U.S. Gulf gas hydrate find most promising yet -DOE
Thu May 14, 2009 7:23pm EDT
By Bruce Nichols
reuters.com
HOUSTON, May 14 (Reuters) - A U.S. research team has found the most promising natural gas hydrate deposits yet under the U.S. Gulf of Mexico, improving chances the ice-like formations will become a major energy source, scientists said on Thursday.
"It's very encouraging. We consider this expedition a major shift in our understanding," said Timothy Collett of the U.S. Geological Survey, a leader of the research effort.
"What's unique about the Gulf of Mexico accumulations identified is this. It's the first time we've seen highly concentrated hydrates in conventional sand reservoirs that could be commercially producible," Collett said.
The program seeks to determine by 2025 how much producible hydrate exists in the United States and whether it can be added to society's energy options, said co-leader Ray Boswell of the U.S. National Energy Technology Laboratory.
Gas hydrate is almost pure methane mixed with water turned to ice by low temperatures and high pressures in permafrost or under the sea. It exists in vast quantities around the world but so far has been unproducible as an energy resource.
Researchers have been studying gas hydrate for years, but deposits examined have been either too thin or too trapped in rock to be commercial, or so shallow as to be environmentally risky to produce.
Methane is a potent global-warming gas and can be fatal if breathed in heavy concentrations.
Collett said the newly found deposits are more promising commercially because they are sizable and located in porous, permeable sands like those from which conventional oil and gas are extracted.
They also are less risky environmentally than shallower hydrate formations because they are trapped under impervious shales more than 2,000 feet under the seabed, Boswell said.
The program, which includes the U.S. Minerals Management Service and an industry team led by Chevron Corp (CVX.N), used seismic data to try to locate promising hydrate deposits in the Gulf.
An important finding was that the drilling validated predictions made from the data, Collett said.
From mid-April to early May, a 21-day expedition drilled seven wells in three locations in Gulf waters 4,800 to 6,600 deep, areas the MMS calls Walker Ridge, Green Canyon and Alaminos Canyon for oil and gas industry purposes.
Four of the wells found high concentrations of hydrate in porous, permeable sands. Two found low concentrations of hydrate in promising sands. One found promising sand but no hydrate.
Among the questions yet to be answered are what concentrations of hydrates at what depth in what kind of reservoir sands are easiest to produce, Boswell said.
Engineering and technology also must be developed to produce hydrates, although industry already produces oil and gas from deeper waters and much deeper wells, the scientists said. (Editing by David Gregorio)
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