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Allied Geophysical Lab Research Presentations April 2, 2014

Allied Geophysical Lab Research Presentations April 2, 2014. Near-Surface Events… Friend of Foe ?. Fred Hilterman Distinguished Research Professor EAS, University of Houston Chief Scientist Geokinetics Data Processing & Integrated Reservoir Geosciences. Field Record

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Allied Geophysical Lab Research Presentations April 2, 2014

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  1. Allied Geophysical LabResearch PresentationsApril 2, 2014 Near-Surface Events… Friend of Foe ? Fred Hilterman Distinguished Research Professor EAS, University of Houston Chief Scientist Geokinetics Data Processing & Integrated Reservoir Geosciences

  2. Field Record Typical Interpretation Problem What are shingles? Are they lateral gaps in the refractor? Objective: Provide quantitative insight into how near-surface events are generated. We’ll go the easy way … generate a catalog of synthetics. Oz Yilmaz

  3. Outline Near-Surface Events … • Elastic synthetics • Identify events • Define asymptotes of events • Vary near-surface thickness • Vary refractor thickness

  4. Modeling Philosophy Half Space Start with Simplest model ! 850 ft 5600, 0, 2.00 ft/s ft/s g/cc Half Space Refractor 9000, 0, 2.24

  5. Simplest Acoustic Model Half Space Acoustic VSHEAR = 0 850 ft 5600, 0, 2.00 ft/s ft/s g/cc Half Space Refractor 9000, 0, 2.24 Source-Receiver Offset 0 ft 5000 ft (P1P1) | | | | | | _ 0s _ _ _ _ _ .5s _ _ _ _ _ 1.0s _ _ _

  6. Acoustic Synthetic Air Acoustic VSHEAR = 0 850 ft 5600, 0, 2.00 ft/s ft/s g/cc Half Space Refractor 9000, 0, 2.24 Source-Receiver Offset 0 ft 0 ft 5000 ft 5000 ft | | | | | | | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ _ PCrit _ _ 1.0s _ _ _

  7. Acoustic Synthetic Air Acoustic VSHEAR = 0 (P1P1) 850 ft 2(P1P1) 5600, 0, 2.00 ft/s ft/s g/cc (P1P2P1) 3(P1P1) Half Space Refractor 4(P1P1) 2(P1P1)(P1P2P1) 9000, 0, 2.24 Source-Receiver Offset (P1P1)(P1P2P1) (P1P1) 0 ft 0 ft 5000 ft 5000 ft | | | | | | | | | | | | _ (P1P1)(P1P2P1) 0s _ 2(P1P1) P2 _ _ _ 3(P1P1) P1 _ .5s _ 4(P1P1) _ _ PCrit _ _ 1.0s _ _ _

  8. Trapped and Leaky Acoustic Modes Air Acoustic VSHEAR = 0 850 ft 5600, 0, 2.00 ft/s ft/s g/cc Half Space Refractor 9000, 0, 2.24 Source-Receiver Offset Trapped Modes 0 ft 0 ft 5000 ft 5000 ft | | | | | | | | | | | | _ 0s _ P2 _ _ _ P1 Leaky Modes _ .5s _ PCrit = P12/P2 _ _ PCrit PCrit _ _ 1.0s _ _ _

  9. Equivalent Elastic Model Air 850 ft 5600, 2600, 2.00 Elastic ft/s ft/s g/cc Half Space Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ _ _ _ _ .5s _ _ _ _ _ 1.0s _ _ _

  10. Event Identification – Elastic Model Air 850 ft Near Surface Direct, Rayleigh, ??? 5600, 2600, 2.00 ft/s ft/s g/cc Half Space Refractor 9000, 3960, 2.24 Rayleigh Wave P1 – Direct Arrival Source-Receiver Offset AGC 0 ft 5000 ft | | | | | | _ 0s _ _ _ S1 _ _ .5s _ _ _ _ _ 1.0s _ _ _

