Anisotropic migration and model building for 4C seismic data: A case study from Alba

Dai, Hengchang; Li, Xiang‐Yang

doi:10.1190/1.1816753

Cited by 17 publications

(11 citation statements)

References 10 publications

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“…The above prestack time migration (PSTM) scheme was applied to several 4C data sets from the North Sea, including Valhall, Mahogany (Li et al . 2001) and Alba (Dai and Li 2001). Here, we select two recent examples for illustrative purposes.…”

Section: D Data Examplementioning

confidence: 99%

“…Since 1999, efforts have also been made to develop converted‐wave anisotropic PSTM to replace the CCP‐binning and DMO approach (e.g. Li and Druzhinin 2000; Dai and Li 2001; Dai 2003). Here, we review these developments and present a unified and interactive approach for converted‐wave imaging and parameter estimation in anisotropic media.…”

Section: Introductionmentioning

confidence: 99%

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Converted‐wave imaging in anisotropic media: theory and case studies

Dai

Mancini

2007

Geophysical Prospecting

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SUMMARYCommon-conversion-point binning associated with converted-wave (C-wave) processing complicates the task of parameter estimation, especially in anisotropic media. To overcome this problem, we derive new expressions for converted-wave prestack time migration (PSTM) in anisotropic media and illustrate their applications using both 2D and 3D data examples.The converted-wave kinematic response in inhomogeneous media with vertical transverse isotropy (VTI) is separated into two parts: the response in horizontally layered VTI media and the response from a point scatter. The former controls the stacking process and the latter controls the process of PSTM. The C-wave traveltime in horizontally layered VTI media is determined by four parameters: the C-wave stacking velocity V C2 , the vertical and effective velocity ratios γ 0 and γ eff , and the C-wave anisotropic parameter χ eff . These four parameters are referred to as the C-wave stacking velocity model. In contrast, the C-wave diffraction time from a point scatter is determined by five parameters: γ 0 , V P2 , V S2 , η eff and ζ eff , where η eff and ζ eff are, respectively, the P-and S-wave anisotropic parameters, and V P2 and V S2 are the corresponding stacking velocities. V P2 , V S2 , η eff and ζ eff are referred to as the C-wave PSTM velocity model. There is a one-to-one analytical link between the stacking velocity model and the PSTM velocity model. There is also a simple analytic link between the C-wave stacking velocities V C2 and the migration velocity V Cmig , which is in turn linked to V P2 and V S2 .Based on the above, we have developed an interactive processing scheme to build the stacking and PSTM velocity model and to perform 2D and 3D C-wave anisotropic PSTM.Real data applications show that the PSTM scheme substantially improves the quality of Cwave imaging compared with the DMO (dip moveout) scheme, and these improvements have been confirmed by drilling.

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Section: D Data Examplementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Converted‐wave imaging in anisotropic media: theory and case studies

Dai

Mancini

2007

Geophysical Prospecting

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“…Equation (6) is derived for a single VTI layer but it is found to be good approximations for time processing. Note that the full velocity model for prestack time migration (PSTM) requires five parameters: γ 0 , V P2, V S2, η eff and ζ eff (Dai and Li, 2001).…”

Section: Model Buildingmentioning

confidence: 99%

Converted‐wave moveout analysis revisited: The search for a standard approach

2003

SEG Technical Program Expanded Abstracts 2003

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Converted-wave (C-wave) moveout is inherently nonhyperbolic, and under existing theories, it requires at least three parameters to describe the non-hyperbolic moveout accurately even for layered isotropic media. As a result, there is still no recognized standard processing flow to handle the converted-waves except the hyperbolic approach. Here, I present revised moveout equations for layered isotropic/anisotropic media, which contain less parameters but retain the same accuracy as the exiting ones. The new equation for layered isotropic media contains two parameters: the stacking velocity V C2 and the velocity ratio γ iso between the squared P-and C-wave stacking velocities; for layered VTI media (vertical transverse isotropy), an additional parameter is needed (anisotropic coefficient χ eff). The new equations reveal that V C2 controls the hyperbolic moveout at near-offsets; γ iso controls the non-hyperbolic moveout at intermediate-offsets due to the asymmetric raypath; χ eff controls the anisotropic moveout at far offsets. Therefore, it is possible to retrieve each parameter by inverting the reflection moveout for the data aperture that is most sensitive to the parameter, hence to build up the velocity model for anisotropic imaging. A 4C dataset from Guillemot, North Sea (Courtesy of Shell Expro) will be used to illustrate these findings and implications for Cwave imaging.

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“…However, anisotropic CCP binning and converted-wave DMO is strongly velocity-dependent and this severely limited the success of this approach. Since 1999, efforts have also been made to develop converted-wave anisotropic PSTM to replace the CCP-binning and DMO approach (e.g., Li and Druzhinin, 2000;Dai and Li 2001;Dai, 2003;amongst others). Here, we review these developments and present a unified and interactive approach for converted-wave imaging and parameter estimation in anisotropic media.…”

Section: Introductionmentioning

confidence: 99%

Converted‐wave imaging in anisotropic media: An overview

Dai

Mancini

2004

SEG Technical Program Expanded Abstracts 2004

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This paper reviews the recent developments in convertedwave (C-wave) processing for vertical transverse isotropy (VTI), and addresses issues such as how many parameters are required to perform C-wave anisotropic prestack time migration (PSTM), and how to estimate these parameters. Both recent 2D and 3D data examples will be used to illustrate these developments. The converted-wave kinematic response in inhomogeneous VTI media is separated into two parts: the zero-dip response for horizontally layered VTI media and the all dip response from a point scatter. The former controls the stacking process and the latter controls the process of PSTM. The C-wave traveltime in horizontally layered VTI media is determined by four parameters: the C-wave stacking velocity V C2 , the vertical and effective velocity ratios γ 0 and γ eff , and the C-wave anisotropic parameter χ eff. These four parameters are referred to as the C-wave stacking velocity model. In contrast, the C-wave diffraction time from a point scatter is determined by five parameters: γ 0 , V P2 , V S2 , η eff and ζ eff , where η eff and ζ eff are, respectively, the P-and S-wave anisotropic parameters, and V P2 and V S2 are the corresponding stacking velocities. V P2 , V S2 , η eff and ζ eff are referred to as the C-wave PSTM velocity model. There is a one-to-one analytical link between the stacking velocity model and the PSTM velocity model. Based on the above understanding, we have developed an interactive processing scheme to build the stacking and PSTM velocity model and to perform 2D and 3D C-wave anisotropic PSTM. Real data applications show that the PSTM scheme substantially improves the quality of Cwave imaging compared with the DMO scheme, and these improvements have been confirmed by drilling.

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Anisotropic migration and model building for 4C seismic data: A case study from Alba

Cited by 17 publications

References 10 publications

Converted‐wave imaging in anisotropic media: theory and case studies

Converted‐wave imaging in anisotropic media: theory and case studies

Converted‐wave moveout analysis revisited: The search for a standard approach

Converted‐wave imaging in anisotropic media: An overview

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