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Raw shot gathers

Learn how to perform reflection velocity analysis for seismic data processing, including topics such as amplitude correction, NMO correction, and stacking.

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Raw shot gathers

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  1. Seismic data processing - Example #2 Raw shot gathers

  2. Amplitude correction

  3. Deconvolved data

  4. Resorting into CMP gathers

  5. Velocity analysis result

  6. Raw shot gathers

  7. NMO Correction

  8. Data “muting”

  9. F Stacking

  10. Amplitude correction

  11. Seismic migration

  12. Reflection velocity analysis • In order to carry out the “Normal Moveout Correction”, we make use of • The rms velocity to each reflector is required • We generate the required velocities using “reflection velocity analysis”

  13. Reflection velocity analysis • The equation indicates that the curvature of each reflection event is determined by (to, vrms) • to is obvious from the data • We require a method for estimating curvature

  14. Reflection velocity analysis • The objective is to find a velocity that “flattens” each event • We could test any given velocity estimate by correcting the reflection event • If the estimate is correct, the event is flattened • Too low a velocity guess, and the event is overcorrected • Too high a velocity, and the event is undercorrected

  15. Reflection velocity analysis • Begin with a test velocity • Apply normal moveout correction to the entire gather • Search for events that flatten, record (to,vrms) • Increment test velocity, repeat step 2 • Final result is a set of (to,vrms) pairs for this gather

  16. Reflection velocity analysis • Begin with a test velocity • Apply normal moveout correction to the entire gather • Search for events that flatten, record (to,vrms) • Increment test velocity, repeat step 2 • Final result is a set of (to,vrms) pairs for this gather

  17. Reflection velocity analysis “Velocity Spectrum” • This is a tool that enables fast picking of velocities The correct velocity is that which produces peak power along the moveout trajectory

  18. Reflection velocity analysis “Velocity Spectrum” • Stack power, or “semblance” is contoured as a function of (to, vrms) • Processor must pick local maxima, to find the velocity function

  19. Reflection velocity analysis “Velocity Spectrum” • Stack power, or “semblance” is contoured as a function of (to, vrms) • Processor must pick local maxima, to find the velocity function

  20. Velocity analysis result

  21. Reflection processing quiz - take one with you!

  22. Reflection velocity analysis

  23. Reflection velocity analysis “Velocity Spectrum” • The spectrum is quite robust in the presence of noise

  24. Reflection velocity analysis

  25. Next lecture: Introduction to Seismic migration

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