HEAT FLOW AND THERMAL HISTORY OF THE ANADARKO BASIN, OKLAHOMA
Larry S. Carter
Chelsea Energy, Inc.
717 North Harwood, Suite 2700
Dallas, TX 75201
Shari A. Kelley
Department of Earth and Environmental Sciences
New Mexico Institute of Mining and Technology
Socorro, NM 87801
David D. Blackwell
Department of Geological Sciences
Southern Methodist University
Dallas, TX 75275
Nancy D. Naeser
U.S. Geological Survey
MS 926A, National Center
12201 Sunrise Valley Drive
Reston, VA 20192
American Ass. of Petroleum Geologists, Feb. 1998, p291-316, v.82.
New heat-flow values for seven sites in the Anadarko Basin, Oklahoma, were determined using high-precision temperature logs and thermal conductivity measurements from nearly 300 core plugs. Three of the sites are from the northern shelf, three are in the deep basin, and one is in the frontal fault zone of the northern Wichita Mountains. The heat flow decreases from 55 to 64 mW/m2 in the north to 39 to 54 mW/m2 in the south due to a decrease in heat generation in the underlying basement rock toward the south. Lateral lithologic changes in the basin, combined with the change in heat flow across the basin, have resulted in an unusual pattern of thermal maturity. The vitrinite reflectance values of the Upper Devonian - Lower Mississippian Woodford Formation are highest 30 to 40 km north-northwest of the deepest part of the basin. The offset in highest reflectance values is due to the contrast in thermal conductivity between Pennsylvanian "granite wash" section adjacent to the Wichita uplift and the Pennsylvanian shale section to the north. The geothermal gradient in the low conductivity shale section is elevated relative to the geothermal gradient in the high conductivity "granite wash" section, thus displacing the highest temperatures to the north of the deepest part of the basin.
Apatite fission-track, vitrinite reflectance, and heat flow data are used to constrain regional aspects of the burial history of the Anadarko Basin. By combining these data sets, we infer that at least 1.5 km of denudation has occurred at two sites in the deep Anadarko Basin since the middle Cenozoic (40 ± 10 Ma). The timing of the onset of denudation in the southern Anadarko Basin coincides with the period of late Eocene erosion observed in the Southern Rocky Mountains and in the northern Great Plains.
Burial history models for two wells from the deep Anadarko Basin predict that shales of the Woodford Formation passed through the hydrocarbon generation window by the end of the Permian. The Late Pennsylvanian to Early Permian section in the deep basin moved into the hydrocarbon generation window during Cretaceous burial of the region. Presently, the depth interval of the main zone of oil generation (% Ro = 0.7 to 0.9) is approximately 2800 to 3800 m in the eastern deep basin and 2200 to 3000 m in the western deep basin. The greater depth to the top of the oil generation zone and larger depth range of the zone in the eastern part of the deep basin is due to the lower heat flow associated with more mafic basement toward the east. The burial history model for the northern shelf indicates that the Woodford Formation has been in the early oil generation zone since Early Permian time.