The Fayetteville Shale
The Fayetteville Shale is a black organic-rich rock of Mississippian age that underlies much of northern Arkansas and adjacent states. It produces natural gas in the central portion of the Arkoma basin. The productive wells penetrate the Fayetteville Shale at depths between a few hundred and 7,000 feet below the surface and at elevations of between a few hundred feet above sea level and 7,000 feet below sea level.
The first wells to produce natural gas from the Fayetteville Shale were traditional vertical wells with low to moderate production rates. However, in the past ten years, vertical wells have been drilled down to just above the Fayetteville Shale, then turned and drilled horizontally through the rock unit. These horizontal wells intersect large numbers of vertical fractures which bring a flow of gas into the well and drain the surrounding rock. Fractures are also induced by pumping pressurized fluids down the well bore to fracture the rock unit. These additional fractures enhance the permeability of the Fayetteville Shale and allow more efficient gas production.