1887
Volume 37 Number 12
  • ISSN: 0263-5046
  • E-ISSN: 1365-2397

Abstract

Abstract

Contemporary depth imaging projects often require final pre-Stack Depth-Migrations (preSDM) to be converted to time for comparison to vintage pre-Stack Time-Migrations (preSTM), or to facilitate conversion to ‘geological’ depth through calibration to well and check-shot data. Here, I consider the situation of having performed an anisotropic Tilted Transverse Isotropy (TTI) preSDM and wanting to convert it to time via vertical stretch in order to compare it, say, to an anisotropic preSTM.

Such a comparison is inherently invalid, as time-migration will explicitly treat any anisotropy as if it were Vertical Transverse Isotropy (VTI), and, in addition, the lateral positioning error inherent in preSTM will render such comparisons questionable on steeply dipping structures.

I show here that the most appropriate type of ‘velocity’ to use for conversion to time of TTI preSDM reflection events should be the vertical component of the phase velocity. Conversely, if we are considering point-to-point measurements, such as the direct arrival travel time, a down-hole or check-shot measurement, then the group velocity should be used, as it is with this speed that energy travels. In addition, subsequent depth conversion of any time product for interpretational purposes would best be accomplished using a velocity calibrated to well check-shots.

Loading

Article metrics loading...

/content/journals/10.3997/1365-2397.2019039
2019-12-01
2024-04-20
Loading full text...

Full text loading...

