local reverse time migration with vsp green’s functions

Local Reverse Time Migration with VSP Green’s Functions

Xiang Xiao

UTAM, Univ. of Utah

May 1, 2008

PhD Defense

99 pages

Outline

• Introduction and overview• SSP VSP SWP interferometric

transform• Local reverse time migration: horizontal

reflector imaging• Local reverse time migration: salt flank

imaging with transmitted P-to-S waves• Summary

Overview SSPVSP Local RTM Local RTM PS Summary

Outline

Offset

ModelD

Offset

r(x) D(g|s)Forward modelling

InverseMigration

Migration Image

Low subsalt resolution,Defocusing!

Subsalt Imaging

G(x|g) g

G(x|s)

m(x) ~

~ G(x|s)

Model- based

G(x|g)*

Model-based

D(g|s)

D(g|s)dg

Subsalt Imaging

G(x|g) g

G(x|s)

m(x) ~

~ G(x|s)

Forwarddirect

D(g|s)

G(x|g)*

Backward reflection

D(g|s)dg

Errors in the overburden

and salt body velocity model

Defocusing

Interferometric Imaging

G(x|g) G(x|s)

m(x) ~ s

~ ds G(x|s)

Data-based

G(x|g)* D(g|s)dg

Model-based

Local Reverse Time Migration

G(x|g) g

G(x|s)

G(x|s)= G(x|g’)* D(g’|s)dg’

Backward Direct wave

g’ Local VSP Green’s function

Local Reverse Time Migration

G(x|g) g

G(x|s)

m(x) ~

~ G(x|s)

Backwardapprox

* G(x|g)*

Backward reflection

D(g|s)dg

Outline

imaging by transmitted P-to-S waves• Summary

Outline

• SSP VSP SWP interferometric transform

– Motivation– Theory – Numerical Tests

• SEG/EAGE salt model• Double datuming

– Conclusions

I. Why we need more VSP?

Surface related statics

SSP VSP

•Twice OnceSeabedSeabed

SaltSalt

TargetTarget

Overburden velocity error

•Twice OnceRaypath

•Longer Shorter Attenuation

•More LessFrequency

Resolution

•Lower Higher

SSPVSP Motivation Theory Numerical Tests Conclusions

How to get more VSP?

dxG(B|A) ~

RVSP VSP

G(A|x)* G(B|x)

3D Application

3D VSP3D SSP

Naturally datuming !

3D RVSP

SSP + VSP RVSP !

Low fold

High fold !

SeabedSeabed

TargetTarget

SaltSalt

SSP/RVSP apertureSSP/RVSP aperture

ggVSP apertureVSP aperture

Shot coverageShot coverageReceiver coverageReceiver coverage

Use it, or lost it…

3D RVSP

SSP + VSP RVSP !

High folds !

SaltSalt

Better image under the salt !

SSP, VSPWell log

Better Geologic interpretation !

What is the benefit ?

– Higher fold virtual RVSP data are obtained;– Sources are closer to the target;

SSP + VSP RVSP

SaltSalt

– No velocity model is needed;– Multi-arrival are considered;

How to skip overburden?

dxG(g|g’) ~

SWP VSP

G(g’|s)* G(g|s)

Virtual Source Gather

No velocity model is needed !

Application of VSPSWP transform:

Virtual Source Gather

Salt flank imaging

P and S wave checkshot

Sediment imaging

Multiple/teleseismic imaging

4D Reservoir monitoring

Shear wave splitting and crack orientation

Seismic while drilling

……

Application

Outline

• SSP VSP SWP interferometric transform

• SEG/EAGE model• Double datuming

– Conclusions

P-wave velocity model0

-7850 7850Offset (m)

Velocity (m/s)4500

15003600

SEG/EAGE Salt Model

-7850 7850Offset (m)

Velocity (m/s)4500

15003600

SSP Data Geometry…SSP

Synthetic SSP CSG

Offset (m)-2000 2000

-7850 7850Offset (m)

