Sequence of Calculations for course participants.pptx

Seismic description and work.

1. Computation Sequence for designing seismic field acquisition parameters Authored by: Albin K. Kerekes Geophysicist Bibi C. Kerekes (Aritman) Geophysicist – Engineer Liberty Seismic Consultants Inc. Preliminary Document – Not to be copied!

2. Study of representative seismic velocity function Tasks to accomplish: Bring all velocity data to a common datum Select the most reliable velocity data Establish velocity function/gradient

3. Mathematics of the Dix equation

4. Multi-layer velocity model Second layer Fifth layer Fourth layer Third layer First layer Receiver Source Task to establish: Establish a multi-layer model where within each layer velocity increases linearly with depth Establish seismic target zone

5. Wavelets and the “Stick-o-gram” Tasks to establish: Establish wavelet characteristics in terms of bandwidth in octaves and Hertz To provide desired vertical resolution To provide desired horizontal resolution To provide desired velocity resolution Establish reflection coefficients (“Stick-o-gram”)

6. Stage-1 of pertinent calculations Calculate instantaneous velocities Calculate average velocities Calculate RMS velocities

7. Stage-2 of pertinent calculations Calculate maximum frequency component Calculate dominant frequency

8. Stage-3 of pertinent calculations Establish maximum interval velocity above target zone Calculate derivative of average velocity with respect to two-way time for target zone

9. Stage-4 of pertinent calculations Establish allowable stretch factor Calculate offsets for allowable stretch factor within target zone

10. Stage-5 of pertinent calculations Establish desired velocity accuracy ( ) Calculate offsets for desired velocity resolution within the target zone

11. Stage-6 of pertinent calculations Establish offset distribution

12. Stage-7 of pertinent calculations Calculate horizontal resolution Calculate vertical resolution

13. Stage-8 of pertinent calculations Establish near surface velocity Calculate beam angle for “diving waves” Calculate beam angle for “transmission window”

14. Stage-9 of pertinent calculations Calculate %Energy beamed Calculate %Energy trapped Calculate dB of energy ratio

15. Stage-10 of pertinent calculations Establish maximum structural dip within the target zone Calculate apparent dip angle Calculate migration aperture

16. Stage-11 of pertinent calculations Calculate spatial sample rate for down-dip, far-trace data Calculate spatial sample rate for zero offset data Calculate temporal sample rate in milliseconds Establish trace interval or surface bin size for shallowest target Establish number of required channels

17. Stage-12 of pertinent calculations Calculate relative amplitude decay Calculate relative spectral decay Calculate relative total decay

18. Stage-13 of pertinent calculations Calculate maximum bend angle for 2D Calculate minimum distance bent for 2D Calculate maximum feathering angle for marine seismic Calculate minimum radius of line curvature

19. Stage-14 of pertinent calculations Calculate pass band of spatial frequencies in line Calculate pass band of spatial frequencies broadside Calculate reject limit of spatial frequencies

20. Stage-15 of pertinent calculations Establish required minimum fold Calculate Migration Stack Fold ratio Calculate Common Conversion Point offset

21. Stage-16 of pertinent calculations Establish the required number of source elements for a single source point Design one-dimensional arrays for 2D seismic survey Design two-dimensional arrays for 3D seismic survey

22. Stage-17 of pertinent calculations Establish near-surface velocity Establish dominant frequency Show source array beaming characteristics in polar coordinates

23. Stage-18 of pertinent calculations Establish the required spectrum of frequencies Design dB/Hz boost functions to also address ground compaction and ground resonance

24. Stage-19 of pertinent calculations Establish the required number of receiver elements for a single channel Design receiver array for ideal spatial anti-aliasing characteristics

25. Stage-20 of pertinent calculations Calculate total temporal multiplicity and the corresponding signal-to-noise ratio Calculate total spatial multiplicity and the corresponding signal-to-noise ratio Calculate total multiplicity and the corresponding signal-to-noise ratio

26. Stage-21 of pertinent calculations Calculate difference between hyperbolic and non-hyperbolic NMO