CROSSWELL IMAGING BY 2-D PRESTACK WAVEPATH MIGRATION H. Sun Geology and Geophysics Department University of Utah.

CROSSWELL IMAGING BY 2-D CROSSWELL IMAGING BY 2-D PRESTACK WAVEPATH PRESTACK WAVEPATH

MIGRATIONMIGRATION

H. SunH. Sun

Geology and Geophysics Department Geology and Geophysics Department University of UtahUniversity of Utah

Offset (km)Offset (km)44 1010

De

pth

(k

m)

De

pth

(k

m)

0.50.5

2.52.5

44 Offset (km)Offset (km) 1010 44 Offset (km)Offset (km) 1010

KM ImageKM Image WM ImageWM ImageModelModel

SEG 2-D Overthrust DataSEG 2-D Overthrust Data

2-D Husky Field Data2-D Husky Field Data

Offset (km)Offset (km)2.52.5 5.55.5

2.52.5

5.05.0

De

pth

(k

m)

De

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(k

m)

KM Image (Zoom A)KM Image (Zoom A) WM Image (Zoom A)WM Image (Zoom A)

Offset (km)Offset (km)2.52.5 5.55.5

2.52.5

De

pth

(k

m)

De

pth

(k

m)

5.05.0

WMWM

ModelModel

KM KM

SubSubWMWM

SEG 3-D Salt DataSEG 3-D Salt Data

Horizontal Slice (Depth=1.4 km)Horizontal Slice (Depth=1.4 km)

CPU:CPU:1/170 1/170

CPU:CPU:1/33 1/33

CPU:CPU:1 1

2-D KM of a Single Trace2-D KM of a Single Trace

RR SSAA

AA

BB

BB

CC

CC

2-D WM of a Single Trace2-D WM of a Single Trace

RR SSAA

BBCC

AABB

CC

Traveltime + Ray DirectionTraveltime + Ray Direction

TrueReflection point

SmallMigration Aperture

FewerFewerArtifactsArtifacts

LessLessExpensiveExpensive

Wavepath MigrationWavepath Migration

OutlineOutline

• WM Crosswell ImagingWM Crosswell Imaging• Synthetic Crosswell Data Synthetic Crosswell Data • McElroy Crosswell DataMcElroy Crosswell Data• Synthetic Single Well DataSynthetic Single Well Data• ConclusionsConclusions

KM Crosswell ImagingKM Crosswell ImagingReceiver Receiver

WellWell

Up-goingUp-going

Down-goingDown-going

Interface 2Interface 2

Source Source WellWell



WellWell

Up-goingUp-going





WellWellDown-goingDown-going





WellWell

Up-goingUp-going





Problems in KM Crosswell ImagingProblems in KM Crosswell Imaging

• Insufficient Stacking Leads to ArtifactsInsufficient Stacking Leads to Artifacts

• Complex Data Cause Difficulty inComplex Data Cause Difficulty in Up-going and Down-going SeparationUp-going and Down-going Separation

• Slow ComputationSlow Computation

WM Crosswell ImagingWM Crosswell ImagingReceiver Receiver

WellWell

Up-goingUp-going





Advantages of WM Crosswell ImagingAdvantages of WM Crosswell Imaging

• Avoid Artifacts by Migrating to theAvoid Artifacts by Migrating to the Primary Reflection PointPrimary Reflection Point

• Handle Complex Data by MigratingHandle Complex Data by Migrating Up-going and Down-going togetherUp-going and Down-going together

• No Constraints NeededNo Constraints Needed

• Fast ComputationFast Computation

Shortcomings of WMShortcomings of WM

• Weaker EventsWeaker Events

• Worse Interface ContinuityWorse Interface Continuity

OutlineOutline


Fault ModelFault Model A Common Shot GatherA Common Shot Gather

00 0000

9090

210210

210210

0.20.2

00Offset (m)Offset (m)

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pth

(m

)D

ep

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m)

Tim

e (

s)T

ime

(s)

Geophone Depth (m)Geophone Depth (m)

ModelModel

Crosswell Imaging of Synthetic Fault Data Crosswell Imaging of Synthetic Fault Data

Offset: 0~90 m, Depth: 0~210 mOffset: 0~90 m, Depth: 0~210 m

WMWMKM KM WM (no separation)WM (no separation)

Better ImageBetter ImageBetter ResolutionBetter Resolution

OutlineOutline


A Common Shot GatherA Common Shot Gather

811811 963963

0.050.05

00

Tim

e (

s)T

ime

(s)

Hydrophone Depth (m)Hydrophone Depth (m)

Traveltime TomogramTraveltime Tomogram

00

8118115656

963963

Offset (m)Offset (m)

De

pth

(m

)D

ep

th (

m)

6.76.7

4.74.7

(k

m /s

)(k

m /s

)

De

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(m

)D

ep

th (

m)

KM ImageKM Image

00 5656Offset (m)Offset (m)

Receiver WellReceiver WellSource WellSource Well

811811

963963SyntheticSyntheticSyntheticSynthetic

Up-goingUp-going


SeparationSeparation

??

??

De

pth

(m

)D

ep

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m)


811811


Up-goingUp-going


SeparationSeparation

WM ImageWM Image


WM ImageWM Image


De

pth

(m

)D

ep

th (

m)


811811


Up-goingUp-going


NO SeparationNO Separation

Receiver WellReceiver Well

SyntheticSynthetic

Source WellSource Well

SyntheticSynthetic

WM (up+down)WM (up+down)WM(CPU=1)WM(CPU=1)KM(CPU=2.5)KM(CPU=2.5)

Offset: 0~56 m, Depth: 811~963 mOffset: 0~56 m, Depth: 811~963 m

OutlineOutline


OYO Salt ModelOYO Salt Model

9900

Velocity (km/s)Velocity (km/s)

00

66

Offset (km)Offset (km)

De

pth

(k

m)

De

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(k

m)

WellWell

SaltSalt

? ? ? ?? ? ? ?

????

????

4.54.52.82.8

KM imageKM image22

55

Dep

th (

km)

Dep

th (

km)

6.56.52.52.5 Offset (km)Offset (km) 6.56.52.52.5 Offset (km)Offset (km) 6.56.52.52.5 Offset (km)Offset (km)

OYO Salt ModelOYO Salt Model

Velocity ModelVelocity Model WM imageWM image

????

????

????? ?????

WellWell

ConclusionsConclusions

Crosswell Synthetic DataCrosswell Synthetic Data• Fewer migration artifactsFewer migration artifacts• Slightly better image resolutionSlightly better image resolution• Better for dipping fault boundaryBetter for dipping fault boundary• No up- and down-going separationNo up- and down-going separation


Crosswell McElroy DataCrosswell McElroy Data• Similar image qualitySimilar image quality• No up- and down-going separationNo up- and down-going separation• 2.5 times faster than KM2.5 times faster than KM• Worse image continuityWorse image continuity• Structure details? Artificial events?Structure details? Artificial events?


Single Well Synthetic DataSingle Well Synthetic Data• Similar image qualitySimilar image quality• Fewer migration artifactsFewer migration artifacts

AcknowledgementsAcknowledgements

I thank UTAM sponsorsI thank UTAM sponsorsfor their financial supportfor their financial support

CROSSWELL IMAGING BY 2-D PRESTACK WAVEPATH MIGRATION H. Sun Geology and Geophysics Department University of Utah.

Documents

synthetic synthetic

d overthrust data slide

s slide

data conclusions conclusions

b c slide

wm model

d husky field data offset

sourcewell interface