Velocity (m/s)4500

15003600

VSP Geometry…

Synthetic VSP CRG0

Offset (m)-7850 7850

Synthetic SSP CSG

Offset (m)-7850 7850

Traces comparisons

Time (s)2 6

Synthetic RVSP CSG

Redatumed RVSP

6Offset (m)-7850 7850

1.4 kmComparison

Zoom area

Zoom View of TracesN

Time (s) 5.53

Redatumed RVSP trace

Direct waves are cut

poor data folds

-7850 7850Offset (m)

Velocity (m/s)4500

15003600

Another Datuming Results

Synthetic RVSP CSGT

Redatumed RVSP

6Offset (m)-2000 2000

Traces comparisons

Time (s)2 6

2.4 kmComparison

Time (s)2.5 6

Zoom viewDirect waves are cut

poor data foldsRedatumed RVSP trace

-7850 7850Offset (m)

Velocity (m/s)4500

15003600

SEG/EAGE Salt Model

Shot 320 SSP primary WEM 20 Hz1.5

-4 4Offset (km)

Shot 320 RVSP WEM 20 Hz

33 shots SSP WEM 20 Hz

33shots VSP WEM 20 Hz

3.6Offset (km)-4 4

33 RVSP+VSP WEM 20 Hz

Offset (km)-4 4

SEG/EAGE salt model0

s’s’

s’s’ g’g’

g’g’ s’s’ g’g’

SSPVSPSWP Transform

1% error in migration model

3.6Offset (km)-8 8

Offset (km)-8 8

645 shots SSP WEM0

3.6Offset (km)-8 8

Offset (km)-8 8

33 shots VSP WEM0

645 shots SSP primary WEM 20 Hz0

-8 8Offset (km)

Shot 320 BSSP WEM 20 Hz

645 shots SSP primary WEM 20 Hz0

-8 8Offset (km)

Shot 320 BSSP WEM 20 Hz

Conclusions

• Natural datuming, no velocity model is needed !

• Higher fold virtual VSP data are obtained !

• Source are closer to the target, less approximation.• Better resolution.

Outline

Motivation Theory Numerical Tests ConclusionsLocal RTM

• Local reverse time migration: horizontal reflector imaging

• Sigsbee VSP Data Set• GOM VSP Data Set

– Conclusions

VSP Forward Modeling

D(g|s)

VSP data

Reverse Time Migration

D(g|s)

VSP data

Reverse Time Migration

G(x|g) g

G(x|s)

BackwardD(g|s)

Forwarddirect

m(x) ~ s

~ ds G(x|s)

Forward direct

G(x|g)* D(g|s)dg

Backward data

Reverse Time Migration (RTM)

G(x|g) g

G(x|s)

BackwardD(g,s)

Forwarddirect

Forward direct:1) Salt velocity model is required, but hard to

build.2) Errors due to imperfect velocity models.

3) Need to estimate statics, anisotropy, etc.

VSPSWP Interferometry

Migrate virtual source gather D(g|g’) Limitations

1) s and x are at different sides of the well2) Image near vertical structures

Outline

– Conclusions

Key Idea of Local RTM

(a) VSP data: P(g|s)=T(g|s)+R(g|s)

Transmission T(g|s)

Reflection R(g|s)

(a) VSP data: P(g|s)=T(g|s)+R(g|s)

T(g|s)

gR(g|s)

(b) Backward reflection

R(g|s)g

R(x|s)= G(x|g)*R(g|s)g

(c) Backward transmission

T(g|s)

T(x|s)= G(x|g)*T(g|s)

(d) Crosscorrelation

m(x)= R(x|s)*T(x|s)s

Local VSP Green’s function

R(g|s)g

Key Idea of Local RTM

(d1) Crosscorrelation imaging condition

R(g|s)g

Deconvolution Imaging Condition

(d2) Deconvolution imaging condition

T(x|s)*T(x|s)

Benefits

• Target oriented!– Only a local velocity model near the well is

needed.– Salt and overburden is avoided.

– Fast and easy to perform.

• Source statics are automatically accounted for.

