RESERVOIR POTENTIAL OF THE ST. JOE GROUP, LOWER MISSISSIPPIAN SYSTEM, IN NORTHEASTERN OKLAHOMA

Reservoir modeling requires accurate stratigraphic correlation and depositional environmental interpretation. This study uses δ¹³C, δ¹⁸O and XRD analysis combined with core and thin-section analysis to correlate the St. Joe Group from outcrop into the subsurface and infer the depositional environment. The St. Joe Group represents carbonate strata deposited in the early Mississippian along the edge of the Burlington shelf margin. The Compton Limestone, Northview Shale, and Pierson Limestone comprise the St. Joe Group and are differentiable in outcrop and subsurface in northeastern Oklahoma on the Cherokee Platform.

The study area stretches across the Cherokee Platform from east of the Nemaha Uplift near Pawnee County to Delaware County where the lower Mississippian crops out. Bulk rock samples and hand specimens were taken from the underlying Woodford Shale, Compton Limestone, Northview Shale, Pierson Limestone, and the Reeds Spring formations to correlate the formations. Also the contacts between these units were sampled to test for evidence of subaerial exposure, particularly at the top of the Northview Shale. Core data from Pawnee County was integrated with geochemical and XRD data and thin-section analysis of outcrop samples from Delaware County to create geological maps across the Cherokee Platform and interpret the depositional environment. Identifying the spatial variation and distribution of the St. Joe Group strata and refining depositional environmental interpretations will support accurate reservoir modeling of the St. Joe Group.

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