Abstract

Mississippian carbonates of northern Oklahoma were deposited on the Anadarko shelf (ramp) as several shallowing-upward sequences. In Woods County, Oklahoma, the Mississippian ranges in thickness from 350 ft (105 m) to the south to as little as 100 ft (30 m) to the north due to uplift and erosion. Lithologies observed in core are chert conglomerate, tripolitic chert (tripolite), dense chert, chert-rich limestone, dense limestone, and shale-rich limestone.

To evaluate the spatial distribution of Mississippian lithologies and petrophysical properties, and to explore the controls on production, this study integrates 3-D seismic with core and well-log data. As a constraint for 3-D lithology modeling, lithology logs were estimated using a neural-network approach with core and log data resulting in 65.1% accuracy. A P-impedance volume from seismic inversion was used to constrain the spatial distribution of tripolite in the model, the main reservoir lithology. Lithology-constrained 3-D porosity and water saturation models show that tripolite is the most porous and heterogeneous lithology. Comparing lithology, porosity, and water saturation models to production data illustrates that production from vertical wells is primarily controlled by porous tripolite distribution, whereas horizontal wells produce from both tripolite and chert-rich limestones and are most sensitive to water saturation variations.