1. 4C Mahogony Data Processing and Imaging by LSMF Method Jianhua Yu and Yue Wang

2. Outline Motivation and Objective Motivation and Objective LSMF Method LSMF Method Examples Graben Model Mahogany Field Data Examples Graben Model Mahogany Field Data Summary Summary

3. Outline Motivation and Objective Motivation and Objective LSMF Method LSMF Method Examples Graben Model Mahogany Field Data Examples Graben Model Mahogany Field Data Summary Summary

4. Geological Objectives Image Complex StructureImage Complex Structure Detect Gas Reservoir Over SaltDetect Gas Reservoir Over Salt

5. Problems P-SV Conversion at Reflector ? P-SV Conversion at Reflector ? How to Get “Pure” P-P and P-SV How to Get “Pure” P-P and P-SV Strong Guided Waves Strong Guided Waves

6. Problems for F-K Use only wave moveout Strong guided waves Near offset distortion

7. P-P Source Point Scatterer P-SV P-P and P-SV Waves

8. Particle Motion Direction + Separation Time offset Moveout Least Squares Migration Filtering

9. Objective Separate P-P & P-S Separate P-P & P-S Suppress Guide Waves Suppress Guide Waves Improve Migration Image Improve Migration Image

10. Outline Motivation and Objective Motivation and Objective LSMF Method LSMF Method Examples Graben Model Mahogany Field Data Examples Graben Model Mahogany Field Data Summary Summary

11. Observed data = > D pp + = > D pp + Offset Time P-P wave P-S wave LSMF Method L p-s m p-s L pp m pp Reflectivty ModelingOperator D p-s D p-s

12. d pp = L pp m pp d p-s = L p-s m p-s P-P wave Offset Time P-S wave Offset Time LSMF Method

13. Conjugate Gradient Method: where LSMF Method

14. Operators are constructed based on moveout and particle-motion direction The migration operators are the transposes of the modeling operators

15. Outline Motivation and Objective Motivation and Objective LSMF Method LSMF Method Examples Graben Model Mahogany Field Data Examples Graben Model Mahogany Field Data Summary Summary

16. Examples Graben ModelGraben Model Mahogony Field DataMahogony Field Data

17. Graben Velocity Model 0 Depth (m) 3000 5000 0X (m) V1=2000 m/s V2=2700 m/s V3=3800 m/s V4=4000 m/s V5=4500 m/s

18. FDSynthetic Data FD Synthetic Data 1.4 0 Time (s) 0 Offset (m) 5000 0 Offset (m) 5000 Horizontal Component Vertical Component P-P P-S P-S P-P

19. LSMF Separation 1.4 0 Time (s) 0 Offset (m) 5000 0 Offset (m) 5000 Horizontal Component Vertical Component P-S P-P

20. F-K Filtering Separation 1.4 0 Time (s) 0 Offset (m) 5000 0 Offset (m) 5000 Horizontal Component Vertical Component P-P P-S P-S P-P

21. Test Results Indicate: LSMF works well for separating P-P and P-SV P-P and P-SV LSMF is superior to F-K filtering LSMF is superior to F-K filtering

22. Examples Graben ModelGraben Model Mahogony Field DataMahogony Field Data

23. Acquisition Survey 9 km OBC Shot Line 29 km

24. Main Processing Flow Geometry assignment, datuming and so on Trace edit, noise elimination, dual-sensor summation Trace edit, noise elimination, dual-sensor summation Amplitude Recovery Amplitude Recovery Static correction, (F-K filtering), multiple suppression Static correction, (F-K filtering), multiple suppression LSMF, velocity analysis LSMF, velocity analysis Migration Migration Output Output

25. 0 Time (s) 725 4 Offset(m) Raw CSG -750 Hydrophone component 725 Offset(m) -750 Vertical component Vertical component Continuous events

26. 0 Time Time (s) 725 4 Offset(m) Raw CSG -750 Radial component Radial component 725 Offset(m) -750 Transverse component Wormy events

27. 0 Time (s) 3750 4 X (m) Raw CRG Raw CRG 0 Hydrophone component 3750 X (m) 0 Vertical component Continuous events

28. 0 Time (s) 3750 4 X (m) Raw CRG 0 Radial component 3750 X (m) 0 Transverse component Continuous events

29. Rough Estimate of Static Shift Station Number Static shift (ms) -4 0 100 12 Receiver static Shot static Source Receiver p s Source Receiver p s

30. TheShear static shifts exist The Shear static shifts exist These shifts mainly come from receivers and one-way Shear path from deeper reflector P-S waves originate from reflectors Data Analysis Indicates:

31. CRG1 Data before Using LSMF CRG1 (Vertical component) 0 4 Guided wave and P-S Time (s)

32. CRG1 Data after Using F-K Filtering CRG1 Data after Using F-K Filtering CRG1 (Vertical component) 0 4 Unwanted waves remain Time (s)

33. CRG1 Data after Using LSMF CRG1 (Vertical component) 0 4 Less Noise remains Time (s)

34. Prestack Migration Image With F-K Separation Time (s) 0 3.5 Midpoint (Km) 4.60 c

35. Prestack Migration Image With LSMF Separation Time (s) 0 3.5 Midpoint (Km) 4.60 c

36. A Zoom View of Box A Time (s) 2.0 3.2 Midpoint (Km) 0.61.4 0.61.4 FK+Mig.LSMF+Mig.

37. A Zoom View of Box C Time (s) 0.2 0.8 Midpoint (Km) 3.44.6 3.44.6 FK+Mig.LSMF+Mig.

38. Outline Motivation and Objective Motivation and Objective LSMF Method LSMF Method Examples Graben Model Mahogany Field Data Examples Graben Model Mahogany Field Data Summary Summary

39. Summary P-SV waves in Mahogony data P-SV waves in Mahogony data originate from the deep reflectors originate from the deep reflectors LSMF gives better separation results LSMF gives better separation results and improves the migration image and improves the migration image

40. Summary LSMF can eliminate unwanted noise, LSMF can eliminate unwanted noise, such as guided waves such as guided waves LSMF has negative impact on the LSMF has negative impact on the fidelity of data to some extent fidelity of data to some extent

41. Summary Multiple Elimination Multiple Elimination Prestack Depth Migration Prestack Depth Migration Converted Wave Imaging Converted Wave Imaging Future Research:

42. Acknowledgement We are grateful to the 1999 sponsors of the UTAM consortium for financial support