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3D Wave-equation Interferometric Migration of VSP Free-surface Multiples

3D Wave-equation Interferometric Migration of VSP Free-surface Multiples. Ruiqing He University of Utah Feb., 2006. Outline. Introduction Wave-equation Interferometric Migration (WEIM) A Synthetic Test Application to A Field 3D VSP Data Set Conclusion. Outline. Introduction

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3D Wave-equation Interferometric Migration of VSP Free-surface Multiples

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  1. 3D Wave-equation Interferometric Migration of VSP Free-surface Multiples Ruiqing He University of Utah Feb., 2006

  2. Outline • Introduction • Wave-equation Interferometric Migration (WEIM) • A Synthetic Test • Application to A Field 3D VSP Data Set • Conclusion

  3. Outline • Introduction • Wave-equation Interferometric Migration (WEIM) • A Synthetic Test • Application to A Field 3D VSP Data Set • Conclusion

  4. Introduction • Migration of VSP multiples has a larger imaging area than migration of primaries.

  5. Mirror image Published Methods • Mirror imaging condition: transfer to a migration of primaries imaging condition. Real model Crosscorrelation migration: transfer VSP data to CDP data.

  6. Difficulties • Crosscorrelation is not cheap. • Kirchhoff migration is not cheap. • Ray tracing. • Storage of time tables. • 3D.

  7. Outline • Introduction • Wave-equation Interferometric Migration (WEIM) • A Synthetic Test • Application to A Field 3D VSP Data Set • Conclusion

  8. WEIM Reciprocity

  9. Line-source Ray tracing Unknown medium Known medium The picked time is imposed as an initial condition in ray tracing.

  10. Advantages of WEIM • Experience similar velocity estimation errors as migrating CDP primaries. • For each receiver gather, only one line-source ray tracing, and one wavefield extrapolation is needed. • In 3D VSP, the saving of ray tracing and timetable storage is enormous.

  11. Outline • Introduction • Wave-equation Interferometric Migration (WEIM) • A Synthetic Test • Application to A Field 3D VSP Data Set • Conclusion

  12. 2D Synthetic Test Synthetic data Synthetic model 0 0 600 shots Time (s) 12 geophpnes Depth (m) 5 4000 0 Offset (m) 0 6000 Offset (m) 6000

  13. Migration Comparison Migration of multiples Migration of primaries 0 0 Depth (m) Depth (m) 4000 4000 0 Offset (m) 0 6000 Offset (m) 6000

  14. Outline IntroductionWave-equation Interferometric Migration (WEIM)A Synthetic TestApplication to A Field 3D VSP Data SetConclusion

  15. Acquisition Geometry ~ 11 km ~ 11 km ~ 4.5 km deep 12 geophones at an interval of 15.25 m.

  16. 2D WEIM Result 0 Depth (m) 7.5 0 11 Offset (km)

  17. 3D WEIM Result Migration of only one receiver gather

  18. Slice Movie Migration of only one receiver gather

  19. Outline • Introduction • Wave-equation Interferometric Migration (WEIM) • A Synthetic Test • Application to A Field 3D VSP Data Set • Conclusion

  20. Conclusion • Proposed 3D WEIM, which is very efficient for migrating 3D VSP multiples. • Migration of 3D VSP free-surface multiples provides an imaging area comparable to a conventional 3D CDP survey, yet the data processing cost is much reduced.

  21. Acknowledgement • Thanks to UTAM 2005 sponsors for financial support.

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