11. juni 2012 / 1

Ocean Bottom Seismic (OBS) applications and acquisition strategies

Kim Gunn Maver and Wolfgang Schnetzer

11. juni 2012 / 2

Seismic resolution using OBS

Streamer

OBC

11. juni 2012 / 3

Ocean Bottom Seismic (OBS)

Ocean Bottom Cables (OBC)

Ocean Bottom Nodes (OBN)

Autonomous nodes

Nodes-on-a-rope

Ocean Bottom Recorder (OBR)

Some definitions……..

11. juni 2012 / 4

• Unique OBS applications

• Resolution

• Field access; obstructions

• Data domain

• Survey design

• Parallel and orthogonal

• Comparison with streamer acquisition

• Final comments

Overview

11. juni 2012 / 5

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

11. juni 2012 / 7

Imaging issues

Towed streamer data can’t succesfully image through channelized Eocene overburden

The channels attenuate the primary energy and

produce strong multiples

11. juni 2012 / 8

Sele

Streamer OBC

Andrew Satellite development, CNS (2009)

OBC imaging through structurally complex areas

Padmos et al, First Break, October 2010

11. juni 2012 / 9

Streamer vs OBC data resolution

Padmos et al, First Break, October 2010

Streamer

OBC

Andrew Satellite development, CNS (2009)

11. juni 2012 / 10

Streamer

OBC Phase1

OBC Phase2

top Sele

top Res

Andrew Satellite development, CNS (2009)

Gradient impedance section through well 16/23-7

11. juni 2012 / 11

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

11. juni 2012 / 12

Resolution and Imaging

Field access

Data domain

Why choose OBS for offshore seismic acquision?

Streamer OBC

Streamer OBC

11. juni 2012 / 13

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

11. juni 2012 / 14

Acquisition in obstructed areas

Cable deployment plot

Source vessel close pass

11. juni 2012 / 15

Close passes

11. juni 2012 / 16

Resolution and Imaging

Field access

Data domain

Why choose OBS for offshore seismic acquision?

Streamer OBC

Streamer OBC

11. juni 2012 / 17

• 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

11. juni 2012 / 18

OBC verifying direct hydrocaron indicator, CNS (2009)

Hughes, NPF Geophysical Seminar, 2010

3D PSTM

2D PZ (PP time)

11. juni 2012 / 19

3D PSTM

2D PS (PS time)

Hughes, NPF Geophysical Seminar, 2010

OBC verifying direct hydrocaron indicator, CNS (2009)

11. juni 2012 / 20

• Unique OBS applications

• Resolution

• Field access; obstructions

• Data domain

• Survey design

• Parallel and orthogonal

• Comparison with streamer acquisition

• Final comments

Overview

11. juni 2012 / 21

Types of OBS seismic acquisition

Parallel

Orthogonal

11. juni 2012 / 22

Parallel acquisition: rolling pattern

11. juni 2012 / 23

Orthogonal acquisition

11. juni 2012 / 24

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

11. juni 2012 / 25

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

11. juni 2012 / 26

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

11. juni 2012 / 27

• 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

11. juni 2012 / 28

Thank you ……….

Ocean Pearl and Vikland