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It could reduce the country's energy dependence on other nations, once necessary technology can be developed for efficient, economic excavation and gas extraction.
However, it is by no means certain that the gas deposit would be sufficient for commercial production.
Methane hydrate is a solid form of water containing a large amount of methane gas within its crystal structure. It exists around the world under arctic permafrost and beneath the ocean floor near continental shelves, but only at such depths as 1,600 feet or more below the ocean’s surface.
A Japanese scholar predicted in 1996 that the country's natural gas needs would be met for hundreds of years by the entire volume of gas buried under the seabed around Japan.
Japan, which imports over 90 percent of its natural gas needs, set up a methane hydrate research committee in 2001 and has invested a total of US$271 million so far to develop the technology and to find promising deposits.
Early this year, it succeeded in the world's first methane hydrate frozen gas extraction by lowering pressure without heating for six days in a row at 3,600 feet below the terrestrial permafrost in Canada.
But as the frozen gas extracted from methane hydrate is stable only under lower temperatures and relatively high pressure, it is normally found at the bottom of oceans, making its commercial production difficult without further technical innovation, experts point out.
Currently, the area with most promising gas deposits is an ocean trench in the Pacific Ocean called the Eastern Nankai Trough, about 30 miles off the coast of Japan’s main island of Honshu. An estimated 40 trillion cubic feet of gas, equivalent to Japan's needs for 14 years, is buried.
Last week, the Ministry of Economy, Trade and Industry decided to start the test drilling at the trough in 2012, targeting commercial extraction by 2016.
A spokesman for the state-controlled Japan Oil, Gas and Metals National Corporation, however, admitted that out of the estimated amount to fulfill 14 years of energy needs, only half that amount of frozen gas can be extracted with the current technology, which was used in Canada early this year, because the other half is not in high density.
Moreover, another expert warns that only 30 percent of the latter half could be extracted even if it continues production for eight years.
"There is some doubt whether it will start the production in the Nankai Trough on a commercial basis if we get only two-year gas needs after spending eight years for production," said Ryo Matsumoto, a panel member of the research committee and professor at the University of Tokyo.
Matsumoto, among others, recommended drilling an area in the Sea of Japan about 20 miles off the coast of Niigata Prefecture in northern Japan rather than at the Nankai Trough, which the government has focused on for over seven years.
Compared with the gas in the Nankai Trough in the Pacific Ocean, which is mixed with sand and buried at depths of more than 6,500 feet below the sea surface and 700 feet under the seabed, the gas in the Sea of Japan is mixed with mud and buried at water depths of 3,200 feet and under 300 feet of seabed.
"We confirmed that the huge amount of gas is buried shallower in the Sea of Japan and that it is more concentrated in one spot. So, I think that extracting it in the Sea of Japan is easier and cheaper than that in the Pacific Ocean. Although the technology is still not established, it is almost sure to start commercial production in or around ten years if we get a budget from the government," said Chiharu Aoyama, director of the Natural Sciences section at Japan's Independent Institute Co., Ltd.
However, while drilling technologies for crude oil or natural gas, which are also mixed with sand, can be applied for the frozen gas mixed with sand in the Pacific Ocean, a totally different technique is required for the frozen gas mixed with mud, Aoyama said.
Because of this situation, the government will allocate budgets to both areas and conduct simultaneous research from next year.
Other countries like China, South Korea, India, and Taiwan, all eager to get more energy sources, are also exploring the technology for methane hydrate gas. Since there are existing disputes over the exclusive economic zones or territorial waterlines among East Asian countries, frictions over resources are likely to break out in the future, some experts warn.
India has found some gas deposits, equivalent to those in Japan's eastern Nankai Trough, while Taiwan found enough deposits to meet its 50-year gas needs in its southern ocean. South Korea also has found deposits to meet its 30-year gas demands in the Sea of Japan, a Korean daily reported last month.
"Some deposits which Taiwan found in its southern ocean are believed to be richer than that of Japan's eastern Nankai Trough. China and Taiwan might engage in disputes over the gas in the future," Matsumoto said.
Methane hydrate has also been found in the Sea of Okhotsk and near the front edge of the Kamchatka Peninsula, as well as off the shores of Canada, Chile, Peru, and Nigeria.
Japan has not conducted research around the Kuril Islands, which are claimed by both Russia and Japan, despite possibilities of gas around those islands, Matsumoto said. Other experts pointed out that the gas would be found under or around disputed islets between Japan and South Korea, known as Takeshima in Japan and Dokdo in South Korea.
The United States, which was not enthusiastic for a long time, recently increased the number of scientists and the budget related to research in methane hydrate to look into the possibilities.
In June this year, Japan’s Trade Ministry and the United States’ Department of Energy agreed to cooperate on developing ways to produce the gas. Both countries will conduct test drilling in Alaska within the next three years.
"Japanese officials are anxious that initiatives in the Sea of Japan might be taken away if the United States cooperates with China or South Korea on developing the drilling technology. Such an anxiety might push the government to have technical cooperation with the United States rather promptly,” Aoyama analyzed.
"Since territorially disputed areas are duplicated with that of methane-rich deposits, some Japanese researchers and scientists express a sense of crisis that the resources would be robbed by other countries unless Japan establishes the drilling technology and extracts the gas as soon as possible," Aoyama said.
