According to The echoes:
Tonight in Asia: Japan attacks a deposit of "burning ice"
The Japanese government launched the prospecting of methane hydrate deposits off its coasts. Some experts assure that these deposits would be, on a world scale, greater than oil reserves, but their extraction promises to be very delicate.
Two years to the day after the destruction of the Fukushima Daiichi power station, the government will today begin prospecting off its coast for deposits of methane hydrates, commonly known as "burning ice", with the hope to update a new source of energy to power the country. An exploration vessel chartered by Jogmec (Japan Oil, Gas and Metals National Corp) and the Ministry of Industry will carry out, in the basement of the Nankai marine trench, the first production tests of these hydrates of methane, compounds of ice and natural gas resulting from the decomposition of organic matter.
Some experts assure that these deposits would be, on a world scale, higher than the current oil reserves, but their extraction promises to be extremely delicate. Jogmec, which has tested a technique for “depressurizing” these methane crystals in Canadian permafrost, hopes to ascend from the depths of tens of thousands of cubic meters of gas per day during the next two weeks of experimentation. If the technique proves effective, commercial exploitation could be launched by 2018
More general information on the exploration and exploitation of gas hydrates