1. Geological Model 0 4 0 3 Depth(km) X(km) 2001 Year

2. Migration Result Using Crosscorrelation Imaging 1.6 0 2.2 Time (s) 2.1 X (km) Too Simple? Widen illumination? If there are static errors in well?

3. Enhancing Illumination Coverage of VSP by Crosscorrelation Migration Jianhua Yu University of Utah

4. Contents Motivation Crosscorrelation Migration SEG/EAGE Model 2-D RVSP Exxon Data Conclusions

5. Contents Motivation Crosscorrelation Migration SEG/EAGE Model 2-D RVSP Exxon Data Conclusions

6. What Affects VSP Imaging Quality? Limited recording aperture Narrow illumination coverage Static errors at drilling well caused by measurement or locating down-motors

7. Why uses Crosscorrelation Migration? Widen the illumination coverage in the deeper depth of VSP image Primary ghost

8. Why uses Crosscorrelation Migration? Widen the illumination coverage in the deeper depth of VSP image VSP geometry Equivalent surface geometry Xcorr

9. Why uses Crosscorrelation Migration? Widen the illumination coverage in the deeper depth of VSP image VSP geometry Equivalent surface geometry Xcorr Do not need to know the receiver locations in well

10. Why uses Crosscorrelation Migration? Widen the illumination coverage in the deeper depth of VSP image Eliminate static errors at drilling well caused by measurement or locating drill bits Not sensitive to receiver positions in well in VSP

11. Objectives: Enhancing the illumination coverage in the deeper VSP image Application to SEG/EAGE model and the field data Eliminating the static errors in drilling well Investigate the crosscorrelation migration method on

12. Contents Motivation Crosscorrelation Migration SEG/EAGE Model 2-D RVSP Exxon Data Conclusions

13. Well Source Receiver Primary Direct Wave Ghost VSP

14. x g s Ghost Reflection Imaging Condition Ghost Reflection Imaging Condition:

15. x g s After Crosscorrelation of Two Traces at Locations g & g’

16. x g s

17. x g s

18. Why not sensitive to static errors in the well? s g’g x Static errors

19. Crosscorrelogram Migration Migrated Image Crosscorrelograms Crosscorrelation Imaging Condition

20. Benefits from Crosscorrelation Migration: Enhancing the illumination coverage in VSP image Eliminating the static errors in drilling well

21. Contents Motivation Crosscorrelation Migration SEG/EAGE Model 2-D RVSP Exxon Data Conclusions

22. Well 2 0 Depth (km) 0 3X (km) SEG/EAGE Model 256 Sources V = 1.5 - 3.0 km/s

23. Well 2 0 Depth (km) 03X (km) Receiver interval: 10 m Receiver depth range: 0.1 -1 km Receiver number: 91 Sample interval: 1 ms Recording length: 3 s Well location: (1.5 km, 0 km) Source interval: 10 m Source number: 256 Acquisition Parameters: 1 km

24. Time (s) 3 0 0.2 0.9 Depth (km) CSG 160

25. Time (s) 3 0 0.2 0.9 Depth (km) Ghosts (CSG 160)

26. Time (s) 3 0 0.2 0.9 Depth (km) Primary (CSG 160)

27. Time (s) 3 0 02.4 X (km) 1.42.4 X (km) Xcross 60 CRG 60

28. 2.0 0.5 Depth (km) 0.5 2.5 X (km) Kirchhoff Migration (45 degree) Well

29. 2.0 0.5 Depth (km) 0.5 2.5 X (km) Crosscorrelation Migration (45 degree) Well

30. 2.0 0.5 Depth (km) 0.5 2.5 X (km) Crosscorrelation Migration (15 degree) Well

31. 2.0 0.5 Depth (km) 0.5 2.5 X (km) Kirchh Mig (45) Xcorr Mig (45) Xcorr. Mig ( 15’)

32. Static errors (ms) -50 50 0 900 Well Depth (m) Raw Data Static Errors at Well

33. 2.0 0.5 Depth (km) 0.5 Kirchhoff Migration Static Error: 0 X (km) Static Error: 25 ms 2.5 Static Error: 50ms

34. 2.0 0.5 Depth (km) 0.5 Crosscorrelation Migration Static Error: 0 X (km) Static Error: 25ms 2.5 Static Error: 50 ms

35. Contents Motivation Crosscorrelation Imaging Condition SEG/EAGE Model 2-D RVSP Exxon Data Conclusions

36. Time (s) 0.3 0 30 900 Depth (ft) Exxon Raw Data(CRG15)

37. Time (s) 0.3 0 30 900 Depth (ft) Ghosts (Exxon)

38. Time (s) 0.3 0 30 900 Depth (ft) Primary(Exxon)

39. 524 Trace No. Time (s) 1.2 0.2 xcorr data (muted) Time (s) 1.4 0.5 524 Trace No. Exxon CSG 25 Raw data (muted) Master trace

40. Depth (ft) 1300 200 0 400 X (ft) Xcorr. mig

41. Depth (ft) 1300 200 0 400 X (ft) Standard mig

42. Depth (ft) 1300 200 0400 X (ft) 0400 X (ft) Standard migCross. mig

43. Depth (ft) 1100 0 Well dataXcorr. Migration Exxon Data

44. Depth (ft) 1100 0 Well dataStandard Migration Exxon Data

45. Depth (ft) 1100 0 Standard Well data Xcorr. Exxon Data

46. Contents Motivation Crosscorrelation Migration SEG/EAGE Model 2-D RVSP Exxon Data Conclusions

47. Conclusions Increase illumination coverage in the deeper part of VSP image Eliminate the static errors in drilling well No need to know source (RVSP) or receiver location (VSP)

48. Conclusions Loss of some lateral resolution? Be careful about virtual multiple Xcorr Narrow Angle Kirchhoff Wide Angle vs Ghost is weak than primary

49. Acknowledgments 2003 UTAM sponsors Exxon for 2-D field data