1887
Volume 60, Issue 6
  • E-ISSN: 1365-2478

Abstract

ABSTRACT

This paper presents a new explicit method for the estimation of layered vertical transverse isotropic (VTI) anisotropic parameters from walkaway VSP data. This method is based on Dix‐type normal moveout (NMO) inversion. To estimate interval anisotropic parameters above a receiver array, the method uses time arrivals of surface‐related double‐reflected downgoing waves. A three‐term NMO approximation function is used to estimate NMO velocity and a non‐hyperbolic parameter. Assuming the vertical velocity is known from zero‐offset VSP data, Dix‐type inversion is applied to estimate the layered Thomsen anisotropic parameters ɛ, δ above the receivers array. Model results show reasonable accuracy for estimates through Dix‐type inversion. Results also show that in many cases we can neglect the influence of the velocity gradient on anisotropy estimates. First breaks are used to estimate anisotropic parameters within the walkaway receiver interval. Analytical uncertainty analysis is performed to NMO parameter estimates. Its conclusions are confirmed by modelling.

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2012-09-28
2024-04-24
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References

  1. Al‐ChalabiM.1974. An analysis of stacking, RMS, average and interval velocities over a horizontally layered ground. Geophysical Prospecting 22, 458–475.
    [Google Scholar]
  2. AlkhalifahT.1997. Velocity analysis using nonhyperbolic moveout in transversely isotropic media. Geophysics 62, 1839–1854.
    [Google Scholar]
  3. AlkhalifahT. and TsvankinI.1995. Velocity analysis for transversely isotropic media. Geophysics 60, 1550–1566.
    [Google Scholar]
  4. BliasE.1983. Reflected wave's travel‐time curve in flat‐bedded medium with transverse layers and their interpretation. Soviet Geology and Geophysics 2, 91–95.
    [Google Scholar]
  5. BliasE.1987. Reflected wave's traveltime in the media with gently dipping curvilinear boundaries and anisotropic layers. Acad. News, Physics of Earth N7, 60–68.
    [Google Scholar]
  6. BliasE.2009a. Interval VTI and orthorhombic anisotropic parameter estimates from walkaway/3D VSP Data. 79th SEG Annual Meeting, Expanded Abstracts.
  7. BliasE.2009b. Stacking velocities in the presence of overburden velocity anomalies. Geophysical Prospecting 57, 323–341.
    [Google Scholar]
  8. GrechkaV. and TsvankinI.1998. Feasibility of nonhyperbolic moveout inversion in transversely isotropic media. Geophysics 63, 957–969.
    [Google Scholar]
  9. GrechkaV. and TsvankinI.1999. 3‐D moveout inversion in azimuthally anisotropic media with lateral velocity variation: Theory and a case study. Geophysics 64, 1202–1218.
    [Google Scholar]
  10. GrechkaV. and TsvankinI.2002. Processing‐induced anisotropy. Geophysics 67, 1920–1928.
    [Google Scholar]
  11. LeaneyW.S.2000. Look‐ahead walkaways using effective VTI models. SEG Annual meeting, 1743–1747.
  12. LouM., ZhaoX., DohertyF. and JacksonJ.2007. Vector Migration of 1st Order Free‐surface Related Downgoing Multiples from VSP Data. 69th EAGE Conference & Exhibition, Expanded Abstracts.
  13. LyakhovitskiyF.M.1981. “Long‐wave elastic anisotropy in transversely isotropic media” by J. G. Berryman, and “Seismic velocities in transversely isotropic media” by F. K. Levin (Geophysics, v. 44, May 1979, p. 896–917 and p. 918–936, respectively). Geophysics 46, 336–338.
    [Google Scholar]
  14. LyakhovitskiyF.M. and NevskiyM.V.1971. Traveltime curves of reflected waves for transversely‐ isotropic medium. Academy of Science, USSR, Doklady 196, 327–330 (in Russian).
    [Google Scholar]
  15. MalovichkoA.A.1978. A new representation of the traveltime curve of reflected waves in horizontally layered media (in Russian). Applied Geophysics 91, 35–44. (English translation in Sword C. 1987. A Soviet look at datum shift. Stanford Exploration Project  51, 313–316).
    [Google Scholar]
  16. MenkeW.1984. Geophysical Data Analysis: Discrete Inverse Theory . Academic Press Inc., p. 260.
    [Google Scholar]
  17. ReiterE.C., ToksőzM.N., KehoT.H. and PurdyG.M.1991. Imaging with deep‐water multiples. Geophysics 56, 1081–1086.
    [Google Scholar]
  18. ThomsenL.1986. Weak elastic anisotropy. Geophysics 51, 1954–1966.
    [Google Scholar]
  19. TsvankinI.1997. Anisotropic parameters and P‐wave velocity for orthorhombic media. Geophysics 62, 1292–1309.
    [Google Scholar]
  20. TsvankinI.2005. Seismic Signatures and Analysis of Reflection Data in Anisotropic Media , 2nd ed. Elsevier Science Publ. Co., Inc.
    [Google Scholar]
  21. TsvankinI. and ThomsenL.1994. Nonhyperbolic reflection moveout in anisotropic media. Geophysics 59, 1290–1304.
    [Google Scholar]
  22. TsvankinI. and ThomsenL.1995. Inversion of reflection traveltimes for transverse isotropy. Geophysics 60, 1095–1107.
    [Google Scholar]
  23. UrsinB. and StovasA.2005. Generalized Dix equations for a layered transversely isotropic medium. Geophysics 70, D77–D81.
    [Google Scholar]
  24. UrsinB. and StovasA.2006. Traveltime approximations for a layered transversely isotropic medium. Geophysics 71, D23–D33.
    [Google Scholar]
  25. ZhouR. and KaderaliA.2006. Anisotropy Evaluation Using an Array Walkaway VSP. Offshore Technology Conference.
    [Google Scholar]
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  • Article Type: Research Article
Keyword(s): Anisotropy; Inversion; Velocity; VSP; Walkaway

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