Capstone — North Sea 4D repeated streamer

Producing North Sea oil fields use 4D seismic to monitor water-flood sweep, gas-cap migration, and pressure depletion. Equinor’s Gullfaks (since 1999), Snorre (1997), and Oseberg (2003) have each accumulated 7–9 streamer-based 4D surveys. Non-Repeat RMS (NRMS) has dropped from ≈40% in the early 2000s to ≈10% by 2020 as vessel infrastructure, streamer-steering birds, source-signature QC, and positioning all matured.

Why streamer 4D works here

North Sea has the densest marine survey infrastructure in the world — CGG, PGS, Fugro, WesternGeco all operate vessels out of Bergen/Stavanger. That makes repeat shoots cheap ($15–$25M per 4D monitor vs $200M+ for a PRM install). The fields are also relatively shallow (1500–2500 m burial) and the reservoir signature-change per year of production is large. So the NRMS noise floor, while worse than PRM, is still below the 4D signal of interest.

Decision support

Each monitor informs three classes of decision: (1) infill-drilling placement — where is the remaining oil column? (2) injector-rate tuning — which injectors are sweeping productively vs short-circuiting? (3) platform life-extension — is the reservoir pressure still viable for continued production economics? Monitoring budget of $15–$25M every 2–4 years is a trivial fraction of the production revenue it guides.

References

• Lumley, D. (2001). Time-lapse seismic reservoir monitoring. Geophysics, 66(1), 50–53.
• Calvert, R. (2005). 4D technology: where are we, and where are we going? Geophysical Prospecting, 53(2), 161–171.
• Tenghamn, R., Brown, J. (2000). A new dual-sensor towed-streamer technology. SEG Annual Meeting Expanded Abstracts, 1–4.
• Vermeer, G. J. O. (2002). 3-D Seismic Survey Design. SEG Geophysical References 12.