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Fast Velocity Analysis through Prestack Wavepath Migration in Geophysics

This study explores the effectiveness of Wavepath Migration Velocity Analysis (WMVA) compared to traditional Kirchhoff Migration Velocity Analysis (KMVA) in improving migration velocity in geophysical data processing. Utilizing both 2-D synthetic and marine field data, we assess the speed and accuracy of WMVA. Results indicate that WMVA can process synthetic data up to twice as fast and field data six times faster than KMVA, with potential improvements seen in 3-D data processing as well. The findings support WMVA as a viable approach for rapid and efficient geological analysis.

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Fast Velocity Analysis through Prestack Wavepath Migration in Geophysics

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

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

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

  4. A 2-D KM of a Single Event A R S

  5. A 2-D WM of a Single Event A R S

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

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

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

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

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

  11. Correct Velocity 0 Depth (m) 40 KM Image CIG 0 Depth (m) 40 Distance (m) 0 50 0 Offset (m) 50

  12. 1st Iteration 7th Iteration KMVA (1st Layer) KM KM CIG CIG V V

  13. 1st Iteration 7th Iteration KMVA (4th Layer) KM KM CIG CIG V V

  14. 1st Iteration 7th Iteration WMVA (1st Layer) WM WM CIG CIG V V

  15. 1st Iteration 6th Iteration WMVA (4th Layer) WM WM CIG CIG V V

  16. Correct Velocity 0 Depth (m) 40 KMVA (CPU=2) WMVA (CPU=1) 0 Depth (m) 40 Distance (m) 0 50 0 50 Distance (m)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  32. KM Image with Initial Velocity 2 km 9 km 1070 Depth (m) 1260 KM Image with KMVAUpdated Velocity 1070 Depth (m) 1260 KM Image with WMVAUpdated Velocity 1070 Depth (m) 1260

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

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

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

  36. Acknowledgements I thank UTAM sponsors for their financial support

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