3D Wave-equation Interferometric Migration of VSP Free-surface Multiples Ruiqing He University of Utah Feb., 2006

3D Wave-equation 3D Wave-equation Interferometric Migration of Interferometric Migration of VSP Free-surface MultiplesVSP Free-surface Multiples

Ruiqing HeRuiqing He

University of UtahUniversity of Utah

Feb., 2006Feb., 2006

OutlineOutline

IntroductionIntroduction

Wave-equation Interferometric Migration Wave-equation Interferometric Migration (WEIM)(WEIM)

A Synthetic TestA Synthetic Test

Application to A Field 3D VSP Data SetApplication to A Field 3D VSP Data Set

ConclusionConclusion

OutlineOutline







Migration of VSP multiples has a larger Migration of VSP multiples has a larger imaging area than migration of primaries.imaging area than migration of primaries.

Mirror image

Published MethodsPublished MethodsMirror imaging condition: transfer to a Mirror imaging condition: transfer to a migration of primaries imaging condition. migration of primaries imaging condition.

Real model

Crosscorrelation migration: transfer VSP Crosscorrelation migration: transfer VSP

data to CDP data. data to CDP data.

DifficultiesDifficulties

Crosscorrelation is not cheap.Crosscorrelation is not cheap.

Kirchhoff migration is not cheap.Kirchhoff migration is not cheap. Ray tracing.Ray tracing. Storage of time tables.Storage of time tables. 3D.3D.

OutlineOutline






WEIMWEIM

),()( txWxI

Reciprocity

Line-source Ray tracingLine-source Ray tracing

Knownmedium

Unknown medium

The picked time is imposed as an initial condition in ray tracing.

Advantages of WEIMAdvantages of WEIM

Experience similar velocity estimation Experience similar velocity estimation errors as migrating CDP primaries.errors as migrating CDP primaries.

For each receiver gather, only one line-For each receiver gather, only one line-source ray tracing, and one wavefield source ray tracing, and one wavefield extrapolation is needed. extrapolation is needed.

In 3D VSP, the saving of ray tracing and In 3D VSP, the saving of ray tracing and timetable storage is enormous. timetable storage is enormous.

OutlineOutline






2D Synthetic Test2D Synthetic Test

Offset (m)0 6000

Dep

th (

m)

0

4000

Offset (m)0 6000

Tim

e (s

)

0

5

Synthetic model Synthetic data

12 geophpnes

600 shots

Migration ComparisonMigration Comparison

Offset (m)0 6000

Dep

th (

m)

0

4000

Migration of primaries Migration of multiples

Offset (m)0 6000

Dep

th (

m)

0

4000

OutlineOutline

IntroductionIntroductionWave-equation Interferometric Migration (WEIM)Wave-equation Interferometric Migration (WEIM)A Synthetic TestA Synthetic TestApplication to A Field 3D VSP Data SetApplication to A Field 3D VSP Data SetConclusionConclusion

Acquisition GeometryAcquisition Geometry

12 geophones at an interval of 15.25 m.

~ 11 km

~ 11 km

~ 4.5 km deep

2D WEIM Result2D WEIM Result

Offset (km)0 11

0

7.5

Depth (m)

3D WEIM Result3D WEIM ResultMigration of only one receiver gather

Slice MovieSlice MovieMigration of only one receiver gather

OutlineOutline







Proposed 3D WEIM, which is very efficient Proposed 3D WEIM, which is very efficient for migrating 3D VSP multiples.for migrating 3D VSP multiples.

Migration of 3D VSP free-surface multiples Migration of 3D VSP free-surface multiples provides an imaging area comparable to a provides an imaging area comparable to a conventional 3D CDP survey, yet the data conventional 3D CDP survey, yet the data processing cost is much reduced.processing cost is much reduced.

AcknowledgementAcknowledgement

Thanks to UTAM 2005 sponsors for Thanks to UTAM 2005 sponsors for financial support.financial support.

Documents

3D Wave-equation Interferometric Migration of VSP Free-surface Multiples Ruiqing He University of Utah Feb., 2006