Scattering versus intrinsic attenuation in periodically layered media

Stovas, Alexey; Roganov, Y.

doi:10.1088/1742-2132/7/2/003

Cited by 9 publications

(2 citation statements)

References 9 publications

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“…the ratio of the imaginary and real parts of stiffness coefficient), Qij is a quality factor, ω is the angular frequency, the plus sign `+’ in front of the imaginary unit follows the Fourier transform in Carcione (2014), and the sign of ω ensures A ij is non‐negative (Stovas and Ursin, 2003; Hao and Greenhalgh, 2019; Hao et al ., 2019).

Q_{i j}^{- 1}

is usually used to quantify intrinsic attenuation (Stovas and Roganov, 2010) and is generally assumed to be independent of frequency in the seismic‐frequency band (Carcione, 1992; Hao and Alkhalifah, 2017a, b). A ij can be considered as frequency‐independent ‘intrinsic attenuation coefficient’.…”

Section: Effective Stiffness For Stratified Viscoelastic Modelmentioning

confidence: 99%

Anisotropic attenuation of stratified viscoelastic media

Zeng

Stovas

Huang

2020

Geophysical Prospecting

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An important cause of seismic anisotropic attenuation is the interbedding of thin viscoelastic layers. However, much less attention has been devoted to layer-induced anisotropic attenuation. Here, we derive a group of unified weighted average forms for effective attenuation from a binary isotropic, transversely isotropic-and orthorhombic-layered medium in the zero-frequency limit by using the Backus averaging/upscaling method and analyse the influence of interval parameters on effective attenuation. Besides the corresponding interval attenuation and the real part of stiffness, the contrast in the real part of the complex stiffness is also a key factor influencing effective attenuation. A simple linear approximation can be obtained to calculate effective attenuation if the contrast in the real part of stiffness is very small. In a viscoelastic medium, attenuation anisotropy and velocity anisotropy may have different orientations of symmetry planes, and the symmetry class of the former is not lower than that of the latter. We define a group of more general attenuation-anisotropy parameters to characterize not only the anisotropic attenuation with different symmetry classes from the anisotropic velocity but also the elastic case. Numerical tests reveal the influence of interval attenuation anisotropy, interval velocity anisotropy and the contrast in the real part of stiffness on effective attenuation anisotropy. Types of effective attenuation anisotropy for interval orthorhombic attenuation and interval transversely isotropic attenuation with a vertical symmetry (vertical transversely isotropic attenuation) are controlled only by the interval attenuation anisotropy. A type of effective attenuation anisotropy for interval TI attenuation with a horizontal symmetry (horizontal transversely isotropic attenuation) is controlled by the interval attenuation anisotropy and the contrast in the real part of stiffness. The type of effective attenuation anisotropy for interval isotropic attenuation is controlled by all three factors. The magnitude of effective attenuation anisotropy is positively correlated with the contrast in the real part of the stiffness. Effective attenuation even in isotropic layers with identical isotropic attenuation is anisotropic if the contrast in the real part of stiffness is non-zero. In addition, if the contrast in the real part of stiffness is very small, a simple linear approximation also can be performed to calculate effective attenuation-anisotropy parameters for interval anisotropic attenuation.

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Q_{i j}^{- 1}

Section: Effective Stiffness For Stratified Viscoelastic Modelmentioning

confidence: 99%

Anisotropic attenuation of stratified viscoelastic media

Zeng

Stovas

Huang

2020

Geophysical Prospecting

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“…Several effects can induce attenuation and dispersion in the medium: multiple scattering, mode conversions and the intrinsic attenuation. For a finely layered medium, the effective properties are affected by induced attenuation (Schoenberg and Levin ; Ursin and Stovas ; Stovas and Roganov ) and velocity dispersion (Helbig ; Roganov and Stovas ). The geological layering creates velocity dispersion and attenuation due to multiple scattering and mode conversions.…”

Section: Introductionmentioning

confidence: 99%

Low‐frequency anisotropy in fractured and layered media

Pang

Stovas

2019

Geophysical Prospecting

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Computing effective medium properties is very important when upscaling data measured at small scale. In the presence of stratigraphic layering, seismic velocities and anisotropy parameters are scale and frequency dependent. For a porous layer permeated by aligned fractures, wave‐induced fluid flow between pores and fractures can also cause significant dispersion in velocities and anisotropy parameters. In this study, we compare the dispersion of anisotropy parameters due to fracturing and layering at low frequencies. We consider a two‐layer model consisting of an elastic shale layer and an anelastic sand layer. Using Chapman's theory, we introduce anisotropy parameters dispersion due to fractures (meso‐scale) in the sand layer. This intrinsic dispersion is added to anisotropy parameters dispersion induced by layering (macro‐scale) at low frequencies. We derive the series coefficients that control the behaviour of anisotropy parameters at low frequencies. We investigate the influences of fracture length and fracture density on fracturing effect, layering effect and combined effect versus frequency and volume fraction of sand layer. Numerical modelling results indicate that the frequency dependence due to layering is not always the dominant effect of the effective properties of the medium. The intrinsic dispersion is not negligible compared with the layering effect while evaluating the frequency‐dependent properties of the layered medium.

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Influence of upscaling on identification of reservoir fluid properties using seismic-scale elastic constants

Wang

Zhang

2019

Sci Rep

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Elastic constants derived from seismic-scale measurements are often used to infer subsurface petrophysical properties based on rock-physics relationships established from either theoretic model or core-scale measurements. However, the spatial heterogeneity of rock physical properties at the local scale has a significant impact on this relation. To understand this problem, we built a scaled physical model comprised of artificial porous layers with different pore fluids. After conducting a two-dimensional marine seismic survey over the physical model, the physical modeling data ware then used to retrieve the elastic constants of the layered package. The seismic-scale results reveal that the identification of reservoir fluid properties is improved using elastic constants that is more sensitive to pore fluid properties. The results of numerical simulations show that Lamé moduli provide more insight into rock properties and pore-fluid contents than P-wave impedances, and that the relationship between the upscaled elastic constants and the effective fluid bulk moduli at the seismic scale is usually not perfectly preserved at the reservoir scale. To interpret seismic-scale elastic constants for petrophysical properties, the rock physics relationship need to be carefully calibrated. The findings will help us understand the upscaling of rock-physics transform, which will improve the accuracy of geological property predictions from seismic-scale elastic constants.

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Scattering versus intrinsic attenuation in periodically layered media

Cited by 9 publications

References 9 publications

Anisotropic attenuation of stratified viscoelastic media

Anisotropic attenuation of stratified viscoelastic media

Low‐frequency anisotropy in fractured and layered media

Influence of upscaling on identification of reservoir fluid properties using seismic-scale elastic constants

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