Comparative Lithology of The Barnett Shale, Central Texas and Age-Equivalent Caney Shale in Southern Oklahoma

Puckette, Jim¹, Darwin Boardman¹, Bill Coffey², Eric Gerding¹, Patrick Kamman², Naranjan Aryal¹, Manish Singh¹, Andy Rihn¹, Stan Paxton³ (1) Oklahoma State University, Stillwater, OK (2) Devon Energy Corporation, Oklahoma City, OK, (3) United States Geological Survey, Oklahoma City, OK

Gas production from Upper Mississippian siliciclastic mudrock reservoirs in Texas and the southern Midcontinent region is generating intense interest in the Barnett Shale and age-equivalent Caney Shale. The Barnett Shale at the type Chappel locality near San Saba, Texas consists of 39.4 feet (12 m) of gray to black phosphatic shales that contain thin lenticular carbonates. Six prominent, shale to carbonate, depositional cycles are evident. Biostratigraphic analyses indicate that the upper Meramecian and entire Chesterian Stages are represented at this locality. Caney Shale outcrops were examined on the Arbuckle and Lawrence uplifts, near Ardmore and Ada, Oklahoma, respectively. Total measured thickness of the Caney exceeds 325 feet (99 m) on the south flank of the Arbuckle uplift and 280 feet (85 m) feet along partially exposed sections near Ada. The Caney consists of three lithologically distinct members: the Ahloso, Delaware Creek and Sand Branch. The Ahloso Member is coarser-grained and primarily dark grey to brown silstones and silty shale. Faunal evidence places the Osagian-Meramecian boundary near the base. The Delaware Creek Member consists of dark grey to olive shales that contain prominent carbonate concretions (bullion). Faunal evidence places the Meramecian-Chesterian boundary in the upper part of the Delaware Creek. The Sand Branch is black to dark gray phosphatic shale with sparse carbonate concretions. Ammonoid and conodont faunas, place the Sand Branch as upper Chesterian. Caney lithologies reflect high frequency depositional cycles and a generalized upward increasing water depth during deposition from lowest in the Ahloso to maximal in the Sand Branch.