Diagenetic Controls on Reservoir Heterogeneity in St. Peter Sandstone, Deep Michigan Basin

D. A. Barnes, T. M. Turmelle, Rusli-Ben Adam

The St. Peter Sandstone is a highly productive gas and condensate reservoir throughout the central part of the Michigan basin. Production occurs in several intervals: a laterally continuous zone at the top of the formation typified in the Woodville, Falmouth, and Rose City fields and less continuous intervals lower in the formation typified in the Ruwe Gulf zone of the Reed City field. Porosity is not limited to hydrocarbon productive zones, however.

Diagenesis has dramatically modified primary mineralogy and textures in the formation. Dominant diagenetic components are quartz, dolomite, and clay authigenic cements, extensive chemical compaction, and pervasive mineral leaching. Our model for sandstone diagenesis is consistent throughout the basin. Variation in the significance of these diagenetic components is strongly templated by stratigraphically predictable facies variations within the St. Peter Sandstone.

Comparison of mercury injection, pore cast, and petrographic data indicate two distinct end-member reservoir facies that correlate with lithofacies and depositional environment. Burrowed and bioturbated facies in the upper portions of the formation are storm-dominated shelf deposits. This reservoir facies is characterized by early carbonate cement, minor quartz overgrowths, abundant secondary porosity, late authigenic clay, relatively high porosity, low permeability, elevated mercury injection displacement pressure, poor sorting, and small size of pore throats. Cross-bedded to laminated facies lower in the formation were deposited in coastal environments. This reservoir facies is strongly quartz cemented; has lower porosity, higher permeability, and lower displacement pressure; and ha better sorted and larger pore throats. These reservoir quality characteristics are consistent with preliminary production histories of these distinct producing horizons within the St. Peter Sandstone.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.