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Regional Map of the 0.70 Psi/Ft Pressure Gradient and Development of the Regional Geopressuregradient Model for the Onshore and Offshore Gulf of Mexico Basin, U.S.A.

Lauri A. Burke, Scott A. Kinney, Russell F. Dubiel, and Janet K. Pitman
U.S. Geological Survey, Denver Federal Center, Box 25046, MS 939, Denver, Colorado 80225–0046, U.S.A.

The U.S. Geological Survey has created a comprehensive geopressure-gradient model of the regional pressure system spanning the onshore and offshore portions of the U.S. Gulf of Mexico basin. Over 300,000 mud-weight measurements from more than 860,000 wells were examined, of which over 200,000 mud-weight measurements from approximately 70,000 wells were used to create the geopressure-gradient model. The model was used to generate contour maps that characterize the depth and distribution of isopressure-gradient surfaces from 0.60 psi/ft to 1.00 psi/ft, in 0.10 psi/ft increments, as well as supporting maps that display the spatial density of the data used to construct the isopressure-gradient maps. In this paper, we focus on the details of the geopressure-gradient model and the creation of the 0.70 psi/ft pressure-gradient map. The depth at which the 0.70 psi/ft pressure gradient occurs is significant as it is generally considered to represent the “top of overpressure” or the “top of the overpressure transition zone.”

Characterization of the regional pressure system is critical for assessing the occurrence of undiscovered petroleum resources, evaluating areas with potential pressure-related production, identifying potential pressure-related geohazard issues, evaluating hydrocarbon reservoir-seal integrity, and determining the feasibility of geological sequestration and long-term containment of fluids.

 

AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012