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Wavelet phase estimation without accurate time-depth conversion. Jiangbo Yu Advisor: Dr. John Castagna AGL update meeting May 2, 2012. content. Introduction Theory Results Conclusion. Introduction-Seismic-TO-well-tie. CONVOLUTION. Statistical wavelet from seismic. - PowerPoint PPT Presentation
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WAVELET PHASE ESTIMATION WITHOUT ACCURATE TIME-DEPTH CONVERSION
J IANGBO YUADVISOR: DR. JOHN CASTAGNAAGL UPDATE MEETINGMAY 2, 2012
CONTENT• Introduction• Theory• Results• Conclusion
INTRODUCTION-SEISMIC-TO-WELL-TIE
Edgar and van der Baan, 2009
Statistical wavelet from seismic Reflectivity series from well logs
QC initial tie
Phase rotate wavelet until maximum correlation is found
Final tie
CONVOLUTION
PROBLEMS OF SONIC LOG CALIBRATION• P-wave velocity from sonic log is different with seismic
velocity• Short logging runs, or gaps in sonic log coverage• Inaccurate time-depth conversion• Aggressively forcing a well tie will affect the estimated
wavelet
THEORY-- HISTOGRAM MATCHING PHASE ESTIMATION
-50 0 50
Zero-phase wavelet from seismic
0 20 40 60 80
0.05
0.1
0.15
0.2
0.25
0.3
Frequency (Hz)
Nor
mal
ized
spe
ctra
l am
plitu
de
Normalized Amplitude Spectrum
1. Zero-phase wavelet estimation
THEORY – HISTOGRAM MATCHING0
500
1000
1500
2000
Deconvolution output0
500
1000
1500
2000
Narrow-band reflectivity
0 20 40 60 80
0.05
0.1
0.15
0.2
Frequency (Hz)
Nor
mal
ized
spe
ctra
l am
plitu
de
Amplitude spectrum
0 20 40 60 80
0.05
0.1
0.15
0.2
Frequency (Hz)N
orm
aliz
ed s
pect
ral a
mpl
itude
Amplitude spectrum
-0.4 -0.2 0 0.2 0.4 0.60
0.5
1
1.5
2
2.5
Data
Den
sity
Amplitude histogram of inverted reflectivity
-0.4 -0.2 0 0.2 0.4 0.60
0.5
1
1.5
2
Data
Den
sity
Amplitude histogram of narrow-band reflectivity
2. Frequency domain deconvolution
THEORY – HISTOGRAM MATCHING
13-Oct-2011 10:26:46
-60
-40
-20
0
20
40
60
Tim
e (m
s)
Phase rotated waveletTrue wavelet
13-Oct-2011 10:26:46
-60
-40
-20
0
20
40
60
Tim
e (m
s)
Estimated WaveletEstimated wavelet
-200 -150 -100 -50 0 50 100 150 20018
20
22
24
26
28
30
32
97
Phase Rotation
Mis
fitTrue phase 90degree
THEORY – HISTOGRAM MATCHINGAssumption:Major part of the difference between inverted reflectivity amplitude distribution with well log derived reflectivity amplitude distribution is caused by the incorrect phase of waveletAdvantage:Will not be affected by inaccurate time-depth conversion
REAL DATA
Correlation:0.924
REAL DATA
-200 -150 -100 -50 0 50 100 150 2001.58
1.585
1.59
1.595
1.6
1.605
1.61
1.615x 107
-89
Phase rotation
Mis
fit
Estimated from seismic-to-well tie (-86 degree) Estimated from histogram matching (-89 degree)
RESULT– REAL REFLECTIVITY
07-Mar-2012 17:41:13
-60
-40
-20
0
20
40
60
Tim
e (m
s)
Wiener Filter
RESULT– ACCURATE TIME-DEPTH CONVERSION
13-Oct-2011 10:26:46
-60
-40
-20
0
20
40
60
Tim
e (m
s)
Phase rotated waveletTrue wavelet
13-Oct-2011 10:26:46
-60
-40
-20
0
20
40
60
Time (m
s)
Estimated WaveletHistogram matching Wiener filter
RESULT– BULK SHIFT100
200
300
400
500
600
Tim
e (m
s)
Synthetic trace (black) vs. Bulk shifted synthetic trace (w)
-60
-40
-20
0
20
40
60
Tim
e (m
s)
True wavelet
-60
-40
-20
0
20
40
60
Tim
e (m
s)
Wiener Filter
13-Oct-2011 10:26:46
-60
-40
-20
0
20
40
60
Time (m
s)
Estimated WaveletHistogram matching Wiener filter
True wavelet
RESULT– DYNAMIC SHIFT100
200
300
400
500
600
Tim
e (m
s)
Synthetic trace (black) vs. Dynamic shifted synthetic trace (w)
-60
-40
-20
0
20
40
60
Tim
e (m
s)
Wiener Filter
13-Oct-2011 10:26:46
-60
-40
-20
0
20
40
60
Time (m
s)
Estimated WaveletHistogram matching-60
-40
-20
0
20
40
60
Tim
e (m
s)
True waveletTrue wavelet Wiener filter
CONCLUSION• Inaccurate time-depth conversion will affect seismic
wavelet estimation through well-tie• Histogram matching could estimate wavelet phase
correctly even with a wrong time-depth conversion