New energy source discovered below Alaskan ice

13 November 2012
By David Spencer
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Oil pipes and drilling rig on Endicott Island

Just north-east of Prudhoe Bay, Endicott is the first continuously producing offshore field in the Arctic

Half a mile below the ground above the vast North Slope oil field, Prudhoe Bay, Alaska, that helped trigger construction of the trans-Alaska pipeline, a drilling rig has uncovered what could be the next big energy source.

The US Department of Energy (DOE) and industry partners drilled into a reservoir of methane hydrate over two winters. The chemical looks like ice but burns like a candle if struck by a match. Methane, the main chemical component of natural gas, is in little demand today. The USA is awash in natural gas for the near future after the boom in production from hydraulic fracturing. The controllers are considering exporting it but the DOE wants to be ready with methane if there's a need.

Ray Boswell, the technology manager for methane hydrates within the DOE’s National Energy Laboratory, has said: "If you wait until you need it, and then you have 20 years of research to do, that's not a good plan."

The experiment, which took place on the North Slope and cost an estimated $29m, has produced 30,000 cubic metres of methane. Researchers are now beginning the complex task of analysing how the reservoir responded to extraction.

Currently much is unknown, but research interest has accelerated over the last decade according to research geologist Dr Tim Collett, of the US Geological Survey in Denver.

US operators in Alaska, Dr Collett has said, may want to harvest methane so they can re-inject it into the ground. Crude oil is more lucrative than natural gas, which is routinely injected into North Slope fields to maintain underground pressure to aid oil extraction. Other countries, notably Japan, South Korea, India and China, however, want to cut down on natural gas imports by burning methane. Japan is setting up for a production test on a gas hydrate accumulation in the Nankai Trough south of Honshu, its main island.

"That will be the first marine gas hydrate test anywhere in the world," Dr. Collett said.

The US Energy Department describes methane hydrate as a lattice of ice that traps methane molecules, although substance does not bind them chemically. The molecules are released when warmed or depressurised.

Dr Brendan Cummings of the Center for Biological Diversity argues that research money should be poured into renewable resources, not more fossil fuel sources. Methane may be 20 times more effective at trapping heat in the atmosphere than CO2, but Dr Cummings states it is not as long-lived: "Any exploration activities designed to extract methane hydrates run the risk of unintended consequences, of unleashing the monster." And despite safe extraction, the burning of the gas will add considerably to global warming.

The world has an abundance of methane hydrate, and the Minerals Management Service study in 2008 estimated methane hydrate resources in the northern Gulf of Mexico to be at 21,000 trillion cubic feet (595 trillion cubic meters). This translates to 100 times current US reserves of natural gas. The combined energy content of methane hydrate may exceed all other known fossil fuels, according to the DOE.

Despite abundance not all is accessible, but high concentrations in permeable rock where there's existing drilling infrastructure would be among early candidates for development. The USGS in 2008 estimated 85 trillion cubic feet (2.41 trillion cubic meters) of undiscovered, technically recoverable gas within methane hydrate deposits on Alaska's North Slope.

Extraction will not be solely based upon earth extraction:  "One of the basic messages is, we're not mining," said Boswell. "It's using existing drilling techniques."

The alternative is that methane could be extracted by lowering pressure or increasing temperature in an underground reservoir. Boswell explained: "One of the issues with that, though, is that you are melting the ice, and adding a lot of gas and water to the reservoir, which can compromise the reservoir's strength."

Alaska research is focused on a method aimed at conserving the underground ice structure. The extraction technique is based on studies conducted by ConocoPhillips and the University of Bergen in Norway. Researchers injected carbon dioxide into methane hydrate. CO2 molecules swapped places with methane molecules, thereby freeing the methane to be harvested but preserving the ice.

The DOE worked closely with ConocoPhillips and Japan Oil, Gas and Metals National Corp to see if it would work in the field. The North Slope has been named after an Inupiat Eskimo phrase that translates as "fire in the ice". 

"From the lab data we had, it seemed like strong evidence that it was not a lot of wholesale destruction of the solid hydrate," Boswell said. Researchers remain optimistic.

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