Shear‐wave birefringence and ultrasonic shear‐wave attenuation measurements

Lucet, Nathalie; Tarif, P.

doi:10.1190/1.1892407

Cited by 2 publications

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“…In spite of the fact that shale formations exhibit high anisotropies, the study of fracture related anisotropy has been more intensive, both theoretically [5][6][7][8][9][10][11][12] and experimentally [13][14][15]. This is most likely explained because when anisotropy is observed it can be associated with fractures, which have a strong impact on permeability.…”

Section: Introductionmentioning

confidence: 99%

Estimation of the Effect of Anisotropy on Young’s Moduli and Poisson’s Ratios of Sedimentary Rocks Using Core Samples in Western and Central Part of Tripura, India

Brahma¹,

Sircar²

2014

IJG

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The velocity anisotropy parameters and elastic constants play a very important role to estimate Young's modulus and Poisson's ratios accurately. For geomechanics applications such as hydraulic fracturing design, analysis of wellbore stability and rock failure, determination of in situ stress and assessment of the response of reservoirs and surrounding rocks to changes in pore pressure and stress, Young's modulus and Poisson's ratios play a very important role. Four rock samples were collected from four different wells situated in study area. The ultrasonic transmission method has been used to measure P-wave, Sh-wave and Sv-wave travel times as a function of orientation and confining pressure. The five independent stiffnesses constants, Young's moduli, Poisson's ratios and Bulk moduli of the samples were estimated. The Poisson's ratios ( 12 13 , ϑ ϑ and 31 ϑ ) are varying as the confining pressure is changed. The axial strain is larger than the lateral strain, resulting 31 12 ϑ ϑ < . For shales, the Young's modulus measured parallel to bedding E 1 is usually greater than the Young's modulus measured perpendicular to bedding E 3 . Through this study it has been observed that, there is a strong effect of anisotropy parameters on Young's modulus and Poisson's ratio.

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Section: Introductionmentioning

confidence: 99%

Estimation of the Effect of Anisotropy on Young’s Moduli and Poisson’s Ratios of Sedimentary Rocks Using Core Samples in Western and Central Part of Tripura, India

Brahma¹,

Sircar²

2014

IJG

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Pore fluid effects on seismic velocity in anisotropic rocks

1994

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A simple new technique predicts the high‐ and low‐frequency saturated velocities in anisotropic rocks entirely in terms of measurable dry rock properties without the need for idealized crack geometries. Measurements of dry velocity versus pressure and porosity versus pressure contain all of the necessary information for predicting the frequency‐dependent effects of fluid saturation. Furthermore, these measurements automatically incorporate all pore interaction, so there is no limitation to low crack density. The velocities are found to depend on five key interrelated variables: frequency, the distribution of compliant crack‐like porosity, the intrinsic or noncrack anisotropy, fluid viscosity and compressibility, and effective pressure. The sensitivity of velocities to saturation is generally greater at high frequencies than low frequencies. The magnitude of the differences from dry to saturated and from low frequency to high frequency is determined by the compliant or crack‐like porosity. Predictions of saturated velocities based on dry data for sandstone and granite show that compressional velocities generally increase with saturation and with frequency. However, the degree of compressional wave anisotropy may either increase or decrease upon saturation depending on the crack distribution, the effective pressure, and the frequency at which the measurements are made. Shear‐wave velocities can either increase or decrease with saturation, and the degree of anisotropy depends on the microstructure, pressure, and frequency. Consequently great care must be taken when interpreting observed velocity anisotropy for measurements at low frequencies, typical of in situ observations, will generally be different from those at high frequencies, typical of the laboratory.

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Shear‐wave birefringence and ultrasonic shear‐wave attenuation measurements

Cited by 2 publications

References 1 publication

Estimation of the Effect of Anisotropy on Young’s Moduli and Poisson’s Ratios of Sedimentary Rocks Using Core Samples in Western and Central Part of Tripura, India

Estimation of the Effect of Anisotropy on Young’s Moduli and Poisson’s Ratios of Sedimentary Rocks Using Core Samples in Western and Central Part of Tripura, India

Pore fluid effects on seismic velocity in anisotropic rocks

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