  11. Event Identification – Elastic Model Air (P1P1) 850 ft Reflections: P1P1 Head Waves: P1P2P1 2(P1P1) 5600, 2600, 2.00 ft/s ft/s g/cc (P1P2P1) 3(P1P1) Half Space Refractor 4(P1P1) 2(P1P1)(P1P2P1) 9000, 3960, 2.24 Asymptote P1 Source-Receiver Offset AGC (P1P1)(P1P2P1) 0 ft 5000 ft | | | | | | _ 0s _ _ _ _ _ .5s _ _ _ _ _ 1.0s _ _ _

  12. Event Identification – Elastic Model Air (P1P1)(P1S1) (P1S1) 850 ft Reflections: P1S1 Head Waves: P1P2S1 5600, 2600, 2.00 ft/s ft/s g/cc 2(P1P1)(P1S1) (P1P2S1) Half Space Refractor 2(P1P1)(P1P2S1) 9000, 3960, 2.24 3(P1P1)(P1S1) Source-Receiver Offset AGC (P1P1)(P1P2S1) 0 ft 5000 ft | | | | | | _ 0s _ _ _ _ _ .5s _ _ _ _ _ 1.0s _ _ _

  13. Event Identification – Elastic Model Air (S1S1) (S1P2S1) 850 ft Reflections: S1S1 Head Waves: S1P2S1 5600, 2600, 2.00 ft/s ft/s g/cc Half Space Refractor (P1P1)(S1S1) 9000, 3960, 2.24 (P1S1)(S1S1) Source-Receiver Offset 2(P1P1)(S1S1) AGC 0 ft 5000 ft (S1S2S1) | | | | | | _ 2(S1S1) 0s _ _ _ _ _ .5s _ _ _ Asymptote S1 _ _ 1.0s _ _ _

  14. Event Identification – Elastic Model Air 850 ft 24 Event Summary Four Groups 5600, 2600, 2.00 ft/s ft/s g/cc Half Space Refractor 9000, 3960, 2.24 Source-Receiver Offset (S1S1) AGC 0 ft 5000 ft (P1P1) (S1P2S1) | | | | | | _ 0s _ (P1P2P1) (S1S2S1) _ _ _ (P1S1) S1 P1 _ .5s _ (P1P2S1) Rayleigh _ _ _ _ 1.0s _ _ _

  15. Outline Near-Surface Events … • Elastic synthetics • Identify events • Define asymptotes of events • Vary near-surface thickness • Vary refractor thickness

  16. Limits and Asymptotes Air 850 ft Guided Waves Ground Roll 5600, 2600, 2.00 ft/s ft/s g/cc Half Space Refractor 9000, 3960, 2.24 Source-Receiver Offset AGC R1 .92 S1 R2 .92 S2 PCRIT = P12/P2 SCRIT= S12/S2 0 ft 5000 ft | | | | | | _ 0s _ Guided Waves (Trapped Modes) P2 _ _ P1 asymptote for all n(P1P1) _ S1 asymptote for all n(S1S1) P1 _ .5s _ Rayleigh Waves (Ground Roll) _ S2 R2 _ SCRIT PCrit R1 S1 _ _ 1.0s _ _ _

  17. Outline Near-Surface Events … • Elastic synthetics • Identify events • Define asymptotes of events • Vary near-surface thickness • Vary refractor thickness

  18. Near Surface Thickness Air 850 ft Thickness = 850 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit S1 _ _ 1.0s _ _ _

  19. Near Surface Thickness Air 450 ft Thickness = 450 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ Guided waves collect in PCrit-P1 cone .5s _ Post-critical S-waves collect in SCrit-S1 Cone _ R2 _ SCRIT R1 PCrit S1 _ _ 1.0s _ _ _

  20. Near Surface Thickness Air 400 ft Thickness = 400 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit _ _ 1.0s _ _ _

  21. Near Surface Thickness Air 350 ft Thickness = 350 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit _ _ 1.0s _ _ _

  22. Near Surface Thickness Air 300 ft Thickness = 300 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit _ _ 1.0s _ _ _

