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Salt Flank Imaging by PS Interferometry

Salt Flank Imaging by PS Interferometry. Xiang Xiao Univ. of Utah Feb. 3. Outline. Motivation Theory Numerical Tests Field Data Examples Conclusion. Outline. Motivation Theory Numerical Tests Field Data Examples Conclusion. I . Motivation. Goal:.

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Salt Flank Imaging by PS Interferometry

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  1. Salt Flank Imaging by PS Interferometry Xiang Xiao Univ. of Utah Feb. 3

  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 PS Transmission 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. d(M|s) d(g|s) PP PS (g,M) = d(M|s) d(g|s)* P i wt + i wt -i wt - i wt = e e g i w(t –t) = e M Goal: Image Interface by PS Transmitted Waves Time g M Uninteresting Part of Medium PS PP s m(x)= M, gx Mx

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

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

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

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

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

  12. 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)

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

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

  15. III. Numerical test Synthetic vs. Redatuming Data Synthetic PS VSP Virtual after IR Depth (m) Time (s) Time (s)

  16. 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)

  17. III. Numerical test KM, RM vs. IM Constant Static Shift in Data Each Trace Advances 60 ms

  18. III. Numerical test KM 0 400 Depth (m) Haven’t been imaged Boundary is shifted 1200 -700 X (m) 1200 0

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

  20. 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

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

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

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

  24. 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

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

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

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

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

  29. 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 3000 Velocity (m/s)

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

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

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

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

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

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

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

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

  38. 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)

  39. IV. Field Data Migration of PSS SALT

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

  41. 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)

  42. IV. Field Data Migration of PPS SALT

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

  44. IV. Conclusion • Benefits of IM: • Remove influence of static shifts and migration velocity errors; • Eliminated source statics by correlation; • Remove elliptical artifacts, boost migration image contrast; • Drawbacks of IM: • Migration artifacts from stationary phase approximation; • Extra summations and computation time; • Small range of incidence angle than true SWI data; • Worse vertical resolution than KM;

  45. Thank you! • Thank the sponsor of the 2004 UTAM consortium for their support.

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