OCEAN BOTTOM SEISMICS: Impact on field development

OCEAN BOTTOM SEISMICS:Impact on field development

Mark Thompson, Børge Arntsen* and Lasse Amundsen

Statoil R&D

SEG 2007

Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.

• Introduction

• Experiences from North Sea Fields– Statfjord– Snorre– Volve– Kvitebjørn

• Conclusions


The history.• Late 1980's: Statoil developed "SUMIC", thus

pioneering the marine shear wave (4C) recording technology

• 1993: 2D-4C TOMMELITEN SURVEY

– Objective: Demonstrate potential of 4C technology to image through and below gas chimneys

• 1997: Statoil acquired the first 3D/4C survey in the North Sea

• 1999: Kauffman Gold Medal Award (to the inventors for an outstanding contribution to the development of new geophysical methods)

• 2002: Statoil acquire worlds first 4D/4C dataset acquired at Statfjord

• 2002: Statoil acquire one of the worlds largest 4C datasets at Statfjord


The experience.• Offshore tests (SUMIC)

– Gullfaks, 1989

– Gullfaks and Troll, 1993

• Tommeliten 2D, 1993

• Gullfaks 2D, 1995

• Statfjord 3D, 1997

• Block 24/12 (PL 204) 2D, 1997

• Sleipner Øst 2D, 1997

• Faeroes/Shetland Basin 2D, 1997

• Huldra 2D, 1998

• MN4C98-2, Møre Basin (Bl. 6303)

• MN4C98-3, Fles (Bl. 6605)

• MN4C98-4, Helland Hansen (Bl. 6505)

• MN4C98-5, Modgunn Arch (Bl. 6403)

• Gullfaks South 3D, 2000

• Gullfaks 3D, 2001

• Gullfaks South 3D, 2002• Statfjord 3D, 2002• Statfjord Øst 3D, 2002• Volve 3D, 2002• Gullfaks 3D, 2003• Visund 3D, 2003• Tyrihans 2.5D, 2003 (eField

Evaluation)• Heidrun 3D, 2003• Exploration 2D, 2003 (5 lines ?)• Kvitebjørn 3D, 2003• Vigdis/Borg 3D, 2004• Snorre 3D, 2004• Kvitebjørn 3D, 2004• Gullfaks 3D(4D), 2005• Valemon 3D, 2006• Snøhvit 2.5D, 2006


The experience.• Imaging through a gas cloud

– Tommeliten 2D (1993), Gullfaks South 3D (2000), Gullfaks South 3D (2002)

• Structural imaging of a complex structure– Statfjord 3D (1997), Gullfaks 3D (2001), Statfjord 3D (2002), Statfjord Øst 3D (2002),

Volve 3D (2002),Gullfaks 3D (2003), Visund 3D (2003), Heidrun 3D (2003), Kvitebjørn 3D (2003), Vigdis/Borg 3D (2004), Snorre 3D (2004), Kvitebjørn 3D (2004)

• Exploration – Lithology and fluid prediction– Block 24/12 (PL 204) 2D (1997), Faeroes/Shetland Basin 2D (1997), MN4C98-2, Møre

Basin (Bl. 6303), MN4C98-3 Fles (Bl. 6605), MN4C98-4 Helland Hansen (Bl. 6505), MN4C98-5 Modgunn Arch (Bl. 6403), Exploration 2D, 2003

• Reservoir characterisation

– Sleipner Øst 2D (1997), Huldra 2D (1998)

• Reservoir monitoring

– Statfjord (2002), Gullfaks (2001, 2003, 2005)


• Introduction• Experiences From North Sea Fields

• Statfjord 1997 & 2002• Volve 2003• Snorre 2004• Kvitebjørn

• Conclusions

Bergen

Florø

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Statfjord OBS 1997 – One of Worlds First 3D OBS

SFC

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Statfjord Unit

• Gravitational failure at the crest of the field generated the 3 slump blocks termed A-, B- and C-block.

A

B

CBrent Gp.

Statfjord Fm.Dunlin Gp.

BSF

Courtesy of Maren Dybwad

• Main field consists of a rotated fault block with the Brent Gp., Dunlin Gp. and the Statfjord Fm.

