Chesapeake Energy Corp,the Oklahoma-based firm is the No. 1 driller in Ohio.
Rig Count Interactive Map by Baker Hughes, an energy services company.
Shale Sheet Fracking, a Youngstown Vindicator blog.
The Ohio Environmental Council, a statewide eco-group based in Columbus.
Earthjustice, a national eco-group.
People's Oil and Gas Collaborative-Ohio, a grass-roots group in Northeast Ohio.
Concerned Citizens of Medina County, a grass-roots group.
No Frack Ohio, a Columbus-based grass-roots group.
Fracking: Gas Drilling's Environmental Threat by ProPublica, an online journalism site.
Pipeline, blog from Pittsburgh Post-Gazette on Marcellus shale drilling.
Allegheny Front, environmental public radio for Western Pennsylvania.
Oklahoma-based Chesapeake Energy Corp. was No. 1 in Pennsylvania for 2011 gas production from the Marcellus shale.
Those wells produced 3,329 mcf per day and resulted in 2011 earnings of $879 million, according to state data reported by the Marcellus Drilling News.
A total of 2,755 Marcellus wells were drilled in Pennsylvania in 2011, according to the Department of Environmental Protection.
That's up from 1,386 wells in 2010. That's nearly a 200 percent increase.
Chesapeake has 401,000 acres leased in Pennsylvania and has 2,199 workers, the Marcellus Drilling News reported.
It is the biggest player in eastern Ohio's developing Utica shale.
The other companies in the Top 10 were:
2. EQT Production.
3. Anadarko E & P Co.
4. CNX Gas (Consol Energy).
5. Range Resources Appalachia LLC.
6. Talisman Energy USA.
7. Chevron Appalachia (Atlas Energy).
8. Cabot Gas & Oil.
9. Seneca Resources (National Fuel Gas Co.).
10. Shell Appalachia.
Those 10 companies together have leases on 5.1 million acres in Pennsylvania, according to state records. Range Resources is NMo. 1 with 1.1 million acres.