Probable Reservoir Facies of the Wapanucka Limestone (Morrowan), Frontal Ouachita Mountains, Southeastern Oklahoma
MAULDIN, DARRELL L., Baylor University, Waco, TX
Considerable recent exploration and significant discoveries in the frontal Ouachita Mountains can be attributed to structural and stratigraphic relationships within the overthrust belt. Although, most of the production has been from the early Atokan Spiro Formation, the late Morrowan Wapanucka Formation has locally proven to be a gas reservoir. Surface imbrications allow outcrop study of the Wapanucka lithofacies and form a basis for predicting the character of rocks in the subthrust region.
Repetitive sequences of platform, platform margin, and basinal facies characterize the Wapanucka Formation in outcrop. These sequences record several southward progradations of the ramp-like shelf margin. Oolitic and bioclastic calcarenites accumulated on the shallow shelf, while algal micrites developed near the shelf edge. Spiculitic limestones characterize the platform margin, and slope and basinal depositional environments are inferred for the noncalcareous spiculites and shale.
Within the Wapanucka, several facies are potentially hydrocarbon reservoir rocks. These include oolitic grainstone and spiculitic packstone. The former lithology might preserve primary porosity, while the latter facies could develop significant fracture porosity in certain structural configurations. Thus, mapping their surface extent is significant because well control and seismic data do not provide this kind of information. However, detailed surface work in association with the subsurface geology can aid in locating potential hydrocarbon reservoirs.
AAPG Search and Discovery Article #91008©1991 AAPG Mid-Continent Section Meeting, Kansas Geological Society, Wichita Kansas, September 22-24, 1991 (2009)