REVERSE -TIME DATUMINGREVERSE -TIME DATUMING

M. ZhouM. ZhouY. Luo Y. Luo (Saudi Aramco)(Saudi Aramco)

Geology and Geophysics Department Geology and Geophysics Department

University of UtahUniversity of Utah

OutlineOutline• ObjectiveObjective• How to ImplementHow to Implement• ExamplesExamples• ConclusionsConclusions

AccurateAccurateExpensiveExpensiveRTMRTM

ObjectiveObjectiveD

epth

(K

m)

Dep

th (

Km

)

Offset (km)Offset (km)

ComplexComplexRough topographyRough topography

Large velocity variationLarge velocity variation

Less ComplexLess Complex

RTDRTD

Phase-shift Phase-shift KirchhoffKirchhoff EfficientEfficient

Approx.Approx.

++

OutlineOutline• ObjectiveObjective• How to ImplementHow to Implement• ExamplesExamples• ConclusionsConclusions

d(s|r)d(s|r)

DistancDistancee

Dep

thD

epth

RRSS

x’x’ x’’x’’

d(s|x’’)=d(s|x’’)= g*(r|x’’)g*(r|x’’) d(s|r)d(s|r)

d(s|x’’)d(s|x’’)

d(x’|x’’)d(x’|x’’)=g*(s|x’) d(s|x”)=g*(s|x’) d(s|x”)

d(x’|x’’)d(x’|x’’)

d(s|x’’)d(s|x’’)

Implement RTDImplement RTD

d(s|r)d(s|r)

DistancDistancee

Dep

thD

epth

RRSS

x’x’ x’’x’’

Target-oriented RTD Target-oriented RTD (Luo , 2002)(Luo , 2002)

g(s|x’)g(s|x’) g(r|x’’)g(r|x’’)** d(s|r)d(s|r)

= d(x’|x’’)= d(x’|x’’)

== d(x’|x’’)d(x’|x’’)

Implement RTDImplement RTD

OutlineOutline• ObjectiveObjective• ImplementImplement• ExamplesExamples

• ConclusionsConclusions

2-D Salt Model2-D Salt Model Pluto 1.5 (Smarrt Jv.)Pluto 1.5 (Smarrt Jv.)

2-D Salt Model2-D Salt ModelD

epth

(Km

)D

epth

(Km

)

00

33

15151515Offset (km)Offset (km) 00 Offset (km)Offset (km)

Velocity ModelVelocity Model

Zero-offset DataZero-offset Data

After RedatumingAfter RedatumingD

epth

(K

m)

Dep

th (

Km

)

00

33

1515

1515Offset (km)Offset (km)

00 Offset (km)Offset (km)

Velocity ModelVelocity Model

Zero-offset Data Zero-offset Data at datumat datum

2D Salt Model2D Salt ModelD

epth

(K

m)

Dep

th (

Km

)

00 55

22

33

1010 1515Offset (km)Offset (km)

Dep

th (

Km

)D

epth

(K

m)

00 55

22

33

1010 1515Offset (km)Offset (km)

KM Image After RedatumingKM Image After Redatuming

KM Images Before RedatumingKM Images Before RedatumingD

epth

(K

m)

Dep

th (

Km

)

00 55

22

33

1010 1515Offset (km)Offset (km)

KM Image After RedatumingKM Image After Redatuming

Whole Volume RTMWhole Volume RTMD

epth

(K

m)

Dep

th (

Km

)

00 55

22

33

1010 1515Offset (km)Offset (km)

KM Image After RedatumingKM Image After Redatuming

CPU Time ComparisonCPU Time Comparison

Whole volume RTM:Whole volume RTM:

RTD + KMRTD + KM

KM before datumingKM before datuming

13.4 (50832 sec)13.4 (50832 sec)

6.88 (26147 sec)6.88 (26147 sec)

1 (3801 sec)1 (3801 sec)

S1400, 2048MB memoryS1400, 2048MB memory

After RedatumingAfter RedatumingD

epth

(K

m)

Dep

th (

Km

)

00

33

1515

1515Offset (km)Offset (km)

00 Offset (km)Offset (km)

Velocity ModelVelocity Model

Zero-offset Data Zero-offset Data at datumat datum

KM Image After RedatumingKM Image After RedatumingD

epth

(K

m)

Dep

th (

Km

)

00 55

33

33

1010 1515Offset (km)Offset (km)

KMKM

ModelModel

KM Before and After RedatumingKM Before and After RedatumingD

epth

(K

m)

Dep

th (

Km

)

00 55

33

33

1010 1515Offset (km)Offset (km)

KMKMBeforeBefore

KMKMAfterAfter

KM After Redatuming vs. RTMKM After Redatuming vs. RTMD

epth

(K

m)

Dep

th (

Km

)

00 55

33

33

1010 1515Offset (km)Offset (km)

BeforeBefore

KMKMAfterAfter

DatumDatum

Whole Whole volumevolume

RTMRTM

Save Save 40%40% w.r.t whole volume RTM w.r.t whole volume RTM

KM After RedatumingKM After RedatumingD

epth

(K

m)

Dep

th (

Km

)

00 55

33

33

1010 1515Offset (km)Offset (km)

ShallowShallowDatumDatum

DeepDeepDatumDatum

OutlineOutline• ObjectiveObjective• ImplementImplement• ExamplesExamples

• ConclusionsConclusions

2-D Salt Model2-D Salt Model Pluto 1.5 (Smarrt Jv.)Pluto 1.5 (Smarrt Jv.)

SMARRT JV. Pluto 1.5 Vp modelSMARRT JV. Pluto 1.5 Vp model D

epth

(K

m)

Dep

th (

Km

)

99

Distance (km)Distance (km)00 3030

00

Zero-offset DataZero-offset Data

Tim

e (S

ec)

Tim

e (S

ec)

55

Distance (km)Distance (km)55 2525

11

Reflectivity Model Below DatumReflectivity Model Below Datum

Dep

th (

Km

)D

epth

(K

m)

77

Distance (km)Distance (km)1010 2020

55

Tim

e (S

ec)

Tim

e (S

ec)

Zero-offset Data After DatumingZero-offset Data After Datuming

11

00

OutlineOutline• ObjectiveObjective• How to ImplementHow to Implement• ExamplesExamples• ConclusionsConclusions

ConclusionsConclusions• RTD is faster than RTM RTD is faster than RTM

• RTD helps reveal deeper RTD helps reveal deeper structurestructure

• RTD + KM is cost efficient and RTD + KM is cost efficient and provides good depth imageprovides good depth image

ConclusionsConclusions

• RTD introduces artifacts due toRTD introduces artifacts due todata boundarydata boundary

10 km10 km

2000 ms2000 ms

Courtesy of Yi Luo (Saudi Aramco)Courtesy of Yi Luo (Saudi Aramco)

We thank Utah Tomography and We thank Utah Tomography and Modeling/Migration ConsortiumModeling/Migration Consortium

sponsors for their financial supportsponsors for their financial support

AcknowledgementsAcknowledgements