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Salt Flank Delineation by Interferometric Imaging of Transmitted P-to-S Waves

MS thesis. Salt Flank Delineation by Interferometric Imaging of Transmitted P-to-S Waves. Xiang Xiao Advisor: Gerard T. Schuster Committee: Michael Zhdanov Bob Smith Cari Jonson Univ. of Utah Nov. 15. Outline. Motivation Theory

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Salt Flank Delineation by Interferometric Imaging of Transmitted P-to-S Waves

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  1. MS thesis Salt Flank Delineation by Interferometric Imaging of Transmitted P-to-S Waves Xiang Xiao Advisor: Gerard T. Schuster Committee: Michael Zhdanov Bob Smith Cari Jonson Univ. of Utah Nov. 15

  2. Outline • Motivation • Theory • Numerical Tests • Field Data Examples • Conclusion

  3. Outline • Motivation • Theory • Numerical Tests • Field Data Examples • Conclusion

  4. I. Motivation • Goal: • Salt Flank Imaging with Migration of Transmitted P-to-S Waves; • Method: • Standard Migration (KM); • Reduced-time Migration (RM), Sheley and Schuster, 2003; • Interferometric Migration (IM), and Interferometric Redatuming (IR), Schuster, 2004;

  5. Outline • Motivation • Theory • Numerical Tests • Field Data Examples • Conclusion

  6. Time Uninteresting Part of Medium s P PS M d(M|s) PP g d(g|s) – m(x) = d(M|s) sx xM i w(t+ t) e w,s,M Goal: Image Interface by PS Transmitted Waves Standard Kirchhoff Migration: X

  7. Time Uninteresting Part of Medium s P PS M d(M|s) PP g – m(x) = d(M|s) sx xM error d(g|s) pick pick =( t + t )- ( t + t ) pick pick i w(t+ t + t) ~( t + t )- ( t + t ) t e sx xM sx xM error sx xg sx xg w,s,M Goal: Image Interface by PS Transmitted Waves Reduced-time migration: X

  8. Time Uninteresting Part of Medium s P PS M d(M|s) (g,M) = d(M|s) d(g|s)* PP g i wt + i wt -i wt - i wt d(g|s) ~ e e i w(t –t) = e Goal: Image Interface by PS Transmitted Waves Interferometric migration: PS PP

  9. (g,M) = d(M|s) d(g|s)* s Goal: Image Interface by PS Transmitted Waves Time Uninteresting Part of Medium s P PS M d(M|s) PP g d(g|s)

  10. Goal: Image Interface by PS Transmitted Waves Time Uninteresting Part of Medium s P PS M d(M|s) (g,M) = d(M|s) d(g|s)* PP g d(g|s) s

  11. (g,M) = d(M|s) d(g|s)* m(x) = (g,M) xM xg i w(t –t) – e w,g,M s Goal: Image Interface by PS Transmitted Waves Time Uninteresting Part of Medium s Datuming P PS M d(M|s) X Migration PP g d(g|s) Unique Specular Point Snell’s Law OK

  12. Eliminates src/rec statics and uninteresting parts of the medium. Move surface src to interesting inter.   m(x) = (g,M) x x i w(t –t) – e g,M Interferometric PS Datuming

  13. Outline • Motivation • Theory • Numerical Tests • Field Data Examples • Conclusion

  14. III. Numerical Tests • Rugose Lower Salt Boundary • Elastic Salt Model

  15. III. Numerical test Salt Velocity Model Salt P-wave Velocity Model Salt S-wave Velocity Model 2540 4400 0 Depth (m) P-to-S ratios = 30.5 1170 2000 1200 0 1200 0 1200 m/s m/s X (m) X (m)

  16. III. Numerical test VSP Gathers P Wave Shot @ (0,0) PS Waves Shot @ (0,0) Depth (m) Time (s) Time (s)

  17. Eliminates src/rec statics and uninteresting parts of the medium. Move surface src to interesting inter.   m(x) = (g,M) x x i w(t –t) – e g,M Interferometric PS Datuming

  18. III. Numerical test Synthetic vs. Redatuming Data Synthetic S-P SWI Data S-P Data from IR Depth (m) Time (s) Time (s)

  19. III. Numerical test KM vs. IM with Correct Velocity Model KM IM 7E4 963 0 Depth (m) -8E4 1313 1200 0 1200 0 X (m) 1200 X (m)

  20. III. Numerical test KM, RM vs. IM Constant Static Shift in Data Each Trace Advances 8 ms

  21. III. Numerical test KM 0 400 Depth (m) Incorrectly imaged Boundary is shifted 1200 -700 X (m) 1200 0

  22. III. Numerical test RM 0 850 Depth (m) Correctly imaged Poor focused 1200 -950 X (m) 1200 0

  23. III. Numerical test IM Additionally imaged 0 7E4 Depth (m) Correctly imaged Small cover of PS ray Strong focused! 1200 -8E4 X (m) 1200 0

