Several hundred Marcellus shale wells have been drilled in this county making it one of the most prolific areas of the play. The companies most active in this county are Range Resources, Chesapeake Energy, and Atlas Energy Resources. Drilling companies produced 67 Bcf of natural gas from the Marcellus shale during the second half of 2011. This was up from 45.9 Bcf during the first half. The total year's production was almost 113 Bcf. This volume of gas was produced by 353 wells, up 75 from 2010. A March, 2012 report indicated that 560 Marcellus wells had been drilled in the county since 2007. It is unknown why (according to the above) so few of the total number drilled actually appear to be producing, unless many of the wells have never been completed and connected to gathering lines.