FILE - In this Oct. 14, 2011 file photo, a drilling rig is set up near a barn in Springville, Pa., to tap gas from the giant Marcellus Shale gas field. In an unlikely partnership betwee

 

              FILE - In this Oct. 14, 2011 file photo, a drilling rig is set up near a barn in Springville, Pa., to tap gas from the giant Marcellus Shale gas field. In an unlikely partnership betwee
FILE - In this Oct. 14, 2011 file photo, a drilling rig is set up near a barn in Springville, Pa., to tap gas from the giant Marcellus Shale gas field. In an unlikely partnership between longtime adversaries, some of the nation's biggest energy companies and environmental groups announced Wednesday, March 20, 2013 that they have agreed on a voluntary set of standards for gas and oil fracking in the Northeast. (AP Photo/Alex Brandon, File)