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The Upper Devonian-Lower Mississippian Woodford Shale is an important source rock in the Anadarko basin. Because of its stratigraphic relationship to the Hunton Group and other productive reservoirs, it has been the subject of several recent studies attempting to evaluate hydrocarbon potential. Standard geochemical analyses were performed on a 5-well cross-section beginning in the northeastern shelf of the Anadarko basin at a depth of 5,700 ft (1,737 m) and ending in the southeastern part
of the deep Anadarko basin at 22,000 ft (6,706 m). The data reveal systematic changes in geochemical parameters with increasing depth and maturity level. Such changes are consistent with maturation effects seen in other basins around the world.
Vitrinite reflectance data for progressively deeper wells yielded mean Ro values of 0.60, 0.88, 1.23, 1.86, and 2.03%. These values are indicative of maturation levels ranging from the main zone of oil generation to the zone of dry gas generation. Bitumen ratios (expressed as milligrams of soluble organic matter per gram of total organic carbon) agree well with these maturation levels. Infrared spectroscopy, used to assess the changes in functional groups of the soluble organic matter and kerogen, shows a corresponding increase in the aromaticity of the organic compounds with increasing maturity level. Elemental analysis of kerogen (carbon, hydrogen, nitrogen, and oxygen) and gas chromatography of whole-rock bitumen extracts exhibit maturation effects similar to those noted in other basins.
In addition, organic matter (O.M.) isolated by conventional palynologic techniques was examined under white light and shows progressive changes from yellow-amber and translucent O.M. at Ro = 0.60%, to dark brown, partially translucent and partially opaque O.M. at Ro = 0.88%. Samples with Ro values of 1.23% and greater are completely opaque. Visual kerogen studies support the obtained geochemical parameters.
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