What's getting all of the attention is hydraulic fracturing, a process that involves injecting a mixture of water, sand and chemicals under high pressure to break through shale formations to reach enormous deposits of natural gas several miles underground. New advances in seismic imaging are used to find the shale gas, and horizontal drilling enables companies to reach the gas and bring it to the surface.
Largely through the use of these techniques, U.S. natural gas production has increased 40 percent in recent years, reversing what was once thought to be an irreversible decline in domestic drilling.
Geologists have identified about two dozen large shale gas beds in North America that could contain 100 years worth of natural gas. One field alone -- the Marcellus shale formation in Appalachia that extends from upstate New York through Pennsylvania to West Virginia -- holds an estimated 50 trillion cubic feet of natural gas. Without hydraulic fracturing technology, much of these rich domestic energy resources would be inaccessible.