Frozen gas offers help for energy woes

RESEARCHERS at the US Department of Energy’s (DOE) Brookhaven National Laboratory in San Diego have recreated the low temperature and high pressure of the ocean floor in order to help work out how to access a hidden treasure trove of natural energy.

“The amount of natural gas that is tied up in methane hydrates beneath the sea floor in permafrost on Earth is several orders of magnitude higher than all other known conventional sources of natural gas – enough to meet our energy needs for several decades,” said Brookhaven chemist Devinder Mahajan.

Mining methane hydrates is currently not a viable proposition as they are only stable at the low temperature and high pressure of sea floor conditions, attempts to bring them to the surface causing them to decompose and release the methane trapped by the enclosing water molecules before it can be harvested.

The Brookhaven team is studying the conditions required to keep the methane hydrates stable in order to develop methods of successfully extracting the gas for fuel purposes. Mahajan has constructed a vessel that mimics the required conditions, allowing the study of methane hydrate kinetics under laboratory conditions.

“You fill the vessel with water and sediment, put in methane gas, and cool it down under high pressure. After a few hours, the hydrates form. You can actually see it. They look like ice, but they are not. They are stable at 4C,” said Mahajan.

The research may get a boost later this month with the launch of the “Uncle John”, a semi-submersible drilling vessel being launched as part of $US23 million joint venture by the DOE and Chevron-Texaco to study ocean floor samples. The sub will spend 35 days in the Gulf of Mexico collecting sediment samples from the methane hydrate deposits almost 1500m below the ocean surface, and keep them under the same conditions in order to study them in the laboratory.

“We’re going to pull up 3.5 inch diameter cylinders of sediments and keep them under the same conditions they were at the bottom,” said DOE technology manager Ray Boswell.

Arctic research by Canada and Japan has shown that onshore hydrates can provide economically viable quantities of methane, but it is estimated that the ocean floor holds exponentially greater amounts available for use as an energy source.