Reservoir-scale stratigraphy, sedimentology, and porosity characteristics of Mississippian reservoirs, northeastern Anadarko Shelf, Oklahoma

Abstract

The ‘Mississippi Lime’ has been a productive carbonate play for several decades. However, geologic controls on production and reservoir quality have frequently been ambiguous to geologists. The Mississippian limestone varies in reservoir quality, with some characterized by high porosity tripolite or spiculite, other parts characterized by lower porosity chert, and some characterized by unaltered limestone. In northern Oklahoma, the Mississippian limestone formed on the east-west trending margin of the Anadarko Shelf. This carbonate system is characterized by a shallowing upward character as well as high-order cyclicity. These shallowing upward high-order cycles are observed in northern Oklahoma. Unconformities in the area are caused by relative falls in sea level in addition to regional tectonics. Pre-Pennsylvanian tectonics created the Nemaha Uplift, the cause of subaerial exposure in the area, which then led to alteration. These limestones demonstrate a variety of alteration types, such as silicification, dolomitization, brecciation, and fracturing. The dominant lithologies include chert-breccia, bedded chert-breccia, grainstone and mudstone, with more alteration and brecciation occurring near the top of the Mississippian interval. This variability is established through core, thin section, and XRF analysis. Lithologies, lithofacies, and pore types observed in core, thin sections, and XRF data are calibrated to open-hole logs to predict and map their spatial distribution.

AAPG Datapages/Search and Discovery Article #90221 © 2015 Mid-Continent Section, Tulsa, Oklahoma, October 4-6, 2015