A New, Integrated Velocity Solution for Interpreters · 2017. 7. 27. · [email protected]....

© 2016, PARADIGM. ALL RIGHTS RESERVED. © 2016, PARADIGM. ALL RIGHTS RESERVED.

A New, Integrated Velocity Solution for

InterpretersParadigm Time Preserving Tomography

Masako Robb

© 2016, PARADIGM. ALL RIGHTS RESERVED. 2

Time Preserving Tomography (TPT)

• A post-stack depthing tool for interpreters to improve seismic-to-well misties

• Refines the original, mis-tied velocity model in a more geologically plausible way

• Produces a matched, tied set of markers, interpretation, velocity and seismic

• A fast and easy, yet more sophisticated methodology than traditional approaches


Issues – Misties in Depth

• Interpret in depth on PSDM, have

issues with depth surfaces tying

depth markers…

• Interpret in time on PSTM, scale

results to depth using seismic

velocity, get misties…

• Interpret in time on PSTM, use

well velocity (krigging, layer cake

velocity model, V0-K…), still get

misties after scaling to depth

• How do we handle this issue…?


Velocity Refinement

Goal:

To Reduce misties

Geologically plausible

No velocity anomaly

No distortion in seismic

Repeatable, non-subjective way

© 2016, PARADIGM. ALL RIGHTS RESERVED.


5

• TPT uses the concept of seismic reflection tomography

(that traditionally requires pre-stack gathers)

But…!!

• TPT is a post-stack solution, and does not require pre-

stack gathers

Solution for interpreter


Short Primer - What is Seismic

Reflection Tomography?


Seismic Reflection Tomography – An Inversion

• An analogy…Impedance inversion

• Start point: Observe seismic

reflectivity behavior caused by

some unknown impedance model

• Low detail, constraining

background model is globally

updated and errors are minimized

• End point: Updated, detailed

impedance model that must have

caused those reflectivity contrasts


(Prestack) Seismic Reflection Tomography

Offset Offset

Offset Offset

• Start point: Observe

gather flatness behavior

caused by some unknown

velocity model


background model is

globally updated and errors

are minimized

• End point: Updated,

detailed velocity model that

must cause the gathers to

be flat



Offset Offset

Offset Offset

• Start point: Observe gather

flatness behavior caused

by some unknown velocity

model


background model is

globally updated and errors

are minimized

• End point: Updated,

detailed velocity model that

must cause the gathers to

be flat Global Update + Ray Tracing


Challenge: The non-uniqueness of the solution

CMP offset CMP offset

Mistie



Additional constraint: Mistie Maps

0 tZAAASAl

lZS

Traveltime errorDepth error

Tomography equation in the welltie mode

Epsilon errorVelocity error Delta error

Inputs: RMOs From Dept

h migrated gathers

∆𝑡1∆𝑡2∆𝑡3......

∆𝑡𝑀

=

𝐴𝑣11 𝑨𝒛𝟏𝟏 𝐴𝛿11𝐴 11 … 𝐴𝑣1𝑁𝑨𝒛𝟏𝑵𝐴𝛿1𝑁 𝐴 1𝑁.........

⋱

.

.

.

..

.

.

.

.𝐴𝑣𝑀1 𝑨𝒛𝑴𝟏𝐴𝛿𝑀1𝐴 𝑀1 ⋯ 𝐴𝑣𝑀𝑁𝑨𝒛𝑴𝑵𝐴𝛿𝑀𝑁 𝐴 𝑀𝑁

∆𝑣1∆𝒛𝟏∆𝛿1∆휀1...

∆𝑣𝑁∆𝒛𝑵∆𝛿𝑁∆휀𝑁

Outputs: tomography solution:

Residual Medium parameters and

model depth shift (MB)

Coefficients found along traced ray

Seismic Reflection Tomography with Well Constraint

© 2016, PARADIGM. ALL RIGHTS RESERVED. © 2016, PARADIGM. ALL RIGHTS RESERVED. 12

Must have prestack data?

Must have a cluster computer?

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://imgarcade.com/1/mystery-person-clip-art/&ei=OENJVJH4NoPC8QHp1YCYDA&psig=AFQjCNHsAFgpyh_SYK28jXRlKGLq-lP-iw&ust=1414173727366859

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://imgarcade.com/1/mystery-person-clip-art/&ei=OENJVJH4NoPC8QHp1YCYDA&psig=AFQjCNHsAFgpyh_SYK28jXRlKGLq-lP-iw&ust=1414173727366859


Time Preserving Tomography

13

Must have prestack data?

Must have a cluster computer?


∆𝑡 = 𝐴𝑣∆𝑣 + 𝐴𝛿∆𝛿 + 𝐴 ∆휀 + 𝑨𝒛∆𝒛0 =



■ Input:

■ Background model

■ Mistie maps (dz)

■ Output:

■ Updated model

■ Updated depth maps

TPT – Input and Output


Generate Mistie Maps

Generate Pencils

Run Time Preserving Tomography

QC Updated Velocity and Depth

Models

Mistie?

TPT - Workflow


Scale Horizons to Depth

Create Initial Interval Velocity

Mistie?

TPT - Workflow


Generate Pencils



Models


Generate Pencils

TPT - Workflow

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Mistie?

Scale Horizons to Depth

Create Initial Interval Velocity




Models


Example - Taranaki Basin


Mistie Maps (Before Tomography)Mistie Range (-180 ~ 20 m)


Original Velocity and Depth Model

1500

2000

2500

3000

3500

4000

4500

5000

(m/s

)


Updated Velocity and Depth Model

1500

2000

2500

3000

3500

4000

4500

5000

(m/s

)


200

Before TPT After TPT

Horizon 6

-100

-80

-60

-40

-20

0

20

40

60

80

100

(m)

Horizon 6

Mistie Map


Updated Velocity and Depth Model, Seismic


Original Velocity and Depth Model, Seismic


Flexibility of Tomography

• Can update only a single formation (such as within

a channel velocity) if required

• Can choose different update/smooth parameters

per formation

• Can use velocity/anisotropy misties as input

instead of depth misties

26


Time Preserving Tomography Benefits

• A global inversion process which uses ray tracing,

while other solutions are local and use vertical

scaling

• Suitable for the most complex velocity model

• Simple, GUI-driven, post-stack workflow

• Takes account of anisotropy

27


Pitfalls in seismic Data interpretation

Ian Jones, First Break, March 2012

Application to Pull Up/Down Effects


Example : Low Velocity Intrusion in Salt

Mistie

Mistie information is used to update Intrusion only



Model Velocity Input Velocity Salt FloodedUpdated Velocity From TP tomography

Example : Salt Intrusion



Thank [email protected]

A New, Integrated Velocity Solution for Interpreters · 2017. 7. 27. · [email protected]....

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