Global seismic event tracking by traveltime minimization

1. Global seismic event tracking by traveltime minimization Morgan Brown, Scott Morton, and Gary Whittle Hess Corporation

2. Existing Picking Technology • Extrapolation pickers • “Grow” away from seed picks • Short-sighted • Correlation, amplitude • “Runaway” picks • Single-valued horizons • Two-point pickers • Intuitive • Assume small variations about connecting line Brown et al., 2006 SEG

3. Extrapolation Picker Movie Brown et al., 2006 SEG

4. Two-point Picker Movie Brown et al., 2006 SEG

5. Salt Body Picking Woes ? Extrapolation picker: It follows reflector; at the end, it may or may not stop Brown et al., 2006 SEG

6. Salt Body Picking Woes Two-point picker: It knows when to stop, but it can’t stray far from a straight line Brown et al., 2006 SEG

7. Salt Body Picking Woes ? ? Brown et al., 2006 SEG

8. Salt Body Picking Woes ? ? Extrapolation picker: Either stops, or runs free. Neither choice is good. Brown et al., 2006 SEG

9. Existing Picking Technology • Extrapolation pickers… …work great locally, but bad globally • Two point pickers… …intuitive, but how to guide? • Wanted: Local accuracy of extrapolation picker, globality of two-point picker. Brown et al., 2006 SEG

10. Crosswell Seismic Experiment 5000 “Coal Seam” Compute first-arrival traveltimes 4000 3000 2000 1000 Velocity (m/sec) Brown et al., 2006 SEG

11. Crosswell Seismic Experiment 5000 “Coal Seam” Compute first-arrival traveltimes Coal Seam  “wave guide” 4000 3000 2000 1000 Velocity (m/sec) Brown et al., 2006 SEG

12. Traveltime and Tracking? • How do waves get from source to receiver? • Follow the minimum traveltime path • “Wave guide” • Seismic amplitude looks like wave guide! • High amplitude Fast velocity • Low amplitude  Slow velocity • How to track event from pick A to pick B? • Convert seismic amplitude to “pseudo-velocity” • Follow the minimum “traveltime” path Brown et al., 2006 SEG

13. Our Method for Picking pick A pick B Bias seismic amplitude by positive number Are all values > 0? Valid pseudo-velocity Compute “traveltime” from pick A Follow minimum traveltime path to pick B Brown et al., 2006 SEG

14. Following Minimum Traveltime Path pick B • Assumption: Unique, minimum-traveltime path -----.--------.between source and receiver. t +(t – t)=t for all points on the path Compute “traveltime” from pick A Compute “traveltime” from pick B Add them together Global minimum (stationary path) TT from A to B: t TT from A to any point: t TT from B to A: t TT from B to any point: t-t pick A Matsuoka & Ezaka, 1992, Ray tracing using reciprocity, Geophysics, v.57 #2, P.326-333 Brown et al., 2006 SEG

15. Back to the “Salt Body” x pick A pick B z Small on the event Large everywhere else Global guide from A to B Brown et al., 2006 SEG

16. x pick A pick B z Multi-valued Horizons The functional doesn’t care if the horizon is multi-valued, but does your software? Brown et al., 2006 SEG

17. Branching events x pick A pick B z Brown et al., 2006 SEG

18. Amplitude Holes x pick A pick B z Brown et al., 2006 SEG

19. Our Method Movie • Pick endpoints • Trouble? Add pick • No erasing • No toggling Brown et al., 2006 SEG

20. 3D Extensions • Our method intrinsically 2D operation • Divide-and-conquer extension to 3D • Delaunay • Inline/Crossline • Both are spatially bounded • Extrapolation picker: not bounded • Unless user picks • Better anyway? Brown et al., 2006 SEG

21. Delaunay Triangulation x y … Delaunay 3D Picking Pick triangle edges Pick triangle interior = seed pick Brown et al., 2006 SEG

22. Delaunay Triangulation x y Delaunay 3D Picking Loop over triangles { Pick triangle edges Pick triangle interior } = seed pick Brown et al., 2006 SEG

23. Inline/Crossline x y … Loop over inlines { Fill between seed points } Loop over crosslines { Fill between existing picks } = seed pick Brown et al., 2006 SEG

24. Gulf of Mexico Top Salt Example • 600 Lines • 400 CMPs • Pick every 10th line and CMP • Run 3D autotracker once • Compare Our Method to Competitor Brown et al., 2006 SEG

25. Existing Package: 6-line picking movie • Quick-and-dirty • No erasing • Ignore glitches • 83 seconds • 38 button presses • 12 key presses Brown et al., 2006 SEG

26. Our Method: 6-line picking movie • No need to erase • 67 seconds • 39 button presses • no key presses Brown et al., 2006 SEG

27. Existing Package: Depth map x y pick every 10th inline and crossline, 3D extrapolation autotrack Brown et al., 2006 SEG

28. Our Method: Depth map x y Traverse pick every 10th inline and crossline, 3D Inline/Crossline autotrack Brown et al., 2006 SEG

29. Existing Package: Traverse Brown et al., 2006 SEG

30. Our Method: Traverse Brown et al., 2006 SEG

31. Conclusions • Existing: Locally accurate, globally blind • Our method… • Seismic amplitude  pseudo-velocity • Optimal path  minimum “traveltime” between ---------------seed picks • Globally* optimal • Intrinsically multi-valued • Automatic spatial boundary Brown et al., 2006 SEG

32. Discussion • Better pseudo-velocity? • Multi-valued • True 3D? Brown et al., 2006 SEG