Correction for the influence of velocity lenses on nonhyperbolic moveout inversion for VTI media

Takanashi, Mamoru; Tsvankin, Ilya

doi:10.1190/1.3569799

Cited by 7 publications

(23 citation statements)

References 22 publications

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“…Here, we explore the possibility of evaluating the lensinduced distortion in NMO ellipses for horizontallylayered models using the analytic expression of Takanashi and Tsvankin (2011). Their equation accurately describes the NMO ellipses for a layered azimuthally anisotropic medium with weak and smooth lateral velocity variation (Takanashi and Tsvankin, 2011).…”

Section: Estimation Of the Lens-induced Distortion In Nmo Ellipsesmentioning

confidence: 99%

“…2D modeling for layered VTI media by Takanashi and Tsvankin (2010) demonstrates that a velocity lens above the reflector can cause substantial, laterally varying errors in the NMO velocity and the anellipticity parameter η. In the presence of a lens, nonhyperbolic moveout inversion tends to produce even larger errors in Vnmo than does conventional analysis based on the hyperbolic moveout equation.…”

Section: Introductionmentioning

confidence: 99%

“…Such an approach, however, is not only time-consuming but relies on accurate estimates of the overburden parameters. A 2D correction algorithm introduced by Takanashi and Tsvankin (2010) requires less a priori information, provided the lens is embedded in a horizontally layered overburden. Their algorithm computes lens-induced traveltime distortions for each trace separately using VILS.…”

Section: Introductionmentioning

confidence: 99%

“…Here, we study the influence of an elongated velocity lens on the NMO ellipse using the equation introduced by Takanashi and Tsvankin (2011) for LH layers with a smooth velocity field. We show that the laterally- Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…Correcting the effective NMO ellipses from the top and bottom of a layer before applying the generalized Dix equation substantially reduces errors in the interval NMO ellipse. To remove lens-induced distortions in the moveout parameters estimated from nonhyperbolic inversion, we extend the correction algorithm of Takanashi and Tsvankin (2010) to wide-azimuth data. Synthetic tests demonstrate that this 3D algorithm effectively restores the traveltime surface in the reference (laterally homogeneous) medium and substantially reduces errors in the azimuthally varying interval parameters Vnmo and η.…”

Section: Introductionmentioning

confidence: 99%

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Moveout inversion of wide‐azimuth data in the presence of velocity lenses

Takanashi

Tsvankin

2011

SEG Technical Program Expanded Abstracts 2011

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Moveout analysis of wide-azimuth reflection data is usually performed for smoothly varying velocity fields. However, velocity lenses in the overburden can cause significant laterally-varying errors in the moveout parameters and distortions in data interpretation. The main goal of this paper is to develop a correction for the influence of an elongated velocity lens on the NMO ellipse and nonhyperbolic reflection moveout. We show that an analytic expression for the NMO ellipse in stratified media with lateral velocity variation, introduced in our previous paper, adequately represents lens-induced distortions. The correction for lateral heterogeneity is controlled by the second derivatives of the interval vertical traveltime. This analytic correction provides a quick estimate of the contribution of velocity lenses and substantially mitigates lens-induced distortions in the effective and interval NMO ellipses. To remove the influence of velocity lenses on nonhyperbolic moveout inversion of wide-azimuth data, we propose a prestack correction algorithm that involves computation of the lensinduced traveltime distortion for each recorded trace. The method is designed for a horizontally-layered overburden but can handle laterally heterogeneous target layers with dipping or curved interfaces. Synthetic tests confirm that this algorithm accurately removes lens-related traveltime shifts and significantly reduces errors in the azimuthally varying moveout parameters. The developed methods should increase the robustness of seismic processing of wide-azimuth surveys, especially those acquired for fracture-characterization purposes.

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Section: Estimation Of the Lens-induced Distortion In Nmo Ellipsesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Moveout inversion of wide‐azimuth data in the presence of velocity lenses

Takanashi

Tsvankin

2011

SEG Technical Program Expanded Abstracts 2011

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Effects of lateral heterogeneity on time-domain processing parameters

Sripanich

Fomel

Stovas

2019

Geophysical Journal International

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SUMMARY Time-domain processing of seismic reflection data has always been an important engine that is routinely utilized to produce seismic images and to expeditiously construct subsurface models. The conventional procedure involves analysing parameters related to the derivatives of reflection traveltime with respect to offset including normal moveout (NMO) velocities (second-order derivatives) and quartic coefficients (fourth-order derivatives). In this study, we propose to go beyond the typical assumption of 1-D laterally homogeneous medium when relating those ‘processing’ parameters to the subsurface medium parameters and take into account the additional influences from lateral heterogeneity including curved interfaces and smoothly variable velocities. We fill in the theoretical gap from previous studies and develop a general framework for such connection in layered anisotropic media. We show that in general, the influences of lateral heterogeneity get accumulated from all layers via a recursive relationship according to the Fermat’s principle and can be approximately quantified in terms of the lateral derivatives of the layer interface surfaces and velocities. Based on the same general principle, we show that our approach can also be used to study the lateral heterogeneity effects on diffraction traveltime and its second-order derivative related to time-migration velocity. In this paper, we explicitly specify expressions for NMO and time-migration velocities with the influences from both types of heterogeneity suitable for 2-D data sets and also discuss possible extensions of the proposed theory to 3-D data sets and to parameters related to higher-order traveltime derivatives. Using numerical examples, we demonstrate that the proposed theory can lead to more accurate reflection and diffraction traveltime predictions in comparison with those obtained based on the 1-D assumption. Both the proposed theoretical framework and its numerical testing for forward traveltime computation presented in this study aid in understanding the effects from lateral heterogeneity on time-processing parameters and also serve as an important basis for designing an efficient technique to separate those influences in important processes such as Dix inversion for a more accurate subsurface model in the future.

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Moveout analysis of wide-azimuth data in the presence of lateral velocity variation

Takanashi

Tsvankin

2012

GEOPHYSICS

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Moveout analysis of wide-azimuth reflection data seldom takes into account lateral velocity variations on the scale of spreadlength. However, velocity lenses (such as channels and reefs) in the overburden can cause significant, laterally varying errors in the moveout parameters and distortions in data interpretation. Here, we present an analytic expression for the normal-moveout (NMO) ellipse in stratified media with lateral velocity variation. The contribution of lateral heterogeneity (LH) is controlled by the second derivatives of the interval vertical traveltime with respect to the horizontal coordinates, along with the depth and thickness of the LH layer. This equation provides a quick estimate of the influence of velocity lenses and can be used to substantially mitigate the lens-induced distortions in the effective and interval NMO ellipses. To account for velocity lenses in nonhyperbolic moveout inversion of wide-azimuth data, we propose a prestack correction algorithm that involves computation of the lens-induced traveltime distortion for each recorded trace. The overburden is assumed to be composed of horizontal layers (one of which contains the lens), but the target interval can be laterally heterogeneous with dipping or curved interfaces. Synthetic tests for horizontally layered models confirm that our algorithm accurately removes lens-related azimuthally varying traveltime shifts and errors in the moveout parameters. The developed methods should increase the robustness of seismic processing of wide-azimuth surveys, especially those acquired for fracture-characterization purposes.

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Correction for the influence of velocity lenses on nonhyperbolic moveout inversion for VTI media

Cited by 7 publications

References 22 publications

Moveout inversion of wide‐azimuth data in the presence of velocity lenses

Moveout inversion of wide‐azimuth data in the presence of velocity lenses

Effects of lateral heterogeneity on time-domain processing parameters

Moveout analysis of wide-azimuth data in the presence of lateral velocity variation

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