Pennsylvania's attorney general sued one of the nation's largest producers of natural gas on Wednesday over claims it cheated at least 4,000 landowners who signed drilling leases with the company. Oklahoma City-based Chesapeake Energy Corp. tricked landowners into signing one-sided leases in the early years of the Marcellus Shale drilling boom and then improperly deducted certain post-production expenses from their royalty checks, according to the lawsuit filed in Bradford County.