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Impact of MD on AVO Inversion

Impact of MD on AVO Inversion. Jianhua Yu University of Utah. Outline. Motivation. Methodology. Numerical Tests. Synthetic data. Field marine data. Conclusions. Prestack migration to generate the common offset data, CRGs, and angle gathers. AVO analysis or inversion (Shuey, 1985).

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Impact of MD on AVO Inversion

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  1. Impact of MD on AVO Inversion Jianhua Yu University of Utah

  2. Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions

  3. Prestack migration to generate the common offset data, CRGs, and angle gathers AVO analysis or inversion (Shuey, 1985) Prestack migration based AVO Inversion

  4. Preprocessing such as amplitude balance, demultiple etc. Migration noise, footprint due to coarse acquisition What Influences the Accuracy of AVO?

  5. IncorrectContribution Migration Ellipse Actual reflection point Migration Problem Seismic Trace G S Layer 1 Layer 2

  6. Migration Deconvolution • Improve prestack migration image • Reduce prestack migration noise and artifacts

  7. Motivation • Develop a MD-AVO method • Improve data for AVO analysis and seismic attribute analysis • Reduce migration artifacts

  8. Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions

  9. T m’ = Ld L m d = L m but Data Migrated Section Migration Section=Blurred Image of true reflectivity model m Migration Deconvolution

  10. Deconvolve the point scatterer response from the migration image T -1 m = (L L ) m’ Reflectivity Migrated Section Deblurring filter How to Get the True Reflectivity Model m

  11. Data in common offset domain satisfies the local property of MD filter Common offset section is natural domain for AVO analysis How MD conjunct with AVO

  12. Velocity analysis and estimate RMS velocity model for migration in time domain Prestack migration/inversion to generate the migrated COG and angle gathers Processing Steps: Preprocessing : Geometric spreading correction, amplitude balancing, and demultiple

  13. Apply MD to common offset sections Normal AVO parameter inversion Apply MD to AVO section MD-AVO Methodology

  14. Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions

  15. Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions

  16. 0 0 2.5 2.5 Prestack Migrated COG (45-55) Section X(km) X(km) 1 5 1 5 CDP 150 Time (s) Mig Mig + MD

  17. 0.5 0.5 2.5 2.5 Closeup of COG (45-55) Section X(km) X(km) 1 2 1 2 CDP 150 Time (s) Mig Mig+ MD

  18. Spectrums of Mig and MD Images 0.0 0.0 60 60 Trace No. Trace No. 100 110 100 110 CDP 150 Frequency (Hz) Mig Mig + MD

  19. 0.6 0.6 1.8 1.8 Close-up of One CRG X(km) X(km) 1 1.8 1 1.8 Time (s) Mig Mig + MD

  20. Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions

  21. 1.0 1.0 3.0 3.0 Offset (km) Velocity (km/s) 0.26 2.0 1.5 3.5 CDP 150 CDP 150 Time (s)

  22. Shot Number 200 800 -6.0 1.442 Offset (km) Raw data -3.5 -6.0 0.322 -3.5 After preprocessed RMS Amp. before and after preprocessing

  23. -1 T T m = (L L ) Ld Get ghosts: Dg=Lmg Velocity model Seismic data Hyperbolic operator Transpose of L Primary: dp=d-dg Least Squares Inversion for Demultiples(Taner et al. 1969; Lumely et al., 1998; Zhao, 1996)

  24. Offset (km) Offset (km) Offset (km) 0.26 0.26 0.26 2.0 2.0 2.0 0.0 3.0 CDP1300 CDP1300 CDP1300 Time (s) Raw data Multiples Demultiple

  25. 0.0 0.0 3.0 3.0 Offset (km) Offset (km) 0.26 2.0 0.26 2.0 CDP 1300 CDP 1300 Time (s) NMO raw data NMO demultiple

  26. 0.0 0.0 3.0 3.0 Velocity (km/s) Velocity (km/s) 1.5 3.5 1.5 3.5 CDP 1300 CDP 1300 Time (s) Raw data Demultiple

  27. 0.0 0.0 2.1 AVO ? 3.0 3.0 Offset (km) Offset (km) 0.26 2.0 0.26 2.0 CDP 1764 CDP 1764 Time (s) NMO raw data NMO demultiple

  28. RMS Velocity Model X (km) 0 21 0 3.5 Time (s) 1.5 m/s 5.0

  29. Well Vrms Well Vint Estimated Vrms Comparison of Estimated RMS Velocity and Well Sonic Data Time (s) 0 3 5 Velocity (km/s) 1

  30. Stacked Section WELL X (km) 20 7 0 Time (s) 3.5

  31. Migration Section X (km) 20 7 0 Time (s) 3.5

  32. MD Result X (km) 20 7 0 Time (s) 3.5

  33. Reservoir Reservoir Comparison of Mig and MD X (km) X (km) 12 18 12 18 0 Mig Mig+MD Time (s) 3.5

  34. P S P S Reservoir - +2.3 Reservoir - -3.6 * AVO Parameter : X (km) 13.6 12.1 1.98 Before MD 2.20 Time (s) 1.98 After MD 2.20

  35. Reservoir Reservoir HCI Section Before and After MD X (km) X (km) 18 7 18 7 1.6 Time (s) 2.7 After MD Before MD

  36. Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions

  37. Improves stratigraphic resolution Attenuates migration noise and artifacts Helps to identify lithology anomaly in AVO section Conclusions

  38. Blind Test on More Real Data (We look forward to the donation of data from sponsors) Develop 3-D Prestack MD for Field Data Processing Future Work

  39. Acknowledgment • Thank 2001 UTAM sponsors for the financial support

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