Ocean Bottom Seismic (OBS) applications and acquisition ... · PDF file11. juni 2012 1/ Ocean...
Transcript of Ocean Bottom Seismic (OBS) applications and acquisition ... · PDF file11. juni 2012 1/ Ocean...
11. juni 2012 / 1
Ocean Bottom Seismic (OBS) applications and acquisition strategies
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
11. juni 2012 / 6 Padmos et al, First Break, October 2010
Andrew Satellite development, CNS (2009)
Eocene sand channels causing difficulty with streamer data
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Imaging issues
Towed streamer data can’t succesfully image through channelized Eocene overburden
The channels attenuate the primary energy and
produce 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
OBC Phase1
OBC Phase2
top Sele
top Res
Andrew Satellite development, CNS (2009)
Gradient impedance section through well 16/23-7
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main sand fairway
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-salt discovery
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
OBC Streamer 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
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Thank you ……….
Ocean Pearl and Vikland