Migration In a Nutshell Migration In a Nutshell Migration In a Nutshell D.S. Macpherson

- The problem with stacking A. The nature of the seismic image Migrating the seismic image on to the plane of the reflector Un-migrated stacked data Migrated image Un-migrated image surface Migrated image 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) trace by Kirchhoff summation - Kirchhoff summation F - 10

F. Imaging by seismic migration Migration of a diffraction by 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 Model End effect from the 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 feet) E. Seismic data processing - Pre-stack migration E - 28

TRACE SWEEP AMIMATION POSTSTACK

ABCD Source Receiver A A

ABCD Source Receiver B B

ABCD Source Receiver C C

ABCD Source Receiver D D

Composite ABCD

F. Imaging by seismic migration Reflector surface Migration of stacked (ZSR) trace by 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 Stacked trace Moveout corrected traces Common mid-point gather F. Imaging by seismic migration F - 16

Source Location Receiver Location Single Seismic Trace Pre-stack Migrated E. Seismic data processing - Prestack migration E - 24

- The problem with stacking Common mid-point Image point gather Stacked trace Migrated traces Common image point Traces in time Common mid point Image point window 3D bin size F. Imaging by seismic migration F - 17

PreStack Migration Ellipse Sweep

- The problem with stacking A. The nature of the seismic image Common mid-point Image point gather Stacked trace Migrated traces Common image point Traces in time Common mid point Image point window 3D bin size A - 21

Common mid-point Image point window 3D bin size

Common mid-point 1

2

3

4

5

6

7

8

9

Image point window 3D bin size

Image point window 3D bin size Migrated traces Common image point

Stacking traces in the image point gather in offset ranges

Image point window 3D bin size These are all stacked traces, but they are stacked in offset ranges Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 1 Near offsets Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 2 Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 3 Common mid-point Current offset Migrated traces Common image point

Image point window 3D bin size Trace 4 Far offsets Common mid-point Current offset Migrated traces Common image point

Ray Tracing for the Reflections in the Gather

Image point window 3D bin size Migrated traces Common image point Trace 1 Near offsets

Image point window 3D bin size Migrated traces Common image point Trace 2

Image point window 3D bin size Migrated traces Common image point Trace 3

Image point window 3D bin size Trace 4 Far offsets Migrated traces Common image point

Common mid-point Image point window 3D bin size So we started with this

Common mid-point Image point window 3D bin size Image point window 3D bin size And ended up with this

AVO Display

TRACE SWEEP AMIMATION PRESTACK

ABCD Source Receiver A A

ABCD Source Receiver A B

ABCD Source Receiver A C

ABCD Source Receiver A D

ABCD Source Receiver B A

ABCD Source Receiver B B

ABCD Source Receiver B C

ABCD Source Receiver B D

ABCD Source Receiver C A

ABCD Source Receiver C B

ABCD Source Receiver C C

ABCD Source Receiver C D

ABCD Source Receiver D A

ABCD Source Receiver D B

ABCD Source Receiver D C

ABCD Source Receiver D D

Composite ABCD

F. Imaging by seismic migration V1 V2 V3 V4 Depth Time 3D time (stacked) data cube 3D depth velocity model3D ray tracing 3D “sweep” ray tracing Iso-time contours - 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 Map for Both the Shot and Receiver Locations

The Sweep of a Single Prestack Trace Link to TCHART.exe

- Displays in depth and time A. The nature of the seismic image Depth (Kilometers) Time (Seconds) A - 30

PRESTACK WAVE EQUATION AMIMATION

SOURCE

RECIEVER

SOURCE RECIEVER

SOURCE RECIEVER 200 Millisecond Image Source time 60 ms. Receiver time 140 ms.

SOURCE RECIEVER 200 Millisecond Image Source time 70 ms. Receiver time 130 ms.

SOURCE RECIEVER 200 Millisecond Image Source time 80 ms. Receiver time 120 ms.

SOURCE RECIEVER 200 Millisecond Image Source time 90 ms. Receiver time 110 ms.

SOURCE RECIEVER 200 Millisecond Image Source time 100 ms. Receiver time 100 ms.

SOURCE RECIEVER 200 Millisecond Image Source time 110 ms. Receiver time 90 ms.

SOURCE RECIEVER 200 Millisecond Image Source time 120 ms. Receiver time 80 ms.

SOURCE RECIEVER 200 Millisecond Image Source time 130 ms. Receiver time 70 ms.

SOURCE RECIEVER 200 Millisecond Image Source time 140 ms. Receiver time 60 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