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Stratigraphic and Structural Controls on Mississippian Limestone and Tripolitic Chert Reservoir Distribution using Seismic-Constrained Reservoir Characterization and Modeling, Northern Oklahoma


Mississippian limestone and chert reservoirs in northern Oklahoma have been a productive since the early 1900's. Fields were originally produced on closed structural highs and porosity pinch-outs associated with diagenesis and erosion. However, the geological controls on reservoir-quality distribution and production are still elusive. The Mississippian limestone and silica-rich deposits formed on a regionally extensive carbonate ramp and commonly form shoaling-upward lithofacies successions that stack into high-frequency, transgressive-regressive cycles. The cycles form several prograding, clinoformal depositional packages that commonly downlap to the south. Two dominant lithologies are common, tripolitic chert (‘chat’) and dense limestone, and lithofacies vary from mud- to grain-dominated fabrics Core, thin-section, and well-log analyses show that the dominant reservoir lithology is tripolitic chert and to a lesser degree, limestone. Porosity values range from 0 to 37 % and permeability varies from .0002 to 43 mD. Mississippian lithologies observed in core are calibrated to open-hole logs and tied to seismic attributes to predict and map the spatial distribution of tripolitic chert. Three-dimensional lithology and petrophysical models (reservoir models) constrained by well and seismic data including p-impedance inversion and subsequent porosity models from a neural network are used to show how production is related to a specific Mississippian lithologies.