OCEAN BOTTOM SEISMICS: Impact on field development

1. OCEAN BOTTOM SEISMICS:Impact on field development Mark Thompson, Børge Arntsen* and Lasse Amundsen Statoil R&D SEG 2007

2. Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics. • Introduction • Experiences from North Sea Fields • Statfjord • Snorre • Volve • Kvitebjørn • Conclusions

3. 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

4. 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.

5. 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)

6. Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics. • Introduction • Experiences From North Sea Fields • Statfjord 1997 & 2002 • Volve 2003 • Snorre 2004 • Kvitebjørn • Conclusions

7. N Statfjord OBS 1997 – One of Worlds First 3D OBS

8. A B Brent Gp. C BSF Dunlin Gp. Statfjord Fm. SFC SFA SFB Statfjord Unit • Main field consists of a rotated fault block with the Brent Gp., Dunlin Gp. and the Statfjord Fm. • Gravitational failure at the crest of the field generated the 3 slump blocks termed A-, B- and C-block. Courtesy of Maren Dybwad

9. Streamer (1997) OBC (1997) Statfjord OBS 1997 – Worlds First 3D OBS

10. Statfjord OBS 1997 Model 2001 Model 2000 Top Dunlin EF depth maps

11. Model 2001 B - 14 C B – 29 T2 B - 14 A Statfjord OBS 1997 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 Production history B-29 T2

12. 1997 Surface 1 2345 1997 OBS 12345 Courtesy of Maren Dybwad

13. Eiriksson Raude 146 m Improved Seismic Resolution: Well 1 Planned wellpath based on streamer data (red). Planned wellpath based on OBS seismic data (purple). Streamer OBS OBS seismic suggest fault in this position 146 m

14. 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)

15. Statfjord OBS 2002 – One of the worlds largest 3D OBS Streamer Better definiton of onset A-block (Fault between MF and EF) More internal information in the C-block OBC

16. Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics. • Introduction • Experiences From North Sea Fields • Statfjord 1997 & 2002 • Volve 2003 • Snorre 2004 • Kvitebjørn • Conclusions

17. Structural Setting • Key Words. • Reservoir : Stratigraphic & structural trap • Age : Jurassic & Triassic - Hugin formation • Thick sands - Strongly faulted

18. 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

19. Acquisition Geometry Ca. 27 km² covering 5 Wells, one vertical • 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

20. 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 1 km

21. Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics. • Introduction • Experiences From North Sea Fields • Statfjord 1997 & 2002 • Volve 2003 • Snorre 2004 • Kvitebjørn • Conclusions

22. Snorre OBS 2004 Streamer OBS

23. Snorre OBS 2004 34/7-3 34/7-3 BCU BCU SN 11.4 SN 11.4 SN 10.4 SN 10.4 SN 10.1 SN 10.1 SN 9.3 SN 9.3 lfu916 Streamer OBS

24. Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics. • Introduction • Experiences From North Sea Fields • Statfjord 1997 & 2002 • Volve 2003 • Snorre 2004 • Kvitebjørn • Conclusions

25. Kvitebjørn OBS Test 2003 OBS data (Cable 3) PSDM data (arb. line along cable 3) BCU T.Brent T.Etive The OBS test led to a revision of the well targets and the first production well was moved 270 m toward NE Courtesy of Edel Areklett

26. Experiences with Multi-Azimuth Acquisition in Ocean Bottom Seismics. • Introduction • Experiences From North Sea Fields • Statfjord 1997 & 2002 • Volve 2003 • Snorre 2004 • Kvitebjørn • Conclusions

27. 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.

28. 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