A single, vast shale deposit— the Marcellus formation, stretching from Tennessee to New York—might contain enough natural gas to supply the U.S. for more than 40 years at today’s consumption rates, according to recent estimates. Thousands of vertical wells have exploited the shale’s easy-to-reach deposits. But newer technology and improved procedures are making horizontal drilling cost-effective, greatly expanding the amount of gas that can be extracted economically.
Political pressure is increasing to achieve energy independence from overseas suppliers and to use cleaner sources such as natural gas to create electricity, which emits 40 percent less carbon dioxide than burning coal. In response, the rush is on to capture as much Marcellus gas as possible. Drilling is expanding fastest in Pennsylvania’s extensive reserve. Only two Marcellus wells were drilled in that state in 2005, but 210 were drilled in 2008, and 768 were drilled in 2009, according to the Pennsylvania Department of Environmental Protection (DEP). And every year the portion of drilling permits for horizontal wells has increased significantly, accounting for 75 percent in 2009 and 87 percent so far in 2010. Fewer than 3,000 Marcellus drilling permits were approved from 2005 through 2009, yet “we expect about 5,000 applications in 2010,” says John Hanger, secretary of the DEP. Horizontal drilling is spreading rapidly across Europe as well.