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Global seismic event tracking by traveltime minimization

Global seismic event tracking by traveltime minimization. Morgan Brown, Scott Morton, and Gary Whittle Hess Corporation. Existing Picking Technology. Extrapolation pickers “Grow” away from seed picks Short-sighted Correlation, amplitude “Runaway” picks Single-valued horizons

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Global seismic event tracking by traveltime minimization

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  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

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