Crosscorrelation Migration Crosscorrelation Migration of Free-Surface Multiples of Free-Surface Multiples

in CDP Datain CDP Data

Jianming ShengJianming Sheng

University of UtahUniversity of UtahFebruary, 2001February, 2001

OutlineOutline• ObjectiveObjective

• Crosscorrelation migrationCrosscorrelation migration

• Numerical examplesNumerical examples

• SummarySummary

ObjectiveObjectiveTo image free-surface multiplesTo image free-surface multiplesby crosscorrelation migration;by crosscorrelation migration;

To improve the migration imageTo improve the migration imagequality by attenuating the quality by attenuating the artifacts caused by free-surface artifacts caused by free-surface multiples.multiples.

OutlineOutline• ObjectiveObjective

• Crosscorrelation migrationCrosscorrelation migration

• Numerical examplesNumerical examples

• SummarySummary

Principle of CCMPrinciple of CCMG’ GS

X

X’

VIRTUALSOURCE

(CROSSCORRELATION)

G’ GS

X

X’

SOURCE

GG

G’ GS

X

X’

SOURCE

PP

Principle of CCMPrinciple of CCM

xm

Migration imageMigration image

Trial image pointTrial image point

xGxGie '

Imaging ConditionImaging Condition

Asymptotic AnalysisAsymptotic Analysis

xm

xGxGGG '''G

G

S

CrosscorrelogramsCrosscorrelograms

Asymptotic AnalysisAsymptotic Analysis

xmUnder stationary phase conditionUnder stationary phase condition

PPrimaryrimary GGhosthost

Correct imageCorrect image ++ ArtifactsArtifacts

GGhosthost PPrimaryrimary PPrimaryrimaryPPrimaryrimary

GGhosthostGGhosthost3R4R

2R

NegligibleNegligible

Wrong positonWrong positon

Asymptotic AnalysisAsymptotic AnalysisCrosscorrelation migration can Crosscorrelation migration can migrate the multiples to the migrate the multiples to the correct position but generate correct position but generate artifacts as well;artifacts as well;

CCM image alone can not give theCCM image alone can not give thereflectivity distribution!reflectivity distribution!

Key Idea of CCMKey Idea of CCMCCM ImageCCM Image Kirchhoff ImageKirchhoff Image

ReflectorReflector

ArtifactsArtifacts

ArtifactsArtifacts

Key Idea of CCMKey Idea of CCM

Multiplying the Multiplying the two images an two images an improved improved migration migration image can be image can be obtainedobtained

OutlineOutline• ObjectiveObjective

• Crosscorrelation migrationCrosscorrelation migration

• Numerical examplesNumerical examples

• SummarySummary

Numerical ExamplesNumerical Examples

• Three-layered modelThree-layered model

• Nine-layered modelNine-layered model

• SEG/EAGE salt modelSEG/EAGE salt model

Three-Layered ModelThree-Layered Model

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600600

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ModelModel CCM ImageCCM Image

Three-Layered ModelThree-Layered Model

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Kirchhoff ImageKirchhoff Image Product ImageProduct Image

Nine-Layered ModelNine-Layered Model

500 1000 1500 2000 2500500 1000 1500 2000 2500

00

600600

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24002400

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24002400

ModelModel CCM imageCCM image

500 1000 1500 2000 2500500 1000 1500 2000 2500

Nine-Layered ModelNine-Layered Model

500 1000 1500 2000 2500500 1000 1500 2000 2500

00

600600

12001200

18001800

30003000

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th (

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24002400

Kirchhoff ImageKirchhoff Image Product ImageProduct Image

500 1000 1500 2000 2500500 1000 1500 2000 2500

SEG/EAGE Salt ModelSEG/EAGE Salt Model

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600600

12001200

18001800

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36003600

0 5000 10000 150000 5000 10000 15000Distance (m)Distance (m)

320 shots320 shots176 traces per shot176 traces per shot

CCM ImageCCM Image

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Kirchhoff ImageKirchhoff Image

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Product ImageProduct Image

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All right, All right, multiples are migrated, multiples are migrated, … … well, is it useful?well, is it useful?

Yes.Yes.

Kirchhoff ImageKirchhoff Image

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600600

12001200

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24002400

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th (

m)

Dep

th (

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36003600

0 5000 10000 150000 5000 10000 15000Distance (m)Distance (m)

Product ImageProduct Image

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12001200

18001800

24002400

Dep

th (

m)

Dep

th (

m)

30003000

36003600

0 5000 10000 150000 5000 10000 15000Distance (m)Distance (m)

OutlineOutline• ObjectiveObjective

• Crosscorrelation migrationCrosscorrelation migration

• Numerical examplesNumerical examples

• SummarySummary

SummarySummary• Multiples can be considered as signal and correctly Multiples can be considered as signal and correctly

imaged by the crosscorrelation migration;imaged by the crosscorrelation migration;

• By multiplying the crosscorrelation and Kirchhoff By multiplying the crosscorrelation and Kirchhoff

migration images, the true reflectors can be migration images, the true reflectors can be

enhanced and the artifacts can be attenuated.enhanced and the artifacts can be attenuated.

Further WorkFurther Work• To attenuate the artifacts generated by To attenuate the artifacts generated by

CCM;CCM;

• To deal with the high-order multiples and To deal with the high-order multiples and

internal multiples.internal multiples.

AcknowledgmentAcknowledgment

I thank the sponsors of the 2000 University I thank the sponsors of the 2000 University of Utah Tomography and Modeling of Utah Tomography and Modeling /Migration (UTAM) Consortium for their /Migration (UTAM) Consortium for their financial support .financial support .