Abstract: History of Quartz Cementation in the St. Peter Sandstone, Michigan Basin-Fluid Inclusion, Isotopic, and Thermal History Analyses

Tien-Fung Tsui, Mingchou Lee, Joana M. Vizgirda

Quartz cement is the most abundant authigenic mineral in the St. Peter Sandstone, Michigan Basin, and it can have a detrimental effect on reservoir quality. The amount of quartz cement in the St. Peter Sandstone varies widely, and is controlled primarily by the amount of detrital clay in the sandstones. Clean sandstones with <4% clay have significantly more quartz cement (avg: 12.5%) than sandstones with >4% clay (avg: 6.6%). Because depositional facies controls detrital clay content, facies has an indirect control on the extent of quartz cementation.

The intergranular pressure solution and stylolitization contributed to no more than 60% of the silica for quartz cementation in the St. Peter Sandstone. Additional silica had to be imported from outside of the system. The K/Ar dating of diagenetic illite indicates that quartz cementation, which preceded illite, occurred before 340-380 m.y. ago. Fluid inclusion and oxygen isotopic data indicate that the cementing fluid was hot (approx. 130°C), isotopically light (deltaO¹⁸: O^pmil to -2^pmil), extremely saline, and rich in calcium. Modeling of the thermal history of the Michigan Basin suggests that the elevated fluid temperatures at the time of quartz cementation resulted from fluid flow processes which circulated hot fluid from deeper part of the Michigan basin. The int grated data suggest that the quartz-cementing fluid probably had significant meteoric input, but had been extensively modified through rock-water reactions and by mixing with migrating hot basinal brine.

More quartz was precipitated in the clean sandstones than in the clay-rich sandstones because the cementing fluid preferentially migrated through the clean sandstones, which, initially, had more favorable porosity and permeability as well as more nucleation sites. The deeper sandstones were probably exposed to circulating, cementing fluids for a longer duration than the shallow sandstones, resulting in increasing quartz cementation with depth.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994