Anne-Sophie Corbeau, a gas analyst at the International Energy Agency, in a report this week said global gas reserves could have a lifespan of more than 250 years through unconventional gas reserves, including shale. That's roughly double previous estimates.
Corbeau told the BBC that the U.S. energy sector was looking to import natural gas before it emerged in 2009 as the "world's biggest gas producer" in part because of shale gas reserves.
"The gas story is huge," she said.
She said there was "probably" more than "300 times" more unconventional gas on hand than the current annual demand for gas. Not all of the gas locked in hard-to-reach formations is exploitable, however.
Advocates point to the clean-energy gains from natural gas. Fatih Birol, the chief economist at the IEA, told the BBC that burning natural gas produces half of the emissions of coal.
Critics, however, complain that the chemicals used to crack open rock formations, dubbed fracking, could contaminate sensitive water supplies.
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