michelle montano* don lawton gary margrave · unidentified company for access to the field vsp data...
TRANSCRIPT
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Michelle Montano* Don Lawton Gary Margrave
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Outline
Introduction Theory
— Spectral-ratio method — Dominant frequency matching
Study area Synthetic VSP data analysis Field VSP data analysis Conclusions Acknowledgements
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Introduction
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Down-going waves propagating to the borehole receivers. • The downgoing wavefield give us
access to the wavelet at different receiver depths.
• Oversaturation in the amplitudes in the shallow receivers results in an overestimation of Q.
• Shallow layers are expected to show low Q values because poorly consolidated rocks are usually present.
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Introduction
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Up-going waves propagating to the borehole receivers.
• Using the upgoing wavefield may help to estimate Q in the shallow layers.
• Reflectors can be used as secondary sources.
• In this case the source would be farther from the shallow receivers.
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Theory
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Study Area
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VSP Geometry
• Fourteen source points with dynamite and an EnviroVibe source.
• 222 receivers at 2m spacing (60-500m depth).
Taken from, Hall et al. (2012)
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Well log data
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Density and p-wave velocity logs, blocked into five horizontal layers.
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Synthetic VSP data analysis
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Forward Modelling using well log data from Well B.
30m
10m
Receiver Depth
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Synthetic VSP data analysis
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Forward Modelling using well log data from Well B.
50m
10m
Receiver Depth
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Synthetic VSP data analysis
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Forward Modelling using well log data from Well B.
80m
10m
Receiver Depth
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𝑑=30𝑚 𝑑=50𝑚
𝑑=80𝑚
Down-going wavefield
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Synthetic VSP data analysis
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Forward Modelling based on Well B, showing up-going events. Flipped in depth
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𝑑=30𝑚 𝑑=50𝑚
𝑑=80𝑚
Up-going wavefield
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Field VSP Data Analysis Dynamite Source
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Field VSP Data Analysis
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100
200
300
400
500
Rec. Depth (m)
100
200
300
400
500
600
700
Tim
e (m
s)
Seismic gather: Shot point 1 using a dynamite source (Z component)
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Amplitude Spectra – Downgoing wavefield
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50
100
150
200
250
300
350
400
450
100
200
300
400
500
Rec. Depth (m)
Freq
. (Hz
)
-10dB
-20dB
-30dB
-40dB
0dB
-50dB
-60dB
Amp
Shot point 1 using a dynamite source (Z component)
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50
100
150
200
250
Tim
e (m
s)
100
200
300
400
500
Rec. Depth (m) Freq (Hz)
100
200
300
400
500
0
Cum. Attenuation
0.00
4
0.00
8
0.01
2
0
200
300
400
500
100
Depth (m)
Spectral-ratio method from VISTA software Frequency band: 30-130 Hz
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Field VSP Data Analysis
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100
200
300
400
500
600
700
Tim
e (m
s)
100
200
300
400
500
Flipped Rec. Depth (m)
Seismic Gather: Shot point 1 using a dynamite source (Z component) - Flipped
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Amplitude Spectra - Upgoing wavefield
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100
200
300
400
500
Flipped Rec. Depth (m)
-10dB
-20dB
-30dB
-40dB
0dB
-50dB
-60dB
Amp
50
100
150
200
250
300
350
400
450
Freq
. (Hz
)
Shot point 1 using a dynamite source (Z component)
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Freq (Hz)
100
200
300
400
500
0
Cum. Attenuation
0.01
0.02
0.03
0 0.04
100
200
300
400
500
Rec. Depth (m)
550
600
650
700
750
Tim
e (m
s)
Spectral-ratio method from VISTA software
Depth
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Field VSP Data Analysis EnviroVibe Source