  23. Near Surface Thickness Air 250 ft Thickness = 250 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit _ _ 1.0s _ _ _

  24. Near Surface Thickness Air 200 ft Thickness = 200 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ Guided waves show phase velocity .5s _ Shear guided waves appear as ground roll _ R2 _ SCRIT R1 PCrit S1 _ _ 1.0s _ _ _

  25. Near Surface Thickness Air 150 ft Thickness = 150 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit _ _ 1.0s _ _ _

  26. Near Surface Thickness Air 90 ft Thickness = 90 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 Refractions overcome guided waves in PCrit-P1 cone as P1 layer thins _ .5s _ Long  appear in Rayleigh cone R1-R2 _ R2 _ SCRIT R1 PCrit S1 _ _ 1.0s _ _ _

  27. Near Surface Thickness Air 60 ft Thickness = 60 ft 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset P1 and Pcriteffects decrease as upper layer thickness decreases 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ As P1 layer thins refractions move to P2 .5s _ Post S1S1 and Rayleigh merge in SCrit-R2 cone _ R2 _ SCRIT R1 PCrit S1 _ _ 1.0s _ _ _

  28. Outline Near-Surface Events … • Elastic synthetics • Identify events • Define asymptotes of events • Vary near-surface thickness • Vary refractor thickness

  29. Refractor Thickness Variation Air 60 ft Refractor Thickness = Infinite 5600, 2600, 2.00 Half Space ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit S1 _ _ 1.0s _ _ _

  30. Refractor Thickness Variation Air 60 ft Refractor Thickness = 200 ft 5600, 2600, 2.00 200 ft ft/s ft/s g/cc Refractor 9000, 3960, 2.24 • Refractor thickness decreases, head wave • loses amplitude • horizontal velocity is constant Source-Receiver Offset Half 5400, 2380, 2.21 Space 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit _ _ 1.0s _ _ _

  31. Refractor Thickness Variation Air 60 ft Refractor Thickness = 100 ft 5600, 2600, 2.00 100 ft ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset Half 5400, 2380, 2.21 Space 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit _ _ 1.0s _ _ _

  32. Refractor Thickness Variation Air 60 ft Refractor Thickness = 50 ft 5600, 2600, 2.00 50 ft ft/s ft/s g/cc Refractor 9000, 3960, 2.24 Source-Receiver Offset Half 5400, 2380, 2.21 Space 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ P2 layer thins, refractions lose amplitude with offset .5s _ Post-critical S1S1 effects decrease _ R2 _ SCRIT R1 PCrit S1 _ _ 1.0s _ _ _

  33. Refractor Thickness Variation Air Shingling Thin Layer over Thin Refractor 60 ft Upper Layer 50 ft Refractor Lower Layer Source-Receiver Offset Half Space 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit S1 Oz Yilmaz _ _ 1.0s _ _ _

  34. Refractor Thickness Variation Air Shingling Thin Layer over Thin Refractor 60 ft Upper Layer 50 ft Refractor Lower Layer Source-Receiver Offset Half Space 0 ft 5000 ft | | | | | | _ 0s _ P2 _ _ • Shingling • nth Critical-angle reflection (amplitude =1) generates head wave • nth Head wave loses amplitude due to thin refractor layer • nth +1 Critical-angle reflection (amplitude =1) generates head wave • nth + 1 Head wave loses amplitude due to thin refractor layer • Repeat _ P1 _ .5s _ _ R2 _ SCRIT R1 PCrit S1 Oz Yilmaz _ _ 1.0s _ _ _

  35. Summary: Reflectivity Modeling of Near-Surface Events • Velocity asymptotes “quantify” event cones • Guided S-waves • Rayleigh waves • Guided P-waves • Refraction arrivals • Shingling and multiple refractions “quantified” by • P-wave and S-wave velocities • Thickness of upper layer and refractor Lessons from near-surface modeling Start with simplest model and learn with each model variation.

  36. That’s it! Thanks for your attention

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