The math just doesn't work out, they say — America consumes too much.

But some are even more skeptical than that.

Arthur Berman, an oil analyst with Labyrinth Consulting Services, says the promise of America's shale reserves have been vastly overstated.

His main argument: shale is too expensive to drill, and shale wells usually don't last longer than a couple of years.

Last year, he laid out his case at a gathering of the Association for the Study of Peak Oil and Gas in Austin Texas.