Transcript Slide 5: Selecting Seismic Attributes and Proper Display

Selecting Seismic Attributes and
Proper Display Parameters
An abridged review of a study conducted
on 3-D seismic over Sooner Field, CO
By: William C. (Bill) Overman, MS
Geophysicist
Slide 2: Sooner Field overview
• Lower Cretaceous D-sand
• Stratagraphic component
– valley fill sand body
• Structural influence
critical to trap
• Significant IPP for the D-J
Basin
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Slide 3: Amplitude Seismic Attribute
• Amplitude from the top of
the D sand
• Strong energy from the
sand body
• Strong energy everywhere
else!
• Does not discriminate
prospective vs. back
ground
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Slide 4: Peak to Trough Attribute
• Anomaly only identifies
south half of the sand
body
• Does not present
additional drilling
opportunities!
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Slide 5: Instantaneous Frequency
• Crossline 82 through heart of the sand body
– Flattened on top of D-sand (black line)
– Base of D-sand .007 to .009 mils below (heavy red line)
– Horizon picks cycle through many colors, results in “noisy” attribute maps
• Frequency range 35 to 85 Hertz
• Separation of D-sand top and base (isochron) very subtle
• Separation of frequency bands un-mistakable
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Slide 6: Instantaneous Frequency
• Crossline 82 through heart of the sand body
– Base of D-sand .007 to .009 mils below (heavy red line)
– Time picks still cycle through white to blue often, “noisy”
• Frequency range 62 to 64 Hertz
– All data still present but most frequencies display either white or cyan
• Separation of D-sand top and base (isochron) very subtle
• Downward deflection of the white band still obvious
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Slide 7: D-sand Isochron Map
• Isochron variation from
0.007 to 0.009
– Variations mapped at below
seismic sample rate
– See full text for discussion
• Good correlation between
isochron and isopach
– discriminates prospective vs.
back ground
• Extends prospective area
to NW, along trend
• Geometry still does not
“look” like a sand body
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Slide 8: Instantaneous Frequency
from the Top of the D-Sand pick
• Experimentation showed
“best” presentation from
35 and 55 CPS
– Closest agreement with isopach
– Least peripheral “noise”
• All frequencies still
present, color for most just
set to white
• Good spatial correlation
with isochron map
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Slide 9: Isochron vs. Frequency
• Linear relationship of
isochron (Slide 7) to
frequency (Slide 8).
– Lower frequencies with
longer time
– Higher frequencies with
shorter times
– Correlation supports
validity of sub-sample rate
isochron values
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Slide 10: Isochron “Sweet Spots”
• Map of narrowly bounded
Instantaneous Frequency (62
to 64 Hertz), 4 mils. below
the top of the D-sand.
– Narrow frequency range
eliminates most peripheral
events.
• Maps within the isochron
and below the “noise” of the
D-sand interface (Slides 5
and 6).
• “Drill the White and avoid
the Cyan.” too simple?
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Slide 11: IPP vs. Isochron Time,
there is a problem…
• Tests assertions vs.
real life results!
• Color map of Initial
Production Potential
(IPP)
– Green is the color of $
– 900+ BOPD NE Sec.21
• Isochron time contours
– Contoured from Slide 10
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Slide 12: IPP vs. Structure
on the D-sand Top
• D-sand top depth map,
from time structure
map.
• Thick isochron (Slide
11) crosses 40’ low in
W ½, Sec. 21.
• Dry holes were drilled
on well control.
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Conclusions:
•
Peak to Trough attribute could properly locate wildcat
–
•
Isochron, though subtle, is a valid and useful attribute
–
–
–
•
High correlation to Instantaneous Frequency in the south
Good visual correlation to isopach
Good numerical correlation to Instantaneous Frequency
Valid mapping at sub-seismic sample rate interval
Instantaneous Frequency “best” seismic attribute
–
–
–
–
Compact geometry
Looks like expected sand body
Excellent correlation with isopach thick
Suggests field extension along trend
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Conclusions:
• Peripheral “noise” is reduced by:
– limiting frequency display range
– selecting time slice within the isochron interval
• Attribute analysis is not the complete story
– Geologic fundamentals are critical
– Analysis driven to find attributes which reflect the known geology
– Attributes would not find the best IPPs, in sands below seismic
resolution.
– Strong structural influence on IPPs.
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Conclusions:
• Selection of display parameters is critical to analysis
• Selection of display parameters enhances presentation
– Limit display to only data values for best dynamic range
– Display limits can be adjusted so as to:
• increase visual contrast,
• blank out visual “noise” without altering the data and/or
• limit presentation to only features of interest.
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Acknowledgments:
• Barbara, my wife, for her love and endurance!
• William C. Cook, Senior Geophysicist, for helpful
suggestions upon reviewing the first draft of the full paper.
• Coerte Voorhies, Sr. Geologist and Account Manager,
Seismic Micro Technology, Inc. for his patience with
“newbee” questions and his supporting comments
regarding this work.
• Seismic Micro-Technology, Inc., for providing access to
The Kingdom Suite of 3D seismic interpretation software,
through which this study accomplished.
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W.C. Overman, MS, Geophysicist
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