• Immune to salt-related interbed cross-talk.

Motivation Theory Numerical Tests SummaryLocal RTM

Outline

– Conclusions

Sigsbee P-wave Velocity Model0

-12.5 12.5Offset (km)

279 shots

150 receivers

Local Reverse Time Migration Results

-3 3Offset (km)

True modelMigration image

f = fault

(1) specular zone (2) diffraction zone(3) unreliable zone

d = diffractor

Outline

– Conclusions

Offset (m)4878

0 1829

GOM VSP Well and Source LocationSource @150 m offset

2800 m

3200 m

82 receivers

@600 m offset @1500 m offset

P-to-S ratio = 2.7

Velocity ProfileS WaveP Wave

45000 5000 0 5000

2800 m

3200 m

Incorrect velocity model

P-to-S ratio = 1.6

Velocity (m/s) Velocity (m/s)

Z-Component VSP DataD

Traveltime (s)

1.2 3.0

Direct P

Reflected P

Reverberations

X-Component VSP DataD

Traveltime (s)

1.2 3.0

Direct P

Reflected P

Reverberations Direct S

Local Reverse Time Migration Result

(1) specular zone, (2) diffraction zone, (3) unreliable zone

0 100Offset (m)

39receivers

reflectivity

150 m offset

Offset (m) 0 100Offset (m)

Without deconvolution

With deconvolution

600 m offset

With deconvolution

1500 m offset

With deconvolution

Conclusions• Subsalt reflectors are accurately imaged

near the well with subsalt velocity model only.

• Diffractors are also imaged.

• GOM local RTM image agrees with the well reflectivity.

• Deconvolution imaging condition helps.

• Illuminates horizontal subsalt reflectors around a vertical well.

Outline

Local RTM PS Motivation Theory Numerical Tests Summary

• Local reverse time migration: salt flank imaging by transmitted P-to-S waves

• Schlumberger VSP Data Set• GOM VSP Data Set

– Conclusions

Standard P-to-S Migration

m(x) ~ s

~ ds G(x|s)

Forward source P

G(x|g’)*D(g’|s)dg’

Backward data S

Converted wave VSP

D(g|s)

Salt and overburdenvelocity model is needed

Interferometric P-to-S Migration

D(g|g’) ~

D(g’|s) D(g|s)

m(x) ~ g’

~ dg’dgg

D(g|g’)G(x|g) G(x|g’)* *

Virtual source gather

Kirchhoff P-to-S Migration

m(x) ~ s

e-itxg’ D(g’|s)dg’g’

Converted wave VSP

D(g|s)

e-itsx

Reduce Time Migration

~( ~( tt + + tt )- )- ( ( tt + + tt ) )sxsx xxgg

pickpickpickpick

sxsx xxgg

errorerrortt sxsx xxg’g’=( =( tt + + tt )- )- ( ( tt + + tt ) )pickpickpickpick

sxsx xxg’g’

Converted wave VSP

D(g|s)

Local RTM PS Motivation Theory Numerical Tests

m(x) ~ s

~ ds e-itxg’ D(g’|s)dg’g’

e-i(tsx+terror)

Summary

Outline

– Conclusions

m(x) ~ s

~ dsg’

G(x|g’)* D(g’,s) dg’

Backward P

G(x|g)* D(g,s)dg

Backward S

Local Reverse Time Migration Theory

Outline

– Conclusions

Offset (km)

10-12 12

Schlumberger 2D Isotropic Elastic Model

291 shots

287 receivers

Offset (km)-12 120

(a) Ray tracing direct P

(c) PPS events (d) Pp events

(b) PSS events

Offset (km)-12 120

Aperture by Ray Tracing

Direct P

Time (s)

VSP CSG X-component

VSP CSG Z-component4

Two-component VSP Synthetic Data Set

km/s(a) P-wave submodelD

6.0 2.5

km/s(b) S-wave submodel

km/s(c) P background model

Offset (km)0 1.8

km/s(d) S background model

Offset (km)0 1.8

(a) Standard Kirchhoff

(c) Interferometric migration (IM) (d) Local RTM

(b) Reduced-time migration (RM)

