1. CROSSWELL IMAGING BY 2-D PRESTACK WAVEPATH MIGRATION
H. Sun
Geology and Geophysics Department
University of Utah

2. SEG 2-D Overthrust Data KM Image Model WM Image 4 Offset (km) 10 4
0.5
Depth (km)
2.5

3. 2-D Husky Field Data KM Image (Zoom A) WM Image (Zoom A) 2.5
Offset (km)
5.5
2.5
Offset (km)
5.5
2.5
2.5
Depth (km)
Depth (km)
5.0
5.0

4. Horizontal Slice (Depth=1.4 km)
SEG 3-D Salt Data KM WM
CPU: 1
CPU:
1/33
Sub WM
Model
CPU:
1/170
Horizontal Slice (Depth=1.4 km)

5. 2-D KM of a Single Trace C B A R S C B A

6. 2-D WM of a Single Trace C B A R S B C A

7. Wavepath Migration Traveltime + Ray Direction Fewer Artifacts Less
True
Reflection point
Small
Migration Aperture
Fewer
Artifacts
Less
Expensive

8. Outline WM Crosswell Imaging Synthetic Crosswell Data
McElroy Crosswell Data
Synthetic Single Well Data
Conclusions

9. KM Crosswell Imaging Source Well Receiver Well Down-going Interface 1
Up-going

10. KM Crosswell Imaging Source Well Receiver Well Interface 1 Interface 2
Up-going

11. KM Crosswell Imaging Source Well Receiver Well Down-going Interface 1

12. KM Crosswell Imaging Source Well Receiver Well Down-going Interface 1
Up-going

13. Problems in KM Crosswell Imaging
Insufficient Stacking Leads to Artifacts
Complex Data Cause Difficulty in
Up-going and Down-going Separation
Slow Computation

14. WM Crosswell Imaging Source Well Receiver Well Down-going Interface 1
Up-going

15. Advantages of WM Crosswell Imaging
Avoid Artifacts by Migrating to the
Primary Reflection Point
Handle Complex Data by Migrating
Up-going and Down-going together
No Constraints Needed
Fast Computation

16. Shortcomings of WM
Weaker Events
Worse Interface Continuity

17. Outline WM Crosswell Imaging Synthetic Crosswell Data
McElroy Crosswell Data
Synthetic Single Well Data
Conclusions

18. Fault Model A Common Shot Gather
Offset (m) 90
Geophone Depth (m)
210
Depth (m)
Time (s)
210
0.2

19. Crosswell Imaging of Synthetic Fault DataKM
Model WM
WM (no separation)
Better Image
Better Resolution
Offset: 0~90 m, Depth: 0~210 m

20. Outline WM Crosswell Imaging Synthetic Crosswell Data
McElroy Crosswell Data
Synthetic Single Well Data
Conclusions

21. A Common Shot Gather Traveltime Tomogram Offset (m) 56 811
Offset (m) 56
811
Hydrophone Depth (m)
963
811
6.7
Depth (m)
(km /s)
Time (s)
4.7
0.05
963

22. KM Image ? Separation Up-going Down-going 56 Offset (m) Source Well56
Offset (m)
Source Well
Receiver Well
811 ?
Up-going
Depth (m)
Separation
Down-going
963
Synthetic
Synthetic

23. WM Image Separation Up-going Down-going Source Well Receiver Well 81156
Offset (m)
Source Well
Receiver Well
811
Up-going
Depth (m)
Separation
Down-going
963
Synthetic
Synthetic

24. WM Image NO Separation Up-going Down-going Source Well Receiver Well
811
Up-going
Depth (m)
NO Separation
Down-going
963
Synthetic
Offset (m) 56
Synthetic

25. KM(CPU=2.5) WM(CPU=1) WM (up+down)
Source Well
Synthetic
Receiver Well
Synthetic
Offset: 0~56 m, Depth: 811~963 m

26. Outline WM Crosswell Imaging Synthetic Crosswell Data
McElroy Crosswell Data
Synthetic Single Well Data
Conclusions

27. OYO Salt Model Well Salt Offset (km) 9 ? ? Depth (km) ? ? ? ? ? ? 69
Well ? ? ?
Depth (km) ?
Salt
? ? ? ? 6
4.5
2.8
Velocity (km/s)

28. OYO Salt Model KM image Velocity Model WM image ? Well ????? 2
Depth (km)
Well
????? 5
2.5
Offset (km)
6.5
2.5
Offset (km)
6.5
2.5
Offset (km)
6.5

29. Conclusions Crosswell Synthetic Data Fewer migration artifacts
Slightly better image resolution
Better for dipping fault boundary
No up- and down-going separation

30. Conclusions Crosswell McElroy Data Similar image quality
No up- and down-going separation
2.5 times faster than KM
Worse image continuity
Structure details? Artificial events?

31. Conclusions Single Well Synthetic Data Similar image quality
Fewer migration artifacts

32. Acknowledgements
I thank UTAM sponsors
for their financial support