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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 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) Prestack migration based AVO Inversion
Preprocessing such as amplitude balance, demultiple etc. Migration noise, footprint due to coarse acquisition What Influences the Accuracy of AVO?
IncorrectContribution Migration Ellipse Actual reflection point Migration Problem Seismic Trace G S Layer 1 Layer 2
Migration Deconvolution • Improve prestack migration image • Reduce prestack migration noise and artifacts
Motivation • Develop a MD-AVO method • Improve data for AVO analysis and seismic attribute analysis • Reduce migration artifacts
Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions
T m’ = Ld L m d = L m but Data Migrated Section Migration Section=Blurred Image of true reflectivity model m Migration Deconvolution
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
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
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
Apply MD to common offset sections Normal AVO parameter inversion Apply MD to AVO section MD-AVO Methodology
Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions
Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions
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
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
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
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
Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions
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)
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
-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)
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
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
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
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
RMS Velocity Model X (km) 0 21 0 3.5 Time (s) 1.5 m/s 5.0
Well Vrms Well Vint Estimated Vrms Comparison of Estimated RMS Velocity and Well Sonic Data Time (s) 0 3 5 Velocity (km/s) 1
Stacked Section WELL X (km) 20 7 0 Time (s) 3.5
Migration Section X (km) 20 7 0 Time (s) 3.5
MD Result X (km) 20 7 0 Time (s) 3.5
Reservoir Reservoir Comparison of Mig and MD X (km) X (km) 12 18 12 18 0 Mig Mig+MD Time (s) 3.5
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
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
Outline Motivation Methodology Numerical Tests Synthetic data Field marine data Conclusions
Improves stratigraphic resolution Attenuates migration noise and artifacts Helps to identify lithology anomaly in AVO section Conclusions
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
Acknowledgment • Thank 2001 UTAM sponsors for the financial support