Gas hydrate is a solid substance composed of natural gas constrained in water molecules under low temperature and high pressure conditions. The existence of hydrates has been reported to be world-widely distributed, mainly at permafrost and deep ocean floor. Test productions of small amount of natural gas from the on-shore permafrost have been accomplished in U.S.A and Canada, but, world-first and the only production case from off-shore hydrate bearing sediments was in Nankai trough, Japan. In

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... his study, we introduce key technologies in gas production from hydrates by analyzing the Japanese off-shore gas production project in Nankai trough in terms of depressurization-induced dissociation so as to utilize planned domestic gas production test in Ulleung basin.