AAPG Foundation 2019 Grants-in-Aid Projects

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Identification and Characterization of Low Permeability Formations within the Hunton Group, Central Oklahoma


The Ordovician-Devonian Hunton Group is an important oil- and gas-producer in Central Oklahoma. Historically, the Hunton Group produced oil and gas primarily from the Devonian Bois d’Arc/Frisco and Ordovician/Silurian Chimneyhill intervals at the top and base, respectively. Relatively little research is known on the Silurian Henryhouse and Devonian Haragan formations due to their tendency to have low permeability and low porosity. With horizontal drilling and large-volume stimulation, low-permeability reservoirs within the Hunton Group are viable targets for development. Unfortunately, it is difficult to construct a meaningful reservoir model if the stratigraphy is unresolved. In this study, cores will be described to identify and characterize the subunits of the Hunton Group and their stratigraphic relationships to one another. Many interpretations are based on deeper-water outcrop lithofacies and ignore potential facies changes shoreward on the gently sloping carbonate ramp. Consequently, much of the industry work and academic literature misidentified the Hunton Group subunits or combined them for description. This study will focus primarily on the Henryhouse, Haragan, Bois d’Arc, and Frisco because of the paucity of literature on the four formations and their reservoir potential. Several cores in Central Oklahoma have been identified as potential candidates for analysis and will be described, sampled, and analyzed using thin sections, x-ray-diffraction, x-ray fluorescence, SEM, and paleontology to determine their age and correct formation name. Once established, these formations and their corresponding facies will be correlated to wireline logs to establish electrofacies to map the distribution of facies and formations across the region and between cores.