Over a mile beneath an area of Appalachia covering parts of four states lies a mostly untapped reservoir of natural gas that could swell U.S. reserves. Geologists and energy companies have known for decades about the gas in the Marcellus Shale, but only recently have figured out a possible, though expensive, way to extract it from the thick black rock about 6000ft underground. Like prospectors mining for gold, energy executives must decide whether the prize is worth the huge investment. The shale holding the best prospects covers an area of 54,000sq/mi, from upstate New York, across Pennsylvania into eastern Ohio and across most of West Virginia – a total area bigger than the state of Pennsylvania. It could contain as much as 50 trillion cu/ft of recoverable natural gas, according to a recent study by researchers at Penn State University and the State University of New York at Fredonia.
