1. Vladimir Grechka Shell International E&P
S-wave processing
Vladimir Grechka
Shell International E&P
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

2. Reflected PS-wave
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

3. Complications of PS-wave data
• moveout asymmetry
• polarity reversal
• conversion point dispersal
no standard processing flow
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

4. PP + PS = SS method (Grechka and Tsvankin, 2001)
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

5. PP + PS = SS method
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

6. PP + PS = SS method
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

7. PP + PS = SS method • PP and PS event correspondence
 accurate velocity and anisotropy
model not needed
• prestack traveltime picking
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

8. PP + PS = SS method • PP and PS event correspondence
 accurate velocity and anisotropy
model not needed
• prestack traveltime picking
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

9. PP + PS = SS method • PP and PS event correspondence
 accurate velocity and anisotropy
model not needed
• prestack traveltime picking
• convolution of PP and PS traces
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

10. PP + PS = SS method • PP and PS event correspondence
 accurate velocity and anisotropy
model not needed
• prestack traveltime picking
• convolution of PP and PS traces
ΨS data suitable for
S-wave velocity analysis
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

11. ΨS-wave data • integration over all P-wave source and PP data in
reverse time
• integration over all
P-wave source and
receiver locations
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

12. Synthetic example
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

13. Input PP and PS data • PS moveout asymmetry
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

14. Input PP and PS data (zoom)
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

15. Input PP and PS data (zoom)
• polarity
reversal
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

16. Input PP and PS data (zoom)
• polarity
reversal
• different
PP and PS
wavelets
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

17. Generated ΨS data
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

18. Generated ΨS data • correct traveltimes of ΨS arrivals
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

19. Generated ΨS data (zoom 1)
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

20. Generated ΨS data (zoom 1)
• longer ΨS wavelets
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

21. Generated ΨS data (zoom 1)
• longer ΨS wavelets
• no polarity reversal
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

22. Generated ΨS data (zoom 1)
• longer ΨS wavelets
• no polarity reversal
• almost zero ΨS trace
at zero offset
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

23. Generated ΨS data (zoom 2)
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

24. Generated ΨS data (zoom 2)
• ΨS-waves cannot
be reconstructed
at large offsets
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

25. Generated ΨS data (zoom 2)
• ΨS-waves cannot
be reconstructed
at large offsets
 critical angle
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

26. Critical offset for ΨS-wavesP P R
critical ray
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

27. Critical offset for ΨS-wavesP P R
critical ray
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

28. Critical offset for ΨS-wavesP P R
critical ray
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

29. Gulf of Mexico (PP-waves, shallow)
offset = depth
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

30. Gulf of Mexico (ΨS-waves, shallow)
offset = depth
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

31. Gulf of Mexico (PP-waves, deep)
offset = depth
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

32. Gulf of Mexico (ΨS-waves, deep)
offset = depth
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

33. PP- and ΨS-wave gathers
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

34. Evidence for effective anisotropy
• in homogeneous VTI media
• isotropy does not fit data
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

35. Conclusions (I) • complications of PS-wave data irrelevant
 moveout asymmetry
 polarity reversal
 conversion point dispersal
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

36. Conclusions (II) • ΨS data ideal for S-wave velocity analysis
• accuracy of shear-wave stacking velocities governed by the ratio
• straightforward estimating of effective anisotropy
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

37. Further opportunities
Issues
• absence of P-wave data (gas chimneys)
• event correspondence
Further opportunities
• post-critical S events = diving P-waves
• amplitudes
• migration of S data
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

38. Acknowledgements • Helmut Jakubowicz (Veritas) • Joe Dellinger (BP)
• Chris Corcoran, Fons ten Kroode,
Jon Sheiman, Allen Hillery, Jared Martin,
Mark Zama, Paul Milcik, Barbara Yantis,
Richard Cook (Shell)
• Pawan Dewangan (CSM)
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

39. Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

40. Appendix
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

41. ΨS-wave data • integration over all P-wave source and PP data in
reverse time
• integration over all
P-wave source and
receiver locations
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

42. Spectrum of ΨS trace
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

43. Spectrum of ΨS trace (single event)
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

44. Spectrum of ΨS trace (single event)
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

45. Stationary phase conditions
= matching of PP and PS reflection slopes
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

46. Phase at stationary point
• kinematics of pure-S primary
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

47. Spectrum of ΨS trace in 3-D
Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002

48. Grechka, V., S-wave processing: Force Seminar “4C/OBS Data Processing and Interpretation – Old Myths, New Insights,” Stavanger, Norway, April 22, 2002