Modern oil and gas field management is increasingly reliant on detailed and precise 3D reservoir characterisation, and timely areal monitoring. Borehole seismic techniques bridge the gap between remote surface-seismic observations and downhole reservoir evaluation: Borehole seismic data provide intrinsically higher-resolution, higher-fidelity images than surface-seismic data in the vicinity of the wellbore, and unique access to properties of seismic wavefields to enhance surface-seismic imaging. With the advent of new, operationally-efficient very large wireline receiver arrays; fiber-optic recording using Distributed Acoustic Sensing (DAS); the crosswell seismic reflection technique, and advanced seismic imaging algorithms such as Reverse Time Migration, a new wave of borehole seismic technologies is revolutionizing 3D seismic reservoir characterization and on-demand reservoir surveillance. New borehole seismic technologies are providing deeper insights into static reservoir architecture and properties, and into dynamic reservoir performance for conventional water-flood production, EOR, and CO2 sequestration – in deepwater, unconventional, full-field, and low-footprint environments. This lecture will begin by illustrating the wide range of borehole seismic solutions for reservoir characterization and monitoring, using a diverse set of current- and recent case study examples – through which the audience will gain an understanding of the appropriate use of borehole seismic techniques for field development and management. The lecture will then focus on DAS, explaining how the technique works; its capability to deliver conventional borehole seismic solutions (with key advantages over geophones); then describing DAS’s dramatic impact on field monitoring applications and business-critical decisions. New and enhanced borehole seismic techniques – especially with DAS time-lapse monitoring – are ready to deliver critical reservoir management solutions for your fields.

1. Society of Petroleum Engineers
Distinguished Lecturer Program
www.spe.org/dl
Dr Steve Morice
Lead Geophysicist, Shell Todd Oil Services
With contributions from Jorge Lopez, Denis Kiyashchenko, Albena Mateeva, Simon O’Brien &
Paul Zwartjes
Borehole Seismic Solutions
for Integrated Reservoir
Characterization and Monitoring

2. Aims of this Lecture
1. Understand the wide range of borehole seismic
solutions for reservoir characterization & monitoring
2. Recognize when acquisition of a borehole seismic
survey can help your operations
3. Introduce DAS, and its impact on more - and better -
geophysical solutions & business decisions
3

3. Outline
• Introduction
• Borehole seismic solutions:
– High-resolution, high-fidelity imaging
– Integrated 3D seismic processing & inversion
• Focus on Distributed Acoustic Sensing (DAS):
– How it works
– Capability to deliver borehole seismic solutions
– Emerging impacts on field monitoring applications
4

4. Borehole Seismic Advantages
1. Exact TWT-to-depth relationship
2. Translates between seismic and log data
3. Wellbore provides a quiet, stable
environment for high quality data, and
excellent repeatability
4. One-way travel paths, hence less
attenuation
5. Wavefield separation & decon. provides
“perfect” seismic response at the well
6. Can provide drilling “look-ahead” to
reduce risks
7. Solves many seismic processing,
interpretation and reservoir monitoring
problems
5

5. Borehole Seismic Techniques
6

6. VSP Imaging Solutions:
VSP Fault Shadow Imaging
• Seismic “shadow zone”
below major fault
• Well drilled targeting
stranded gas
• VSP provided clear
image, unaffected by
fault shadow
• Elevated velocities
implied diagenetic zone
• Prompted new 3D
PreSDM
6
500m
7

7. VSP Imaging Solutions:
Walkaway VSP for Complex Geology
8

8. VSP Reservoir Characterization Solutions:
Walkaway VSP for Complex Geology
9

9. VSP Imaging Solutions:
Crosswell VSP for Res. Architecture
10

10. VSP Applications for Seismic Processing:
VSP-Integrated Processing Workflow
11

11. VSP Applications for Seismic Processing:
VSP-Integrated Processing
12

12. VSP Applications for Seismic Processing:
Comparison after AVO Inversion
13

13. Distributed Acoustic Sensing (DAS)
DAS VSP Advantages:
• Convenient: Installed behind
tubing, DAS does not require
well-entry for recording
• Built-in: Acquire VSPs in wells
inaccessible to geophones
• Permanent: Lower-cost, on-
demand VSPs
• Retrievable: using coiled tubing
• Full vertical coverage: faster
acquisition / better imaging
Limitations: 1C, S/N, amplitudes
14

14. Distributed Acoustic Sensing (DAS):
Comparison with Geophone Data
15

15. Distributed Acoustic Sensing (DAS):
Comparison with Geophone Data
16

16. DAS VSP Reservoir Monitoring Solutions:
Monitoring in Deepwater – “i4D”
• Time-lapse effects can occur rapidly, e.g. due to:
– Sudden pressure changes / compartmentalization near injectors
– Induced fractures and out-of-zone effects
• Early information often not available with conventional 4D:
– Typical monitor surveys >2 year intervals
– Long duration of a 4D survey can smear-out intermittent effects
• DAS VSP in an injector well ideal for frequent monitoring: “i4D”
17

