Effects of borehole stress concentrations on dipole anisotropy measurements

Winkler, Kenneth W.; Plona, Thomas J.; Hsu, Chaur-Jian; Sinha, Bikash K.; Kostek, Sergio

doi:10.1190/1.1822719

Cited by 21 publications

(18 citation statements)

References 1 publication

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“…The results show that it is feasible to evaluate the anisotropy induced by stress concentrations of the borehole by applying the crossdipole to a cased hole. The dipole dispersion curves confirm our expectations based upon shear-wave velocity studies [4] . At low frequencies, the flexural wave is dominated by the far-field velocities.…”

Section: Distribution Of Wave Velocitysupporting

confidence: 89%

“…According to the theory of acoustoelasticity and using the perturbation procedure, Norris et al [2] and Sinha et al [3] educed the acoustoelasticity formulations of guided waves considering the stress concentrations for an open hole, which provides the bases of theory and method for estimating abnormal stress from cross-dipole sonic logging data. Winkler et al [4] showed experimentally and theoretically how stress concentrations affect the velocity field around a borehole. The cases for open holes are investigated by many authors [2∼7] ,however, the majority of damaged oil wells are cased holes.…”

Section: Introductionmentioning

confidence: 99%

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The Effects of Stress Concentrations of Cased Hole on Induced Azimuthal Velocity Anisotropy

Liu

Wang

Cao

et al. 2005

Chinese J. Geophys.

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In accordance with the need of estimating anisotropy and abnormal stress of formation by applying cross‐dipole logging to a cased hole, we show how stress concentrations affect the velocity distribution of formation around a cased hole, and how the velocity distribution influences the cross‐dipole anisotropy measurements by computing the stress distribution of a cased hole subjected to the tectonic stress and applying acoustoelasticity theory. The introduction of casing and cement in a cased hole results in a reduced range of stress concentration. The crossover of shear‐waves of radial polarization moves towards the borehole. The azimuthal extremum of shear‐waves is changed. But the azimuth of compressional velocity minima can still provide an excellent indicator of the direction of maximum far‐field tectonic stress.

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Section: Distribution Of Wave Velocitysupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

The Effects of Stress Concentrations of Cased Hole on Induced Azimuthal Velocity Anisotropy

Liu

Wang

Cao

et al. 2005

Chinese J. Geophys.

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“…Their analysis showed that, because of the effect of stress concentration around the borehole, a horizontal uniaxial stress in the formation caused a crossover in flexural dispersions for the radial polarization aligned parallel and normal to the stress direction, and this crossover in flexural dispersion can be used as an indicator of stress-induced anisotropy from other sources of formation anisotropy. Experimental verification of the flexural dispersion crossover in uniaxially stressed laboratory samples has been reported [13] . Based on the theory of acoustoelasticity of wave mode in a fluid-filled borehole, a nondestructive technique has been applied to estimate formation stress directions and magnitudes from cross-dipole acoustic logging [6,7] .…”

Section: Introductionmentioning

confidence: 99%

Dipole Flexural Waves Splitting Induced by Borehole Pressurization and Formation Stress Concentration

Cao

Wang

et al. 2003

Chinese J of Geophysics

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We numerically calculate the Stoneley and flexural mode dispersion curves in a fluid‐filled borehole with borehole pressurization and uniaxially stressed solid formation. From the computational results of sensitivity coefficients and velocity‐stress coefficients, we show that the sensitivity coefficient without the third‐order elastic constant is larger than the other sensitivity coefficients , but the velocity‐stress coefficient corresponding to it is less than the other velocity‐stress coefficients with the third‐order elastic constants. Therefore, the fractional changes in the phase velocity hardly relate to the sensitivity coefficient without the third‐order elastic constant. In addition, computational results show that the point of dispersion curve crossover is affected by the borehole pressurization because of the change of velocity dispersion by borehole pressurization increasing with frequency, and as the borehole pressurization increases the velocity of the crossover point increases while the frequency of the point is unchanged.

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“…However, in practice, errors in acoustic curves greatly reduce the effectiveness of acoustic logging. Therefore, elimination of the influence caused by errors in acoustic interval transit times is still an issue that many researchers have attempted to address (Baker and Winbow 1988; Baker 1989; Winkler 1997; Winkler, Sinha and Plona 1998).…”

Section: Introductionmentioning

confidence: 99%

The disturbance of drilling mud on rock formation and a method for error elimination on acoustic log curves

Wei

Liu

et al. 2003

Geophysical Prospecting

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A B S T R A C TErrors in acoustic logs have a significant influence on the assessment of formations, the description of oil deposits and modelling using synthetic seismograms. The elimination of these errors is a problem that many researchers have been trying to solve for many years. We derive theoretical formulae for calculating the radial depth of investigation of acoustic logging, and analyse the relationship between the error in acoustic interval transit time and the altered zone thickness. We explain in detail how mud affects the acoustic interval transit time. We also describe the variation of altered zone thickness with time and a method for calculating the altered zone thickness. Finally, we present a set of new methods that can be directly applied to correct the disturbing influence on acoustic curves. Our results are obtained based on the fact that acoustic velocities in the altered zone show a small lateral variation. Examples are given of analysing the acoustic log data, which are collected from a BS well at three different times. This paper is significant both for selection of the acoustic logging device with proper transmitter-to-receiver distance (spacing) and improvement of the device. C 2003 European Association of Geoscientists & Engineers 479 480 C. Wei et al.

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Effects of borehole stress concentrations on dipole anisotropy measurements

Cited by 21 publications

References 1 publication

The Effects of Stress Concentrations of Cased Hole on Induced Azimuthal Velocity Anisotropy

The Effects of Stress Concentrations of Cased Hole on Induced Azimuthal Velocity Anisotropy

Dipole Flexural Waves Splitting Induced by Borehole Pressurization and Formation Stress Concentration

The disturbance of drilling mud on rock formation and a method for error elimination on acoustic log curves

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