An Energy Coup for Japan: ‘Flammable Ice’

日本能源開採新突破：「可燃冰」

HIROKO TABUCHI 報道 2013年03月14日

Jogmec, via European Pressphoto Agency

在日本中部附近的太平洋海域，天然氣火焰從開採甲烷水合物的深海鑽井船的燃燒器中噴出。

東京——日本周二宣布從海底蘊藏的甲烷水合物中提取出天然氣。甲烷水合物有時被稱為「可燃冰」。官員和專家稱，這個突破可能是向前邁出的一步，最終目標是開發一種極具潛力、但人們仍不甚了解的能源來源。
據信這是世界上首次從海底的水合物儲層提取出天然氣。這些天然氣有望成為已探明油氣儲量的替代能源來源。這對日本來說尤為至關重要，因為日本目前是全球最大的液化天然氣進口國，而且正就應不應該再度嚴重依賴核能展開公開辯論。

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專家估計，全球天然氣水合物的碳含量，至少是地球上所有其它化石燃料碳含量的兩倍，這使其有望在日本這類能源匱乏的國家改變遊戲規則。研究者們此前曾成功地從岸上的甲烷水合物儲層中提取天然氣，但未曾從海床下提取過，而據信世界大部分儲量都蘊藏在海床下。
對於海底水合物的確切性質，其可能對環境產生的影響，以及實現商業可行開採的潛力，人類仍知之甚少。
自21世紀初期以來，日本已投入數億美元勘探太平洋和日本海的甲烷水合物儲量。這項任務在福島第一核電站危機爆發後變得愈加緊迫，因為那次危機促使日本幾乎完全叫停核能發電，同時大幅增加化石燃料的進口。
日本經濟產業省稱，周二早間，地球號(Chikyu)科學鑽井船上的一個團隊對海床下300米深處的甲烷水合物儲層開始天然氣試采。自1月份以來，這艘船一直在太平洋水深1000米的一片區域進行鑽探，該區域位於日本中部渥美半島以南80公里處。
日本經濟產業省在一份聲明中稱，這一團隊使用專業設備鑽入海底甲烷水合物儲層，然後降低壓力，使甲烷和冰分離，再用管道把天然氣泵送至海面。
日本經濟產業省稱，數小時後，船尾的管道口燃起火焰，說明天然氣正被開採出來。
日本石油天然氣金屬礦產資源機構（Japan Oil, Gas & Metals National Corp.，簡稱Jogmec）是領導此次試驗開採的國有公司，該公司發言人川本高見（Takami Kawamoto，音譯）稱，「日本終於擁有了本國的能源來源。」
Jogmec稱，該團隊將繼續進行約兩周的試驗開採，隨後會分析有多少天然氣被開採出來。日本希望在大約5年後使開採技術在商業上可行。
日本經濟產業大臣茂木敏充(Toshimitsu Motegi)在東京的一次新聞發佈會上說，「這是世界上首次從海洋甲烷水合物中試驗開採天然氣，我希望我們將能夠證實穩定的天然氣開採。」他承認，開採工藝仍面臨一些技術障礙和其他問題。
不過他說，「頁岩氣曾被認為在技術上難以開採，但現在已經大規模投產。通過一個接一個地應對這些挑戰，我們有望很快就開始在日本周邊開採這些資源。」
Jogmec估計，日本南海海槽(Nankai submarine trough)周邊地區至少蘊藏了1.1萬億立方米（39萬億立方英尺）的甲烷水合物，相當於日本目前11年的天然氣總量。
日本產業技術綜合研究所(National Institute of Advanced Industrial Science and Technology)另外作出了一個粗略估計，認為日本周邊海域的甲烷水合物總儲量超過7萬億立方米，研究人員早就宣稱，這接近日本100年的天然氣需 求。
該所海洋地質學高級研究員佐藤干夫(Mikio Satoh)並未參與日本南海海槽考察。他說，「既然我們知道開採是可能的。下一步就要看日本能在多大程度上降低成本，使這項技術在經濟上可行。」
甲烷水合物是一種看上去像冰凍果子露的物質，可能在甲烷氣體被封存在海床下或地下的冰中間時形成。儘管它看上去像冰，但在遇熱時會燃燒。
專家說，在海床以及北極部分地區，天然氣水合物的儲量非常豐富。日本攜手加拿大，已成功從永久凍土中的甲烷水合物中提取出天然氣。美國的研究人員正在阿拉斯加的北坡展開類似的試驗項目。
大部分甲烷水合物儲層位於海床下的地層深處，這也是長期以來從其開採天然氣的困難所在。
在陸上試驗中，日本的研究人員曾嘗試使用熱水來加熱甲烷水合物，也曾嘗試通過降低壓力來釋放甲烷分子。日本最後決定用降壓手段，部分原因是，將熱水注入海床以下本身就需要耗費大量能源。
東京明治大學(Meiji University)的地質學教授松本良(Ryo Matsumoto)領導了針對日本天然氣水合物儲量的研究，他說，「我們一直將天然氣水合物視作潛在巨大的能源來源，但問題是：我們如何從海底採掘天然 氣？如今，我們清除了一個巨大的障礙。」
美國地質調查局(U.S. Geological Survey)的資料顯示，最近對北卡羅來納、南卡羅來納海岸的勘測顯示，那裡有大量的近海甲烷水合物儲量。加拿大、中國、挪威和美國都在勘探水合物儲量。
然而，美國地質調查局的科學家們表示，對於在海床上鑽采水合物對環境會有怎樣的影響，我們的認識依然有限，特別是這有可能向大氣釋放溫室氣體甲烷。他們呼籲進行更深入的研究和監測。

