The Lithostratigraphic Architecture and many “facies” (facies) of Lower Mississippian Petroleum Reservoirs in Central and Eastern Kansas and Northern Oklahoma
Sal Mazzullo and Brian Willhite
Mississippian rocks in Kansas and northern Oklahoma are a complex architecture of aggradational ramps and younger progradational shelf and slope wedges, within which are numerous subaerial unconformities of eustatic origin. This motif was over-printed by syndepositional tectonism, which resulted in local uplift-erosion or subsidence-sediment thickening, particularly during Kinderhookian to early Osagean time. Petroleum reservoir objectives in ramp deposits of this age are sandstones, bryozoan-crinoid reefs, and dolomites that are amenable to exploration via subsurface mapping and seismic. In contrast, reservoir objectives in younger Osagean, progradational shelf and slope deposits are siliceous spiculites (Cowley Formation), fractured and cherty lime mudstones, and tripolite (Reeds Spring Formation). Not all of the progradational wedges in this system are reservoirs. Youngest Osagean reservoirs (terminal Cowley-Reeds Spring) deposited along the shelf-break in southern Kansas and northern Oklahoma are cherty and/or spiculitic limestones, locally with dolomite at the top. Youngest Osagean and Meramecian shelf reservoirs are represented by subunconformity dolomite and/or limestone, and weathered chert horizons. These different reservoirs have contrasting pore types, petrophysical attributes, and completion parameters, and because of progradation and multiple periods of tectonism and uplift, different stratal units subcrop beneath the Cherokee section. It is therefore imperative to identify the specific reservoir objectives in an exploration program because not all Mississippian units are the same.
AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013