West Virginia

From Wikimarcellus

According to a report produced by the West Virginia Oil and Natural Gas Association in 2006, there were 46,110 active gas wells in West Virginia. Wells were located in all but two of the state's 55 counties. Only Jefferson and Berkeley Counties in the State's Eastern Panhandle have no gas wells.

According to a July, 2009 report, a partial list of active gas wells by
county includes: 
     County             No. of Gas Wells
     ------             ----------------
    Jackson                  1,175
    Pleasants                  667
    Ritchie                  4,578
    Wirt                       407
    Wood                       283

In West Virginia, the Marcellus shale formation is located at varying depths throughout most of the state. Both the extreme western and eastern portions of the state are the exception. It varies in thickness between 20 and 100 feet. The thickest part of the formation is centered on Taylor and Barbour counties. Successful Marcellus wells have been drilled in shale only 46 feet thick.

The Onondaga Limestone lies immediately below it, and can be used by drillers to estimate the depth of a well drilled all the way through the Marcellus.