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
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

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 Ratios
90
5 00 - 10 00 m s ec H o lla nd la nd
80
( 0 2 . 3 d v s i ze / . c m p s iz e )
C o m p r e s s i o n ra t io
w .r. t . 3 2 b i t i n p u t s e is m i c d a ta
C om p re s s io n ra tio 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
1 50 0 - 20 00 m se c H ollan d la nd
70
60
1 20 0-17 0 0 m se c N orw a y m a r ine
50
10 00 -15 00 m s ec A us tra lia n m arin e
40
1 50 0-2 00 0 m s ec N ige ria m arine
30
20
5 00 - 1 00 0 m s ec ra nd om no ise
10
5 00 m se c s ing le b pa ss w av ele t
0
0
20
40
60
80
1 00
S p ec ifie d D is to r t io n (% R M S a m p l itu d e er ro r / R M S a m p l itu d e o r ig i n a l)
After John Kerr
Comparisons
Raw 32 bit
4.6gb
Compressed (DF=1)
501mb
Comparisons
Notes:
1 Input is 4.6 gb of 32 bit Floating point
2
100  1 / n1 (raw  loaded ) 2
n
1 / n1 (raw) 2
n
Difference Plots
Seismic
8 bit integer
16 bit integer
Compressed DF=1
Comparisons
Time Domain
Compressed DF=1
Instantaneous Frequency
Raw 32 bit
Interpretation
Interpretation From Same Seed
Logistics
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
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.


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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
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
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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
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

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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)