References

  1. Al-Chalabi, M.
    [1974]. An analysis of stacking RMS average and interval velocities over a horizontally layered ground.Geophysical Prospecting, 22 (3), 458–475.
    [Google Scholar]
  2. [1994]. Seismic velocities—a critique.First Break, 12, 589–596.
    [Google Scholar]
  3. [1997]. Parameter nonuniqueness in velocity versus depth functions.Geophysics, 62 (3), 970–979.
    [Google Scholar]
  4. Al-Chalabi, M. and. Rosenkranz, P.L.
    [2002]. Velocity-depth and time-depth relationships for a decompacted uplifted unit.Geophysical Prospecting, 50 (6), 661–664.
    [Google Scholar]
  5. Al-Chalabi, M.
    , [2014]. Principles of Seismic Velocities and Time-to-Depth Conversion.EAGE, Houten, The Netherlands.
    [Google Scholar]
  6. Alkhalifah, T. and Larner, K.
    [1994]. Migration error in transversely isotropic media.Geophysics, 59 (9), 1405–1418.
    [Google Scholar]
  7. Alkhalifah, T. and Tsvankin, I.
    [1995]. Velocity analysis for transversely isotropic media.Geophysics, 60 (5), 1550–1566.
    [Google Scholar]
  8. Alkhalifah, T.
    [1997]. Velocity analysis using nonhyperbolic moveo-ut in transversely isotropic media.Geophysics, 62 (6), 1839–1854.
    [Google Scholar]
  9. [2000]. An acoustic wave equation for anisotropic media.Geophysics, 65, 1239–1250.
    [Google Scholar]
  10. Armstrong, T.
    , [2001]. Velocity anomalies and depth conversion – drilling success on Nelson Field, Central North Sea.63rd EAGE Conference & Exhibition, Extended Abstracts, IV-2.
    [Google Scholar]
  11. Armstrong, T.L., J.McAteer, and P.Connolly
    , [2001]. Removal of overburden velocity anomaly effects for depth conversion.Geophysical Prospecting, 49, 79–99.
    [Google Scholar]
  12. Bakulin, A., Woodward, M., Nichols, D., Osypov, K., and Zdraveva, O.
    , [2010]. Building tilted transversely isotropic depth models using localized anisotropic tomography with well information.Geophysics, 75 (4). D27–D36.
    [Google Scholar]
  13. Bale, R.
    [2007]. Phase-Shift Migration and the Anisotropic Acoustic Wave Equation.EAGE 69th Conference & Exhibition, Expanded Abstracts.
    [Google Scholar]
  14. Bartel, D.C., Busby, M., Nealon, J., and Zaske, J.
    , [2006]. Time to depth conversion and uncertainty assessment using average velocity modeling.SEG, Expanded Abstracts, 25, 2166.
    [Google Scholar]
  15. Berryman, J.G.
    , [1979]. Long-wave elastic anisotropy in transversely isotropic media.Geophysics, 44 (5). 896–917.
    [Google Scholar]
  16. Black, J.L. and Brzostowski, M.A.
    [1994]. Systematics of time migration errors.Geophysics, 59 (9), 1419–1434.
    [Google Scholar]
  17. Cameron, M., Fomel, S., and Sethian, J.
    , [2008]. Time-to-depth conversion and seismic velocity estimation using time-migration velocity.Geophysics, 73, VE205.
    [Google Scholar]
  18. Grechka, V.
    [2009]. Applications of Seismic Anisotropy in the Oil and Gas Industry.EAGE, Houten, The Netherlands.
    [Google Scholar]
  19. Grechka, V., I.Tsvankin, and J. K.Cohen
    , [1999]. Generalized Dix equation and analytic treatment of normal-moveout velocity for anisotropic media: Geophysical Prospecting, 47, 117–148.
    [Google Scholar]
  20. Hubral, P.
    [1977]. Time migration; some ray theoretical aspects.Geophysical Prospecting, 25 (4), 738–745.
    [Google Scholar]
  21. Iversen, E., and Tygel, M.
    , [2008]. Image-ray tracing for joint 3D seismic velocity estimation and time-to-depth conversion.Geophysics, 73, S99.
    [Google Scholar]
  22. Jones, I.F., Bridson, M.L. and Bernitsas, N.X.
    [2003]. Anisotropic Ambiguities in TI Media.First Break, 21 (4), 31–37.
    [Google Scholar]
  23. Jones, I.F.
    [2009]. Tutorial: Time conversion of depth migrated data.First Break, 27 (7), 51–55.
    [Google Scholar]
  24. [2010]. An introduction to velocity model building.EAGE, Houten, The Netherlands.
    [Google Scholar]
  25. Jones, I.F. and Davison, I.
    [2014]. Seismic imaging in and around salt bodies.SEG Interpretation, 2 (4), SL1–SL20.
    [Google Scholar]
  26. Jones, I.F.
    [2015]. Estimating subsurface parameter fields for seismic migration: velocity model building. In: Grechka, V. and Wapenaar, K. (Eds.), Encyclopedia of Exploration Geophysics. SEG, Tulsa, USA.
    [Google Scholar]
  27. Robein, E.
    [2003]. Velocities, time-imaging and depth-imaging: Principles and methods.EAGE, Houten, The Netherlands.
    [Google Scholar]
  28. , [2010]. Seismic Imaging: A Review of the Techniques, their Principles, Merits and Limitations.EAGE, Houten, The Netherlands.
    [Google Scholar]
  29. Sadri, M. and Riahi, M.A.
    [2010]. Ray tracing and amplitude calculation in anisotropic layered media.Geophys. J. Int., 180, 1170–1180.
    [Google Scholar]
  30. Sugrue, M., Osolo, C., Anstey, I., Oladeji, O., and , Gerea, C.
    [2011]. TTI Depth Migration – Advantages for Development Offshore Nigeria.81st Annual International Meeting, SEG.
    [Google Scholar]
  31. Thomsen, L. [1986]. Weak elastic anisotropy. Geophysics, 51 (10), 1954–1966.
  32. Thomsen, L.
    [2002]. Understanding seismic anisotropy in exploration and exploitation.SEG/EAGE DISC course lecture notes.
    [Google Scholar]
  33. Tsvankin, I. and Thomsen, L.
    [1994]. Nonhyperbolic reflection moveout in anisotropic media.Geophysics, 59 (8), 1290–1304.
    [Google Scholar]
  34. Tsvankin, I.
    [1997]. Moveout analysis for transversely isotropic media with a tilted symmetry axis.Geophys. Prosp., 45, 479–512.
    [Google Scholar]
  35. Uren, N.F., Gardner, G.H.F. and McDonald, J.A.
    [1990]. Normal moveout in anisotropic media.Geophysics, 55 (12), 1634–1636.
    [Google Scholar]
  36. Vernik, L. and Liu, X.
    [1997]. Velocity anisotropy in shales: A petro-physical study.Geophysics, 62, 521–532.
    [Google Scholar]
  37. Vestrum, R.W., Lawton, D.L. and Schmid, R.
    [1999]. Imaging structures below dipping TI media.Geophysics, 64 (4), 1239–1246.
    [Google Scholar]
  38. VerWest, B.J.
    [1989]. Seismic migration in elliptically anisotropic media.Geophysical Prospecting, 37 (2), 149–166.
    [Google Scholar]
  39. Wang, Y.
    [2014]. Seismic ray tracing in anisotropic media: A modified Newton algorithm for solving highly nonlinear systems.Geophysics, 79, T1–T7.
    [Google Scholar]
http://instance.metastore.ingenta.com/content/journals/10.3997/1365-2397.2019039
Loading
/content/journals/10.3997/1365-2397.2019039
Loading

Data & Media loading...

  • Article Type: Research Article
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error