ABSTRACT

It has long been apparent to those working the Anadarko Basin and Shelf area of Oklahoma that the nomenclature used is typically erratic and the resulting production allocation less than precise. A correlative and equivalent formation may be called various names and there are all too many instances of nomenclature being vague, too broad or incorrect altogether. Further complicating the understanding of the Anadarko Basin and Shelf's geology is the fact that few detailed regional cross sections are available (or even exist outside of proprietary studies) showing the most up- to-date logs correlated throughout the basin and shelf area. As part of a regional study, the logs from every producing well in a portion of the Anadarko Basin and Shelf were reviewed to verify the actual producing reservoir. Nearly 18,000 wells in an area including T8-29N/R10-26W were examined. Regional cross-sections were constructed and used to determine the stratigraphic relationships and to develop a stratigraphic nomenclature system that could be used across the area with accuracy, detail, and consistency.

The Springer Group, {Upper Mississippian and Lower Pennsylvanian} is often misnamed as the overlying Pennsylvanian Morrow Sandstone or underlying Mississippian Chester Limestone. Generally, the Springer Group consists of the Boatwright, Britt and Cunningham, in ascending order. While the Cunningham was always found to be a sandstone, extensive correlations indicated that the Boatwright and/or Britt in certain areas developed a carbonate facies that was almost always referred to as Chester Limestone. In these areas, the first carbonate below the Morrow and/or Cunningham clastic section has been called Chester Limestone by convention. Correlations from the deep Anadarko Basin demonstrate that these carbonates are the shallow marine facies equivalent of the Boatwright and/or Britt Sandstone members of the Springer Group. A highly conductive Boatwright Shale directly above the true Chester Limestone provides a very reliable regional marker as the base of the Springer Group. This lateral facies change is illustrated by the included log cross-sections. An estimated 1.2 TCF of gas has been produced from the Boatwright and Britt carbonates, as herein defined.