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Field VSP Data Analysis
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100
200
300
400
500
600
700
Tim
e (m
s)
100
200
300
400
500
Rec. Depth (m)
Seismic Gather: Shot point 1 using an EnviroVibe source (Z component)
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Amplitude Spectra - Downgoing wavefield
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100
200
300
400
500
Rec. Depth (m)
50
100
150
200
250
300
350
400
450
Freq
. (Hz
)
-10dB
-20dB
-30dB
-40dB
0dB
-50dB
-60dB
Amp
Shot point 1 using an EnviroVibe source (Z component)
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50
100
150
200
Tim
e (m
s) 200
300
400
500
100
Depth (m)
100
200
300
400
500
Rec. Depth (m) Freq (Hz)
100
200
300
400
500
0
Cum. Attenuation
0.00
4
0.00
8
0.01
2
0
Spectral-ratio method from VISTA software. Frequency band: 30-250 Hz
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50
100
150
200
Tim
e (m
s)
100
200
300
400
500
Rec. Depth (m) Freq (Hz)
100
200
300
400
500
0
Cum. Attenuation
0.00
4
0.00
8
0.01
2
0
200
300
400
500
100
Depth (m)
Spectral-ratio method from VISTA software. Frequency band: 30-130 Hz
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EnviroVibe Source
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Field VSP Data Analysis
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100
200
300
400
500
Rec. Depth (m)
200
400
600
800
1000
Tim
e (m
s)
Seismic Gather: Shot point 1 using an EnviroVibe source (Hmax component)
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Amplitude Spectra - Downgoing shear wave
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100
200
300
400
500
Rec. Depth (m)
50
100
150
200
250
300
350
400
450
Freq
. (Hz
)
-10dB
-20dB
-30dB
-40dB
0dB
-50dB
-60dB
Amp
Shot point 1 using an EnviroVibe source (Hmax component)
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100
200
300
Rec. Depth (m)
400
600
800
1000
Tim
e (m
s)
Freq (Hz)
20
40
60
0
Cum. Attenuation
0.04
0.08
0
200
300
400
500
100
Depth (m)
Spectral-ratio method from VISTA software. Frequency band: 10-40 Hz
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Q estimation from down-going wavefield
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Spectral-ratio method from VISTA software
A B
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QP estimations using dominant frequency
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CREWES Toolbox
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Conclusions
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Conclusions
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Acknowledgements
Don Lawton Gary Margrave Unidentified company for access to the field VSP
data CREWES sponsors NSERC through grant CRDPJ 379744-08. GEDCO/Schlumberger for VISTA software CREWES students and staff
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Thanks!
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References
Aki K., and Richards, P. G., 2002, Quantitative Seismology 2nd Edition, University Science Book.
Cheng, P., Margrave, G. F., Comparison of Q-estimation methods: an update: CREWES Research Report, 25, 14.1-14.38.
Hinds, R. C., Anderson, N. L., and Kuzmiski, R. D., 1996, VSP Interpretive Processing: Theory and Practice, Soc. Expl. Geophys.
Kjartansson, E., 1979, Constant Q-Wave Propagation and Attenuation, Journal of Geophysical Research, 84, 4737-4748.
Margrave, G. F., 2013, Q tools: Summary of CREWES software for Q modelling and analysis: CREWES Research Report, 25, 56.1-56.22.
Margrave, G. F, 2013, Method of Seismic Data Processing. Course Lecture Notes, Univ. of Calgary.
Margrave, G. F., 2014, Synthetic seismograms with Q and stratigraphic filtering: CREWES News, 26, Issue 2, p. 6-7.
Quan, Y., and Harris, J. M., 1997, Seismic attenuation tomography using the frequency shift method: Geophysics, 62, 895-905.
Hall, K. W., Lawton, D. C., Holloway, D., and Gallant, E. V., 2012, Walkaway 3C-VSP: CREWES Research Report, 24, 9.1-9.26.
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OutlineIntroductionIntroductionTheoryStudy AreaWell log dataSynthetic VSP data analysisSynthetic VSP data analysisSynthetic VSP data analysis Synthetic VSP data analysisSlide Number 13Field VSP Data AnalysisField VSP Data AnalysisAmplitude Spectra – Downgoing wavefield Field VSP Data AnalysisAmplitude Spectra - Upgoing wavefield Field VSP Data AnalysisField VSP Data AnalysisAmplitude Spectra - Downgoing wavefield Field VSP Data AnalysisAmplitude Spectra - Downgoing shear wave Q estimation from down-going wavefieldQP estimations using dominant frequencyConclusionsConclusionsAcknowledgementsReferences