"Given the state of the oil market, more and more effort is being put into making shale a viable source," said Stanislaw. He estimated it will take six to eight years before oil companies perfect their extraction methods. "The timeframe is very long," he said.

In the 1970s, oil shale efforts involved mile-wide strip mines and factory-size cookers to boil giant limestone boulders. This time, no company expects to bring in front-loaders, heavy-duty dump trucks or thousands of miners to haul shale from open pits.

"The old technique required them to dig the equivalent of a new Panama Canal every month," said former Colorado Gov. Richard Lamm, whose tenure from 1975 to 1987 included the last attempt to extract oil from shale.

'More sane process'

"This new approach is a much more sane process, but that's all relative," Lamm said in an interview. "They're doing this in an immensely fragile area where wagon ruts from the Oregon Trail in the 1840s are still visible. It doesn't excite me because I think they're about to indelibly change our state."

Local residents are also leery, recalling the ghost towns and job losses left behind from the last shale boom and bust.

Battlement Mesa, Colo., a town Exxon built to house an expected 25,000 shale workers, was abandoned when the company shut its mine on May 2, 1982, a day locals still refer to as "Black Sunday." The town is now a retirement community.

"I don't think this is going to go anywhere," said John Savage, an attorney in Rifle whose father started a shale-oil company in 1956. "It's just too tough to get that oil out of the ground. There's trillions of barrels down there, but there's too much rock on top of it."

Oil companies also are exploring shale fields in Jordan, Morocco and Australia, though preliminary assessments indicate none is as oil-rich as the Colorado and Utah deposits. The final approval for full-scale projects in the U.S. won't be made until after 2010.

"If we waited a few million years, all this stuff would turn to oil," Rand's Bartis says. "Some people don't want to wait that long."