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AAPG Bulletin

Abstract

AAPG Bulletin, V. 89, No. 1 (January 2005), P. 41-60.

Copyright copy2005. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/08170404028

Petrophysics of Lower Silurian sandstones and integration with the tectonic-stratigraphic framework, Appalachian basin, United States

James W. Castle,1 Alan P. Byrnes2

1Department of Geological Sciences, 340 Brackett Hall, Clemson University, Clemson, South Carolina 29634-0919; [email protected]
2Kansas Geological Survey, 1930 Constant Avenue, Lawrence, Kansas 66047; [email protected]

AUTHORS

Jim Castle is an associate professor of geological sciences at Clemson University, where he conducts research and teaches in the areas of sedimentology, subsurface characterization, and structural geology. Prior to joining Clemson in 1995, he was employed for 17 years by Cabot Oil amp Gas and by Chevron. He received his Ph.D. in geology from the University of Illinois.

Alan Byrnes is a research geologist at the Kansas Geological Survey, where he studies lithologic controls on rock petrophysical properties, CO2 enhanced oil recovery, reservoir characterization, and modeling. Alan received his M.S. degree in geophysical sciences from the University of Chicago. He has worked at the Gas Technology Institute, Marathon Oil Research Center, Core Laboratories, and Tetra Tech, and owned the special core laboratory GeoCore.

ACKNOWLEDGMENTS

We appreciate helpful discussions with Katharine Lee Avary, Steve Holsclaw, Chris Laughrey, and Andy Theodos. Matthew Fleahman and Chris Hepler point-counted and photographed the thin sections. The following organizations provided access to cores that were sampled for petrophysical analysis: Cabot Oil amp Gas Corporation; Columbia Gas Transmission; the Ohio Department of Natural Resources, Division of Geological Survey; the West Virginia Geological and Economic Survey; and the National Energy Technology Laboratory of the United States Department of Energy, Morgantown, West Virginia. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research.

We express our sincere appreciation to Katharine Lee Avary, Robert M. Cluff, and Jack Thomas, who reviewed the manuscript and provided many valuable suggestions. We also thank AAPG editor John Lorenz for his helpful comments.

DATASHARE 16

Four additional tables are accessible in an electronic version, Datashare 16, on the AAPG Website (www.aapg.org/datashare/index.html).

ABSTRACT

Petrophysical properties were determined for six facies in Lower Silurian sandstones of the Appalachian basin: fluvial, estuarine, upper shoreface, lower shoreface, tidal channel, and tidal flat. Fluvial sandstones have the highest permeability for a given porosity and exhibit a wide range of porosity (2–18%) and permeability (0.002–450 md). With a transition-zone thickness of only 1–6 m (3–20 ft), fluvial sandstones with permeability greater than 5 md have irreducible water saturation (Siw) less than 20%, typical of many gas reservoirs. Upper shoreface sandstones exhibit good reservoir properties with high porosity (10–21%), high permeability (3–250 md), and low Siw (lt20%). Lower shoreface sandstones, which are finer grained, have lower porosity (4–12%), lower permeability (0.0007–4 md), thicker transition zones (6–180 m [20–600 ft]), and higher Siw. In the tidal-channel, tidal-flat, and estuarine facies, low porosity (average lt6%), low permeability (average lt0.02 md), and small pore throats result in large transition zones (30–200 m; 100–650 ft) and high water saturations.

The most favorable reservoir petrophysical properties and the best estimated production from the Lower Silurian sandstones are associated with fluvial and upper shoreface facies of incised-valley fills, which we interpret to have formed predominantly in areas of structural recesses that evolved from promontories along a collisional margin during the Taconic orogeny. Although the total thickness of the sandstone may not be as great in these areas, reservoir quality is better than in adjacent structural salients, which is attributed to higher energy depositional processes and shallower maximum burial depth in the recesses than in the salients.

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