Skip to Main Content
Book Chapter

The Characteristics of Geopressure Profiles in the Gulf of Mexico Basin

By
John T. Leftwich, Jr.
John T. Leftwich, Jr.
The Pennsylvania State University University Park, Pennsylvania, U.S.A.
Search for other works by this author on:
Terry Engelder
Terry Engelder
The Pennsylvania State University University Park, Pennsylvania, U.S.A.
Search for other works by this author on:
Published:
January 01, 1994

Abstract

This paper is a summary of our work on the relationship between under-compacted shale and abnormal pressure in the Tertiary portion of the Gulf of Mexico Basin. A major objective of this study is to map the depth to the top of the undercompacted shale, as located using shale density (cuttings samples), conductivity, sonic, plus bulk density logs relative to the depth to the top of abnormal pore pressure as determined using bottom-hole pressure (BHP) and repeat formation tester (RFT) data. Geopressure profiles (formation pressure versus depth curves) were most useful for such mapping because the geopressure profiles showed linear segments in which pressure gradients were constant. Although the top of abnormal pressure and the top of undercompaction sometimes occur at the same depth in a given field area, often these boundaries are separated by hundreds of feet (tens of meters) and in some cases by vertical distances of over 2000 ft (600 m). Two types of field areas in the Tertiary portion of the Gulf of Mexico are distinguished based on whether or not the top of undercompaction and the top of abnormal pressure correspond. Tertiary fields have geopressure profiles characterized by pressure gradients showing either three (the Alazan-type field) or four (the Ann Mag-type field) linear segments. One consequence of our work is that electropressure methods which assume that the top of abnormal pressure is always coincident with the top of the zone of undercompaction are unreliable when used for a quantitative estimate of geopressure.

You do not currently have access to this article.

Figures & Tables

Contents

AAPG Memoir

Basin Compartments and Seals

Peter J. Ortoleva
Peter J. Ortoleva
Department of Chemistry Indiana University Bloomington, Indiana
Search for other works by this author on:
American Association of Petroleum Geologists
Volume
61
ISBN electronic:
9781629810935
Publication date:
January 01, 1994

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