17. DAS VSP Reservoir Monitoring Solutions:
Monitoring in Deepwater – “i4D”
Survey Shots Rcvs Comp Traces
3D DAS-VSP 35,000 2 x 600 1 42,000,000
OBS 35,000 288 4 40,320,000
Well 2
Well 1
288
OBS Nodes
~35,000
OBS Shots
Highlights:
• Same fiber optic cables as DTS
• Same seismic shots as OBS
• No well intervention (7 weeks)
• Unfeasible with geophones
18

18. DAS VSP Reservoir Monitoring Solutions:
Monitoring in Deepwater – “i4D”
19

19. DAS VSP Reservoir Monitoring Solutions:
Monitoring in Deepwater – “i4D”
20

20. DAS VSP Monitoring Applications:
Seismic Surveillance for EOR
Challenges with EOR projects onshore:
• Large stock of closely spaced wells
• Marginal economics, esp. injectants
• HSE concerns, incl. operating footprint
Seismic surveillance challenges:
• Often low quality data, intrusive & costly
• Footprint in sensitive areas
DAS technology enablers:
• In-well seismic to improve data & reduce footprint
• Fiber optics to reduce cost and intrusiveness
21

21. DAS VSP Monitoring Applications:
Steam Injection Tracking in Oman
3D-VSP selected for pilot monitoring solution:
• First monitor 2009-2010: Anomaly consistent with well data
• Second monitor 2012 (deeper injection, less steam): More even
• Extended to full-field: 8 observer wells with DAS
22

22. DAS VSP Monitoring Applications:
CO2 Sequestration Monitoring at QUEST
Proof of DAS concept:
• DAS & geophone VSP
images near-identical
• DAS slightly lower
frequency
• Walkaway lines tie
23

23. DAS VSP Monitoring Applications:
CO2 Sequestration Monitoring at QUEST
• Good repeatability (RRR=0.15) in target area
• DAS confirmed for Measurement, Monitoring & Verification
24

24. Summary
• Growing need for more detailed & precise 3D reservoir
characterization, and timely, low-cost reservoir monitoring
• Borehole seismic techniques deliver high-resolution,
highly-repeatable, well-calibrated data
• New technologies for enhanced imaging and time-lapse
monitoring. Reservoir management applications for:
– Conventional
– EOR
– CO2 sequestration
• DAS: Proven technology with emerging major impacts on
field development and business decisions
25

25. Acknowledgements & References
This presentation would not have been possible without the assistance of Denis Kiyashchenko, Simon O’Brien,
Jorge Lopez, Albena Mateeva, Paul Zwartjes, Barbara Cox, Paul Hatchell, Rocky Detomo, Wilfred Berlang, Els
Jooris, Steve Oates, Peter Chia, Henk Tijhof, Bob Whale, and the many specialists at Reservoir Imaging Inc.,
OptaSense, Schlumberger, WesternGeco, and Baker-Hughes.
Data examples courtesy of Shell New Zealand, Todd Energy, OMV New Zealand, Petroleum Development Oman,
Shell Canada, Shell Exploration and Production Co.
Kiyashchenko, D., Lopez, J., Berlang, W., Birch, B., Zwaan, M., Adawi, R., Rocco, G., Ghafri, S., 2013. Steam-
injection monitoring in South Oman – from single-pattern to field-scale surveillance. The Leading Edge, Oct 2013,
Vol. 32, No. 10, pp 1246-1256.
Lopez, J., 2014. Increasing Impact of Borehole Seismic using DAS. W-20 “DAS and Recent Advances and the Road
Ahead in Borehole Geophysics” Workshop, Soc. Expl. Geoph. Ann. Mtg. and Exhib. 31st
Oct. 2014, Denver,
Colorado.
Mateeva, A., Lopez, J., Potters, H., Mestayer, J., Cox, B., Kiyashchenko, D., Wills, P., Grandi, S., Hornman, K.,
Kuvshinov, B., Berlang, W., Yang, Zhaohui, Detomo, R., 2014. Distributed acoustic sensing for reservoir
monitoring with vertical seismic profiling. Geoph. Prosp., No. 62, pp 679-692.
Morice, S., Moseley, S., Blundell, K., Clulow, B., Merry, H. and Roy, J., 2014. Advanced Borehole Seismic
Technologies for Kapuni Field Appraisal. Advantage NZ Geotechnical Petroleum Forum, 1st
-3rd
April 2014,
Wellington, New Zealand.
Morice, S., Puech, J-C. & Leaney, S., 2004. Well-driven seismic: 3D data processing solutions from wireline logs
and VSPs. First Break, Vol. 22, No. 8, August 2004.
Wu, H., Kiyashchenko, D. & Lopez, J. 2011. Time-lapse 3D VSP using permanent receivers in a flowing well in the
deepwater Gulf of Mexico. The Leading Edge, Sep 2011, Vol. 30, No. 9, pp. 1052-1058
Zwartjes, P. & Mateeva, A., 2015. Multi-Fibre DAS Walk-Away VSP at Kapuni. 3rd
EAGE Workshop on Borehole
Geophysics. 19th
April 2015.
26

26. Society of Petroleum Engineers
Distinguished Lecturer Program
www.spe.org/dl 26
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