二氧化碳地中隔离技术及其岩石力学问题

寻求经济又安全的强有力减排技术关系到日本政府能否履行在京都议定书中所作的承诺。二氧化碳是主要的温室气体，二氧化碳地中隔离是把从集中排放源分离得到的二氧化碳注入地下深处具有适当封闭条件的地层中隔离起来，即把二氧化碳归还原处——地球深部。介绍了二氧化碳地中隔离的概念及国际动态，并基于隔离容量、机理、安全性及成本分析，论述其可行性。

CO2 AQUIFER STORAGE AND THE RELATED ROCK MECHANICS ISSUES

Carbon dioxide (CO2) is one of the major greenhouse gases whose concentration in the atmosphere has led to a significant climate change. The greenhouse issue has become a global concern, and some of major developed countries have devoted intensive effects to the development of various CO2 emission control technologies. CO2 aquifer storage is one of the technologies. The generic idea of CO2 aquifer storage is to store the gas in deep permeable sedimentary formations that are constrained by impermeable caprocks so that the gas can be almost completely isolated from the atmosphere for a very long period. Scientific evidences from nature analogues, laboratory experiments and computer simulations indicated that the geologic formations with suitable structure and hydrogeologic conditions are able to trap the gas. Cost estimations and industrial practices also showed that the existing technologies enable the storage with a cost lower than the carbon tax. Our investigations revealed that Japan has many promising storage sites, on land or off shore, with large storage capacities. A considerable part of them are close to emission sources, where there is no need for main pipeline, and therefore, the low-cost storage is possible.The mechanical stability of a storage site is of critical importance for implementing the storage practice in Japan. However, the long-term mechanical process is involved in crustal activities, and geo-chemical and hydrogeologic processes. Such complex coupled processes are difficult to quantitatively assess. At this moment, it is recommended that the relatively stable sites for near-future storages can be found out through surveying and analyzing the information on present and historic geologic activities. However, the development of accurate quantitative assessment technologies is still important for finding more suitable sites and enhancing the contributions of aquifer storages to the emission cutting. This requires a deep understanding of such complex coupled processes, and a drastic improvement in exploration, monitoring and simulation techniques.