In the natural-gas fields of Pennsylvania, Cabot Oil & Gas Corp. has had a split week in federal court — winning its motion to dismiss an amended complaint from a drilling company with which it had a contract and losing its argument that plaintiffs should show a heavy burden of proof before starting discovery in a separate case.

In the case filed by Mickel Drilling Partners, a federal judge held that Mickel couldn’t change the operative lease agreement by filing an amended complaint after it had proceeded in the court for the last 18 months with the assertion that a later contract held sway.