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Wavepath Migration versus Kirchhoff Migration: 3-D Prestack Examples

H. Sun and G. T. Schuster. University of Utah. Wavepath Migration versus Kirchhoff Migration: 3-D Prestack Examples. Outline. Problems in Kirchhoff Migration Wavepath Migration Implementation of WM Numerical Results Conclusions. Specular Ray. Forward Modeling.

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Wavepath Migration versus Kirchhoff Migration: 3-D Prestack Examples

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  1. H. Sun and G. T. Schuster University of Utah Wavepath Migration versus Kirchhoff Migration: 3-D Prestack Examples

  2. Outline • Problems in Kirchhoff Migration • Wavepath Migration • Implementation of WM • Numerical Results • Conclusions

  3. Specular Ray Forward Modeling ( Xg, 0 ) ( Xs, 0 )

  4. 3D Fat Ellipsoid 3D Kirchhoff Migration ( Xg, 0 ) ( Xs, 0 )

  5. A B C 3-D KM of a Single Trace C B A R S

  6. Problems in Kirchhoff Migration Traveltime Information Where Was Wave Reflected ? The Whole Fat Ellipsoid ! Problem 1 Problem 2 Strong Far-Field Migration Artifact Slow for 3-D Iterative Velocity Analysis

  7. Outline • Problems in Kirchhoff Migration • Wavepath Migration • Implementation of WM • Numerical Results • Conclusions

  8. Fat Ray Fat Ellipsoid 3 KM : Fat Ellipsoid, O(N ) WM: Hatching Area, O(N ) 1.5 3D Wavepath Migration ( Xg, 0 )

  9. A B C 3-D WM of a Single Trace C B A R S

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

  11. Key Goals of 3-D WM • To Achieve Higher CPU Efficiency • Compared to 3-D KM • To Generate Comparable or Better • Image Quality than 3-D KM

  12. Related References • Time-Map Migration • Sherrif & Geldhart (1985) • Wave Equation Tomography • Woodward & Rocca (1988) • Gaussian Beam Migration • Ross Hill (1990) • Kirchhoff Beam Migration • Yonghe Sun et al., (1999)

  13. Outline • Problems in Kirchhoff Migration • Wavepath Migration • Implementation of WM • Numerical Results • Conclusions

  14. Quasi-ellipsoid Fresnel Zone Migration Raypath Raypath Key Steps in WM R S Quasi-ellipsoid

  15. Outline • Problems in Kirchhoff Migration • Wavepath Migration • Implementation of WM • Numerical Results • 3-D Prestack Point Scatterer Data • 3-D Prestack SEG/EAGE Salt Data • 3-D Prestack West Texas Field Data • Conclusions

  16. 3-D Prestack KM Point Scatterer Response 0.1 0.4 Reflectivity Reflectivity Z0-9 Z0-1 -0.05 -0.2 1 1 1 1 Y Offset (km) Y Offset (km) X Offset (km) X Offset (km) 0 0 1 0.02 Reflectivity Reflectivity Z0 Z0+8 -0.5 -0.01 1 1 1 1 Y Offset (km) Y Offset (km) X Offset (km) X Offset (km) 0 0

  17. 3-D Prestack WM Point Scatterer Response 0.1 0.4 Reflectivity Reflectivity Z0-9 Z0-1 -0.05 -0.2 1 1 1 1 Y Offset (km) Y Offset (km) X Offset (km) X Offset (km) 0 0 1 0.02 Reflectivity Reflectivity Z0 Z0+8 -0.5 -0.01 1 1 1 1 Y Offset (km) Y Offset (km) X Offset (km) X Offset (km) 0 0

  18. Outline • Problems in Kirchhoff Migration • Wavepath Migration • Implementation of WM • Numerical Results • 3-D Prestack Point Scatterer Data • 3-D Prestack SEG/EAGE Salt Data • 3-D Prestack West Texas Field Data • Conclusions

  19. A Common Shot Gather Trace Number 1 390 0 Time (sec) 5.0

  20. SALT Inline Velocity Model Offset (km) 0 9.2 0 Depth (km) 3.8

  21. Inline KM(CPU=1) Inline WM(CPU=1/33) Offset (km) Offset (km) 0 9.2 0 9.2 0 Depth (km) 3.8

  22. Inline KM(CPU=1) Inline WM(CPU=1/170) (subsample) Offset (km) Offset (km) 0 9.2 0 9.2 0 Depth (km) 3.8

  23. Zoom Views of Inline Sections KM WM Sub WM Model Offset: 3~6.5 km, Depth: 0.3~1.8 km

  24. Zoom Views of Crossline Sections KM WM Sub WM Model Offset: 1.8~4 km, Depth: 0.6~2.1 km

  25. Horizontal Slices (Depth=1.4 km) KM WM Sub WM Model Inline: 1.8~7.2 km, Crossline: 0~4 km

  26. Outline • Problems in Kirchhoff Migration • Wavepath Migration • Implementation of WM • Numerical Results • 3-D Prestack Point Scatterer Data • 3-D Prestack SEG/EAGE Salt Data • 3-D Prestack West Texas Field Data • Conclusions

  27. A Common Shot Gather 54 Trace Number 193 0 Time (sec) 3.4

  28. Inline KM (CPU=1) Inline WM(CPU=1/14) Offset (km) Offset (km) 0.4 4.5 0.4 4.5 0.8 Depth (km) 3.8

  29. Inline KM(CPU=1) Inline WM(CPU=1/50) (subsample) Offset (km) Offset (km) 0.4 4.5 0.4 4.5 0.8 Depth (km) 3.8

  30. Crossline KM (CPU=1) Crossline WM(CPU=1/14) Offset (km) Offset (km) 0.3 3.5 0.3 3.5 0.8 Depth (km) 3.3

  31. Crossline KM(CPU=1) Crossline WM(CPU=1/50) (subsample) Offset (km) Offset (km) 0.3 3.5 0.3 3.5 0.8 Depth (km) 3.3

  32. Horizontal Slices (Depth=2.5 km) WM (Sub, CPU=1/50) KM (CPU=1) WM (CPU=1/14) Inline: 0~4.6 km, Crossline: 0~3.8

  33. Outline • Problems in Kirchhoff Migration • Wavepath Migration • Implementation of WM • Numerical Results • Conclusions

  34. Conclusions • SEG/EAGE Salt Data • Fewer Migration Artifacts • Better for Complex Salt Boundary • Higher Computational Efficiency • CPU • KM: 1 WM: 1/33 • Subsampled WM: 1/170

  35. Conclusions • West Texas Field Data • Fewer Migration Artifacts • Similar Image Quality • Higher Computational Efficiency • CPU • KM: 1 WM: 1/14 • Subsampled WM: 1/50

  36. Acknowledgements We thank UTAM sponsors for their financial support

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