According to a talk given by John Harper, chief, oil, gas and subsurface services at the Pennsylvania Geological Survey, some 792 wells suspected to target Marcellus shale have been permitted in the Keystone state. Of those, 571 were vertical and 221 were horizontal locations. Prior to 2003, only a handful of wells produced from the formation outside of Erie County, along the shores of Lake Erie in far northwestern Pennsylvania. The current flurry of Marcellus-directed drilling surged in 2007, when 307 such wells were permitted, versus 54 in 2006. As of Fall 2008, 402 permits were issued by the state for wells believed to target Marcellus. Many operators are active in the Marcellus play across Pennsylvania: EOG Resources has locations in Bradford and Elk counties; Rex Energy in Butler County; Atlas Resources in Fayette, Greene, Washington and Westmoreland counties; CNX Gas Co. in Greene County; Turm Oil in Susquehanna County and Range Resources in Washington County, among others, reports IHS Inc. Harper gave his talk at the AAPG-SPE Eastern Meeting, held in Pittsburgh in mid-October. --by Peggy Williams, Senior Exploration Editor, Oil and Gas Investor