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Ocean Bottom Seismic (OBS)
applications and acquisitionstrategies
Kim Gunn Maver and Wolfgang Schnetzer
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Seismic resolution using OBS
Streamer
OBC
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Ocean Bottom Seismic (OBS)
Ocean Bottom Cables (OBC)
Ocean Bottom Nodes (OBN)
Autonomous nodes
Nodes-on-a-rope
Ocean Bottom Recorder (OBR)
Some definitions..
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Unique OBS applications Resolution
Field access; obstructions
Data domain
Survey design
Parallel and orthogonal
Comparison with streamer acquisition
Final comments
Overview
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Resolution and Imaging
Field access
Data domain
Why choose OBS for offshore seismic acquision?
Streamer OBC
Streamer OBC
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Andrew Satellite development, CNS (2009)
Eocene sand channels causing difficulty withstreamer data
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Imaging issues
Towed streamer data cant succesfully image
through channelized Eocene overburden
The channels attenuate the primary energy andproduce strong multiples
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Sele
Streamer OBC
Andrew Satellite development, CNS (2009)
OBC imaging through structurally complex areas
Padmos et al, First Break, October 2010
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Streamer vs OBC data resolution
Padmos et al, First Break, October 2010
Streamer
OBC
Andrew Satellite development, CNS (2009)
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Streamer
OBCPhase1
OBCPhase2
topSele
topRes
Andrew Satellite development, CNS (2009)
Gradient impedance section through well 16/23-7
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main sandfairway
16/24a-1
16/23-2
16/23-3
1km
16/23-7
16/23-1
16/24a-1
16/23-2
16/23-3
1km
16/23-7
16/23-1
Streamer OBC
2009 CNS Andrew Satellite development
Amplitude map from gradient impedance
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Resolution and Imaging
Field access
Data domain
Why choose OBS for offshore seismic acquision?
Streamer OBC
Streamer OBC
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Campos Basin, Pre-salt imaging (2011)
OBC imaging through structurally complex areas
Full azimuth acquisition
4C data to be used for
development of pre-saltdiscovery
Veiera et al, SBGf conference Ex. Abstracts, 2011
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Acquisition in obstructed areas
Cable deployment plot
Source vessel close pass
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Close passes
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Resolution and Imaging
Field access
Data domain
Why choose OBS for offshore seismic acquision?
Streamer OBC
Streamer OBC
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Acquisition:
P-wave down
Reflected up as P-wave (PP)
Reflected up as S-wave (PS)
4C OBS acquisition
4C sensor:
3 component geophone
1 hydrophone
OBCStreamer seismic
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OBC verifying direct hydrocaron indicator, CNS (2009)
Hughes, NPF Geophysical Seminar, 2010
3D PSTM
2D PZ (PP time)
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3D PSTM
2D PS (PS time)
Hughes, NPF Geophysical Seminar, 2010
OBC verifying direct hydrocaron indicator, CNS (2009)
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Unique OBS applications Resolution
Field access; obstructions
Data domain
Survey design Parallel and orthogonal
Comparison with streamer acquisition
Final comments
Overview
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Types of OBS seismic acquisition
Parallel
Orthogonal
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Parallel acquisition: rolling pattern
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Orthogonal acquisition
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Azimuth displays courtesy of BP
Predicted survey duration of 72 days
600 fold over 100km2
OBC acquisition: Typical North Sea field 100km2
Survey lay-out
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Azimuth displays courtesy of BP
Frade Field:
Dual Azimuth 3 obstructions Survey duration ~ 60 days
Multi-azimuth seismic ~ 100km2
Cooke et al, SBGf conference Ex. Abstracts 2011
Streamer acquisition
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Azimuth displays courtesy of BP
OBC acquisition
Veiera et al, SBGf conference Ex. Abstracts 2011
Campos Basin prospect:
Full azimuth 6 obstructions Survey duration ~ 100 days
Full-azimuth seismic ~ 100km2
Survey design
Azimuthal coverage
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OBS have some unique attributes and applications: Resolution and Imaging
Field access
Data domain
Smaller OBS survey: As efficient as streamer seismic and with better resolution/imaging
OBS is becoming a strategic technology
Final remarks
h k
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Thank you .
Ocean Pearl and Vikland