Quantifying Seismic Reflectivity

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Quantifying Seismic Reflectivity
Fred Hilterman Distinguished Research Professor
University of Houston Chief Scientist
Geokinetics Data Processing and
Interpretation April 28, 2010
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Birth of Fluid Factor George Smith Maurice
Gidlow South Africa - 1986
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Fluid Factor Review
Class 1 AVO
2.9
Stack
3.0
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Fluid Factor Review
Class 1 AVO
2.9
Stack
3.0
2.9
NIP
3.0
Brine saturated ?F 0 Gas Saturated ?F
NIPGAS- NIPWET
2.9
NIS
3.0
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Fluid Factor Review
2.9
Stack
3.0
2.9
Gas
Oil
NIP - 0.56 NIS
3.0
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Calibrating Fluid Factor to Well-Log Data
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Fluid Factor from Normal Incidence
151 wells from South Marsh Island
(NIGAS-NIWET)
Wet
Oil
Gas
NIHYDROCARBON-NIWET ? Fluid Factor
NI varies significantly for gas- and
brine-saturated sand but (NIGAS-NIWET) changes
little.
Reservoir porosity 10-33 Encasing shale
2600-4200 m/s
How is Fluid Factor extracted from seismic data?
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Fluid Factor from NIP NIS
?F(t) NIP(t) - ? NIS(t) (Smith
and Gidlow) ?F ? 0
In wet zones ?F ?
(NIP,GAS-NIP,WET) At top of reservoir

151 wells in South Marsh Island
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Unique Properties of Fluid Factor
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Fluid Factor Boundary or Layer Property?
NIGAS NIWET ?F
-
?
-
?F relates to gas/water contact -NIGWC not
encasing shale.
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Fluid Factor 9-m Wet Thin Bed
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Fluid Factor 9-m Gas Thin Bed
VP 2280 m/s
VP 2280 m/s
VP 1628 m/s
VP 3370 m/s

VP 3490 m/s

VP 2280 m/s
NIP
NIS
Approximately 109 increase in amplitude
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Thin Bed Fluid Factor vs. NI
Normal-Incident Reflectivity
NI f( VP1, VP2, Rho1, Rho2) 2? ?t/T ?t
thin-bed traveltime T wavelet period

• Fluid factor independent
• shale properties
• reservoir porosity
• upper shale ? lower shale

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Field Data
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GOM Oil and Gas Reservoir
Reservoir exhibits fault shadow velocity anomaly
Well Production Early 1970s Seismic Data
1996 as OBS Seismic Processing 2008
Seismic data from Fairfield Industry, Inc.
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AVO Inversion NIP NIS
Seismic NIP
Seismic NIS
400
1500
WET
WET
4.2 miles
0
-200
-1500
-800
4.6 miles
Zhou 2009
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Fluid-Factor Projection Line
Calibrated Fluid Factor
NIP(2)0.3266 NIS(2)0.0022 R20.8408
NIP 0.33 NIS .002 R2 0.84
0.02
0
Calibrated NIP
-0.04
Fault
Wet area Whole survey
-0.08
Fluid Factor NIP -.33 NIS - .002
Calibrated NIS
Zhou 2009
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Fluid Factor Prediction of Pore Fluid
3 producing wells correctly located
Gas zone correctly located
Gas and oil zones generally tie depth contours
Calibrated fluid factor is an accurate pore-fluid
discriminator.
Zhou 2009
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Summary Fluid-Factor Properties

1. independent of shale properties above or below
   reservoir.

1. independent of reservoir porosity.

3. independent of wavelet shape.
4. related to NI of hydrocarbon/water contact.
5. function of thin-bed traveltime and pore
fluid.
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Field Study Conclusions

• NIP vs. NIS horizon crossplot provides
• E?FWET 0.

2. Regional well-log curves provide
Seismic to well-log amplitude calibration.
3. With questionable wavelet and low-frequency
control, ?F was better pore-fluid
discriminator than PI or ??.
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Thanks for your attention.