Marcellus Shale in Pennsylvania and West Virginia has surpassed Permian Basin as leading U.S. destination for hydraulic fracturing crews, according to Houston investment advisory group Tudor, Pickering, Holt and Co. The firm said last week 31 percent of active crews were in Marcellus Shale followed by 30 percent in Permian Basin, and 14 percent each in Eagle Ford Shale in south Texas and Haynesville Shale in east Texas and Louisiana. Tudor said 70 of 450 hydraulic fracturing crews currently are deployed (16 percent).