Complex Lithofacies Relationships between the Ste. Genevieve and Paoli Limestones: Clarifying Reservoir Relationships in the Indiana Subsurface

Abstract

Typically irregular vertical and lateral distribution of lithofacies within the Ste. Genevieve and Paoli Limestones (Mississippian Blue River Group) has historically resulted in the inaccurate correlation of uppermost Ste. Genevieve lithologies (Joppa Member) with Paoli units of similar composition and appearance (Aux Vases and Renault Members). The Joppa Member of the Ste. Genevieve thins northeastward toward the Illinois Basin margin, losing the distinctive log signature that characterizes this unit in more basinward locations. The Aux Vases and Renault Members of the Paoli Limestone also become difficult to distinguish from each other and from the Joppa Member in basin margin locations because of rapid changes in composition and bed distribution. As a consequence, many Ste. Genevieve and Paoli Limestone pay zones have been assigned to the wrong reservoir pool, sometimes within the same field. Pay zones from Ste. Genevieve and Paoli Limestone reservoirs were reassigned according to current stratigraphic divisions. These new correlations more accurately reflect spatial relationships within and between hydrocarbon pools, and could contribute to more effective reservoir management. Improved correlations should also provide a useful tool for future hydrocarbon exploration and development activities in Indiana. Our investigation also suggests that revisions to formal Ste. Genevieve-Paoli stratigraphic nomenclature should be considered.