Specular Interferometric Migration of Specular Interferometric Migration of Free Surface Multiples in Free Surface Multiples in

VSP Land DataVSP Land Data

C. Boonyasiriwat and M. ZhouC. Boonyasiriwat and M. Zhou

Dept. of Geology & GeophysicsDept. of Geology & GeophysicsUniversity of UtahUniversity of Utah

OutlineOutline

• Numerical ResultsNumerical Results

• ConclusionConclusion

• Specular Interferometric MigrationSpecular Interferometric Migration

• Data ProcessingData Processing

• ProblemProblem

ProblemProblem

• Specular interferometric migration is cheaperSpecular interferometric migration is cheaper

• Land data have problems with the Land data have problems with the weathering zonesweathering zones

• Interferometric migration is expensiveInterferometric migration is expensive

• Marine data have very strong multiplesMarine data have very strong multiples

OutlineOutline

• Numerical ResultsNumerical Results

• ConclusionConclusion

• Specular Interferometric MigrationSpecular Interferometric Migration

• Data ProcessingData Processing

• ProblemProblem

Specular Interferometric MigrationSpecular Interferometric Migration

s s’ s*

g

x

Specular reflection

gsxssx ''~

Diffraction time

gsxssx **~

Specular time

Specular Interferometric Migration Specular Interferometric Migration of first-order multiplesof first-order multiples

)(*

,

1 **)|()|()|()( gsxssxi

gs

egsdgsGgsdxm

)|()|()|()|( ******1 gsGsxGxsGgsG

Migration Equation:

Natural Green’s Function

Natural Time

Calculated Time

Model-based Green’s Function

Specular Interferometric Migration Specular Interferometric Migration vsvs

Interferometric MigrationInterferometric Migration

s g

sxGxsGgsGgsdxm )|()|()|()|()( *****

Specular Interferometric Migration:

x

s

g

s*

Specular Interferometric Migration Specular Interferometric Migration vsvs

Interferometric MigrationInterferometric Migration

',

*** )'|()|()|'()|()(ss g

sxGxsGgsdgsdxm

Interferometric Migration:

x

s

g

s’

Specular Interferometric Migration Specular Interferometric Migration vsvs

Interferometric MigrationInterferometric Migration

s g

sxGxsGgsGgsdxm )|()|()|()|()( *****

Specular Interferometric Migration:

',

*** )'|()|()|'()|()(ss g

sxGxsGgsdgsdxm

Interferometric Migration:

OutlineOutline

• Numerical ResultsNumerical Results

• ConclusionConclusion

• Specular Interferometric MigrationSpecular Interferometric Migration

• Data ProcessingData Processing

Processing Steps for Primary ReflectionsProcessing Steps for Primary Reflections

Raw Data

AGC

Normalization

Separate Upgoing Wave

Kirchhoff Migration withResidual Statics Corrections

Processing Steps for Ghost ReflectionsProcessing Steps for Ghost Reflections

Raw Data

Normalization

AGC

Separate Downgoing Wave

Specular Interferometric Migration withResidual Statics Corrections

OutlineOutline

• Numerical ResultsNumerical Results

• ConclusionConclusion

• Specular Interferometric MigrationSpecular Interferometric Migration

• Data ProcessingData Processing

Forward Modeling ResultsForward Modeling Results

S-wave ghosts

P-wave ghost0

3.5

Tim

e (s

)

-4 4Offset (km) -4 4Offset (km)

Primaries from Acous. Wave Eq.Primaries + Ghosts from Elastic

Wave Eq.

s

g

x

Comparison between Field and Synthetic ResultsComparison between Field and Synthetic Results

S-wave ghosts

P-wave ghost

-4 4Offset (km)-4 4Offset (km)

0

3.5

Tim

e (s

)

Field Data Synthetic Data

Residual Statics CorrectionResidual Statics Correction

-4 4Offset (km)-4 4Offset (km)

0.2

2

Tim

e (s

)

Before statics correction After statics correction

-2 2Offset (km)

0

5

Dep

th (

km)

Kirchhoff Migration of Primaries

-2 2Offset (km)

0

5

Dep

th (

km)

Specular Interferometric Migration of Ghosts

Primary migration result overlaid on the surface data

Ghost migration result overlaid on the surface data

OutlineOutline

• Numerical ResultsNumerical Results

• ConclusionConclusion

• Specular Interferometric MigrationSpecular Interferometric Migration

• Data ProcessingData Processing

ConclusionsConclusions

• Both Kirchhoff and specular interferometric images correlate well with Both Kirchhoff and specular interferometric images correlate well with the CDP image.the CDP image.

• Migration image of primaries has a better S/N ratio for the P-wave image Migration image of primaries has a better S/N ratio for the P-wave image zone.zone.

• VSP land data contain strong primaries compared to P- and S-wave VSP land data contain strong primaries compared to P- and S-wave multiples.multiples.

• Migration image of ghosts has a wider subsurface coverage and flatter Migration image of ghosts has a wider subsurface coverage and flatter layers.layers.

• Specular interferometric migration gives comparable results to the Kirchhoff Specular interferometric migration gives comparable results to the Kirchhoff migration.migration.