Transcript Impact of MD on AVO Inversion

MD + AVO Inversion
Jianhua Yu,
University of Utah
Jianxing Hu
GXT
Outline
Motivation
Methodology
Numerical Tests
Conclusions
Amplitude Preserved Prestack
Migration + AVO Inversion
Seismic Trace
S
G
Incorrect Contribution
Layer 1
Migration
Ellipse
Layer 2
Actual reflection point
Influences on CRG Image
Migration noise
Footprints due to the coarse
acquisition geometry
How to deal with above problems?
Motivation
MD:
• Reduce prestack migration noise
and artifacts
• Increase CRG spatial resolution
• Improve AVO attribute inversion
Outline
Motivation
Methodology
Numerical Tests
Conclusions
Prestack Migration
m’ = L L
d mbut d = L m
T
Migrated Section
Data
Migration Image m’ =
True Reflectivity Model m
Migration Deconvolution
T
-1
m = (L L ) m’
Reflectivity
Migrated Imaage
or CRG
Deblurring operator
Processing Steps:
Preprocessing : Filtering, amplitude
balancing, and demultiple
Velocity analysis and velocity estimate for
migration in time domain
Prestack migration to generate the migrated
common offset (CO) sections
Processing Steps:
Apply MD to common offset sections
Normal AVO parameter Inversion
Apply MD to AVO section
Outline
Motivation
Methodology
Numerical Tests
Conclusions
Outline
Motivation
Methodology
Numerical Tests
Synthetic data
Field marine data
Conclusions
CO (45-55) Section
1
X(km)
0
5
0
1
X(km)
CDP 150
2.5
Mig
2.5
MD
5
Closeup of COG (45-55) Section
1
X(km)
0.5
2
1
X(km)
0.5
CDP 150
2.5
Mig
2.5
MD
2
Closeup of One CDP Gather
1
X(km)
1.8
1
0.6
Mig
1.8
0.6
1.8
X(km)
MD
1.8
Spectrums of Mig and MD Images
100
Trace No.
0.0
110
100
Trace No.
0.0
CDP 150
Mig
60
MD
60
110
Outline
Motivation
Methodology
Numerical Tests
Synthetic data
Field data I
Conclusions
Offset (km)
0.26
1.0
3.0
Velocity (km/s)
2.0
CDP 150
1.5
1.0
3.0
3.5
CDP 150
RMS Amplitudes
200
Shot Number
800
-6.0
-3.5
Raw data
-6.0
-3.5
After preprocessed
Offset (km)
0.0
0.26
2.0
Raw data
3.0
Offset (km)
0.26
2.0
Demultiple
Offset (km)
0.26
2.0
Multiples
Offset (km)
0.0
0.26
2.0
Offset (km)
0.0
raw data
3.0
0.26
2.0
Demultiple
3.0
Offset (km)
0.0
0.26
2.0
Offset (km)
0.0
raw data
0.26
2.0
Demultiple
AVO
?
3.0
3.0
Comparison of Estimated RMS
Velocity and Well Sonic Data
Time (s)
0
3
5
Well Vrms
1
Well Vint
Estimated Vrms
MD Result in Time Domain
12.1
0
7
X (km)
Zone of interest
Mig
13.6
Before 20
MD
Mig+MD
- +2.3
-3.6
3.5
Zone of interest
After MD
Crossplot of A and B before MD
0.4
Near Well A
Time interval:
1900-2900 ms
-0.4
-0.4
A
0.4
Crossplot of A and B after MD
0.4
Near Well A
Time interval:
1900-2900 ms
-0.4
-0.4
A
0.4
Crossplot of A and B Based on Well log from Well
1 (from C.-S. Yin, M.L. Batzle, and C. C. Mosher)
0.4
Depth:
1900-3100 m
-0.4
-0.4
A
0.4
Well Data
After MD
Before MD
0.4
-0.4
-0.4
A
0.4 -0.4
A
0.4 -0.4
A
0.4
Outline
Motivation
Methodology
Numerical Tests
Synthetic data
Field data II
Conclusions
Amplitude within Geometry Map
1
Shot Number
800
177
0.03
0.005
1
0
8
Velocity Scanning of CMP Gathers
CDP 4600
CDP 4750
CDP 4850
CDP 5000
CDP 5500
CDP 6000
CRG before and After MD
0.5
Offset (km)
Before MD
Before
MD
After MD
After MD
Multiple
Multiple
AVO Parameter: A*B
0
0
2.0
Before MD
X (km)
15
AVO Parameter: A*B
0
2.0
X (km)
0
After MD
15
Outline
Motivation
Methodology
Numerical Tests
Conclusions
Conclusions
Improves stratigraphyic resolution
Attenuate migration noise and
artifacts
Help to identify lithology
anomaly in AVO attribute
sections
Conclusions
Amplitude fidelity is still explored
when designing MD operator
Acknowledgments
• Thank Alan Leeds for his constructive
comments and suggestions.
• Thank ChevronTxaco and WesternGeco for
providing the data sets
• Thank UTAM sponsors for their financial
support