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Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments : 2. Small-strain mechanical properties

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dc.contributor.author Lee, J. Y.
dc.contributor.author Francisca, Franco M.
dc.contributor.author Santamarina, J. Carlos
dc.contributor.author Ruppel, Carolyn D.
dc.date.accessioned 2010-12-06T14:44:53Z
dc.date.available 2011-05-09T08:24:40Z
dc.date.issued 2010-11-09
dc.identifier.citation Journal of Geophysical Research 115 (2010): B11105 en_US
dc.identifier.uri http://hdl.handle.net/1912/4160
dc.description Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): B11105, doi:10.1029/2009JB006670. en_US
dc.description.abstract The small-strain mechanical properties (e.g., seismic velocities) of hydrate-bearing sediments measured under laboratory conditions provide reference values for calibration of logging and seismic exploration results acquired in hydrate-bearing formations. Instrumented cells were designed for measuring the compressional (P) and shear (S) velocities of sand, silts, and clay with and without hydrate and subject to vertical effective stresses of 0.01 to 2 MPa. Tetrahydrofuran (THF), which is fully miscible in water, was used as the hydrate former to permit close control over the hydrate saturation Shyd and to produce hydrate from dissolved phase, as methane hydrate forms in most natural marine settings. The results demonstrate that laboratory hydrate formation technique controls the pattern of P and S velocity changes with increasing Shyd and that the small-strain properties of hydrate-bearing sediments are governed by effective stress, σ′v and sediment specific surface. The S velocity increases with hydrate saturation owing to an increase in skeletal shear stiffness, particularly when hydrate saturation exceeds Shyd≈ 0.4. At very high hydrate saturations, the small strain shear stiffness is determined by the presence of hydrates and becomes insensitive to changes in effective stress. The P velocity increases with hydrate saturation due to the increases in both the shear modulus of the skeleton and the bulk modulus of pore-filling phases during fluid-to-hydrate conversion. Small-strain Poisson's ratio varies from 0.5 in soft sediments lacking hydrates to 0.25 in stiff sediments (i.e., subject to high vertical effective stress or having high Shyd). At Shyd ≥ 0.5, hydrate hinders expansion and the loss of sediment stiffness during reduction of vertical effective stress, meaning that hydrate-rich natural sediments obtained through pressure coring should retain their in situ fabric for some time after core retrieval if the cores are maintained within the hydrate stability field. en_US
dc.description.sponsorship Initial support for this research to J.C.S. and C.R. at Georgia Tech was provided by the Chevron Joint Industry Project on Methane Hydrates under contract DE‐FC26‐01NT41330 from the U.S. Department of Energy. Additional support to J.C.S. was provided by the Goizueta Foundation at Georgia Tech and to J.Y.L. by KIGAM, GHDO, and MKE. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Geophysical Union en_US
dc.relation.uri http://dx.doi.org/10.1029/2009JB006670
dc.subject Gas hydrate en_US
dc.subject Mechanical properties en_US
dc.subject Seismic velocity en_US
dc.title Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments : 2. Small-strain mechanical properties en_US
dc.type Article en_US
dc.identifier.doi 10.1029/2009JB006670


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