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Wavepath Refraction Migration on Near-Surface Refraction Data

Wavepath Refraction Migration on Near-Surface Refraction Data. Jianming Sheng. Outline. Motivation. Numerical Examples. Wavepath Refraction Migration. Summary. Motivation. Produce better seismic image by Traveltime Tomography + Refraction Migration.

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Wavepath Refraction Migration on Near-Surface Refraction Data

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  1. Wavepath Refraction Migration on Near-Surface Refraction Data Jianming Sheng

  2. Outline • Motivation • Numerical Examples • Wavepath Refraction Migration • Summary

  3. Motivation • Produce better seismic image by Traveltime Tomography + Refraction Migration • Help to reduce the uncertainties in the tomograms.

  4. Outline • Motivation • Numerical Examples • Wavepath Refraction Migration • Summary

  5. G S Imaging Condition T=TSX+TXY+TYG X Y Refraction Migration

  6. Outline • Motivation • Numerical Examples • Refraction Migration • Summary

  7. Numerical Examples • 2D refraction data from INCO • 2D marine data from WesternGeco and ChevronTexaco

  8. 2D INCO Refraction Data Courtesy of Alan King Shot spacing: 50 m Shots: 105 Channel: 24 Receiver: 10 m Length: 2.56 sec. Sample: 0.625 ms 2025 traveltimes were picked by Prof. Schuster

  9. CSG #3 Residual vs. Iterations 0 55 Traveltime (sec.) Traveltime (msec.) 0.26 0 220 Offset (m) 5 0 Iterations 40

  10. Traveltime Tomogram 3500 0 2500 Depth (m) 1500 500 150 (m/s) 0 Distance (m) 2000

  11. Ray Density 200 0 140 Depth (m) 80 20 150 (m/s) 0 Distance (m) 2000

  12. Refraction Migration 5 0 Depth (m) 0 150 -5 0 Distance (m) 2000

  13. Tomogram/Refraction Migration 3500 0 2500 Depth (m) 1500 500 150 (m/s) 0 Distance (m) 2000

  14. Numerical Examples • 2D refraction data from INCO • 2D marine data from WesternGeco and ChevronTexaco

  15. Gulf of Mexico seismic line Courtesy of Alan Leeds Shot spacing: 25 m Shots: 990 Channel: 180 Receiver: 25 m Sample: 4 ms Length: 8 sec. A total of 86,736 traveltimes were picked and inverted.

  16. Traveltime Velocity Tomogram 0 2100 1900 Depth (m) 1700 1500 1000 (m/s) 5500 CDP NUMBER 6500

  17. 0.60 2700 0.40 0.20 2000 0.00 -0.20 1300 -0.40 -0.60 600 -0.80 -1.00 Ray Density/Refraction Migration 0 Depth (m) 1000 5500 CDP NUMBER 6500

  18. Reflection migration 0 Depth (m) 1000 5500 CDP NUMBER 6500

  19. Outline • Motivation • Numerical Examples • Wavepath Refraction Migration • Summary

  20. Summary • Wavepath refraction migration method • was applied to two field data sets. • Refraction migration can help • reducing uncertainties in tomograms.

  21. Acknowledgment I thank the sponsors of the 2002 UTAM Consortium for their financial support . I thank Alan King and Alan Leeds for providing the data set and helpful instructions. I thank Prof. Schuster for picking the traveltimes.

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