Skip to Main Content
Book Chapter

Sequence-stratigraphic and Paleogeographic Distribution of Reservoir-quality Dolomite, Madison Formation, Wyoming and Montana

By
Langhorne B. Smith, Jr.
Langhorne B. Smith, Jr.
New York State Museum, Albany, New York, U.S.A.
Search for other works by this author on:
Gregor P. Eberli
Gregor P. Eberli
University of Miami, Miami, Florida, U.S.A.
Search for other works by this author on:
Mark Sonnenfeld
Mark Sonnenfeld
iReservoir.com, Greenwood Village, Colorado, U.S.A.
Search for other works by this author on:
Published:
January 01, 2004

ABSTRACT

Exploration-scale cross sections of the Mississippian Madison Formation of Wyoming and Montana show variations in the distribution of dolomite and porous dolomite in a sequence-stratigraphic hierarchy along a 500-km dip transect. These variations in the distribution of dolomite across the ramp have significant implications for exploration and dolomitization models. This study also shows how understanding of rock and porosity types and vertical and lateral reservoir distribution and compartmentalization can be better understood through outcrop studies.

The Madison Formation is composed of a fivefold hierarchy of sequences and cycles. The entire Madison Formation comprises a single, unconformity-bounded second-order supersequence that consists internally of two composite sequences. The composite sequences are composed of two to four third-order sequences, with a total of as much as six sequences. The third-order sequences are composed of two orders of higher-frequency cycles. Most of the porous dolomite occurs in the transgressive portion of the second-order supersequence.

Downdip on the ramp, fabric-selective dolomitization is dominant, as more than 90% of the mud-dominated strata and less than 5% of the grain-dominated strata were dolomitized. The only porous dolomite occurs in laterally extensive mud-dominated strata in the transgressive portions of the two composite sequences. Moving updip, fabric-selective dolomitization is still common, but porosity occurs in the transgressive portions of progressively higher-frequency sequences and cycles. In the middle part of the ramp, all rock types in the transgressive systems tract (TST) of the second-order super-sequence are pervasively dolomitized, and porosity occurs throughout the interval. Farther updip, the amount of dolomite and porous dolomite decreases upward in the TST of the supersequence, and rock fabric played only a small role, as 70% of the grainstones and only 50% of the mudstones were dolomitized.

Any models for dolomitization and porosity development should explain the variations in dolomite and porous dolomite distribution across the ramp. Exploration concepts for Madison dolomitized reservoirs and dolomitized reservoirs worldwide should include possible variations in dolomite distribution in sequences across carbonate ramps and platforms.

You do not currently have access to this article.

Figures & Tables

Contents

AAPG Memoir

Integration of Outcrop and Modern Analogs in Reservoir Modeling

G. Michael Grammer
G. Michael Grammer
Search for other works by this author on:
Paul M. “Mitch” Harris
Paul M. “Mitch” Harris
Search for other works by this author on:
Gregor P. Eberli
Gregor P. Eberli
Search for other works by this author on:
American Association of Petroleum Geologists
ISBN electronic:
9781629810478
Publication date:
January 01, 2004

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal