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Crosscorrelation Migration of Free-Surface Multiples in RVSP Data

Crosscorrelation Migration of Free-Surface Multiples in RVSP Data. Jianming Sheng University of Utah February, 2001. Outline. Objective Crosscorrelation migration Numerical examples Summary. Objective. Validate the feasibility of crosscorrelation migration for RVSP data;.

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Crosscorrelation Migration of Free-Surface Multiples in RVSP Data

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

  2. Outline • Objective • Crosscorrelation migration • Numerical examples • Summary

  3. Objective Validate the feasibility of crosscorrelation migration for RVSP data; (Schuster and Rickett, 2000) Image the reflectivity distribution without knowing the source position.

  4. Outline • Objective • Crosscorrelation migration • Numerical examples • Summary

  5. Crosscorrelation Migration Principle Asymptotic analysis Key steps

  6. G G’ S X Principle of CCM Crosscorrelogram

  7. G G’ Virtual source S X Principle of CCM Imaging condition

  8. Crosscorrelograms Migration image Trial image point Asymptotic Analysis

  9. Negligible contribution from: Direct Direct Contribution from: Contribution from: Ghost Ghost Direct Direct Ghost Ghost Reflection coefficient Asymptotic Analysis Under stationary phase condition

  10. CCM image gives the reflectivity distribution except contaminated by artifacts up to order Asymptotic Analysis

  11. Key Steps of CCM Step 1: Bandpass filter and other preprocess; Step 2: Dip filter; Step 3: Generate crosscorrelograms; Step 4: Filter aliasing in crosscorrelograms; Step 5: Migrate the crosscorrelograms.

  12. Outline • Objective • Crosscorrelation migration • Numerical examples • Summary

  13. Numerical Examples • Three-layered model • Exxon’s Friendswood RVSP data

  14. Three-Layered Model RECEIVERS V1 = 762 m/s 91.4 m V2 = 1067 m/s 182.8 m V3 = 1372 m/s 98 shots 24 traces per shot SOURCES

  15. Direct Primary Ghost 1st-CRG Before dip-filtered Dip-filtered 0 0 0.2 0.2 0.4 0.4 Time (sec.) 0.6 0.6 0.8 0.8 0 150 300 0 150 300 Depth (m) Depth (m)

  16. D G 1st-CSG Pseudo-Shot Gather Shot Gather Crosscorrelogram 0 0 0.2 0.2 0.4 0.4 Time (sec.) Time (sec.) 0.6 0.6 0.8 0.8 High-order Ghost 0 60 120 180 0 60 120 180 Offset (m) Offset (m)

  17. True Reflectors Crosscorrelation migration image 0 Depth (m) 150 300 0 90 180 Offset (m)

  18. 98 shots 23 traces per shot Exxon’s Friendswood RVSP Data 365.7 m 7.6 m RECEIVERS 9.1 m 304.8 m SOURCES

  19. Exxon’s Friendswood RVSP Data 0 100 Depth (m) 200 300 Well-log Reflectivity CCM

  20. Exxon’s Friendswood RVSP Data Offset (m) 0 24 12 0 Depth (m) 180 360 CCM image

  21. Outline • Objective • Crosscorrelation migration • Numerical examples • Summary

  22. Summary • Asymptotic analysis shows that CCM is capable of imaging the reflectivity distribution; • The results of synthetic and Exxon’s Friendswood RVSP data validate the feasibility of CCM.

  23. Further Work • To attenuate the artifacts generated by CCM; • To deal with the amplitude preservation problem.

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

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