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Topographic Phase Shift with Applications to Migration and Multiple Prediction. Ruiqing He University of Utah Feb. 2005. Outline. Wavefield extrapolation. Topographic phase-shift method. Application to migration. Application to multiple prediction. Summary. Outline.

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Topographic phase shift with applications to migration and multiple prediction

Topographic Phase Shift with Applications to Migration and Multiple Prediction

Ruiqing He

University of Utah

Feb. 2005


Outline

Outline

Wavefield extrapolation.

Topographic phase-shift method.

Application to migration.

Application to multiple prediction.

Summary.


Outline1

Outline

Wavefield extrapolation.

Topographic phase-shift method.

Application to migration

Application to multiple prediction.

Summary.


Wavefield extrapolation

Wavefield Extrapolation

One-way wave-equation.

- Phase-shift method (Gazdag, 1984).

Iterative (depth-by-depth) implementation.

Horizontal velocity variation:

- PSPI, Split-step, Fourier-FD, etc.

Irregular surfaces.


Reshef s approach for topography

Reshef’s Approach for Topography

Geophone line

Datum lines


Issues with reshef s approach

Issues with Reshef’s Approach

Non-uniform geophone spacing problem


Outline2

Outline

Wavefield extrapolation.

Topographic phase-shift method.

Application to migration.

Application to multiple prediction.

Summary.



Synthetic test

Synthetic Test

z = 0

z = Z(x)






Outline3

Outline

Wavefield extrapolation.

Topographic phase-shift method.

Application to migration.

Application to multiple prediction.

Summary.





Waveform tomography sheng and buddensiek 2004

Waveform Tomography (Sheng and Buddensiek, 2004)


Outline4

Outline

Wavefield extrapolation.

Topographic phase-shift method.

Application to migration.

Application to multiple prediction.

Summary.


Water layer multiple wlm

Water-layer Multiple (WLM)

Major free-surface multiples in marine data.

Can be very precisely predicted.

Very few acquisition requirements.

(even in a single shot gather).


Finite difference experiments

Finite-difference Experiments

  • Unpredictable WLM resemble their predictable counterparts.

Only one type WLM can be predicted.

  • Improvement can be made by using the receiver-side ghost rather than the data in the prediction.




Waveform comparison1
Waveform Comparison

At a geophone above non-flat water bottom

At a geophone above flat water bottom







A nmo panel after demultiple
A NMO Panelafter Demultiple


Stack before demultiple
Stack before Demultiple

Time (S)

Offset (m)


Stack after demultiple
Stack after Demultiple

Time (S)

Offset (m)


Poststack migration before demultiple
Poststack Migration before Demultiple


Poststack migration after demultiple
Poststack Migration after Demultiple


3d synthetic experiment

3D Synthetic Experiment

128

11

dy= 50 m

dx= 25 m

Sea Floor

Reflector





Outline5

Outline

Wavefield extrapolation.

Topographic phase-shift method.

Application to migration

Application to multiple prediction.

Summary.


Summary

Summary

Topographic phase shift is efficient for wavefield extrapolation from irregular surfaces.

It is useful for migration and multiple prediction, especially for large and 3D data sets.


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