Migration and Attenuation of Surface-Related and Interbed Multiple Reflections

1. Migration and Attenuation of Surface-Related and Interbed Multiple Reflections Zhiyong Jiang University of Utah April 21, 2006

2. Outline • Overview • Surface Multiple Migration • Interbed Multiple Migration • Multiple Attenuation in • Multiple Imaging • Conclusions

3. Surface Multiple s g x Interbed Multiple High-order Multiple s s x g g Primary s g x

4. Technical Contributions • For the first time, I examine the imaging and computational properties of three different surface multiple imaging methods, and apply them to both synthetic and field data • I develop two novel methods for imaging interbed multiples, and apply them to field and synthetic data • I attenuate high-order multiples to solve a major problem in multiple imaging: the interference from other multiples. This strategy makes multiple imaging a more practical tool

5. Outline • Overview • Surface Multiple Migration • Interbed Multiple Migration • Multiple Attenuation in • Multiple Imaging • Conclusions

6. Outline • Overview • Surface Multiple Migration • Motivation • Methodology • Numerical Results • Summary

7. Better Fold Wider Coverage Why Migrate Surface Multiples? Better Vert. Res.

8. 3D VSPSurvey Shot radius Z

9. Outline • Overview • Surface Multiple Migration • Motivation • Methodology • Numerical Results • Summary

10. Modeling Equation d(s,g)mult. = m(x0 , ω) W(ω) ~ ~ ~ . exp[iω (τsx+τx g+τg g)] 0 0 0 0 g0 x0 s B0 g

11. Method 1: Model-based Multiple Imaging g’ m(x, ω) = ∫∫ d(s, g)mult. . exp[-iω (τsx +τxg’+τg’g)] dsdg 0 0 τxg’+τg’g = min (τxg’+τg’g) 0 0 g’ B0 B0 g’0 s τg’g g’ : diffraction point g0’: specular pointX : trial image point 0 τsx τxg’ 0 x g

12. Method 2: Mig. with Semi-natural Green’s functions g’ m(x, ω) = ∫∫ d(s, g)mult. ~ . exp[-iω (τsx +τxg’+τg’g)] dsdg 0 0 ~ ~ τxg’+τg’g = min (τxg’+τg’g) 0 0 g’ B0 B0 g’0 s ~ τg’g g’ : diffraction point g0’: specular pointX : trial image point 0 τsx τxg’ 0 x g

13. Method 3: Interferometric Imaging m(x, ω) = ∫∫∫ d(s, g)mult. ~ . exp[-iω (τsx +τxg’ +τg’g)] dsdgdg’ g’ s B0 g’ : diffraction point X : trial image point τsx x g

14. Imaging Properties of Migration Methods

15. Outline • Overview • Surface Multiple Migration • Motivation • Methodology • Numerical Results • Summary

16. Numerical Results • 2-D Dipping Layer Model • 3-D Real Data • 3-D Synthetic Data

17. Velocity Model Well X (m) 925 0 0 V (m/s) 4000 Depth (m) 1900 1300 Shots: 92; Receivers: 91 (50m -950 m)

18. CSG 51 Ghost Component 0 S A Time (s) Well G X 3 50 950m 50 950m

19. CSG 51 Primary Component 0 Time (s) S A Well G X 3 50 950m 50 950m

20. 8 Receivers Primary 1st-order multiple 0 Depth (m) 1300 X (m) 0 0 X (m) 925 925

21. Numerical Results • 2-D Dipping Layer Model • 3-D Real Data • 3-D Synthetic Data

23. Numerical Results • 2-D Dipping Layer Model • 3-D Real Data • 3-D Synthetic Data

24. Sources/Wells Locations Y (m) 0 2000 0 Well X (m) 1089 shots 111 receivers 2000

25. CSG10 CSG540 0 Time (s) X 3.5 1 111 1 Receiver Number Receiver Number 111

26. X=1000m Primary 100 Depth (m) 1100 Velocity Model 100 Depth (m) 1100 0 Y (m) 2000

27. X=1000m 1st order ghost 100 Depth (m) 1100 Velocity Model 100 Depth (m) 1100 0 Y (m) 2000

28. Y=1000m Primary 100 Depth (m) 1100 Velocity Model 100 Depth (m) 1100 0 X (m) 2000

29. Y=1000m 1st order ghost 100 Depth (m) 1100 Velocity Model 100 Depth (m) 1100 0 X (m) 2000

30. Outline • Overview • Surface Multiple Migration • Motivation • Methodology • Numerical Results • Summary

31. Summary Advantages Wider subsurface coverage can be achieved by migrating multiples Multiples illuminate areas invisible to primaries

32. Summary Limitation Multiple is weak Interferences from primary and other events, such as high-order multiples

33. Outline • Overview • Surface Multiple Migration • Interbed Multiple Migration • Multiple Attenuation in • Multiple Imaging • Conclusions

34. Outline • Overview • Interbed Multiple Migration • Motivation • Methods • Numerical Tests • Summary

35. What is below the salt? ?

36. Challenge with VSP Surface Multiples: Long raypath, strong attenuation, triple passage through salt s g

37. Challenge with CDP primary reflections:strong attenuation, double passage through salt g s

38. Can we try interbed multiples?Advantages: short raypth, less attenuation, single passage through salt s g

39. Outline • Overview • Interbed Multiple Migration • Motivation • Methods • Numerical Tests • Summary

40. Modeling Equation d(s,g)inter. = m(x0 , ω) W(ω) ~ ~ ~ . exp[iω (τsx +τx g+τg g)] 0 0 0 0 g0 x0 B0 s B1 g

41. Method 1: Fermat’s principle g’ m(x, ω) = ∫∫ d(s, g)inter. . exp[-iω (τsx +τxg’+τg’g)] dsdg 0 0 τxg’+τg’g = min (τxg’+τg’g) 0 0 g’ B1 B0 s g’0 B1 τg’g τsx 0 τxg’ 0 x g

42. Method 2: Summation of all the diffraction energy m(x, ω) = ∫∫∫ d(s, g)inter. . exp[-iω (τsx +τxg’ +τg’g)] dsdgdg’ B0 s g’ B1 τsx x g

43. Outline • Overview • Interbed Multiple Migration • Motivation • Methods • Numerical Tests • Summary

44. Numerical Tests • SEG/EAGE Model • Large Salt Model • Field Data Test

45. Velocity Model X (m) 3000 0 Depth (m) 2000 Shots: 301; Receivers: 61 (1000m - 1600m)

46. Upper-salt-boundary Interbed Multiple 0 s g’0 Depth (m) g x 2000 3000 0 X (m)

47. Velocity Model Interbed Multiple Migration Image 800 Depth (m) 2000 1200 1200 0 0 X (m) X (m)

48. Lower-salt-boundary Interbed Multiple 0 s Depth (m) g’0 g x 2000 3000 0 X (m)

49. Interbed Multiple Migration Image Velocity Model 800 Depth (m) 2000 1200 1200 0 0 X (m) X (m)

50. Numerical Tests • SEG/EAGE Model • Large Salt Model • Field Data Test