翻譯：曹莉、林蒙克

An Energy Coup for Japan: ‘Flammable Ice’

By HIROKO TABUCHI March 14, 2013

 

TOKYO — Japan said Tuesday that it had extracted gas from offshore deposits of methane hydrate — sometimes called “flammable ice” — a breakthrough that officials and experts said could be a step toward tapping a promising but still little-understood energy source.
The gas, whose extraction from the undersea hydrate reservoir was thought to be a world first, could provide an alternative source of energy to known oil and gas reserves. That could be crucial especially for Japan, which is the world’s biggest importer of liquefied natural gas and is engaged in a public debate about whether to resume the country’s heavy reliance on nuclear power.

Experts estimate that the carbon found in gas hydrates worldwide totals at least twice the amount of carbon in all of the earth’s other fossil fuels, making it a potential game-changer for energy-poor countries like Japan. Researchers had previously successfully extracted gas from on-shore methane hydrate reservoirs, but not from beneath the seabed, where much of the world’s deposits are thought to lie.
The exact properties of undersea hydrates and how they might affect the environment are still poorly understood, however, as is the potential for making extraction commercially viable.
Japan has invested hundreds of millions of dollars since the early 2000s to explore offshore methane hydrate reserves in both the Pacific and the Sea of Japan. That task has become all the more pressing after the Fukushima Daiichi nuclear crisis, which has all but halted Japan’s nuclear energy program and caused a sharp increase in the country’s fossil fuel imports.
The Japanese Ministry of Economy, Trade and Industry said a team aboard the scientific drilling ship Chikyu had started a trial extraction of gas from a layer of methane hydrates about 300 meters, or 1,000 feet, below the seabed Tuesday morning. The ship has been drilling since January in an area of the Pacific about 1,000 meters deep and 80 kilometers, or 50 miles, south of the Atsumi Peninsula in central Japan.
With specialized equipment, the team drilled into and then lowered the pressure in the undersea methane hydrate reserve, causing the methane and ice to separate. It then piped the natural gas to the surface, the ministry said in a statement.
Hours later, a flare on the ship’s stern showed that gas was being produced, the ministry said.
“Japan could finally have an energy source to call its own,” said Takami Kawamoto, a spokesman for the Japan Oil, Gas & Metals National Corp., or Jogmec, the state-run company leading the trial extraction.
The team will continue the trial extraction for about two weeks before analyzing how much gas has been produced, Jogmec said. Japan hopes to make the extraction technology commercially viable in about five years.
“This is the world’s first trial production of gas from oceanic methane hydrates, and I hope we will be able to confirm stable gas production,” Toshimitsu Motegi, the Japanese trade minister, said at a news conference in Tokyo. He acknowledged that the extraction process would still face technical hurdles and other problems.
Still, “shale gas was considered technologically difficult to extract but is now produced on a large scale,” he said. “By tackling these challenges one by one, we could soon start tapping the resources that surround Japan.”
Jogmec estimates that the surrounding area in the Nankai submarine trough holds at least 1.1 trillion cubic meters, or 39 trillion cubic feet, of methane hydrate, enough to meet 11 years’ worth of gas imports to Japan.
A separate, rough estimate by the National Institute of Advanced Industrial Science and Technology has put the total amount of methane hydrate in the waters surrounding Japan at more than 7 trillion cubic meters, or what researchers have long said is closer to 100 years’ worth of Japan’s natural gas needs.
“Now we know that extraction is possible,” said Mikio Satoh, a senior researcher in marine geology at the institute who was not involved in the Nankai trough expedition. “The next step is to see how far Japan can get costs down to make the technology economically viable.”
Methane hydrate is a sherbet-like substance that can form when methane gas is trapped in ice below the seabed or underground. Though it looks like ice, it burns when it is heated.
Experts say there are abundant deposits of gas hydrates in the seabed and in some Arctic regions. Japan, together with Canada, has already succeeded in extracting gas from methane hydrate trapped in permafrost soil. U.S. researchers are carrying out similar test projects on the North Slope of Alaska.
The difficulty had long been how to extract gas from the methane hydrate far below the seabed, where much of the deposits lie.
In onshore tests, Japanese researchers explored using hot water to warm the methane hydrate, and tried lowering pressure to free the methane molecules. Japan decided to use depressurization, partly because pumping warm water under the seabed would itself require a lot of energy.
“Gas hydrates have always been seen as a potentially vast energy source, but the question was, How do we extract gas from under the ocean?” said Ryo Matsumoto, a professor in geology at Meiji University in Tokyo who has led research into Japan’s hydrate deposits. “Now we’ve cleared one big hurdle.”
According to the U.S. Geological Survey, recent mapping off the North Carolina and South Carolina coasts shows large offshore accumulations of methane hydrates. Canada, China, Norway and the United States are also exploring hydrate deposits.
Scientists at the U.S.G.S. note, however, that there is still a limited understanding of how drilling for hydrates might affect the environment, particularly the possible release of methane, a greenhouse gas, into the atmosphere, and are calling for continued research and monitoring.