Some estimates indicate that reserves of the "fire ice" or methane hydrate could represent a 100-year supply of natural gas for Japan, which relies on imports for more than 99 percent of its oil.
The Japanese Ministry of Trade has requested a budget of more than $1 billion for the drilling -- to be carried out by the Japan Oil, Gas and Metals National Corporation, in association with the Japanese government -- slated to begin next spring. Commercial output is hoped for by 2018.
Lucia van Geuns, an energy analyst at the international energy program of the Clingendael Institute in the Netherlands told The Guardian: "Methane hydrates could make Japan energy independent. Whether they can commercialize methane hydrates remains to be seen.
"If it does succeed, and that's very much a long shot, it will have a huge impact -- equivalent to the use of gas shale in the U.S."
What makes methane hydrate unique is that it is a seemingly frozen and yet flammable material. Formed in cold, high-pressure environments, it is found throughout the world's oceans as well as under the frozen ground of countries with high latitudes.
While global estimates vary considerably, the U.S. Department of Energy says, the energy content of methane occurring in hydrate form is "immense, possibly exceeding the combined energy content of all other known fossil fuels."
Drilling for the gas will pose a challenge for Japan. The hydrates in the Sea of Kumano are approximately 19 miles offshore in about 328 feet of water, at a depth below the seabed of 2,150 feet.
Japan has tested experimental production of methane gas by injecting hot water into a borehole in the Mackenzie Delta in the arctic region of Canada, as part of an international joint research team.
But environmentalists fear that tapping methane hydrates could adversely affect the world climate.
Although methane is a clean-burning fuel, it is still a powerful greenhouse gas, with about 21 times the heat-trapping capability of carbon dioxide.
Japan Oil, Gas and Metals National Corp. acknowledges the risks inherent in the drilling process, stating on its Web site: "Not least that when you drill you create heat, which turns the frozen methane into gas, which could then leak uncontrollably through the sea to our atmosphere."
Other dangers include inadvertently triggering undersea landslides, which could wipe out surrounding seafloor life.