Acoustic Measurements of the Anisotropy of Dynamic Elastic and Poromechanics Moduli under Three Stress/Strain Pathways

Scott, T.E.; Abousleiman, Younane N.

doi:10.1061/(asce)0733-9399(2005)131:9(937)

Cited by 24 publications

(21 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In Figure 1b, we also show (as circles) the values of the e=c ratio for uniaxial stress and uniaxial strain experiments on Berea sandstone, reported by Scott and Abousleiman (2005). These values plot near the B ¼ 0.4 line, which is within the typical range for sandstones (Sayers, 2002;Gurevich et al, 2009b).…”

Section: Elasticity Tensors and Anisotropy Parameterssupporting

confidence: 58%

“…The dashed and dotted lines are predictions of the current anisotropy model for uniaxial stress, and the circles and triangles denote the corresponding measurements of Nur and Simmons (1969). Figure 1b show the values of the e=c ratio for uniaxial stress and uniaxial strain experiments on Berea sandstone, respectively, reported by Scott and Abousleiman (2005).…”

Section: Figure 2 Measured Velocities Of P-waves (Solid Symbols) Andmentioning

confidence: 97%

“…This assumption is clearly not universally valid. One effect not covered by this assumption is an increase of the number of cracks parallel to the direction of uniaxial compression (see, e.g., Sayers, 1988;Scott and Abousleiman, 2005). It is still a matter of debate whether such crack opening occurs at all stresses or only above a certain threshold.…”

Section: Assumptionsmentioning

confidence: 99%

See 2 more Smart Citations

An analytic model for the stress-induced anisotropy of dry rocks

2011

View full text Add to dashboard Cite

One of the main causes of azimuthal anisotropy in sedimentary rocks is anisotropy of tectonic stresses in the earth's crust. We have developed an analytic model for seismic anisotropy caused by the application of a small anisotropic stress. We first considered an isotropic linearly elastic medium (porous or nonporous) permeated by a distribution of discontinuities with random (isotropic) orientation (such as randomly oriented compliant grain contacts or cracks). The geometry of individual discontinuities is not specified. Instead, their behavior is defined by a ratio B of the normal to tangential excess compliances. When this isotropic rock is subjected to a small compressive stress (isotropic or anisotropic), the number of cracks along a particular plane is reduced in proportion to the normal stress traction acting on that plane. This effect is modeled using the Sayers-Kachanov noninteractive approximation. The model predicts that such anisotropic crack closure yields elliptical anisotropy, regardless of the value of the compliance ratio B. It also predicts the ratio of Thomsen's anisotropy parameters e=c as a function of the compliance ratio B and Poisson's ratio of the unstressed rock. A comparison of the model predictions with the results of laboratory measurements indicates a reasonable agreement for moderate magnitudes of uniaxial stress (as high as 30 MPa). These results can be used for differentiating stress-induced anisotropy from that caused by aligned fractures. Conversely, if the cause of anisotropy is known, then the anisotropy pattern allows one to estimate P-wave anisotropy from S-wave anisotropy.

show abstract

Section: Elasticity Tensors and Anisotropy Parameterssupporting

confidence: 58%

Section: Figure 2 Measured Velocities Of P-waves (Solid Symbols) Andmentioning

confidence: 97%

Section: Assumptionsmentioning

confidence: 99%

See 1 more Smart Citation

An analytic model for the stress-induced anisotropy of dry rocks

2011

View full text Add to dashboard Cite

show abstract

“…Given that there are no noticeable fractures observed in the image logs, the most probable cause of the observed azimuthal seismic anisotropy is anisotropy of the stress field and related opening and closure of microcracks or compliant grain contacts (Nur, 1971, Sayers, 2002, Scott and Abousleiman, 2005, Gurevich et al, 2011. Indeed, this area is known for large differences between maximum and minimum horizontal stresses (Hillis and Reynolds, 2003).…”

Section: Shear Wave Anisotropy Estimationmentioning

confidence: 99%

Estimation of azimuthal anisotropy from VSP data using multicomponent S-wave velocity analysis

2011

View full text Add to dashboard Cite

Observation of azimuthal shear wave anisotropy can be useful for characterization of fractures or stress fields. Shear wave anisotropy is often estimated by measuring splitting of individual shear wave events in vertical seismic profile (VSP) data. However, this method may become unreliable for zero-offset (marine) VSP where the seismogram often contains no strong individual shear events, such as direct downgoing shear wave, but often contains many low-amplitude PS mode converted waves. We have developed a new approach for estimation of the fast and slow shear wave velocities and orientation of polarization planes based on the multicomponent linear traveltime moveout velocity analysis. This technique is applicable to zerooffset VSP data, and should take advantage of the presence of a large number of shear wave events with the same apparent velocity (which, for a horizontally layered medium, should be close to the interval velocity). The approach assumes that the VSP data are acquired in a vertical well drilled in an orthorhombic medium with a horizontal symmetry plane (including horizontal transverse isotropy). The main idea is to estimate the dominant apparent velocity for a given polarization direction by measuring the coherency of the seismic signal of a large number of events as a function of the apparent velocity. The algorithm was tested on marine three-component (3C) VSP acquired in the North West Shelf of Australia, and on land 3C VSP acquired with different sources in the same borehole located in Otway Basin, Victoria. These tests show good agreement between anisotropy parameters (magnitude and orientation) derived from the VSP and cross-dipole sonic log data.

show abstract

“…In yet another set of experiment [33], Berea sandstone was tested. The circular cylinder was 7.62 cm in diameter and 15 cm in length.…”

Section: Stress-dependent Biot Effective Stress Coefficientmentioning

confidence: 99%

Intrinsic poroelasticity constants and a semilinear model

Cheng

Abousleiman

2007

Num Anal Meth Geomechanics

View full text Add to dashboard Cite

SUMMARYThis paper presents an intrinsic micromechanical model for poroelasticity that leads to an alternative set of material constants. In the intrinsic model, the deformations of the solid phase, the fluid phase, and the pore space are explicitly modeled, and porosity is considered as a primary variable. The averaging process distinguishes an external frame surface averaging and an internal phase volume averaging. The variational principle leads to a porosity equilibrium equation that defines the nonlinear deformation of pore volume. Three fundamental deformation modes with their intrinsic material constants are identified: the shape preserving volumetric deformation of the solid phase, the porosity change due to solid grain rearrangement, and the porosity change associated with the microanisotropy and microinhomogeneity of solid phase. The linearized model is fully consistent with the Biot theory of poroelasticity. A semilinear model considering only porosity deformation nonlinearity with linear material constant leads to a universal exponential strain hardening law. The theory is tested against laboratory data of sandstone.

show abstract

Acoustic Measurements of the Anisotropy of Dynamic Elastic and Poromechanics Moduli under Three Stress/Strain Pathways

Cited by 24 publications

References 36 publications

An analytic model for the stress-induced anisotropy of dry rocks

An analytic model for the stress-induced anisotropy of dry rocks

Estimation of azimuthal anisotropy from VSP data using multicomponent S-wave velocity analysis

Intrinsic poroelasticity constants and a semilinear model

Contact Info

Product

Resources

About