Case study of estimation of anisotropy

Toldi, John L.; Alkhalifah, Tariq; Berthet, Philippe; Arnaud, J.; Williamson, Paul; Conche, Bruno

doi:10.1190/1.1438341

Cited by 29 publications

(10 citation statements)

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“…First, several Dix-derived interval parameters η (1,2,3) are too large for shale formations and lie outside the range suggested by laboratory and field studies (Toldi et al, 1999;Wang, 2002). The interval value of η (2) for the first superbin even exceeds unity.…”

Section: Field-data Examplementioning

confidence: 96%

“…Alkhalifah and Tsvankin (1995) suggested a particularly convenient, simplified form of equation 3.3 for P-waves in VTI media that includes just two moveout parameters, the NMO velocity of horizontal events and the anellipticity parameter η. The Alkhalifah-Tsvankin equation has been widely used for estimating η from nonhyperbolic semblance analysis and for building vertically heterogeneous VTI models in the time domain (e.g., Alkhalifah, 1997;Toldi et al, 1999). Below, this equation is extended to orthorhombic and HTI media by making the NMO velocity and parameter η azimuthally dependent.…”

Section: Nonhyperbolic Moveout Equationsmentioning

confidence: 98%

See 1 more Smart Citation

Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

Tsvankin¹,

Grechka²

2011

180

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Section: Field-data Examplementioning

confidence: 96%

Section: Nonhyperbolic Moveout Equationsmentioning

confidence: 98%

Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

Tsvankin¹,

Grechka²

2011

180

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“…The key issue in anisotropic processing, however, is reliable estimation of the velocity model from reflection data combined with borehole and other information. The parameter η responsible for time processing in VTI media can be obtained by inverting either dip-dependent NMO velocity or nonhyperbolic (longspread) reflection moveout (Alkhalifah and Tsvankin, 1995;Alkhalifah, 1997;Toldi et al, 1999;Fomel, 2004;Ursin and Stovas, 2006). Then the ηfield can be refined in the migrated domain using migration velocity analysis (Sarkar and Tsvankin, 2004) or reflection tomography (Woodward et al, 2008).…”

Section: P-wave Velocity Analysis and Imagingmentioning

confidence: 99%

Seismic anisotropy in exploration and reservoir characterization: An overview

Gaiser²,

et al. 2010

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Recent advances in parameter estimation and seismic processing have allowed incorporation of anisotropic models into a wide range of seismic methods. In particular, vertical and tilted transverse isotropy are currently treated as an integral part of velocity fields employed in prestack depth migration algorithms, especially those based on the wave equation. Here, we briefly review the state of the art in modeling, processing, and inversion of seismic data for anisotropic media. Topics include optimal parameterization, body-wave modeling methods, P-wave velocity analysis and imaging, processing in the τ -p domain, anisotropy estimation from vertical seismic profiling (VSP) surveys, moveout inversion of wide-azimuth data, amplitude-variation-with-offset (AVO) analysis, processing and applications of shear and mode-converted waves, and fracture characterization. When outlining future trends in anisotropy studies, we emphasize that continued progress in data-acquisition technology is likely to spur transition from transverse isotropy to lower anisotropic symmetries (e.g., orthorhombic). Further development of inversion and processing methods for such realistic anisotropic models should facilitate effective application of anisotropy parameters in lithology discrimination, fracture detection, and time-lapse seismology.

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“…The trade-off between these parameters, however, may lead to sizable errors in η which can reach ±0.1, even for this simple model (Grechka and Tsvankin, 1998). Numerical and field examples of nonhyperbolic moveout analysis of PP-wave data are given by Alkhalifah (1997), Le Bougeant et al (1997), Grechka and Tsvankin (1998), Toldi et al (1999), Tsvankin (2001), and others.…”

Section: Inversion Of Pp Moveout and Conventional-spread Ps Datamentioning

confidence: 99%

The joint nonhyperbolic moveout inversion of PP and PS data in VTI media

Grechka

Tsvankin

2002

GEOPHYSICS

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Nonhyperbolic moveout of P-waves in horizontally layered transversely isotropic media with a vertical symmetry axis (VTI) can be used to estimate the anellipticity coefficient η in addition to the NMO velocity V nmo,P. Those two parameters are sufficient for time processing of P-wave data (despite a certain instability in the inversion for η), but they do not constrain the vertical velocity V P0 and the depth scale of the model. It has been suggested in the literature that this ambiguity in the depthdomain velocity analysis for layer-cake VTI media can be resolved by combining long-spread reflection traveltimes of P-waves and mode-converted PSV-waves. Here, we show that reflection traveltimes of horizontal PSV events help to determine the ratio of the P-and S-wave vertical velocities and the NMO velocity of SVwaves, and they give a more accurate estimate of η. However, nonhyperbolic moveout of PSV-waves turns out to be mostly controlled by wide-angle P-wave traveltimes and does not provide independent information for the inversion. As a result, even for a single-layer model and uncommonly large offsets, traveltimes of P-and PSVwaves cannot be inverted for the vertical velocity and anisotropic parameters and δ. To reconstruct the horizontally layered VTI model from surface data, it is necessary to combine long-spread traveltimes of pure P and SV reflections.

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Case study of estimation of anisotropy

Cited by 29 publications

References 0 publications

Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

Seismology of Azimuthally Anisotropic Media and Seismic Fracture Characterization

Seismic anisotropy in exploration and reservoir characterization: An overview

The joint nonhyperbolic moveout inversion of PP and PS data in VTI media

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