Methane hydrate, a form of natural gas, was successfully extracted from the seafloor about 80 kilometers off the coast of Aichi Prefecture, the industry ministry announced Tuesday.
The feat is believed to be a world's first.
The seas near Japan are estimated to hold enough methane hydrate to supply the nation with natural gas for 100 years at current consumption levels.
The government is aiming to commercialize methane hydrate by fiscal 2018, according to the Economy, Trade and Industry Ministry. If stable production could be achieved, it could serve as a rich source of domestic energy.
Before 6 a.m. on the day, the deep-sea drilling vessel Chikyu lowered an excavator to the seafloor about 1,000 meters below, where it began separating solidified methane hydrate into water and natural gas, and transporting the gas up to the surface.
About four hours later, around 10 a.m., a flare appeared from a burner on the stern of the boat, indicating that gas was being produced.
The area around the test site is believed to hold enough natural gas to fuel the nation for more than 10 years at current consumption levels.
The government plans to continue the experiment for about two weeks to see if stable production can be achieved.
Methane hydrate consists of crystallized methane gas molecules trapped in water. It is called "burnable ice" because at high pressures and low temperatures, the solid substance will burn when lit. Compared with petroleum, methane hydrate emits less carbon dioxide when burned.
Canada successfully extracted methane hydrate from underground permafrost in 2007 and 2008, but high costs have hindered seafloor extraction.
In the test extraction, lowering the ground pressure on the seafloor made it easier to separate solidified methane hydrate to extract the gas.
Going forward, technologies to bring down extraction costs will be needed to make stable production a reality.
"By overcoming problems one by one, we want reach a stage where we can utilize the resources around our nation," industry minister Toshimitsu Motegi said at a press conference after a Cabinet meeting on the day.
With most of the nation's nuclear power plants idled, imports of liquefied natural gas to run thermal power plants have soared. A weaker yen has pushed energy costs even higher, prompting some of the nation's power companies to increase electricity rates.
Commercialized methane hydrate could help stabilize the energy supply and bring down power rates.
The ministry commissioned the Japan Oil, Gas and Metals National Corporation and others for the test-drilling, which began in January.