1. 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 MS thesis

2. Outline I.Motivation II.Theory III.Numerical Tests IV.Field Data Examples V.Conclusion

3. Outline I.Motivation II.Theory III.Numerical Tests IV.Field Data Examples V.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 I.Motivation II.Theory III.Numerical Tests IV.Field Data Examples V.Conclusion

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

7. Goal: Image Interface by PS Transmitted Waves M g Uninteresting Part of Medium of Medium sTime P d(M|s) d(g|s) PPPPPPPP PSPSPSPS X Reduced-time migration: e i w (t + t + t) – w,s,M m(x) = d(M|s) sx xMxMxMxMerror ~( t + t )- ( t + t ) sx xgxgxgxgpickpicksx xgxgxgxg error t sx xMxMxMxM =( t + t )- ( t + t ) pickpicksx xMxMxMxM

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

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

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

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

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

13. Outline I.Motivation II.Theory III.Numerical Tests IV.Field Data Examples V.Conclusion

14. III. Numerical Tests I.Rugose Lower Salt Boundary II.Elastic Salt Model

15. Salt Velocity Model Salt S-wave Velocity ModelSalt P-wave Velocity Model Depth (m) X (m) m/s III. Numerical test P-to-S ratios = 3 0.5 0 1200 0 4400 2000 01200 2540 1170

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

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

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

19. KM vs. IM with Correct Velocity Model IM KM Depth (m) X (m) III. Numerical test 0 1200 0 963 1313 01200 7E 4 -8E 4

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

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

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

23. IM Depth (m) X (m) 0 1200 0 7E 4 -8E 4 Correctly imaged Strong focused! Small cover of PS ray Additionally imaged III. Numerical test

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

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

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

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

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

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

30. II. Elastic Salt Model

31. P-wave velocity model 0 Depth (m) 11000 016000X (m) Velocity (m/s) 4500 1500 Gas target lower boundary

32. a) P-wave velocity modelb) S-wave velocity model 0 Depth (m) 11000 016000 X (m) 016000 X (m) 0 Depth (m) 11000 0 12 c) CRG 1 X-componentd) CRG 1 Z-component Shot number Time (s) 0 319 Shot number 0 319 0 12 Time (s)

33. a) Ray tracing: direct Pb) Ray tracing: PPS events 0 Depth (km) 11 0 16 X (km) 016X (km) 0 Depth (km) 11 c) Ray tracing: PSS events 0 Depth (km) 11 0 16 X (km)

34. a) PP Standard Migrationb) PS Standard Migration 0 Depth (m) 11000 5000 8000 016000 X (m) c) Zoom View of PS KMd) Zoom View of PS IM X (m) 016000 X (m) 0 Depth (m) 11000 Depth (m) 6900 8700 5000 8000 X (m) Depth (m) 6900 8700

35. PS IM PS interferometric migration X (m) Depth (m) 0800016000 0 3000 6000 9000 Correctly imaged!

36. Outline I.Motivation II.Theory III.Numerical Tests IV.Field Data Examples V.Conclusion

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

38. P-to-S ratios = 2.7 Velocity Profile S Wave P Wave Depth (m) Velocity (m/s) 0 4500 050000 2800 m 3200 m Salt IV. Field Data Incorrect velocity model P-to-S ratios = 1.6

39. 150 Z Component Depth (m) Traveltime (s) 2652 3887 1.23.0 Salt Direct P Reflect P Alias (Reverberation) IV. Field Data

40. 150 X Component Depth (m) Traveltime (s) 2652 3887 1.23.0 Salt Direct P Reflect P Alias (Reverberation)Direct S IV. Field Data

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

42. Depth (m) Traveltime (s) 2652 3887 1.23.0 IV. Field Data 150 X Before Rotation

43. Depth (m) Traveltime (s) 2652 3887 1.23.0 IV. Field Data 150 X After Rotation P wave energy was maximized

44. Depth (m) Traveltime (s) 2652 3887 1.23.0 III. Field Data 150 X PSS Events Transmitted at upper boundary

45. 150 X PPS Events Depth (m) Traveltime (s) 2652 3887 1.23.0 III. Field Data Transmitted at lower boundary

46. Migration of PSS IV. Field Data Ray Path Coverage 2000 4200 0200 Depth (m) SALT Offset (m)

47. Migration of PSS IV. Field Data SALT 150 offset RM150 offset IM 02000 Offset (m) 150 offset KM 2000 4200 0200 Depth (m)

48. Ray Path Coverage 2000 4200 0200 Depth (m) Migration of PPS IV. Field Data SALT Offset (m)

49. IV. Field Data Migration of PPS SALT 150 offset RM150 offset IM 02000 150 offset KM 2000 4200 0200 Depth (m) Offset (m)

50. Outline I.Motivation II.Theory III.Numerical Tests IV.Field Data Examples V.Conclusion

51. IV. Conclusion Advantage of PS transmission migration –it is capable of illuminating the boundary of salt flanks above the receivers (and nearly vertical boundaries if they exist).

52. IV. Conclusion Benefits of IM: –Remove influence of static shifts and/or migration velocity errors; –Eliminated source statics by correlation; –Accurately image the salt boundary above the receivers; Drawbacks of IM: –Migration artifacts due to violation of stationary phase approximation; –Extra summations and computation time; –Small range of incidence angle than true SWI data; –Worse spatial resolution than KM; –Does not require knowledge of the overburden velocity;

53. V. Future Work Pp/Ps reflection interferometric migration Anisotropy migration –Try different VTI FD synthetic walkaway VSP data set; –Apply it to a real data set; Preprocessing: –Reorientation, separation, filtering, statics correction Postprocessing: –Deconvolution Potential application –Kirchhoff multi arrival migration –Subsalt imaging –Interferometric tomography

54. Thanks to Jerry Schuster and my committee members: Dr. Michael Zhdanov, Dr. Bob smith, Dr. Cari Johnson for their advice and constructive criticism; Scott Leaney and Hornby Brian for their help on modeling;

55. Thanks to UTAM friends: –Jianhua Yu for his help on Linux programming; –Jianming Sheng and Min Zhou for their experiences on interferometric imaging; –Zhiyong Jiang and Ruiqing He for their help on classes; –Travis Crosby and all UTAM students for their cheerful attitude; All UTAM sponsors for their support; Family –My parents, brother and sister; Friends –Liyun Ma, Huajian Yao, Zhaoyu Luo and Meiping Tong, who encouraged me to continue on with my research.

56. Questions?