Lithofacies and Chemostratigraphy of the Woodford Shale in the Western Arkoma and Eastern Anadarko Basins, Oklahoma

Abstract

The purpose of this study was to evaluate the chemo- and lithostratigraphic properties of the Woodford Shale in the Anadarko and Arkoma Basins of Oklahoma. Woodford Shale lithology varies considerably throughout Oklahoma due to depositional history and diagenesis. To understand the chemo- and lithostratigraphic properties of the Woodford, two cores, one from Garvin County in the Anadarko Basin, and another from Coal County in the Arkoma Basin were characterized using geochemical and lithologic properties. The two cores were described in detail at a one foot (30.48 cm) interval to record lithology, sedimentary, biogenic, structural and diagenetic features. Wireline logs were used to evaluate how gamma-ray, neutron, density, and resistivity signatures relate to changes in lithofacies. X-ray diffraction (XRD) and thin section petrography established bulk mineralogy whereas X-ray fluorescence (XRF) identified proxies for paleo-redox conditions during deposition, allowed an estimate of the geochemistry of bottom water, and estimation of frequency of disruption of stratification. The roles of radiolaria and tasmanites as sources of silica and organic matter, respectively, were analyzed. The relative abundance of silica and other non-clay components as quantified by XRD were compared to wireline log curves to determine if a set of parameters could be developed whereby conventional log curves could be used to detect and map brittle zones with a propensity to fracture naturally or artificially. If these brittle zones are mappable, log signatures can be used to help explore for and develop oil and gas reserves in the Woodford Shale.