migration in a nutshell migration in a nutshell migration in a nutshell d.s. macpherson

Migration

In a

NutshellMigration

In a

NutshellMigration

In a

Nutshell

D.S. MacphersonD.S. Macpherson

- The problem with stackingA. The nature of the seismic image

Migrating the seismic imageon to the plane of the reflector

Un-migratedstacked data

Migratedimage

Un-migratedimage surface

Migratedimage surface

A - 17

F. Imaging by seismic migration

Un-migrated trace

Migrated trace

- Kirchhoff summation

F - 9

F. Imaging by seismic migration

Reflector surface

Migration of stacked (ZSR) traceby Kirchhoff summation

- Kirchhoff summation

F - 10

F. Imaging by seismic migration

Migration of a diffractionby Kirchhoff summation

Diffraction hyperbola

- Kirchhoff summation

F - 13

F. Imaging by seismic migration

Un-migrated stack

Migrated stack

- Kirchhoff summation

F - 15

Un-migrated Model

E. Seismic data processing - Pre-stack migration

E - 26

Migrated ModelEnd effect fromthe model

Migration noise

E. Seismic data processing - Pre-stack migration

E - 25

Decimated Model(Every fifth trace)

E. Seismic data processing - Pre-stack migration

E - 27

Migrated Model(Single offset - 600 feet)

E. Seismic data processing - Pre-stack migration

E - 28

TRACE SWEEPAMIMATION

POSTSTACK

A B C D

Source Receiver

A A

A B C D

Source Receiver

B B

A B C D

Source Receiver

C C

A B C D

Source Receiver

D D

Composite

A B C D

F. Imaging by seismic migration

Reflector surface

Migration of stacked (ZSR) traceby Kirchhoff summation

- Kirchhoff summation

F - 10

Seismic section in depth showing productive intervals

Case 3 6

- The problem with stacking

Common mid-point

Moveout in the presence of dip

Stackedtrace

Moveoutcorrected

traces

Commonmid-point

gather

F. Imaging by seismic migration

F - 16

SourceLocation

ReceiverLocation

Single Seismic TracePre-stack Migrated

E. Seismic data processing - Prestack migration

E - 24

- The problem with stacking

Common mid-point

Image point gather

Stackedtrace

Migratedtraces

Common imagepoint

Tracesin time

Common midpoint

Image pointwindow

3D bin size

F. Imaging by seismic migration

F - 17

PreStack MigrationEllipse Sweep

- The problem with stackingA. The nature of the seismic image

Common mid-point

Image point gather

Stackedtrace

Migratedtraces

Common imagepoint

Tracesin time

Common midpoint

Image pointwindow

3D bin size

A - 21

Common mid-point

Image pointwindow

3D bin size

Common mid-point

1

Common mid-point

2

Common mid-point

3

Common mid-point

4

Common mid-point

5

Common mid-point

6

Common mid-point

7

Common mid-point

8

Common mid-point

9

Image pointwindow

3D bin size

Image pointwindow

3D bin size

Migratedtraces

Common imagepoint

Stacking traces in the image point gather in

offset ranges

Image pointwindow

3D bin size

These are all stacked traces,

but they are stacked in

offset ranges

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 1Near offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 2

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 3

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Image pointwindow

3D bin size

Trace 4Far offsets

Common mid-pointCurrent offset

Migratedtraces

Common imagepoint

Ray Tracing for the Reflections in the

Gather

Image pointwindow

3D bin size

Migratedtraces

Common imagepoint

Trace 1Near offsets

Image pointwindow

3D bin size

Migratedtraces

Common imagepoint

Trace 2

Image pointwindow

3D bin size

Migratedtraces

Common imagepoint

Trace 3

Image pointwindow

3D bin size

Trace 4Far offsets

Migratedtraces

Common imagepoint

Common mid-point

Image pointwindow

3D bin size

So we started with this

Common mid-point

Image pointwindow

3D bin size

Image pointwindow

3D bin size

And ended up with this

AVO Display

TRACE SWEEPAMIMATION

PRESTACK

A B C D

Source Receiver

A A

A B C D

Source Receiver

A B

A B C D

Source Receiver

A C

A B C D

Source Receiver

A D

A B C D

Source Receiver

B A

A B C D

Source Receiver

B B

A B C D

Source Receiver

B C

A B C D

Source Receiver

B D

A B C D

Source Receiver

C A

A B C D

Source Receiver

C B

A B C D

Source Receiver

C C

A B C D

Source Receiver

C D

A B C D

Source Receiver

D A

A B C D

Source Receiver

D B

A B C D

Source Receiver

D C

A B C D

Source Receiver

D D

Composite

A B C D

F. Imaging by seismic migration

V1V2

V3

V4

Dep

th

Dep

th

Dep

thT

ime

3D time (stacked) data cube

3D depth velocity model 3D ray tracing

3D “sweep” ray tracing

Iso-timecontours

- Depth migration

F - 22

Depth Migration Iso-time Map for the Shot Location

Depth Migration Iso-time Map for the Receiver Location

Depth Migration Iso-time Mapfor Both the Shot and Receiver Locations

The Sweep of a Single Prestack Trace

Link to TCHART.exe

- Displays in depth and timeA. The nature of the seismic image

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

De

pth

(Kilo

me

ters

)

Tim

e (S

ec

on

ds

)

A - 30

PRESTACKWAVE EQUATION

AMIMATION

SOURCE

RECIEVER

SOURCE RECIEVER

SOURCE RECIEVER

200 Millisecond Image

Source time60 ms.

Receiver time140 ms.

SOURCE RECIEVER

200 Millisecond Image

Source time70 ms.

Receiver time130 ms.

SOURCE RECIEVER

200 Millisecond Image

Source time80 ms.

Receiver time120 ms.

SOURCE RECIEVER

200 Millisecond Image

Source time90 ms.

Receiver time110 ms.

SOURCE RECIEVER

200 Millisecond Image

Source time100 ms.

Receiver time100 ms.

SOURCE RECIEVER

200 Millisecond Image

Source time110 ms.

Receiver time90 ms.

SOURCE RECIEVER

200 Millisecond Image

Source time120 ms.

Receiver time80 ms.

SOURCE RECIEVER

200 Millisecond Image

Source time130 ms.

Receiver time70 ms.

SOURCE RECIEVER

200 Millisecond Image

Source time140 ms.

Receiver time60 ms.

SOURCE RECIEVER

200 Millisecond Image

F. Imaging by seismic migration

3D Post-stack Time Migration

3D Pre-ststack Depth Migration

Data Courtesy of CGG

- Depth migration

F - 24