1. Seeing the Invisible with Seismic Interferometry: Datuming and Migration Gerard T. Schuster, Jianhua Yu, Xiao Xiang and Jianming Sheng University of Utah

2. Outline Seismic Interferometry Interferometric Migration Interferometric Datuming Interferometric Tomography Conclusions

3. Constructive Interference Wave 1 Wave 2 = Destructive Interference Wave 1 Wave 2 eiwt eiwt + 12 = 2 - 2cos(w(t - t )) 2 1 Interferometry uses interference patterns or time differences = e iwt e -iwt 1 2 = e iw(t - t ) 12

4. Is the Lens Broken? Interference Pattern Optical Lens t LASER LASER Buried sources redatumed to target Interferogram only sensitive to lens geometry

5. Is the Lens Broken? Interference Pattern Optical Lens t LASER LASER Buried sources redatumed to target Interferogram only sensitive to lens geometry

6. Outline Seismic Interferometry Interferometric Migration Interferometric Datuming Interferometric Tomography Conclusions

7. Goal: Transform Ghost Reflections into Primary Reflection Traveltimes Uninteresting Part of Medium of Medium Time Direct LASER Greens Thm: Every Point on Surface acts as a Secondary Source Direct Ghost Ghost To Remove Kinematics of Traveling in Uninteresting Medium Time Shift Traces by Direct Times {MTBASIN

8. Goal: Transform Ghost Reflections into Primary Reflection Traveltimes Uninteresting Part of Medium of Medium Time Direct Greens Thm: Every Point on Surface acts as a Secondary Source Direct Ghost Ghost To Remove Kinematics of Traveling in Uninteresting Medium Time Shift Traces by Direct Times Ghost Ghost

9. Goal: Transform Ghost Reflections into Primary Reflection Traveltimes Uninteresting Part of Medium of Medium Time Direct Greens Thm: Every Point on Surface acts as a Secondary Source Direct Ghost To Remove Kinematics of Traveling in Uninteresting Medium Time Shift Traces by Direct Times Source Moved to Surface. Statics Eliminated

10. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s

11. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s

12. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s

13. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s

14. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s (g, M,s)= d( M |s)* d(g|s) s,s Every VSP source at different S reflects off M And recorded at g

15. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s (g, M,s)= d( M |s)* d(g|s) s,s Every VSP source at different S reflects off M And recorded at g

16. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s (g, M,s)= d( M |s)* d(g|s) s,s Every VSP source at different S reflects off M And recorded at g We accidentally found specular ray for given (M,g), & stationary phase says this is dominant contribution.

17. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s (g, M,s)= d( M |s)* d(g|s) s,s Every VSP source at different S reflects off M And recorded at g Above Datuming Formula = CSG for source at M and receiver at g

18. Interferometric VSP Datuming Eliminates well statics and uninteresting parts of the medium. Raise buried src to surface. (g, M,s)= d( M |s)* d(g|s) s,s

19. Interferometric VSP Datuming by Least Squares (g, M,s)= d( M |s)* d(g|s) s,s d = E d z 0 Data with source at depth Data with source at surface Natural extrapolation operator T [E E] E d z T -1 T 0 d = Extrapolation Deconvolution ED

20. Interferometric Deviated VSP Datuming Eliminates well statics and uninteresting parts of the medium. Lower surface src to well. (g, M,s)= d( M |s)* d(g|s) s,s

21. Interferometric CDP Datuming Eliminates src/rec statics and uninteresting parts of the medium. Lower buried src to reference inter. (g, M,s)= d( M |s)* d(g|s) s,s reference reflector reference reflector

22. Outline Seismic Interferometry Interferometric Migration Interferometric Datuming Interferometric Tomography Conclusions

23. Outline Seismic Interferometry Interferometric Migration Interferometric Datuming Interferometric Tomography Conclusions

24. Uninteresting Part of Medium of Medium Time Replace Time Shifting by Crosscorrelation d(M|s) d(g|s) M g s (g, M,s)= d( M |s)* d(g|s) s,s Above Formula = CSG for source at M and receiver at g’ Every surface pt at different M acts as secondary source To contribute to g Shot gather for source at M and geophone at g

25. Uninteresting Part of Medium of Medium Time M g s Above Formula = CSG for source at M and receiver at g’ Every surface pt at different M acts as secondary source To contribute to g (g, t + t ) (g, t + t )M g MxMxMxMx gxgxgxgx M, m(x)= X = trial image pt.

26. Outline Seismic Interferometry Interferometric Migration: Exxon VSP Interferometric Datuming Interferometric Tomography Conclusions

27. Time (s) 0.3 0 30 900 Depth (ft) Raw Data(CRG15)

28. Time (s) 0.3 0 30 900 Depth (ft) Ghosts

29. Depth (ft) 1300 200 0400 X (ft) 0400 X (ft) Standard migXcorr. mig

30. Outline Seismic Interferometry Interferometric Migration: CDP Interferometric Datuming Interferometric Tomography Conclusions

31. Shots: 280 Shot interval: 10 m Receivers: 300 Receiver interval: 10 m Temporal interval:1ms X (km) 0 3 0 1.8 Depth (km) Salt model

32. X (km) 0 3 0 3 Time (s) CSG 100

33. X (km) 0 3 0 1.8 Depth (km) Velocity model with inaccurate salt boundary, oceam bottom, and overburden

34. X (km) 0 3 0 1.8 Depth (km) Kirmig with inaccurate salt boundary, ocean bottom, and overburden

35. X (km) 0 3 0 1.8 Depth (km) RT mig with inaccurate salt boundary, ocean bottom, and overburden

36. X (km) 0 3 0 1.8 Depth (km) Standard mig Correct velocity X (km) 0 3 0 3 Standard mig Incorrect velocity RT mig

37. Summary Seismic Interferometry d(g)d(g’)* d(g) d(g’) *

38. Summary d(g)d(g’) * d(g) d(g’) * Time Shift = Remove Uninteresting Kinematics+Statics Kinematics+Statics DatumingMigrationTomography

39. Issues 1. VSP Natural Home for Interferometry 2. CDP Interferometry Eliminates statics+overburden. Widens coverage Effective if Guide Star/Reference Interface Known Less Effective if Reference not Known 3. Interferometric Datuming Naturally Datumed Data can be Filtered ID vs ED

40. Outline Seismic Interferometry Interferometric Migration: CDP Interferometric Datuming Interferometric Tomography Conclusions Salt Flank Imaging PS Waves

41. Uninteresting Part of Medium of Medium Time Goal: Image Interface by PS Transmitted Waves M g s P d(M|s) d(g|s) PPPPPPPP PSPSPSPS M g d(g|s)* (g,M) = MxMxMxMx gxgxgxgx M, m(x)= = e e i w t + i w t -i w t - i w t PSPSPSPS PPPPPPPP = e= e= e= e i w (t – t)

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

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

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

45. 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. Raise buried src to interesting inter.