OCEAN BOTTOM SEISMICS: Impact on field development
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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
Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.
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
Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.
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
Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.
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)
Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.
• Introduction• Experiences From North Sea Fields
• Statfjord 1997 & 2002• Volve 2003• Snorre 2004• Kvitebjørn
• Conclusions
Bergen
Florø
3 00`2 00 4 00 5 00
61 0061 00`
62 00`
2 00`
34 35 36
29
30 31
1 2 3 1 2 3 12
3
8
64
5 64 5 6
45
9
7 8 9 7 8 97
8
1210 11 12 10
1112 10
11
3 1 2 3 1 23 1
2
4 5 6 46
45
7 9 78
9
4
1
Snorre
Huldra
Statfjord
Vigdis
Visund
Rimfaks
Tordis
Gullfaks
GF Gamma
SF Nord
SF Øst
Kvitebjørn
Gullfaks Sør
A
B
C
A
A'
33/9-1N
445000
Kilometer
0 1 2 3 4 5
432500
435000 437500 440000 442500
2400
2400
2400
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3100
3200SFA
SFB
OLSB
6785000
6787500
receiver lines
shot area
N
Statfjord OBS 1997 – One of Worlds First 3D OBS
SFC
SFB
SFA
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
300
400
500
600
01.0
1.19
99
01.0
3.19
99
01.0
5.19
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01.0
7.19
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01.0
9.19
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01.1
1.19
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1.20
00
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02
Oil
rat
e (S
m3/
d)
0
10
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Wat
er c
ut
(%)
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
Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.
• Introduction• Experiences From North Sea Fields
• Statfjord 1997 & 2002• Volve 2003• Snorre 2004• Kvitebjørn
• 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
Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.
• Introduction• Experiences From North Sea Fields
• Statfjord 1997 & 2002• Volve 2003• Snorre 2004• Kvitebjørn
• 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
Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.
• Introduction• Experiences From North Sea Fields
• Statfjord 1997 & 2002• Volve 2003• Snorre 2004• Kvitebjørn
• 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
Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics.
• Introduction• Experiences From North Sea Fields
• Statfjord 1997 & 2002• Volve 2003• Snorre 2004• Kvitebjørn
• 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
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