1. Salt Boundary Delineation by Transmitted PS Waves David Sheley

2. Outline MotivationMotivation Transmission Migration TheoryTransmission Migration Theory ResultsResults –Synthetic –Gulf of Mexico VSP ConclusionsConclusions

3. Problem: Limited Illumination SEDIMENT Receiver Well SEDIMENT P PP SALT

4. Solution: PS Transmission Migration SEDIMENT PS Receiver Well SEDIMENT P SALT

5. Outline MotivationMotivation Transmission Migration TheoryTransmission Migration Theory ResultsResults –Synthetic –Gulf of Mexico VSP ConclusionsConclusions

6. Conventional PP Migration m(r) = S(z g,  sr +  rg )   sr  rg s r g

7. m(r) = S(z g,  sr +  rg )   sr s r g Transmission PS Migration  rg P-wave S-wave

8. m(r) = S(z g,  sr +  rg )   sr s r g Transmission PS Migration  rg

9. Outline MotivationMotivation Transmission Migration TheoryTransmission Migration Theory ResultsResults –Synthetic –Gulf of Mexico VSP ConclusionsConclusions

10. Depth (m) Offset (m) 1000 100 0 ds = 1 m dg = 1 m Vertical Boundary RVSP Model V = 5500 m/s P V = 5000 m/s P V = 3333 m/s S V = 3666 m/s S Source = 1500 Hz

11. Synthetic RVSP Data 0 One-way Traveltime (ms) 20 40 60 Offset (m) 1000

12. Synthetic RVSP Data 0 One-way Traveltime (ms) 20 40 60 Offset (m) 1000 Direct P PS Direct S SP PS PP SP

13. Depth (m) Offset (m) 1000 100 0 PP Reflection Migration P PP

14. PP Reflection Kirchhoff Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

15. PP Kirchhoff Migration: 90% Velocity Depth (m) Offset (m) 0 100 0 100 Reduced-TimeConventional Depth (m) Offset (m) 0 100 0 100

16. PP Reflection Wavepath Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

17. PP Wavepath Migration: 90% Velocity Depth (m) Offset (m) 0 100 0 100 Reduced-TimeConventional Depth (m) Offset (m) 0 100 0 100

18. Depth (m) Offset (m) 1000 100 0 PS Transmission Migration PS P

19. PS Transmission Kirchhoff Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

20. PS Kirchhoff Migration: 90% Velocity Depth (m) Offset (m) 0 100 0 100 Reduced-TimeConventional Depth (m) Offset (m) 0 100 0 100

21. PS Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

22. PS Wavepath Migration: 90% Velocity Depth (m) Offset (m) 0 100 0 100 Reduced-TimeConventional Depth (m) Offset (m) 0 100 0 100

23. Depth (m) Offset (m) 1000 100 0 SP Transmission Migration S SP

24. SP Transmission Kirchhoff Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

25. SP Kirchhoff Migration: 90% Velocity Depth (m) Offset (m) 0 100 0 100 Reduced-TimeConventional Depth (m) Offset (m) 0 100 0 100

26. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

27. SP Wavepath Migration: 90% Velocity Depth (m) Offset (m) 0 100 0 100 Reduced-TimeConventional Depth (m) Offset (m) 0 100 0 100

28. SP Transmission Kirchhoff Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

29. SP Transmission Kirchhoff Migration Depth (m) Offset (m) 0 100 0 100 True Velocity Single Gather Depth (m) Offset (m) 0 100 0 100

30. SP Transmission Kirchhoff Migration Depth (m) Offset (m) 0 100 0 100 90% Velocity Depth (m) Offset (m) 0 100 0 100 Single Gather

31. True Velocity Depth (m) Offset (m) 0 100 0 100 SP Transmission Kirchhoff Migration 90% Velocity Depth (m) Offset (m) 0 100 0 100

32. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

33. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 Depth (m) Offset (m) 0 100 0 100 KM Single Gather True Velocity

34. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 Depth (m) Offset (m) 0 100 0 100 Ray Tracing True Velocity

35. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 Depth (m) Offset (m) 0 100 0 100 Fresnel Zone True Velocity

36. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 Depth (m) Offset (m) 0 100 0 100 Wavepath Image True Velocity

37. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 True Velocity 90% Velocity Depth (m) Offset (m) 0 100 0 100

38. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 90% Velocity Depth (m) Offset (m) 0 100 0 100 KM Single Gather

39. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 Depth (m) Offset (m) 0 100 0 100 Ray Tracing 90% Velocity

40. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 Depth (m) Offset (m) 0 100 0 100 Fresnel Zone 90% Velocity

41. SP Transmission Wavepath Migration Depth (m) Offset (m) 0 100 0 100 Depth (m) Offset (m) 0 100 0 100 Wavepath Image 90% Velocity

42. Outline MotivationMotivation Transmission Migration TheoryTransmission Migration Theory ResultsResults –Synthetic –Gulf of Mexico VSP ConclusionsConclusions

43. Acquisition Geometry Depth (kft) Offset (kft) 4 0 8 12 4 SALT Depth (kft) Offset (kft) 4 0 8 12 4 SALT

44. P-Wave Velocity Depth (kft) Offset (kft) 150 4 0 8 12 4 5 0 Velocity (kft/s) 5 15 Depth (kft) 0 4 8 12 10

45. S-Wave Velocity Depth (kft) Offset (kft) 150 4 0 8 12 4 5 0 Velocity (kft/s) 5 15 Depth (kft) 0 4 8 12 10

46. Offset 500 ft Z-Component Depth (ft) 8700 12900 One-way Traveltime (s) 1.81.42.22.6 SALT Direct P Reflected P

47. 500 ft Offset: PP Reflections Depth (ft) 8700 12900 One-way Traveltime (s) 1.81.42.22.6 SALT

48. 500 ft Depth (ft) 8000 14700 2000 ft Synthetic 8000 14700 SALTSALT PP Reflection Migration Receivers Receivers

49. Offset 500 ft X-Component Depth (ft) 8700 12900 One-way Traveltime (s) 1.81.42.22.6 SALT Reflected PS Direct P

50. 500 ft Offset: PS Reflections Depth (ft) 8700 12900 One-way Traveltime (s) 1.81.42.22.6 SALT

51. 500 ft Depth (ft) 8000 14700 2000 ft Synthetic 8000 PS Reflection Migration Receivers Receivers 14700 SALTSALT

52. Offset 500 ft X-Component Depth (ft) 8700 12900 One-way Traveltime (s) 1.81.42.22.6 SALT Direct P Transmitted PS

53. 500 ft Offset: PS Transmissions Depth (ft) 8700 12900 One-way Traveltime (s) 1.81.42.22.6 SALT

54. 500 ft Depth (ft) 8000 14700 2000 ft Synthetic 8000 PS Transmission Migration Receivers Receivers 14700 SALTSALT

55. Outline MotivationMotivation Transmission Migration TheoryTransmission Migration Theory ResultsResults –Synthetic –Gulf of Mexico VSP ConclusionsConclusions

56. Conclusions Reduced-time is shown to reduce migration errors in PP reflection images.Reduced-time is shown to reduce migration errors in PP reflection images. The top and bottom of the salt tablet were successfully imaged using the three VSP gathers.The top and bottom of the salt tablet were successfully imaged using the three VSP gathers. PS transmission migration sucessfully imaged a tranmitting boundary above the receiver array.PS transmission migration sucessfully imaged a tranmitting boundary above the receiver array.

57. Implications Can vertical salt boundaries be imaged using PS transmissions.Can vertical salt boundaries be imaged using PS transmissions. VSP transmission migraion an alternative to single well imaging ?VSP transmission migraion an alternative to single well imaging ? Greater illumination using combined PP reflection and PS transmissionsGreater illumination using combined PP reflection and PS transmissions = Cheaper VSP. = Cheaper VSP.