the use of compression technology to aid seismic interpretation in the northwest shelf - australia...
TRANSCRIPT
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)