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

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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 Frequencyfrom 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. Structureon 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

– High correlation to Instantaneous Frequency in the south

• Isochron, though subtle, is a valid and useful attribute– 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.