Offset (km) 1.80

Comparison with Migration Methods

80Offset (km)0 1.8

Local RTM without wavefield separationD

81Offset (km)0 1.8

Local RTM with wavefield separationD

82Offset (km)0 1.8

Local RTM using Z component onlyD

Outline

Motivation Theory Numerical Tests

Schlumberger VSP Data Set GOM VSP Data Set

Conclusions

Offset (m)4878

0 1829

GOM VSP Well and Source LocationSource @150 m offset

2800 m

3200 m

82 receivers

@600 m offset @1500 m offset

P-to-S ratio = 2.7

Velocity ProfileS WaveP Wave

45000 5000 0 5000

2800 m

3200 m

Incorrect velocity model

P-to-S ratio = 1.6

Velocity (m/s) Velocity (m/s)

Z-Component VSP DataD

Traveltime (s)

1.2 3.0

Direct P

Reflected P

Reverberations

X-Component VSP DataD

Traveltime (s)

1.2 3.0

Direct P

Reflected P

Reverberations Direct S

Processing WorkflowOriginal Data

Rotate components

Pick desired events

Median filtering

Migration (KM, RM, IM, RTM)

Raypath Coverage

Migration of PPS

Offset (m)

39receivers

Migration of PPS

0 200 0 200

Offset (m)Offset (m) Offset (m)

Migration of PPS

IM, sediment flood Local RTM

0 200 0 200

Offset (m)Offset (m) Offset (m)

Offset (m)0 100

(a) Without deconvolution (b) With deconvolution

Offset (m)0 100

150 m Offset LRM Image

Offset (m)0 600

a) Synthetic b) 150 m offsetReduce time migration

c) 600 m offsetReduce time migration

Reduce Time Migration Image

2800 m

3200 m

Summary

• Target oriented!– Only a local velocity model near the well is

needed.– Salt and overburden is avoided.

– Fast and easy to perform.

• Source statics are automatically accounted for.

• Immune to salt-related interbed cross-talk.

Summary

Acknowledgements

• Dr. Gerard Schuster and my committee members: Dr. Michael Zhdanov, Dr. Robert smith, Dr. Cari Johnson, Dr. Jianming Sheng for their advice and constructive criticism;

• Scott Leaney and Hornby Brian for their help on modeling;

Acknowledgements

• UTAM friends:– Jianhua Yu and Yonghe Sun on the research;– Jianming Sheng and Min Zhou for their experiences

on interferometric imaging;– Zhiyong Jiang and Ruiqing He for their help on

classes;– Travis Crosby and all UTAM students for their

cheerful attitude; All UTAM sponsors for their support;• Family

– My parents, brother and sister;

• Friends– Liyun Ma, Min Zhou, Jun Wang, Shuqian Dong,

Chaoxiong Ma, who encouraged me to continue on with my research.

Questions?

local reverse time migration with vsp green’s functions

Documents

vsp measurement

ഠwith vsp vision care. · the vsp choice network includes...

green’s functions theory for quantum many body...

vsp vision coverage -...

1.1 vsp fx00 モデル,vsp gx00 モデル概要system...

ansfa la ecna de iualiacin flexibilidad … · storage...

walkaway vsp

green’s victorian

ventose speciali piane - gamavuoto · 2017. 2. 28. · 42...

hitachi vantara qualified professional vsp g200 to vsp

local migration with extrapolated vsp green’s functions...

flache sonder-saugnäpfe · 2017. 3. 24. · vsp 85 art....

local reverse time migration with extrapolated vsp green’s...

a green’s function approach for the thermoelastic … ·...

2installations - vivamusica.de und spielhinweise vsp...

hitachi vsp g - hyosung information systems€¦ · hitachi...

deep dive on new avaya networking products · vsp 8400...

joey green · joey green’s magic health remedies, joey...

micronas vsp 94x5b, vsp 94x7b optimus color decoder … ·...

green’s functions theory for quantum many body systems ·...