8/12/2019 386 AVO Class Modeling

1/24

Modeling AVO Classes

This document describes modeling of the gas sand AVO classes and thederived AVO attributes for both positive and reverse polarity wavelets.

Feby HapsariVHR Jakarta - October 2006

8/12/2019 386 AVO Class Modeling

2/24

Last Updated: October 2006 2

Rutherford/Williams Classification

Rutherford and Williams (1989) derived the following classif ication scheme for AVO

anomalies, with further modifications by Ross and Kinman (1995) and Castagna(1997):

Class 1: High impedance sand with decreasing AVO

Class 2: Near-zero impedance contrast

Class 2p: Same as 2, with polarity changeClass 3: Low impedance sand with increasing AVO

Class 4: Low impedance sand with decreasing AVO

8/12/2019 386 AVO Class Modeling

3/24

Last Updated: October 2006 3

This figure from Castagna et

al (1998) il lustrates all 5 of

the gas sand AVO classes.

Gas Sand AVO Classes

8/12/2019 386 AVO Class Modeling

4/24

8/12/2019 386 AVO Class Modeling

5/24

8/12/2019 386 AVO Class Modeling

6/24Last Updated: October 2006 4

Depth (m) P-wave (m/s) S-wave (m/s) Density (g/cc)

0 2900 1330 2.29

1000 2900 1330 2.29

1010 3220 1620 2.35

2000 2900 1330 2.29

Class 1

Depth (m) P-wave (m/s) S-wave (m/s) Density (g/cc) Depth (m) P-wave (m/s) S-wave (m/s) Density (g/cc)0 2900 1330 2.29 0 2900 1330 2.29

1000 2900 1330 2.29 1000 2900 1330 2.29

1010 2800 1620 2.28 1010 3000 1620 2.3

2000 2900 1330 2.29 2000 2900 1330 2.29

Depth (m) P-wave (m/s) S-wave (m/s) Density (g/cc) Depth (m) P-wave (m/s) S-wave (m/s) Density (g/cc)0 2900 1330 2.29 0 2900 1330 2.29

1000 2900 1330 2.29 1000 2900 1330 2.29

1010 2540 1620 2.09 1010 2540 1120 2.39

2000 2900 1330 2.29 2000 2900 1330 2.29

Class 4

Class 2 Class 2p

Class 3

The model was a 10 m thick sand at 1000 m depth. The data used for creating simple 3-

layer models is as shown:

Data

8/12/2019 386 AVO Class Modeling

7/24Last Updated: October 2006 5

Class 1

8/12/2019 386 AVO Class Modeling

8/24Last Updated: October 2006 6

Class 1

8/12/2019 386 AVO Class Modeling

9/24Last Updated: October 2006 7

Class 2

8/12/2019 386 AVO Class Modeling

10/24

Last Updated: October 2006 8

Class 2

8/12/2019 386 AVO Class Modeling

11/24

Last Updated: October 2006 9

Class 2p

8/12/2019 386 AVO Class Modeling

12/24

Last Updated: October 2006 10

Class 2p

8/12/2019 386 AVO Class Modeling

13/24

Last Updated: October 2006 11

Class 3

8/12/2019 386 AVO Class Modeling

14/24

Last Updated: October 2006 12

Class 3

8/12/2019 386 AVO Class Modeling

15/24

Last Updated: October 2006 13

Class 4

8/12/2019 386 AVO Class Modeling

16/24

Last Updated: October 2006 14

Class 4

8/12/2019 386 AVO Class Modeling

17/24

Last Updated: October 2006 15

Positive Polarity A*B Product

8/12/2019 386 AVO Class Modeling

18/24

Last Updated: October 2006 16

Reverse Polarity A*B Product

8/12/2019 386 AVO Class Modeling

19/24

Last Updated: October 2006 17

Positive Polarity SPR

8/12/2019 386 AVO Class Modeling

20/24

Last Updated: October 2006 18

Reverse Polarity SPR

8/12/2019 386 AVO Class Modeling

21/24

Last Updated: October 2006 19

Positive Polarity Rs

8/12/2019 386 AVO Class Modeling

22/24

Last Updated: October 2006 20

Reverse Polarity Rs

8/12/2019 386 AVO Class Modeling

23/24

Last Updated: October 2006 21

Positive Polarity Fluid Factor

8/12/2019 386 AVO Class Modeling

24/24

Last Updated: October 2006 22

Reverse Polarity Fluid Factor