Crosscorrelation Migration of Free-Surface Multiples in CDP Data Jianming Sheng University of Utah February, 2001

Outline ObjectiveObjective Crosscorrelation migrationCrosscorrelation migration Numerical examplesNumerical examples SummarySummary

Objective To image free-surface multiples by crosscorrelation migration; To improve the migration image quality by attenuating the artifacts caused by free-surface multiples.

Outline ObjectiveObjective Crosscorrelation migrationCrosscorrelation migration Numerical examplesNumerical examples SummarySummary

Principle of CCM G’GS X X’ VIRTUAL SOURCE (CROSSCORRELATION) G’GS X X’ SOURCE G G’GS X X’ SOURCE P

Principle of CCM Migration image Trial image point Imaging Condition

Asymptotic Analysis Crosscorrelograms

Under stationary phase condition P rimary G host Correct image + Artifacts G host P rimary G host Negligible Wrong positon

Asymptotic Analysis Crosscorrelation migration can migrate the multiples to the correct position but generate artifacts as well; CCM image alone can not give the reflectivity distribution!

Key Idea of CCM CCM Image Kirchhoff Image Reflector Artifacts Artifacts

Key Idea of CCM Multiplying the two images an improvedmigration image can be obtained

Outline ObjectiveObjective Crosscorrelation migrationCrosscorrelation migration Numerical examplesNumerical examples SummarySummary

Numerical Examples Three-layered modelThree-layered model Nine-layered modelNine-layered model SEG/EAGE salt modelSEG/EAGE salt model

Three-Layered Model Depth (m) Model CCM Image

Three-Layered Model Depth (m) Kirchhoff Image Product Image

Nine-Layered Model Depth (m) Model CCM image

Nine-Layered Model Depth (m) 2400 Kirchhoff Image Product Image

SEG/EAGE Salt Model Depth (m) Distance (m) 320 shots 176 traces per shot

CCM Image Depth (m) Distance (m)

Kirchhoff Image Depth (m) Distance (m)

Product Image Depth (m) Distance (m)

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

Kirchhoff Image Depth (m) Distance (m)

Product Image Depth (m) Distance (m)

Outline ObjectiveObjective Crosscorrelation migrationCrosscorrelation migration Numerical examplesNumerical examples SummarySummary

Summary Multiples can be considered as signal and correctly imaged by the crosscorrelation migration;Multiples can be considered as signal and correctly imaged by the crosscorrelation migration; By multiplying the crosscorrelation and Kirchhoff migration images, the true reflectors can be enhanced and the artifacts can be attenuated.By multiplying the crosscorrelation and Kirchhoff migration images, the true reflectors can be enhanced and the artifacts can be attenuated.

Further Work To attenuate the artifacts generated by CCM;To attenuate the artifacts generated by CCM; To deal with the high-order multiples and internal multiples.To deal with the high-order multiples and internal multiples.

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