Top shale oil producer Pioneer Natural Resources Co (PXD.N) has found an unusual way to both save water and cut costs for its wells: tapping the treated runoff from toilets, sinks and showers in west Texas. Pioneer has signed an 11-year, $117 million deal with the city of Odessa, Texas that will guarantee it access to millions of gallons of treated municipal wastewater each day, for use in nearby oilfields.