Geology of the Fayetteville Shale, Northern Arkoma Basin, Arkansas

Nicki Atkinson1

¹Southwestern Energy Company

The Fayetteville Shale is a Mississippian-age gas shale reservoir that is the geologic equivalent of the Caney Shale found on the Oklahoma side of the Arkoma Basin and the Barnett Shale found in north Texas. This unconventional gas play is located on the Arkansas side of the Arkoma Basin, ranging in thickness from 50 to 550 feet, and in depth from 1,500 to 6,500 feet within the Southwestern Energy play area. The Fayetteville Shale is a marine shelf deposit which includes transgressive and highstand system tracts of the Chesterian cycle separated by maximum flooding over a broad shelf area that comprises the northern Arkoma Basin and southern Ozark region. Across most of northern Arkansas, the Chesterian cycle buries an erosional unconformity on the Boone Limestone (Lower Mississippian), whereas in eastern Arkansas, the Moorefield Shale represents the low-stand wedge filling the Middle Mississippian unconformity in the region. Across the area, the Fayetteville Shale is overlain by the Pitkin Limestone or its shale equivalent. In the western side of the play area, the Fayetteville Shale encases the Wedington Sandstone and its associated Middle Fayetteville prodelta facies. Moving eastward to the center of the play, the Fayetteville lacks development of both the Wedington Sandstone and the Pitkin Limestone. From a geochemical standpoint, the Total Organic Carbon content of the Fayetteville Shale ranges from 4.5% to 9.5%, and the thermal maturity ranges from 1.5 to 4.5, placing the Fayetteville firmly in the gas window.

AAPG Search and Discover Article #90097 © 2009 Tulsa Geological Society, Tulsa, Oklahoma