Analysis of Attenuation Anisotropy in Multi-Azimuth VSP Data from the Clair Field

Maultzsch, S.; Chapman, Mark; Liu, E.; Li, X.-Y.

doi:10.3997/2214-4609-pdb.1.e040

Cited by 5 publications

(5 citation statements)

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“…Due to the fact that fracture sizes are usually much smaller than the seismic wavelength, it is difficult to image fractures directly on seismic profiles. For this reason, seismic attributes are often used in fracture detection and characterization (e.g., Bakulin et al, , , ; Gao, ; Guo et al, ; Guo, Rubino, Glubokovskikh, et al, ; Guo, Shuai, et al, ; Guo, Rubino, Barbosa, et al, ; Maultzsch et al, , ; Tsvankin, ). Under the in situ stress field, parallel fractures are often developed in the direction of the maximum stress (e.g., Schoenberg & Sayers, ).…”

Section: Introductionmentioning

confidence: 99%

Effective Elastic Properties of Rocks With Transversely Isotropic Background Permeated by Aligned Penny‐Shaped Cracks

Guo

Han

et al. 2019

JGR Solid Earth

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Seismic characterization of fractures is of great importance in many disciplines, for which rock physics models provide the basis to link fracture properties to seismic attributes. However, to date, most rock physics models neglect the background anisotropy that may exist in many fractured formations. Hence, in this work, we developed a theoretical model for rock effective elastic properties with penny-shaped cracks embedded in the transversely isotropic (TI) background medium. We first derived analytical solutions for the case with dry or fluid-filled penny-shaped cracks parallel to the isotropic plane of TI background medium. Further, the results were extended to the case with cracks inclined to the isotropic plane with any angles. We then studied, based on the developed theoretical model, two tight sand samples with TI and isotropic background, respectively, to illustrate effects of background anisotropy on effective elastic properties of fractured rocks. The results show that the background anisotropy has significant influence on P and S wave velocity anisotropy, as well as on shear wave splitting. The background anisotropy can either increase or decrease P and SH wave velocity anisotropy depending on crack inclination angles, whereas it has relatively small influence on SV wave velocity anisotropy. To further illustrate the important effects of background anisotropy, we compared theoretical predictions to ultrasonic measurements on a synthetic fractured sandstone sample with TI background medium. The results show notable improvement of the agreement between theoretical predictions and experimental results after considering background anisotropy.

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Section: Introductionmentioning

confidence: 99%

Effective Elastic Properties of Rocks With Transversely Isotropic Background Permeated by Aligned Penny‐Shaped Cracks

Guo

Han

et al. 2019

JGR Solid Earth

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“…Attenuation anisotropy of P-and S-waves in rocks is studied in laboratory ultrasonic experiments by Yin and Nur (1992), Best (1994), Kern et al (1997), Kim et al (1983), Domnesteanu et al (2002), Johansen (1999, 2000), Prasad and Nur (2003), Shi and Deng (2005), and Best et al (2007). Besides ultrasonic experiments, there are several field experiments on fracture-direction estimation from azimuthally varying P-wave attenuation in surface seismic reflection data and VSPs (Clark et al, 2001;Vasconselos and Jenner, 2005;Varela et al, 2006;Maultzsch et al, 2007;Liu et al, 2007). In laboratory experiments on anisotropy, it is preferable to simulate an ideal transversely isotropic medium using synthetic specimens formed by thin micro-layers, or models with embedded parallel penny-shaped cracks, e.g.…”

Section: Generalization Of Schoenberg's Linear Slip Model To Attenuatmentioning

confidence: 99%

Generalization of Schoenberg's linear slip model to attenuative media: Physical modeling versus theory

Chichinina

Obolentseva

Ronquillo-Jarillo

et al. 2009

SEG Technical Program Expanded Abstracts 2009

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We propose a mathematical formalism of introducing attenuation in Schoenberg's Linear Slip model. This formalism consists in replacing the real-valued weaknesses, normal and tangential, entering in the stiffness matrix by the complex-valued quantities. To test the validity of this procedure, an ultrasonic experiment was performed with the use of a plate-stack model made from plexiglass plates. We measured velocities and attenuations of P-, SH-and SV-wave versus the angle between the ray and the symmetry axis of TI model for air-filled and oil-saturated state of the model under uniaxial pressure of 2 and 4 MPa. The data on velocities and attenuations were fitted by the derived theoretical functions. We have estimated the values of the imaginary and real parts of the complex-valued weaknesses. The real parts of the weaknesses are threefold for the air-filled model in comparison with the oil-saturated one. The imaginary parts of the weaknesses, responsible for attenuation, are one order of magnitude less than the values of the real parts of the weaknesses. Both P-wave anisotropies, the velocity anisotropy and the attenuation anisotropy, are greater in the air-filled model than in the oil-saturated one. Besides, in the air-filled model, the symmetry-axis attenuation of the P-wave is much greater than the S-wave symmetry-axis attenuation, whereas in the oil-saturated model these attenuations are similar.

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“…To this end, seismic methods have been widely used due to their non‐invasive feature and relatively large detection areas (e.g. Tsvankin, 1996; Bakulin et al ., 2000a, 2000b, 2000c; Maultzsch et al ., 2003, 2007; Liu and Martinez, 2012; Gao, 2013). For this purpose, it is essential to link the measured seismic signatures to fracture properties, which requires the rock physics models for effective elastic properties of fractured rocks.…”

Section: Introductionmentioning

confidence: 99%

Analytical model for rock effective elastic properties with aligned elliptical cracks embedded in transversely isotropic background

Guo

Zhao

Yang

et al. 2021

Geophysical Prospecting

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Seismic methods are often used for fracture detection and characterization, for which many analytical rock physics models have been developed to link fracture parameters to rock elastic properties. However, most of these models are limited to isotropic background and circular (penny‐shaped) fractures. In this work, we derived a more general analytical model for effective elastic properties of rocks embedded with aligned elliptical cracks in transversely isotropic background. The solutions for the case with dry cracks parallel to isotropic plane of transversely isotropic background were first derived using the corresponding Eshelby's tensor. Then, the results were extended to the case with inclined and rotated cracks under the assumption of constant crack opening displacement tensor. Finally, to obtain the results for fluid‐filled crack case, the Brown–Korringa equation was applied. To investigate the controlling factors on rock elastic properties, we studied one fractured tight sandstone sample with transversely isotropic background. The results show that rock elastic properties are insensitive to crack spin angle, but sensitive to crack inclination angle. Depending on crack inclination angle and fluid saturation, background anisotropy can either amplify or reduce the anisotropy of seismic wave velocity. Crack density and aspect ratio are found to be controlling crack parameters for rock elastic properties. The crack plane shape has negligible direct influence on rock elastic properties, whereas it has indirect influence by affecting values of crack density and aspect ratio. Compared with the numerical model and the previous analytical model for the special case with circular cracks, our model agrees well with them, which validates the accuracy of our model.

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Analysis of Attenuation Anisotropy in Multi-Azimuth VSP Data from the Clair Field

Cited by 5 publications

References 0 publications

Effective Elastic Properties of Rocks With Transversely Isotropic Background Permeated by Aligned Penny‐Shaped Cracks

Effective Elastic Properties of Rocks With Transversely Isotropic Background Permeated by Aligned Penny‐Shaped Cracks

Generalization of Schoenberg's linear slip model to attenuative media: Physical modeling versus theory

Analytical model for rock effective elastic properties with aligned elliptical cracks embedded in transversely isotropic background

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