Advanced drilling techniques that blast millions of gallons of water into 400-million-year-old shale formations a mile underground are opening up "unconventional" gas fields touted as a key to the nation's energy future.
These deposits, where natural gas is so tightly locked in deep rocks that it's costly and complicated to extract, include the Barnett shale in Texas, the Fayetteville of Arkansas, and the Haynesville of Louisiana. But the mother lode is the Marcellus shale underlying the Appalachians.