See Gas Drillers Ranked by the Number of Active Gas Wells.

According to Gas Business Briefing and Pennsylvania Department of Environmental Protection data, 218 companies have a minimum of 100 active wells.

Who is number 1?  Chevron who just bought Atlas and its wells and other assets.  Chevron now operates 5,459 total active wells, the vast majority being not Marcellus wells but traditional, shallow Pennsylvania gas wells.

Number 2 is Range Resources with 5,360 active wells.

Number 3 is Exco Resources with 4,066 active wells.

Number 4 is Consol Gas Co. with 3,341 active wells.

Number 5 is the privately held Snyder Bros Inc. with 3,302 gas wells.

Twenty-six companies have more than 1,000 active wells.  Again the vast majority of these wells are not Marcellus and were drilled 3 or more years ago.  In some cases the wells are decades old.