ARTICLE

Physical model study of reflection pitfalls and anisotropy parameter estimation in a transversely isotropic medium

CHIH-HSIUNG CHANG1 YOUNG-FO CHANG2 PO-YEN TSENG2 CHAO-MING LIN3
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1 General Education Centre, Centre of Energy Research and Sensor Technology, National Chiayi University, Chiayi 60004, Taiwan. charles@mail.nccu.edu.tw,
2 Institute of Seismology, National Chung Cheng University, Chiayi 62102, Taiwan.,
3 Department of Electronic Engineering, Hsiuping Institute of Technology, Taichung 41280, Taiwan.,
JSE 2016, 25(5), 399–418;
Submitted: 28 October 2015 | Accepted: 20 June 2016 | Published: 1 October 2016
© 2016 by the Authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution -Noncommercial 4.0 International License (CC-by the license) ( https://creativecommons.org/licenses/by-nc/4.0/ )
Abstract

Chang, C.-H., Chang, Y.-F., Tseng, P.-Y. and Lin, C.-M., 2016. Physical model study of reflection pitfalls and anisotropy parameter estimation in a transversely isotropic medium. Journal of Seismic Exploration, 25: 399-418. Imaging problems due to velocity anisotropy were investigated using forward modelling. Zero-offset and constant-offset reflection experiments were performed to image spherical domes that were carved into the bottom of VTI and HTI models, respectively, along three different layout directions. Subject to velocity anisotropy, the spherical dome was projected as laterally stretched images. The curvature radius of the spherical dome was increasingly imaged in the seismic profiles due to polar velocity variation in the VTI model. An ellipsoidal dome was detected in the HTI model, instead of a spheroidal dome, due to azimuthal velocity variation. To address the problems of erroneous images in reflections, laboratory data were processed by anisotropic 2D Kirchhoff migration. Although true images were not satisfactorily restored, the effects of 'lateral stretch' were significantly reduced. Due to azimuthal velocity variations, Common Depth Point (CDP) reflections acquired from different azimuths on the horizontal symmetry axis plane of the HTI model cannot be well-tied. Making use of the 'mis-tie' in the CDP, which was observed in the profiles, the feasibility of estimating the Thomsen’s P-wave anisotropy parameter (€) was evaluated. Although the physical models used are relatively simple, erroneous images caused by velocity anisotropy were confirmed, and the prospect of estimating the P-wave anisotropy parameter (€) from arrival time difference was addressed.

Keywords
modelling
anisotropy
reflection
image
migration
CDP
References
  1. Chang, C.H. and Chang, Y.F., 2003. A simplified nonhyperbolic moveout formula for atransversely isotropic medium. TAO, 14: 99-112.
  2. Cheng, J.B., Wang, T.F., Wang, C.L. and Geng, J.H., 2012. Azimuth-preserved localangle-domain prestack time migration in isotropic, vertical transversely isotropic andazimuthally anisotropic media. Geophysics, 77: -S64.
  3. Claerbout, J., 1997. Introduction to Kirchhoff Migration Programs. Stanford Exploration Project,Report 73: 385-391.
  4. Dellinger, J. and Vernik, L., 1994. Do traveltimes in pulse-transmission experiments yieldanisotropic group or phase velocity? Geophysics, 59: 1774-1779.
  5. French, W.S., 1974. 2-D and 3-D migration of model-experiment reflection profiles. Geophysics,39: 265-277.
  6. Grechka, V., Theophanis, S$. and Tsvankin, I., 1999. Joint inversion of P- and PS-waves inorthorhombic media: Theory and a physical modeling study. Geophysics, 64: 146-161.
  7. Holt, R., 2006. Constraining anisotropy - Lessons from 2D modeling. Abstr., CSEG-CWLSConvent.: 296-299.418 CHANG, CHANG, TSENG & LIN
  8. Helbig. K., and Thomsen. L., 2005. 75-plus years of anisotropy in exploration and reservoirseismics: A historical review of concepts and methods. Geophysics, 70: 9ND-23ND.
  9. Isaac, J.-H. and Lawton, D.C., 1999. Image mispositioning due to dipping TI media: A physicalseismic modeling study. Geophysics, 64: 1230-1238.
  10. Mah, M. and Schmitt, D.R., 2003. Determination of the complete elastic stiffnesses from ultrasonicphase velocity measurements. J. Geophys. Res., 108: ECV 6-1—6-11.doi: 10. 1029/2001jb001586.
  11. Martin, D., Ehinger, A. and Rasolofosaon, P., 1992. Some aspects of seismic modeling and imagingin anisotropic media using laser ultrasonics. Expanded Abstr., 62nd Ann. Internat. SEG
  12. Mtg., New Orleans: 1373-1376. doi: 10.1190/1.1821998
  13. Okoye, P.N., Uren, N.F., McDonald, J.A. and Ebrom, D.A., 1995. The dependence of lateralresolution on the orientation of symmetry axis and elastic parameter in transversely isotropicmedia. Expanded Abstr., 65th Ann. Internat. SEG Mtg., Houston: 567-571.doi: 10.1190/1.1887425.
  14. Okoye, P.N. and Uren, N.F., 2000. Fresnel zones and spatial resolution for P- and SH-waves intransversely isotropic media. Geophysics, 65: 1168-1178. doi: 10.1190/1.1444810.
  15. Sullivan, M.F. and Cohen, J.K., 1987. Prestack Kirchhoff inversion of common-offset data.Geophysics, 52: 745-754. doi: 10.1190/1.1442341
  16. Thomsen, L., 2002. Understanding Seismic Anisotropy in Exploration and Exploitation. SEG-EAGE
  17. Distinguished Instructor Series, 5. SEG, Tulsa, OK.
  18. Vestrum, R.W. and Fowler, P.J., 2005. Quantifying imaging and position problems beneath TT]media. Extended Abstr., 67th EAGE Conf., Madrid: E026.
  19. Vestrum, R. and Lawton, D., 2010. Reflection point sideslip and smear in imaging below dippinganisotropic media. Geophys. Prosp., 58: 541-548.
  20. Waluyo, W., Uren, N.F. and McDonald, J.A., 1995. Poisson’s ratio in transversely isotropic mediaand its effects on amplitude response: An investigation through physical modellingexperiments. Expanded Abstr., 65th Ann. Internat. SEG Mtg., Houston: 585-588.
  21. Wild, P., 2011. Practical applications of seismic anisotropy. First Break, 29: 117-124.
  22. Yilmaz, O., 1987. Migration and ambient noise. In: Doherty, $.M. (Ed.), Seismic Data Processing.SEG, Tulsa, OK: 324-328.
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Journal of Seismic Exploration, Electronic ISSN: 0963-0651 Print ISSN: 0963-0651, Published by AccScience Publishing