--> --> Abstract: Three-Dimensional Modeling of the Mississippian Ste. Genevieve Limestone Shoal Complex at Owensboro North Consolidated Field, Gibson County, Indiana, by C. W. Zuppann and M. O'Neal; #90926 (1999)

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ZUPPANN, CHARLES W., and MICHAEL O'NEAL , Indiana Geological Survey, Bloomington, IN

Abstract: Three-Dimensional Modeling of the Mississippian Ste. Genevieve Limestone Shoal Complex at Owensboro North Consolidated Field, Gibson County, Indiana

Intervals of porous and permeable limestone that occur within less porous carbonate strata commonly have been used to infer the depositional geometry of oolite "bars" in the Ste. Genevieve Limestone (Mississippian) in the Illinois Basin subsurface. Understanding the distribution and geometry of these "porosity bodies" is economically significant because they represent some of the more productive hydrocarbon reservoirs in the basin. However, Ste. Genevieve porosity bodies are notoriously difficult to correlate because typically they exhibit thin, lens-shaped geometries that are locally distributed and develop in multiple stratigraphic positions. Furthermore, the geophysical log signatures of the porous zones become indistinct on the margins of the porosity bodies.

More than 400 wells were used in an interactive computer model developed at the Indiana Geological Survey to visualize the three-dimensional geometries of the "shoal" facies at Owensville North Consolidated Field. Our initial correlation step was to group all apparent shoal-related facies together (porous and nonporous grainstones and packstones), and to model the geometry of this composite group. The porous intervals were then correlated and interpreted relative to their position within in the shoal body. The Ste. Genevieve does not appear to represent a collection of isolated bars, but rather a large shoal complex on which sites of oolite deposition shifted, expanded, and contracted overtime. Oolitic porosity bodies only formed in local parts of the bigger shoal, especially where the shoal is relatively thick. Porosity may have developed in these areas as a result of vadose diagenesis that developed as the shoal built up sufficiently to be influenced by meteoric water. 

AAPG Search and Discovery Article #90926©1999 AAPG Eastern Section Meeting, Indianapolis, Indiana