Warning Signs On The Ocean Floor  

Posted by Big Gav in , , ,

Methane Hydrates ("the ice that burns") are one of the alternative sources of hydrocarbons - and one with reserves estimated to be larger than those of oil, gas and coal combined - that seem to live in a perpetual twilight on the verge of being harvested.

While the topic seems to pop up somewhere every couple of months, thus far I haven't noticed any actual progress in this area (which is probably a good thing from a global warming point of view).

The latest manifestation of the search for fire from the deeps is described in an article in Der Spiegel - "China and India Exploit Icy Energy Reserves" - which describes efforts in Asia to slake their thirst for energy by finding a way to utilise offshore methane hydrate fields. The article also describes a theoretical way of sequestering carbon dioxide while extracting methane from the frozen hydrates, which sounds like a carbon addict's wildest fantasy come true.

China and India have reported massive finds of frozen methane gas off their coasts, which they hope will satisfy their energy needs. But environmentalists fear that tapping these resources could have adverse effects on the world climate.

On the surface, it looked like any other drill core from the ocean floor. Its shimmering grayish-green surface was both slippery and grainy at the same time. But the sample only revealed its exciting secret when the geologists on board the "Bavenit," a drilling ship, lowered the pressure in the steel tube and held a lit match to the upper end. Suddenly a yellowish-red flame began licking from the slick material.

"As astonishing phenomenon," noted the scientists from the Guangzhou Marine Geological Survey. So astonishing, in fact, that when their ship pulled into the harbor at Shenzen on June 12 of this year, the scientists were all smiles.

Shengxiong Yang and Nengyou Wu, the two expedition leaders, stand an excellent chance of going down in the history of their country as heroes. The material they pulled from the muddy ocean floor of the South China Sea has the potential to satisfy the energy needs of China and its fast-growing economy.

The flames in the drill core were coming from methane hydrate, a material first discovered in the 1970s. Its unique characteristic is that it is a seemingly frozen and yet flammable material.

In the West, this potential fuel from the ocean floor has for the most part been the stuff of fantasy. But it's a different story in Asia. The People's Republic of China is investing millions to study this massive source of energy. The same holds true for India, South Korea and Taiwan, all nations that are on a fast track to surpassing the West as economic powers. ...

Methane, trapped in an icy cage of water molecules, occurs in permafrost and, in even greater quantities, beneath the ocean floor. It forms only under specific pressure and temperature conditions. These conditions are especially prevalent in the ocean along the continental shelves, as well as in the deeper waters of semi-enclosed seas (see graphic).

World reserves of the frozen gas are enormous. Geologists estimate that significantly more hydrocarbons are bound in the form of methane hydrate than in all known reserves of coal, natural gas and oil combined. "There is simply so much of it that it cannot be ignored," says leading expert Gerhard Bohrman of the Research Center for Ocean Margins (RCOM) in the northern German city of Bremen.

A few months ago, Chinese Premier Wen Jiabao held the material in his hand -- or rather, in a metal ice bucket with flames shooting from the top. He was visiting an Australian research center at the time, but now he can just as easily watch the same spectacle unfold in Chinese research laboratories.

The Chinese researchers found the methane hydrate, also known as crystal gas, because of its molecular structure, in a layer of sediment 15 to 20 meters (50 to 65 feet) thick off the Chinese coast. "It was embedded in clay and silt ," says John Roberts, whose firm Geotek provided the technical equipment for the drilling expedition.

This is the sort of information natural gas companies like to hear. The porosity of this sediment mix is well suited to drilling for the gas. "The gas hydrate has never found in this form before," Roberts explains. It suddenly seems conceivable that production using conventional techniques could work.

One possible method would involve the use of drilling tubes that would conduct heated fluid into the cold reservoirs. This would dissolve the icy cage encasing the methane. The next step would be to capture the gas through a second opening.

These are the kinds of prospects that have inspired others to emulate the Chinese researchers' success. Japan has built the world's largest research drilling ship, the Chikyu, primarily to study methane hydrate. India has invested €200 million to launch a major national program -- and has already reported successes.

Indian researchers discovered a 132-meter (433-foot) thick layer of methane hydrate in the Krishna-Godavari Basin. "One of the thickest that's ever been found in the world," says Malcolm Lall, the director of the Indian gas hydrate program. The team has also been successful in the Andaman Islands, were they discovered, 600 meters (984 feet) beneath the ocean floor, a layer of frozen methane embedded in ash sediments from prehistoric volcanic eruptions. "This too is a first," says Lall.

But many scientists see the flames licking out of samples in Indian and Chinese laboratories as a warning sign. They fear that one day the methane from the ocean floor will heat up the world's climate to a far greater extent than coal, oil and natural gas do today.

This is precisely what scientists at the Institute for Marine Research (GEOMAR) based in the northern German seaport of Kiel want to avert. They hope to be able to transform a potential curse into a blessing before it's too late. They envision a method whereby the flammable gas would be extracted from the sediment with the help of carbon dioxide.

"The carbon dioxide could be obtained from the exhaust gases of coal power plants, for instance," says Klaus Wallmann, the direct of a research project known as SUGAR, which was recently formed to study the issue. What he proposes sounds almost too good to be true: producing fuel while sequestering greenhouse gas deep beneath the ocean floor -- eliminating energy bottlenecks while simultaneously putting the brakes on global warming.

Wallmann and his colleagues base their theories on a reaction scientists noticed more than a decade ago. When a certain amount of pressure is applied to the cage-like crystal structure, carbon dioxide can penetrate the layer of ice, at which point it displaces the methane. Then a new cage of frozen water molecules forms around the carbon dioxide. "This behavior has already been demonstrated in laboratory experiments," says Wallmann.

He is also impressed by the ratio at which the gases are exchanged. For each dissolved molecule of methane, up to five molecules of carbon dioxide disappear into the ice cage.


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