Statfjord OBS 1997 – Worlds First 3D OBS

Streamer (1997) OBC (1997)

Model 2000 Model 2001

Top Dunlin EF depth maps

Statfjord OBS 1997

0

100

200

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400

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1.19

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er c

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(%)

Oil rate (Sm3/d) Water cut (%)

•The new fault pattern based on OBS seismic puts B-14 A and B-29 T2 in different fault blocks

•The injector was moved north of B-29 T2

•Production has increased from 200 Sm3/d to 520 Sm3/d

Model 2001

B - 14 C

B – 29 T2

B - 14 A

Production history B-29 T2

Statfjord OBS 1997

1997 Surface

1 2 3 4 5

1997 OBS

1 2 3 4 5

Courtesy of Maren Dybwad

OBS

Streamer

146 m

Eiriksson

Raude

146 m

Improved Seismic Resolution: Well 1Planned wellpath

based on streamer data (red).

Planned wellpath based on OBS seismic data

(purple).

OBS seismic suggest fault in this position

Statfjord 2002 – One of the worlds largest 3D OBS

• Areal extent: 120 km2

• Receiver line spacing: 300m

• Receiver line length: 6000m

• Receiver station spacing: 25m

• Source line length: 3000m

• Max source line offset: 1200m

• Source interval 25m (flip – flop)

Statfjord OBS 2002 – One of the worlds largest 3D OBS

Streamer

OBC

•Better definiton of onset A-block (Fault between MF and EF)

•More internal information in the C-block




• Conclusions

•Key Words.

•Reservoir : Stratigraphic & structural trap

•Age : Jurassic & Triassic - Hugin formation

•Thick sands - Strongly faulted

Structural Setting

Volve OBS 2003• History

– Oil discovered in 1993.

– Two appraisal wells drilled in 1997/98.

– Ambiguous seismic data.

• Challenges.

– Common structural interpretation.

– Volume uncertainties.

– Field development concept.

• Goal

– New well or high quality seismic data in order to decrease the structural uncertainties

and hence increase the proven volumes in the field

– Agree upon the decision basis for development of the field

Acquisition Geometry• Swath geometry with inline shooting

• 2 x 6km receiver lines per swath

• 400m receiver line separation

• 24 sail lines @ 12km per swath

• 3km inline offset; 975m x-line offset

(max.)

• 100m sail line separation

• Dual source, 50m source

separation, 25m flip/flop

Ca. 27 km² covering 5 Wells, one vertical

1 km

streamer

OBS

•Plan for development and production (PDO) approved April 2005

•Resources

•Oil 11.4 Million Sm3

•Gas 1.5 Billion. Sm3

•Field development

•Jackup process and drilling facility

•Interim storage on ship

•On stream spring 2007




• Conclusions

Snorre OBS 2004

OBS

Streamer

Snorre OBS 2004

SN 10.1

SN 9.3

SN 10.4

SN 11.4

BCU

lfu916

34/7-3

Streamer

SN 10.1

SN 9.3

SN 10.4

SN 11.4

BCU

34/7-3

OBS




• Conclusions

BCU

T.BrentT.Etive

Kvitebjørn OBS Test 2003OBS data (Cable 3) PSDM data (arb. line along cable 3)

The OBS test led to a revision of the well targets

and the first production well was moved 270 m

toward NECourtesy of Edel Areklett




• Conclusions

Ocean Bottom Seismic. A good business case !

Conclusions.

• Value has consistently been obtained from OBS in areas of

seismically challenged data.

• Data quality has generally improved when using OBS

• In spite of :-

– OBS costs a lot more than 3D streamer seismic.

– OBS data is more challenging to process and interpret.

Acknowledgements

• Statoil R&D• Statfjord

– Statoil ASA, ExxonMobil, ConocoPhillips, Norske Shell, ConocoPhillips,Centrica Resources, BP, Enterprise Oil

• Snorre– Petoro, Norsk Hydro, Statoil ASA, ExxonMobil, Idemitsu

Petroleum, RWE Dea, Total, Amerada Hess • Volve

– Statoil, ExxonMobil, Total, Norsk Hydro

Documents

OCEAN BOTTOM SEISMICS: Impact on field development