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.
The U.S. Energy Department has cut its estimate for natural gas reserves in the Marcellus shale by 66 percent, citing improved data on drilling and production.
About 143 trillion cubic feet of natural gas can be recovered using current technologies, the agency said.
That's down from the previous estimate of 410 trillion cubic feet, the agency said on Monday.
The estimated Marcellus reserve is enough to fuel the U.S. for six years, down from 17 years in the previous report, the agency said.
It said about 462 trillion cubic feet can be produced from shale basins across the United States, down 42 percent from the 827 trillion cubic feet in last year's outlook.
Shale gas is expected to account for 40 percent of total U.S. dry gas in 2035, up from the 23 percent in 2010, Energy said.
The U.S. could become a net exporter of liquefied natural gas in 2016 and a net exporter of natural gas in 2012, the agency said.