The Mississippian age Fayetteville Shale produces gas in the Arkansas part of the Arkoma Basin. The productive section varies in thickness from 50 to 550 feet (170 m), and in depth from 1,500 to 6,500 feet (460 to 1,980 m). The shale gas was originally produced through vertical wells, but operators are increasingly going to horizontal wells in the Fayetteville.