa时进一步转变为正交晶填充冰I_h结构（MH-ice I_hi），如先前所观察到的。MH-ice的I_h值在42 GPa下仍能保持。另一方面，其它气体水合物在5 ~ 6 GPa以下分解为冰VII和客体气体组分的固相。甲烷水合物的特征稳定性的主要原因是由于甲烷分子之间的相互吸引作用和甲烷分子和水分子之间的框架。在42 GPa以上，MH-ice Ih向更高的高压结构转变，但由于XED图像较宽，无法进行详细的结构分析。