  24. III. Numerical test Comparison 0 Depth (m) KM RM IM 1200 X (m) 1200 0

  25. III. Numerical test Incorrect Migration Model KM, RM vs. IM 90% Velocity Above Salt

  26. III. Numerical test KM 0 850 Incorrectly imaged Depth (m) Correct place 1200 -1000 X (m) 1200 0

  27. III. Numerical test RM 0 850 Depth (m) Correctly imaged Incorrectly imaged, Should image as black boundary Elliptical artifacts 1200 -1000 X (m) 1200 0

  28. III. Numerical test IM 0 4E4 Depth (m) Correctly imaged Correctly imaged! Elliptical artifacts are removed 1200 -6E4 X (m) 1200 0

  29. III. Numerical test Comparison 0 Depth (m) KM RM IM 1200 X (m) 1200 0

  30. II. Elastic Salt Model

  31. P-wave velocity model Velocity (m/s) 0 4500 Depth (m) Gas target lower boundary 11000 1500 0 X (m) 16000

  32. a) P-wave velocity model b) S-wave velocity model 0 0 Depth (m) Depth (m) 11000 11000 0 16000 0 16000 X (m) X (m) c) CRG 1 X-component d) CRG 1 Z-component 0 0 Time (s) Time (s) 12 12 319 319 0 0 Shot number Shot number

  33. a) Ray tracing: direct P b) Ray tracing: PPS events 0 0 Depth (km) Depth (km) 11 11 0 X (km) 16 0 X (km) 16 c) Ray tracing: PSS events 0 Depth (km) 11 0 X (km) 16

  34. a) PP Standard Migration b) PS Standard Migration 0 0 Depth (m) Depth (m) 11000 11000 0 16000 0 16000 X (m) X (m) c) Zoom View of PS KM d) Zoom View of PS IM 5000 5000 Depth (m) Depth (m) 8000 8000 8700 8700 6900 6900 X (m) X (m)

  35. PS interferometric migration 0 PS IM 3000 Depth (m) 6000 Correctly imaged! 9000 0 8000 16000 X (m)

  36. Outline • Motivation • Theory • Numerical Tests • Field Data Examples • Conclusion

  37. IV. Field Data Well and Source Location Source @150 m offset 0 Depth (m) 4878 Offset (m) 1829 0 X (m)

  38. IV. Field Data Velocity Profile S Wave P Wave 0 Incorrect velocity model Depth (m) P-to-S ratios = 2.7 2800 m Salt P-to-S ratios = 1.6 3200 m 4500 0 5000 0 5000 Velocity (m/s)

  39. IV. Field Data 150 Z Component 2652 Reflect P Salt Depth (m) Alias (Reverberation) Direct P 3887 1.2 3.0 Traveltime (s)

  40. IV. Field Data 150 X Component 2652 Reflect P Salt Depth (m) Direct S Alias (Reverberation) Direct P 3887 1.2 3.0 Traveltime (s)

  41. Processing Flow Chart Original Data Reoriented Pick desired events Flatten, median filter, unflatten Migration (KM, RM, IM)

  42. IV. Field Data 150 X Before Rotation 2652 Depth (m) 3887 1.2 3.0 Traveltime (s)

  43. IV. Field Data 150 X After Rotation P wave energy was maximized 2652 Depth (m) 3887 1.2 3.0 Traveltime (s)

  44. III. Field Data 150 X PSS Events Transmitted at upper boundary 2652 Depth (m) 3887 1.2 3.0 Traveltime (s)

  45. III. Field Data 150 X PPS Events Transmitted at lower boundary 2652 Depth (m) 3887 1.2 3.0 Traveltime (s)

  46. IV. Field Data 2000 Depth (m) 4200 0 200 Migration of PSS Ray Path Coverage SALT Offset (m)

  47. IV. Field Data 150 offset KM 2000 Depth (m) 4200 0 0 0 200 200 200 Migration of PSS 150 offset RM 150 offset IM SALT Offset (m)

  48. IV. Field Data 2000 Depth (m) 4200 0 200 Migration of PPS Ray Path Coverage SALT Offset (m)

  49. IV. Field Data 150 offset KM 2000 Depth (m) 4200 0 0 0 200 200 200 Migration of PPS 150 offset RM 150 offset IM SALT Offset (m)

  50. Outline • Motivation • Theory • Numerical Tests • Field Data Examples • Conclusion

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