Offshore sediment overpressures of passive margins; mechanisms, measurement, and models

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doi: 10.1029/2011RG000379
Author(s): Dugan, B.; Sheahan, T. C.
Author Affiliation(s): Primary:
Rice University, Department of Earth Science, Houston, TX, United States
Other:
Northeastern University, United States
Volume Title: Reviews of Geophysics
Source: Reviews of Geophysics, 50(3). Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 8755-1209
Note: In English. 120 refs.; illus.
Summary: Fluid pressure in excess of hydrostatic equilibrium, or overpressure, in offshore environments is a widespread phenomenon that contributes to the migration and storage of fluids, solutes, and energy and to the potential mechanical instability of these sediments. Overpressure exists in deep and shallow systems and is most likely to be found where low-permeability (<10-16 m2) layers have inhibited pore fluid escape or there have been large forcing mechanisms (e.g., rapid sedimentation, tectonic stressing, heating, and volume-creating reactions). The genesis and magnitude of overpressure can be controlled by physical processes (e.g., rapid sedimentation (>mm/yr), tectonic loading, and lateral fluid transfer) and thermal and chemical processes (e.g., aquathermal expansion, hydrocarbon generation, mineral diagenesis, and organic maturation). In systems where near-lithostatic overpressures are generated, potentially unstable sediments are created. Failures of these sediments can create large-scale natural disasters, generate fractures, and damage seafloor and subseafloor infrastructure. Detailed characterization of overpressured systems has been accomplished through geological and geotechnical analyses, including investigation of physical-mechanical properties (mainly porosity, consolidation state, and shear strength), inversion of geophysical data (e.g., compressional and/or shear velocities), measurement of in situ properties, and postevent analyses. Process-based models have been developed to explain the origin of overpressure in terms of rate of overpressure genesis. This allows identification of potentially unstable zones and assessment of the potential for failure. Future development in measurements and in coupling of models will lead to more accurate analysis and prediction of fluid pressure in offshore sediments, which in turn will facilitate better hazard analyses and will enable safer and more cost-effective offshore drilling practices and other offshore infrastructure development.
Year of Publication: 2012
Research Program: ODP Ocean Drilling Program
Key Words: 22 Environmental Geology; 30 Engineering Geology; Atlantic Ocean; Deep-sea sedimentation; Engineering properties; Geologic hazards; Leg 174A; Marine environment; Marine installations; Marine sedimentation; Measurement; Mechanism; Natural hazards; North Atlantic; Numerical models; ODP Site 1073; Ocean Drilling Program; Ocean floors; Overpressure; Passive margins; Penetrometers; Permeability; Physical models; Plate tectonics; Pore pressure; Porosity; Sedimentary rocks; Sedimentation; Sediments; Simulation; Stability
Coordinates: N391331 N391331 W0721633 W0721633
Record ID: 2017044027
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