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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