Ultrasonic velocity and shear‐wave splitting behavior of a Colton sandstone under a changing triaxial stress

Dillen, Menno; Cruts, Helma M. A.; Groenenboom, Jeroen; Fokkema, J.T.; Duijndam, A. J. W.

doi:10.1190/1.1444664

Cited by 20 publications

(15 citation statements)

References 10 publications

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“…The standard deviation of each predicted quantity is equal to half the length of the error bar. It was also observed in shales by Hornby (1998) and in Colton Sandstone by Dillen et al (1999). Figure 11a compares the measured and predicted P-wave velocities.…”

Section: Predicting Transmission Velocitiesmentioning

confidence: 69%

Anisotropic inversion of seismic data for stressed media: Theory and a physical modeling study on Berea Sandstone

2003

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Nonhydrostatic stress, an often-ignored source of seismic anisotropy, is universally present in the subsurface and may be as common as intrinsic or fracture-induced anisotropy. Nonhydrostatic stress, applied to an initially transversely isotropic solid with vertical symmetry axis (VTI), results in an effective medium having almost orthorhombic symmetry (provided that one of the principal stresses is aligned with the symmetry axis). The symmetry planes observed in this orthorhombic medium are aligned with the orientations of the principal stresses, and anisotropic parameters ( (1,2) , δ (1,2,3) , and γ (1,2) ) can reveal information about the stress magnitudes. Thus, time-lapse monitoring of changes in anisotropy potentially can provide information on temporal variations in the stress field.We use nonlinear elasticity theory to relate the anisotropic parameters to the magnitudes of the principal stresses and verify these relationships in a physical modeling study. Under the assumption of weak background and stress-induced anisotropy, each effective anisotropic parameter reduces to the sum of the corresponding Thomsen parameter for the unstressed VTI background and the corresponding parameter associated with the nonhydrostatic stress. The stress-related anisotropic parameters depend only on the differences between the magnitudes of principal stresses; therefore, principal stresses can influence anisotropic parameters only if their magnitudes differ in the symmetry plane in which the anisotropic parameters are defined.We test these predictions on a physical modeling data set acquired on a block of Berea Sandstone exhibiting intrinsic VTI anisotropy. Uniaxial stress, applied normal to the VTI symmetry axis, i.e., horizontally, produces an effective medium that is close to orthorhombic. We use two different methods to estimate the anisotropic parameters and study their variation as a function of stress. The first method utilizes conventional measurements of transmission velocities along the principal axes of the sample. The second method uses PP and PS reflection data acquired along seven different azimuths on the surface of the block.In accordance with theoretical predictions, the anisotropic parameters in the vertical plane normal to the stress are almost insensitive to the magnitude of the stress. In contrast, anisotropic parameters in the vertical plane of the applied stress increase approximately in a linear fashion with increasing stress. Except for the parameter δ (1) , comparison of the measured values of anisotropic parameters with theoretical predictions shows satisfactory agreement.Despite some documented discrepancies, we believe that nonlinear elasticity may provide a suitable framework for estimating pore pressure and 3D stresses from seismic data.

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Section: Predicting Transmission Velocitiesmentioning

confidence: 69%

Anisotropic inversion of seismic data for stressed media: Theory and a physical modeling study on Berea Sandstone

2003

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“…The stress anisotropy in the reservoir (and around the wellbore) is therefore significant and could potentially affect our results. There exist several studies in the literature of stress‐induced anisotropy (Mavko, Mukerji and Godfrey 1995; Dillon et al 1999; Bakulin 2003). They all estimated stress sensitivity based on cracks (or planes of weakness) in the rocks.…”

Section: Discussionmentioning

confidence: 99%

Deriving effects of pressure depletion on elastic framework moduli from sonic logs

Furre

Andersen

Moen

et al. 2009

Geophysical Prospecting

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A B S T R A C TWe have developed a method to determine the effect of pore pressure depletion on elastic framework moduli, by utilizing sonic logs from wells drilled at different locations through a reservoir at varying depletion stages. This is done by first inverting the sonic logs for elastic framework bulk and shear moduli, thus carefully removing pressure dependent fluid effects. By crossplotting these elastic framework moduli against an increase in net stress (which is directly related to depletion), we derive the stress sensitivity of the elastic framework moduli. We found that the observed stress sensitivity was consistent with time-lapse seismic results and that the sensitivity derived from the sonic logs was much smaller than predicted by hydrostatic measurements on core samples. This method is applicable to depletion scenarios in mature fields and can be used both for modelling and inverting time-lapse seismic data for effects of pore pressure depletion on seismic data.

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“…Such states of stress produce wave speed anisotropy in both granular (Sayers, 2002(Sayers, , 2007Walton, 1987) and cracked (Horii and Nemat-Nasser, 1983;Sayers and Kachanov, 1995) rocks. Since then the effect has been documented by many workers under more controlled stress state conditions (e.g., Babuska and Pros, 1984;Becker et al, 2007;Bonner, 1974;Gurevich et al, 2011;Johnson and Rasolofosaon, 1996;Stanek et al, 2013) in cracked rock, (Nur, 1971) in granular rock (e.g., Dillen et al, 1999;Khidas and Jia, 2010;Prioul et al, 2004;Rai and Hanson, 1988;Roesler, 1979) and numerically (Gallop, 2013;Hu et al, 2010). In the latter, the anisotropy is primarily a consequence of the preferred closure of those cracks whose plane is aligned normal to the greatest principle compression.…”

Section: Pressure Dependence In Granular Materialsmentioning

confidence: 97%

Geophysical Properties of the Near Surface Earth: Seismic Properties

Schmitt

2015

Treatise on Geophysics

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Ultrasonic velocity and shear‐wave splitting behavior of a Colton sandstone under a changing triaxial stress

Cited by 20 publications

References 10 publications

Anisotropic inversion of seismic data for stressed media: Theory and a physical modeling study on Berea Sandstone

Anisotropic inversion of seismic data for stressed media: Theory and a physical modeling study on Berea Sandstone

Deriving effects of pressure depletion on elastic framework moduli from sonic logs

Geophysical Properties of the Near Surface Earth: Seismic Properties

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