 The watershed has no oil or conventional natural gas fields . However , a potentially large source of natural gas is the <unk> shale , which lies 1 @.@ 5 to 2 @.@ 0 miles ( 2 @.@ 4 to 3 @.@ 2 km ) below the surface here and stretches from New York through Pennsylvania to Ohio and West Virginia . Estimates of the total natural gas in the black shale from the Devonian period range from 168 to 516 trillion cubic feet ( 4 @.@ 76 to 14 @.@ 6 trillion m3 ) , with at least 10 percent considered <unk> . 
