MD + AVO Inversion Jianhua Yu, University of Utah Jianxing Hu GXT

Outline Motivation Methodology Numerical Tests Conclusions

Seismic Trace G S Layer 2 Layer 1 Incorrect Contribution Actual reflection point Amplitude Preserved Prestack Migration + AVO Inversion Migration Ellipse

Influences on CRG Image Migration noise How to deal with above problems? Footprints due to the coarse acquisition geometry

Motivation Increase CRG spatial resolutionIncrease CRG spatial resolution Reduce prestack migration noise and artifactsReduce prestack migration noise and artifacts Improve AVO attribute inversionImprove AVO attribute inversion MD:

Outline Motivation Methodology Numerical Tests Conclusions

m’ = L d T Prestack Migration but d = L m Migrated Section Data L m Migration Image m’ = True Reflectivity Model m

T m = (L L ) m’ Migration Deconvolution Reflectivity Deblurring operator Migrated Imaage or CRG

Processing Steps: Preprocessing : Filtering, amplitude balancing, and demultiple Prestack migration to generate the migrated common offset (CO) sections Velocity analysis and velocity estimate for migration in time domain

Apply MD to common offset sections Normal AVO parameter Inversion Apply MD to AVO section Processing Steps:

Outline Motivation Methodology Numerical Tests Conclusions

Outline Motivation Methodology Numerical Tests Conclusions Synthetic data Field marine data

Time (s) CDP 150 X(km) CO (45-55) Section MDMig

Time (s) CDP 150 X(km) Closeup of COG (45-55) Section MDMig

Time (s) X(km) Closeup of One CDP Gather MD Mig

Frequency (Hz) CDP 150 Trace No. Spectrums of Mig and MD Images MDMig

Outline Motivation Methodology Numerical Tests Conclusions Synthetic data Field data I

Time (s) CDP 150 Offset (km)Velocity (km/s) CDP 150

Offset (km) Shot Number RMS Amplitudes Raw data After preprocessed

Time (s) Offset (km) Offset (km) Offset (km) Raw dataDemultipleMultiples

Time (s) Offset (km) raw dataDemultiple

Time (s) Offset (km) AVO AVO ? raw dataDemultiple

Velocity (km/s) Time (s) Comparison of Estimated RMS Velocity and Well Sonic Data Well Vint Well Vrms Estimated Vrms

Time (s) X (km) MD Result in Time Domain Mig+MDMig Before MD After MD Zone of interest

B A Crossplot of A and B before MD Near Well A Time interval: ms

B A Crossplot of A and B after MD Near Well A Time interval: ms

B A Crossplot of A and B Based on Well log from Well 1 ( from C.-S. Yin, M.L. Batzle, and C. C. Mosher) Depth: m

B A Well Data A A After MDBefore MD

Outline Motivation Methodology Numerical Tests Conclusions Synthetic data Field data II

Amplitude within Geometry Map 1 Receiver Number 177 Shot Number

Velocity Scanning of CMP Gathers CDP 4600 CDP Time (s) 0 CDP 4850 CDP 5000CDP 5500CDP 6000

Time (s) Offset (km) CRG before and After MD Before MD After MD Before MDAfter MD Multiple

Time (s) X (km) AVO Parameter: A*B Before MD

Time (s) X (km) AVO Parameter: A*B After MD

Outline Motivation Methodology Numerical Tests Conclusions

Conclusions Improves stratigraphyic resolution Help to identify lithology anomaly in AVO attribute sections Attenuate migration noise and artifacts artifacts

Conclusions Amplitude fidelity is still explored when designing MD operator

Acknowledgments Thank ChevronTxaco and WesternGeco for providing the data setsThank ChevronTxaco and WesternGeco for providing the data sets Thank UTAM sponsors for their financial supportThank UTAM sponsors for their financial support Thank Alan Leeds for his constructive comments and suggestions.Thank Alan Leeds for his constructive comments and suggestions.