Methane hydrates, or clathrates, are a type of frozen "cage" of molecules of methane and water, and if Japan’s claims are accurate their achievement would go down as a world first.
Pilot experiments in recent years, using methane hydrates found under land ice, have shown that methane can be extracted from the deposits. Japan says its engineers used a depressurisation method that turns methane hydrate into methane gas. Production tests are expected to continue for about two weeks.
The gas field in question is about 50 kilometres away from Japan's main island, in the Nankai Trough, where a survey is currently being run by state-owned Japan Oil, Gas and Metals National Corporation (JOGMEC).
Researchers say it could provide an alternative energy source for Japan which imports all its energy needs. A Japanese study estimated that at least 1.1 trillion cubic metres of methane hydrate exist in offshore deposits, which is the equivalent of more than a decade of Japan's gas consumption.
