Skip to Main Content
Book Chapter

The Deepwater Upper Cretaceous Lewis Shale: Sequence Stratigraphy, Facies Variation and Petrophysical Properties

By
William R. Almon
William R. Almon
1
ChevronTexaco E & P Technology Company, 4800 Fournace Place, Bellaire, Texas 77401
Search for other works by this author on:
William C. Dawson
William C. Dawson
1
ChevronTexaco E & P Technology Company, 4800 Fournace Place, Bellaire, Texas 77401
Search for other works by this author on:
Sally J. Sutton
Sally J. Sutton
1
ChevronTexaco E & P Technology Company, 4800 Fournace Place, Bellaire, Texas 77401
Search for other works by this author on:
Frank G. Ethridge
Frank G. Ethridge
1
ChevronTexaco E & P Technology Company, 4800 Fournace Place, Bellaire, Texas 77401
Search for other works by this author on:
Bellatrix Castelblanco
Bellatrix Castelblanco
1
ChevronTexaco E & P Technology Company, 4800 Fournace Place, Bellaire, Texas 77401
Search for other works by this author on:
Published:
January 01, 2003

Abstract

A predictive model to estimate the distribution, sealing capacity and petrophysical properties of shale seals and flow barriers will significantly reduce the risks associated with hydrocarbon exploration and exploitation. Such a sequence stratigraphy-based predictive model must be grounded in outcrop and field analogs, such as this examination of the sealing capacity, petrophysical properties and distribution of Upper Cretaceous Lewis marine shales in two wells from south-central Wyoming. The measured sealing capacity of these shales varies with textural and compositional factors that allow division of the Lewis Shale depositional sequence six argillaceous microfacies. Each microfacies displays distinctive compositional and petrophysical properties and occupies a well-defined sequence stratigraphic position including transgressive, highstand, and condensed section deposits, with characteristic seal and seismic properties. The microfacies, in order of greatest seal capacity to least, are phosphatic shales, pyritic fissile shales, silty shales, silty calcareous shales, silty calcareous mudstones, and bioturbated argillaceous siltstones. The most promising seals, the phosphatic and pyritic shales, belong to the condensed section and uppermost transgressive systems tract. The phosphatic shale is also characterized by the highest content of both total organic carbon (TOC) and authigenic minerals. Interestingly, neither of these two high sealing capacity microfacies shows more detrital clay than other microfacies. The microfacies with lower sealing capacities belong to the highstand systems tract and are generally poorer in iron-rich minerals than the better sealing microfacies. Petrophysical properties, including high bulk density, shear velocity, Young’s modulus and shear modulus, distinguish the best sealing microfacies from highstand systems tract microfacies with poorer seal capacity. This correspondence between sealing capacity and petrophysical properties suggests that seismic data may have good potential as a tool for seal evaluation.

You do not currently have access to this article.

Figures & Tables

Contents

SEPM Miscellaneous Publication

Siltstones, Mudstones and Shales: Depositional Processes and Characteristics

Erik D. Scott
Erik D. Scott
Shell International Exploration & Production, 200 North Dairy Ashford, Houston, Texas 77079
Search for other works by this author on:
Arnold H. Bouma
Arnold H. Bouma
Dept. of Geology & Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803
Search for other works by this author on:
William R. Bryant
William R. Bryant
Dept. of Oceanography, Texas A&M University, College Station, Texas 77843
Search for other works by this author on:
SEPM Society for Sedimentary Geology
Volume
1
ISBN electronic:
9781565760943
Publication date:
January 01, 2003

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