Pressure prediction in the shallow Ursa Basin; deepwater Gulf of Mexico

Author(s): Flemings, Peter B.; Hui, Long
Author Affiliation(s): Primary:
University of Texas at Austin, Department of Geological Sciences, Austin, TX, United States
ExxonMobil Upstream Research Company, United States
Volume Author(s): Smith, Michael A., editor; Hammond, Angela; Willis, James J.; Willis, Kristen M.; Willis, Jill C.; Boyles, J. Michael; Kumar, Anish; Bennett, Jim
Source: Transactions - Gulf Coast Association of Geological Societies, Vol.58, p.285-286; 58th annual convention of the Gulf Coast Association of Geological Societies, AAPG regional meeting and the 55th annual meeting of the Gulf Coast Section of the Society of Economic Paleontologists and Mineralogists, Houston, TX, Oct. 5-9, 2008, edited by Michael A. Smith, Angela Hammond, James J. Willis, Kristen M. Willis, Jill C. Willis, J. Michael Boyles, Anish Kumar and Jim Bennett. Publisher: Gulf Coast Association of Geological Societies, New Orleans, LA, United States. ISSN: 0533-6562 CODEN: TGCGA9
Note: In English
Summary: Overpressures measured with pore-pressure penetrometers during Integrated Ocean Drilling Program (IODP) Expedition 308 reach 70% and 60% of the hydrostatic effective stress (lambda* =0.7 and 0.6) in the first 200 meters below sea floor (mbsf) at sites U1322 and U1324, respectively, in the deepwater Gulf of Mexico, offshore Louisiana. We conducted extensive uniaxial consolidation tests on whole core samples to obtain the consolidation properties of the Ursa mudstones. The results suggest that the compression index linearly decreases with in situ void ratio. We show that the relationship of compressibility index versus void ratio can be obtained from a single consolidation test by compressing the soil over a large range in effective stress. A virgin compression curve can then be constructed based on this relationship to predict pore fluid pressure. In the Ursa Basin, this new approach successfully predicted pressures interpreted from the penetrometer measurements within the non-deformed sediments. We interpret that the high overpressures observed are driven by rapid sedimentation of low permeability material from the ancestral Mississippi River.
Year of Publication: 2008
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; Atlantic Ocean; Clastic rocks; Cores; Deep-water environment; Expedition 308; Gulf of Mexico; Integrated Ocean Drilling Program; Louisiana; Mudstone; North Atlantic; Offshore; Overpressure; Penetrometers; Pore pressure; Sedimentary rocks; Sediments; Uniaxial tests; United States; Ursa Basin
Record ID: 2017024220
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.

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