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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Abstract
DOI: 10.1306/08182221123
Difference in
overpressure
environments for the western and central deep-water
Gulf
of Mexico




Sharon Cornelius1 and Peter A. Emmet2
1Department of Earth and Atmospheric Sciences, College of Natural Sciences and Mathematics, University of Houston, Houston, Texas; slcornelius@uh.edu
2Brazos Valley GeoServices, Inc., Cypress, Texas; pete.emmet.53@gmail.com
ABSTRACT
Previous results from the central Gulf
of Mexico (CGOM) protraction areas of Garden Banks, Green Canyon, Keathley Canyon, and Walker Ridge included calculation of both geopressure and geothermal gradients from 150 wells and produced a new understanding of the geopressure
distribution
within the deep-water CGOM. Disequilibrium compaction is a major component of the overall GOM
overpressure
but is more easily discernible in the interval from the seafloor down to where formation temperatures are >65°C, at which point temperature-based chemical reactions commenced sequentially with rising temperature. These reactions, which usually produce greater quantitative
overpressure
than disequilibrium compaction, include
hydrocarbon
generation, smectite-to-illite transformation, and sandstone diagenesis. This study has incorporated the western
Gulf
of Mexico (WGOM) protraction areas of East Breaks, Alaminos Canyon, Corpus Christi, and Port Isabel, where 249 wells were analyzed to verify the CGOM results. The result is that the WGOM is geothermally warmer and considerably underpressured compared to the CGOM. Measured and calculated temperature–pressure pair data points at varying depths within the boreholes were plotted separately for both regions. The
distribution
of the data on each plot is regionally unique. In the CGOM, most
overpressure
was likely created in situ or proximal to its source. In the WGOM, the formations fractured at some point and geopressure escaped. Compressional velocities versus density crossplots were created for four wells, each well representative of a different protraction area, to indicate the source of local
overpressure
.
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