Sonic dispersion curves identify TIV anisotropy in vertical wells

Valero, Henri‐Pierre; Ikegami, Tsutomu; Sinha, Bikash K.; Bose, Sandip; Plona, Thomas J.

doi:10.1190/1.3255663

Cited by 6 publications

(2 citation statements)

References 3 publications

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“…That is why in many geophysical and geomechanical applications, the parameter δ ≈0 is considered. Such a simplified approach is known as the AN-NIE model (Valero et al, 2009;Gu et al, 2016). Regarding all these discussions, we conclude that the Thomsen's anisotropic index δ that was predicted by the extreme gradient boosting model (Fig.…”

Section: Discussionmentioning

confidence: 99%

Study the elastic properties and the anisotropy of rocks using different machine learning methods

Nguyen‐Sy

et al. 2020

Geophysical Prospecting

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This paper aims to demonstrate that the elastic stiffnesses and the anisotropic parameters of rocks can be accurately predicted from geophysical features such as the porosity, the density, the compression stress, the pore pressure and the burial depth using relevant machine learning methods. It also suggests that the extreme gradient boosting method is the best method for this purpose. It is more accurate, extremely faster to train and more robust than the artificial neural networks and the support vector machine methods. Very high R‐squared scores was obtained for the predicted elastic stiffnesses of a relevant dataset that is available in the literature. This dataset contains different types of rocks, and the values of the features are in large ranges. An optimal set of parameters was obtained by considering an appropriate sensitivity analysis. The optimized model is very easy to implement in Python for practical applications.

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Section: Discussionmentioning

confidence: 99%

Study the elastic properties and the anisotropy of rocks using different machine learning methods

Nguyen‐Sy

et al. 2020

Geophysical Prospecting

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“…We can distinguish the transverse isotropic formation from isotropic medium according to Stoneley waves, 25 and also may identify features of the medium according to the dipole and Stoneley dispersion curves. 26 Fritz 27 listed the nine independent third-order elastic (TOE) constants for solid materials which are transversely isotropic on a macroscopic scale, however, Hearmon 28 listed ten third-order elastic constants. It is stressed that in contrast to hexagonal second-order elastic (SOE) tensors, TOE tensors considered in Hearmon's paper were not "transversely isotropic" in the sense that they are not invariant with respect to arbitrary rotations around the six-fold symmetry axis.…”

Section: Introductionmentioning

confidence: 99%

Acoustoelastic effects of Stoneley waves in a borehole surrounded by a transversely isotropic elastic solid

et al. 2014

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Stoneley wave in a fluid-filled pressurized borehole surrounded by a transversely isotropic elastic solid with nine independent third-order elastic constants in presence of biaxial stresses are studied. A simplified acoustoelastic formulation of Stoneley wave is presented for the parallelism of the borehole axis and the formation axis of symmetry. Sensitivity coefficients and velocity dispersions for Stoneley wave due to the presence of stresses are numerically investigated, respectively. The acoustoelastic formulation explicitly shows that the velocity dispersions of Stoneley wave depend on seven independent third-order elastic constants in presence of biaxial stresses and on six independent third-order elastic constants in the presence of borehole pressurization alone. Numerical results of both sensitivity coefficients and velocity dispersions of Stoneley wave show that at low frequency the velocity change of Stoneley wave is sensitive to c111 and c112. Stoneley wave velocity at low frequencies can be simplified by 3 independent third order elastic constants (c111, c112 and c123) instead of nine constants. In presence of biaxial stresses, at low frequencies the speed of the Stoneley wave is similar to White’s formula.

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Relating shear sonic anisotropy directions to stress in deviated wells

Sun

Prioul

2010

GEOPHYSICS

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We develop a model that relates the polarization direction of a dipole sonic fast shear wave propagating along the borehole (hereafter called FSA) to the relative deviatoric stress tensor for arbitrary well orientations. We first define stress quantities, or “subsidiary principal stress,” relevant for sonic dipole shear characterized sufficiently far away into the formation to be unaffected by borehole stress concentration. Next, we show analytically for wells oriented within principal stress planes and numerically for wells outside principal stress planes that the stress-induced FSA coincides with the maximum normal stress direction orthogonal to the borehole (“maximum subsidiary principal stress”) using a nonlinear elastic model for isotropic unstressed background media and plane wave solutions. This model is independent of stress sensitivity parameters. This result is a consequence of, first, the direct relationship between the stressellipsoid factor and the shear stiffness difference ratio, [Formula: see text], and, second, the almost elliptical nature of stress-induced orthorhombic media. Using published laboratory data relating stiffnesses to applied differential stress for isotropic unstressed limestone and sandstone rocks, the model is confirmed for most well orientations except in the vicinity of the stress nodal point within the maximum and minimum principal stress plane, due to small anellipticity as stress increases. The orientations near the nodal point are also the zones of weakest stress-induced anisotropy zones and are therefore the least likely to be measured in practice as long as a quality indicator depending on both the degree of anellipticity and the strength of the shear anisotropy is below 0.5. Finally, we present a synthetic example of the application of this model to estimate the relative deviatoric stress tensor using two wells with different orientations.

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Sonic dispersion curves identify TIV anisotropy in vertical wells

Cited by 6 publications

References 3 publications

Study the elastic properties and the anisotropy of rocks using different machine learning methods

Study the elastic properties and the anisotropy of rocks using different machine learning methods

Acoustoelastic effects of Stoneley waves in a borehole surrounded by a transversely isotropic elastic solid

Relating shear sonic anisotropy directions to stress in deviated wells

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