国産エネルギー資源としてのメタンハイドレート

Abstract

Depending on imports for 98.6% for oil and natural gas requirements, it has been a long-cherished dream for Japan to have domestic hydrocarbon energy resources. Methane hydrate, an ice-like white solid composed of water and methane gas, is believed to be widely distributed in the sea area off Japan. Therefore, Japan's Methane Hydrate R & D Program was established by the Ministry of Economy, Trade and Industry in FY2001. The organization established to execute this program is the Research Consortium for Methane Hydrate Resources in Japan (MH21). This program is divided into three phases, extending over 18 years. Phase 1 ended in FY2008. The main results of Phase 1 are as follows: (1) World's first successful continuous production of methane gas from methane hydrate-bearing layers in onshore production tests, (2) For the first time in the world, methane hydrate concentrated zones, which have development potential, were identified in the eastern Nankai Trough area, (3) Experimental in-situ testing methods of artificial and natural core samples of methane hydrate-bearing sediments were established, (4) Probabilistic resource assessment method based on well and seismic data was established, and the amount of methane gas trapped in the eastern Nankai Trough area was estimated, (5) Japan's own simulator dedicated to evaluating the production behavior of methane gas from methane hydrate-bearing layers was developed. Besides the above-mentioned achievements, fundamental studies were conducted on the Environmental Impact Assessment and Methane Hydrate System. The following technological issues have been identified by a sensitivity analysis of the Economic Evaluation: (1) increasing gas production rate (2) improving recovery factor, (3) reducing rate of sand-induced problems, and (4) reducing cost of subsea system. Phase 2 began in April 2009 to resolve these issues. The most important issue in Phase 2 is to conduct two offshore production tests in the sea off Japan. This paper introduces detailed results of Phase 1 and issues to be tackled during and after Phase 2.