Abstract

An extensive regional study covering the Anadarko Basin and shelf of Oklahoma and Texas has been conducted with the generation of regional cross sections, production allocation, and reservoir characterization. It has long been apparent to those working the Anadarko Basin and shelf area of Oklahoma and Texas that the nomenclature used typically is erratic and the resulting production allocation less than precise. A correlative and equivalent formation may be termed by various names and there are all too many instances of nomenclature being vague, too broad, or incorrect. As part of a regional study, the logs from every producing well within the majority of the Anadarko Basin and shelf were reviewed to verify the actual producing reservoir. Approximately 35,000 wells in northwestern Oklahoma and the Panhandles of Oklahoma and Texas 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. Although the entire stratigraphic section has been subjected to elements of this study, the Springer Group, Upper Mississippian, and Lower Pennsylvanian, are the most demonstrative of a carbonate platform and slope system with its stratigraphically equivalent basinal clastic system.

The Springer Group may be misnamed as the overlying Pennsylvanian Morrow sandstone or underlying Mississippian Chester limestone. Historically, the first carbonate encountered below the Morrow/Springer clastic section has been termed Chester limestone. Generally, the Springer Group consists of the Boatwright, Britt, and Cunningham, in ascending order. Whereas in Oklahoma, the Cunningham was a sandstone, extensive correlations indicated that the Boatwright or Britt in certain areas developed a carbonate facies that generally was referred to as Chester limestone. Regional correlations in both Oklahoma and Texas from the deep Anadarko Basin, through the slope and onto the shelf, indicate that the Springer clastics of the deep basin are equivalent stratigraphically to Springer carbonate facies on the slope and shelf. As a result of these correlations, Britt and Boatwright carbonates have been identified which heretofore have been identified generally as Chester limestone. A highly conductive Boatwright shale directly above the true Chester limestone provides a reliable regional marker as the base of the Springer Group. In Texas, the Cunningham was observed to develop a carbonate facies that was rare and nonproductive.

Regional cross sections will be presented showing these facies changes and indicating trapping mechanisms along with production maps delineating trends and lithofacies maps.