--> Abstract: The Significance of Stylolitization and Intergranular Pressure Solution in the Formation of Pressure Compartment Seals in the St. Peter Sandstone, Ordovician, Michigan Basin, by P. A. Drzewiecki, T. Simo, G. Moline, J. M. Bahr, G. Nadon, L. Shepherd, and M. R. Vandrey; #91004 (1991)
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The Significance of Stylolitization and Intergranular Pressure Solution in the Formation of Pressure Compartment Seals in the St. Previous HitPeterNext Hit Sandstone, Ordovician, Michigan Basin

DRZEWIECKI, Previous HitPETERNext Hit A., T. SIMO, G. MOLINE, J. M. BAHR, G. NADON, L. SHEPHERD, and M. R. VANDREY, University of Wisconsin, Madison, WI

The Middle to Late Ordovician St. Previous HitPeterNext Hit Sandstone of the Michigan basin is a fine- to medium-grained quartz sandstone. Extensive stylolitization and intergranular pressure solution have been major factors in reducing the porosity of certain horizons within the St. Previous HitPeterNext Hit, resulting in pressure compartmentation of the reservoir.

Pressure versus depth data for various Michigan basin wells indicate that the basin contains compartments that are overpressured by as much as 500 psi. Horizons bounding these compartments are often affected by intense stylolitization (or intergranular pressure solution) and quartz cementation and have been correlated with zones of low porosity and permeability (porosity = 0-3%, permeability = 50 microdarcies). These tight zones can be correlated within single gas fields, and some may extend across the Michigan basin.

The St. Previous HitPeterNext Hit Sandstone has been buried to depths of about 3500 m in the central part of the basin and 1500 m at the margins. Intensely stylolitized zones are found at all depths throughout the basin and do not appear to change in abundance or style with depths. Factors that influence the formation, morphology, and abundance of stylolites in the St. Previous HitPeterTop include (1) clay intraclasts, (2) intergranular clay, and (3) fine-grained, feldspar-rich sand. Stylolites also occur at contacts between quartz-cemented and carbonate-cemented zones and within well-cemented sands.

Intergranular pressure solution and stylolites may be responsible for the formation of a compartment seal. Understanding their genesis can allow prediction of variations in porosity in Michigan basin well cores. (Research supported by the Gas Research Institute.)

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)