The other wonder gas

Three years after an earthquake, tsunami and nuclear shutdown hammered Japan’s energy supply, the country is taking steps to produce an entirely new domestic fuel from deep beneath the sea: “fire ice”, a frozen form of combustible methane. The estimated reserves are so enormous that they could meet Japan’s energy needs for the next century.

Researchers from the Japan Oil, Gas and Metals National Corporation successfully extracted these methane hydrates for the first time in March 2013. Now they will further explore the Nankai trough (80 km off the Pacific coast), using a deep-sea drilling vessel and custom-designed robots that can dive down 7 km.

Methane hydrates are sorbet-like, highly concentrated stores of methane held in a water-molecule cage, or clathrate, which form under high-pressure conditions of at least 23 atm. One cubic meter of methane hydrate contains the equivalent of 164 m³ of methane gas. Methane hydrates are found either relatively close to the surface under Arctic permafrost or beneath the seabed, where the deposits tend to collect in sediments along geological fault lines. The global reserves of fire ice are estimated to be 20,000 trillion m³ – more than double the total known reserves of coal, oil and natural gas – even if much of it is inaccessible.

Little wonder that countries from Canada and Russia to New Zealand that have known fire ice reserves are eager to develop this new source of energy. But none are as far along as Japan, which hopes to have its first wells up and running by 2018.

Analysts caution that this may be optimistic. So far, the only production has been from small-scale field experiments. Scaling up to commercial production is at least 10 years off, says Professor Geoffrey Maitland of Imperial College London, who has been investigating its potential for more than a decade.

Risky business

“To release the gas, you need to destabilise the hydrates either by increasing the temperature or, more usually, by decreasing the pressure in an enclosed well bore,” Maitland explains. “But they are held in loose sediments in the seabed and require a certain pressure so as not to destabilise the entire area. Otherwise the methane explodes like uncorked champagne. That could sink the well and cause subsea landslides and trigger a tsunami. There is a very narrow pressure-window of opportunity, and the risks are far higher and production is much more expensive than, say, for shale gas.”

Another problem is that methane is a greenhouse gas with 25 times the global warming potential of carbon dioxide over a century; leaks of the highly concentrated gas could prove disastrous. There are warnings from history: 55 million years ago, at the end of the Paleocene, methane hydrate released by melting clathrates led to rapid global warming, and a subsequent devastation of coral reefs.

None of these concerns is slowing down the Japanese effort. The rest of the world is watching.



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