The Use of Compression Technology to Aid Seismic Interpretation in the Northwest Shelf - Australia

Keith Woollard - GeoCom Services Australia Pty Ltd

Introduction Technical evaluation of compression

from the viewpoint of interpreters and data managers

No performance testing Pre-beta test software

The Need

3D seismic surveys continue to grow at least as fast as disc capacity increases

Trend toward multi-volume interpretation Trend to higher resolution Disc may be cheap, but remains a

significant cost• Data management• Backups/archiving

Performance degradation for large surveys

What Is Being Offered Compression available in next landmark

release, version 1998.5 3D seismic only Applications reading 3D seismic in R98 plus

will be able to read compressed seismic in 1998.5• Seisworks• Syntool• Stratworks• Poststack• Zap

Compression Traditional compression methods

• LZI, huffman etc. Not suitable for seismic• Integerisation is a form of compression using a

BFI algorithm • Data reduction, resample

Landmark’s seismic compression• Designed specifically for seismic• Not reversible, some loss of data• User controls overall distortion level

• 1 df 99

Worldwide Compression RatiosC om p re s s io n ra t io c om p a ris o ns fo r d a ta fr o m H o llan d , N o rw a y , N ige r ia a n d A us tra lia

0

10

20

30

40

50

60

70

80

90

0 20 40 60 80 1 00

S p ec ifie d D is to r t io n (% R M S a m pl itu d e er ro r / R M S a m pl itu d e or ig i n a l)

Co

mp

res

sio

n r

ati

o

w.r

.t.

32 b

it i

np

ut

seis

mic

da

ta(

02.

3dv

size

/ .

cmp

siz

e )

5 00 - 10 00 m s ec H o lla nd la nd

1 50 0 - 20 00 m se c H ol lan d la nd

1 20 0-17 0 0 m se c N orw a y m a r ine

10 00 -15 00 m s ec A us tra lia n m arin e

1 50 0-2 00 0 m s ec N ige r ia m arine

5 00 - 1 00 0 m s ec ra nd om no ise

5 00 m se c s ing le b pa ss w av ele t

After John Kerr

Comparisons

Raw 32 bit Compressed (DF=1) 4.6gb 501mb

Comparisons

Notes:

1 Input is 4.6 gb of 32 bit Floating point

n

n

rawn

loadedrawn

1

2

1

2

)(/1

)(/11002

Difference Plots

Seismic 8 bit integer 16 bit integer Compressed DF=1

Comparisons

Raw 32 bit Compressed DF=1

Tim

e Dom

ain Instantaneous

Frequency

Interpretation

Interpretation From Same Seed

Logistics

Able to load from seg-y to compressed using bcm3d and PSDL

Able to convert from 3dv to compressed• Generally better to reload

Seisworks able to display one volume and track another

Zap able to read compressed directly without need to reduce to 8 bit range

Issues

Implications for visualisation and immersion

Electronic data transfer • Intra-company• Inter-company• Quick-look seismic for farm-outs

Data loading means choosing distortion, not scale & clip

Issues - Cont. Compression retains absolute numbers Compression is too good, prefer DF < 1 Compression is a route to image

individual 3D projects greater than 62 gb Compression is able to deal with

spatially variable amplitudes better than integerisation

Performance Issues Bcm3d to compressed runs 5% slower Trace ordering of seg-y tapes is

significant Large reduction on network traffic No testing done on seismic display

speeds

Recommendations Always load data compressed rather than

integer Choose DF for standard tracking

• Survey by survey• Company standard• GeoCom recommends DF=1

Additional volume for display / transmitting• GeoCom recommends DF=90

Load ALL volumes (offsets, velocities etc)

Summary Potentially huge savings in disc usage With DF=1, 16 bit quality in 20% of space Still a compromise, but a far better one than

converting to integer Peace between interpreters and system

administrators (for a while)