But one of Shell's recent moves has raised some eyebrows, as they are in the process of buying up water rights in Colorado to process the shale.

The freeze wall is created by pumping refrigerated fluid through a series of wells drilled around the extraction zone. The freeze wall prevents groundwater from entering the extraction zone,

and keeps hydrocarbons and other products generated by the in-situ

Shale country tends to be dry country, and Shell's process uses a lot of water.

Some officials, however, worry that the demands of the oil-shale industry could drain every drop of the region's remaining water.

"On the upper end, we're looking at potentially several hundred thousand acre-feet of water — more than people think is commonly available to develop in the Colorado River," said Dan Birch, deputy general manager for the Colorado River Water Conservation District.

The energy return is already going to be very marginal.