1. FAST VELOCITY ANALYSIS BY PRESTACK WAVEPATH MIGRATION H. Sun Geology and Geophysics Department University of Utah

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

3. KM (CPU=1) 3-D West Texas Data Sub WM (CPU=1/50) WM (CPU=1/14) Inline Slice (Offset: 0.4~4.5 km) 0.8 3.8 Depth (km)

4. 2-D KM of a Single Event RS A A

5. 2-D WM of a Single Event RS A A

6. Outline Objectives Objectives Migration Velocity Analysis Migration Velocity Analysis 2-D Synthetic Data 2-D Synthetic Data 2-D Marine Field Data 2-D Marine Field Data Conclusions Conclusions

7. Objectives Can WMVA effectively improve the Can WMVA effectively improve the migration velocity? migration velocity? Whether the WMVA updated velocity Whether the WMVA updated velocity differs much from the KMVA updated differs much from the KMVA updated velocity? velocity? Can WMVA be much faster than Can WMVA be much faster than KMVA? KMVA?

8. Outline Objectives Objectives Migration Velocity Analysis Migration Velocity Analysis 2-D Synthetic Data 2-D Synthetic Data 2-D Marine Field Data 2-D Marine Field Data Conclusions Conclusions

9. COG Migration Pick Layer Boundaries Pick Depth Residuals in CIGs Stacked Image & CIGs Depth Residual --> Time Residual Ray Tracing Updating: s=s+ds Initial Velocity MVAFlowChart Nemeth 1995

10. Outline Objectives Objectives Migration Velocity Analysis Migration Velocity Analysis 2-D Synthetic Data 2-D Synthetic Data 2-D Marine Field Data 2-D Marine Field Data Conclusions Conclusions

11. Correct Velocity 0 40 Depth (m) 050 Offset (m) 050 Distance (m) CIG KM Image 0 40 Depth (m)

12. 1st Iteration 7th Iteration KMVA (1st Layer) KMKM CIGCIG VV

13. 1st Iteration 7th Iteration KMVA (4th Layer) KMKM CIGCIG VV

14. 1st Iteration 7th Iteration WMVA (1st Layer) WMWM CIGCIG VV

15. 1st Iteration 6th Iteration WMVA (4th Layer) WMWM CIGCIG VV

16. Correct Velocity 0 40 Depth (m) 050050 Distance (m) WMVA (CPU=1) KMVA (CPU=2) 0 40 Depth (m) Distance (m)

17. Outline Objectives Objectives Migration Velocity Analysis Migration Velocity Analysis 2-D Synthetic Data 2-D Synthetic Data 2-D Marine Field Data 2-D Marine Field Data Conclusions Conclusions

18. Initial Migration Velocity 0 0 18 1.5 Horizontal Distance (km) Depth (km) 2.1 1.5 (km /s) (km /s)

19. KM Image with Initial Velocity 0 0 18 1.5 Horizontal Distance (km) Depth (km) B T

20. KMVA CIGs with Initial Velocity 0 1.5 Depth (km) 1.2

21. KM Image with Initial Velocity 0 0 18 km 1.5 Depth (km) 0 1.5 KMVA Velocity Changes in the 1st Iteration 50 0 (m /s) (m /s)

22. KM Image with Initial Velocity 0 0 18 km 1.5 Depth (km) 0 1.5 KM Image with Updated Velocity

23. KM Image with Initial Velocity KM Image with Updated Velocity 9 km 1260 Depth (m) 2 km 1070 1260 Depth (m) 1070

24. KMVA CIGs with Initial Velocity 0 1.5 Depth (km) KMVA CIGs with Updated Velocity

25. KM Image with Initial Velocity 0 0 18 km 1.5 Depth (km) 0 1.5 WM Image with Initial Velocity BT BT

26. WMVA CIGs with Initial Velocity 0 1.5 Depth (km) 1.2

27. 0 0 18 km 1.5 Depth (km) 0 1.5 KMVA Velocity Changes in the 1st Iteration (CPU=6) 50 0 (m /s) (m /s) WMVA Velocity Changes in the 1st Iteration (CPU=1) 50 0 (m /s) (m /s)

28. 0 0 18 km 1.5 Depth (km) 0 1.5 WM Image with Initial Velocity WM Image with Updated Velocity

29. WM Image with Initial Velocity WM Image with Updated Velocity 9 km 1260 Depth (m) 2 km 1070 1260 Depth (m) 1070

30. WMVA CIGs with Initial Velocity 0 1.5 Depth (km) WMVA CIGs with Updated Velocity

31. 0 0 18 km 1.5 Depth (km) 0 1.5 KM Image with KMVA Updated Velocity KM Image with WMVA Updated Velocity

32. KM Image with Initial Velocity 9 km 1260 Depth (m) 2 km 1070 KM Image with KMVA Updated Velocity 1260 Depth (m) 1070 KM Image with WMVA Updated Velocity 1260 Depth (m) 1070

33. Outline Objectives Objectives Migration Velocity Analysis Migration Velocity Analysis 2-D Synthetic Data 2-D Synthetic Data 2-D Marine Field Data 2-D Marine Field Data Conclusions Conclusions

34. Can WMVA effectively improve the Can WMVA effectively improve the migration velocity? Yes migration velocity? Yes Whether the WMVA updated velocity Whether the WMVA updated velocity differs much from the KMVA updated differs much from the KMVA updated velocity? No velocity? No Conclusions

35. Can WMVA be much faster than Can WMVA be much faster than KMVA? Yes KMVA? Yes Synthetic data: twice as fast as KMVA Synthetic data: twice as fast as KMVA Field data : 6 times faster than KMVA Field data : 6 times faster than KMVA How about 3-D data? How about 3-D data? Could be more than 10 times faster Could be more than 10 times faster Conclusions

36. Acknowledgements Acknowledgements I thank UTAM sponsors I thank UTAM sponsors for their financial support