A geochemical study of potential source rocks and crude oils in the Anadarko Basin, Oklahoma.

摘要

Source rock and crude oil samples from the Anadarko Basin, Oklahoma have been characterized by a number of organic geochemical techniques. The source rocks investigated include the Late Ordovician Viola Limestone and Sylvan Shale, the Early Mississippian Lower Mississippian Limestone, and the Late Mississippian to Pennsylvanian Chester, Springer, and Morrow Formations. Since the Late Devonian Woodford Shale is an important source rock in the basin and has been investigated intensively in previous studies, the Woodford Shale was also analyzed and used as an "internal standard" or a reference formation to compare with other formations examined in this study. The crude oils examined in this study were obtained from various reservoir formations of different ages throughout the Basin.;Based on the results of screening analyses and geological information, a source rock evaluation model (PGI maps) has been built to evaluate the five source rock formations. Besides the Woodford Shale (which is proved by the model to be a very good source rock) the model indicates that the Lower and Middle sub-facies of the Viola Limestone are good source rocks, especially at the eastern Anadarko Basin. The Sylvan shale in the Anadarko area is probably not a good source rock. The black shales in the Springer and Morrow Formations are fairly good source rocks, especially for generation of natural gas. The results of this study support the proposal of multiple sources oil and gas generation in the Anadarko Basin.;Selected source rock and crude oil samples were processed for further organic geochemical analyses, which included stable carbon isotope (;Petrographic descriptions and graptolite reflectance (or vitrinite reflectance) measurements were made to evaluate petrographic properties of source rocks and kerogens and to evaluate the maturity levels of the Viola and Lower Mississippian Limestones. There was a reasonable correlation between measured graptolite and calculated vitrinite reflectance values.