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

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

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

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

5. Migration Problem Seismic Trace Migration Ellipse Layer 1 Layer 2
Incorrect Contribution
Layer 1
Layer 2
Actual reflection point

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

38. Future Work 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

39. Acknowledgment
Thank 2001 UTAM sponsors for the financial support