2. Crosscorrelation Migration of Free-Surface Multiples in CDP Data Jianming Sheng University of Utah February, 2001

3. Outline ObjectiveObjective Crosscorrelation migrationCrosscorrelation migration Numerical examplesNumerical examples SummarySummary

4. Objective To image free-surface multiples by crosscorrelation migration; To improve the migration image quality by attenuating the artifacts caused by free-surface multiples.

5. Outline ObjectiveObjective Crosscorrelation migrationCrosscorrelation migration Numerical examplesNumerical examples SummarySummary

6. Principle of CCM G’GS X X’ VIRTUAL SOURCE (CROSSCORRELATION) G’GS X X’ SOURCE G G’GS X X’ SOURCE P

7. Principle of CCM Migration image Trial image point Imaging Condition

8. Asymptotic Analysis Crosscorrelograms

9. Under stationary phase condition P rimary G host Correct image + Artifacts G host P rimary G host Negligible Wrong positon

10. Asymptotic Analysis Crosscorrelation migration can migrate the multiples to the correct position but generate artifacts as well; CCM image alone can not give the reflectivity distribution!

11. Key Idea of CCM CCM Image Kirchhoff Image Reflector Artifacts Artifacts

12. Key Idea of CCM Multiplying the two images an improvedmigration image can be obtained

13. Outline ObjectiveObjective Crosscorrelation migrationCrosscorrelation migration Numerical examplesNumerical examples SummarySummary

14. Numerical Examples Three-layered modelThree-layered model Nine-layered modelNine-layered model SEG/EAGE salt modelSEG/EAGE salt model

15. Three-Layered Model 0600 1200 1800 3000 Depth (m) 0600 1200 1800 3000 100 200 300 400 500 100 200 300 400 500 Model CCM Image

16. Three-Layered Model 0600 1200 1800 3000 Depth (m) 0600 1200 1800 3000 100 200 300 400 500 100 200 300 400 500 Kirchhoff Image Product Image

17. Nine-Layered Model 500 1000 1500 2000 2500 500 1000 1500 2000 25000600 1200 1800 3000 Depth (m) 2400 0600 1200 1800 3000 2400 Model CCM image 500 1000 1500 2000 2500 500 1000 1500 2000 2500

18. Nine-Layered Model 500 1000 1500 2000 2500 500 1000 1500 2000 25000600 1200 1800 3000 Depth (m) 2400 Kirchhoff Image Product Image 500 1000 1500 2000 2500 500 1000 1500 2000 2500

19. SEG/EAGE Salt Model 0 600 1200 1800 2400 Depth (m) 3000 3600 0 5000 10000 15000 Distance (m) 320 shots 176 traces per shot

20. CCM Image 0 600 1200 1800 2400 Depth (m) 3000 3600 0 5000 10000 15000 Distance (m)

21. Kirchhoff Image 0 600 1200 1800 2400 Depth (m) 3000 3600 0 5000 10000 15000 Distance (m)

22. Product Image 0 600 1200 1800 2400 Depth (m) 3000 3600 0 5000 10000 15000 Distance (m)

23. All right, multiples are migrated, … well, is it useful? Yes.

24. Kirchhoff Image 0 600 1200 1800 2400 Depth (m) 3000 3600 0 5000 10000 15000 Distance (m)

25. Product Image 0 600 1200 1800 2400 Depth (m) 3000 3600 0 5000 10000 15000 Distance (m)

26. Outline ObjectiveObjective Crosscorrelation migrationCrosscorrelation migration Numerical examplesNumerical examples SummarySummary

27. Summary Multiples can be considered as signal and correctly imaged by the crosscorrelation migration;Multiples can be considered as signal and correctly imaged by the crosscorrelation migration; By multiplying the crosscorrelation and Kirchhoff migration images, the true reflectors can be enhanced and the artifacts can be attenuated.By multiplying the crosscorrelation and Kirchhoff migration images, the true reflectors can be enhanced and the artifacts can be attenuated.

28. Further Work To attenuate the artifacts generated by CCM;To attenuate the artifacts generated by CCM; To deal with the high-order multiples and internal multiples.To deal with the high-order multiples and internal multiples.

29. Acknowledgment I thank the sponsors of the 2000 University of Utah Tomography and Modeling /Migration (UTAM) Consortium for their financial support.