Paper submitted to IMAGE 2026, by Lazizi, C., Marinets, S., Hovden, A., De Pierrepont, S., Lecerf, D., (TGS) Hidalgo, C., Haavik, K. E., Milne, R., (AKER BP).
Abstract
Recent advances in 4D seismic workflows have renewed interest in leveraging non-dedicated acquisition for reservoir monitoring. In this study, we examine the performance of an opportunistic 4D monitor derived from Multi-Client data and compare it with a dedicated time-lapse survey acquired eight years later. The dataset includes a 2005 baseline, a high-quality dedicated monitor from 2017, an opportunistic monitor in 2022, and an ongoing dedicated monitor in 2025. The opportunistic 2017–2022 pair successfully detected production-related changes, though its broader acquisition differences and higher noise levels required more careful analysis to separate true subsurface responses from acquisition-related effects. In contrast, the dedicated 2017– 2025 pair shows significantly improved repeatability, allowing more confident identification of pressure depletion, gas-cap evolution, and impedance changes associated with water flooding. Processing enhancements such as more effective debubbling and more precise time-shift corrections further improved the consistency and reliability of the dedicated 4D signal. Preliminary results indicate that while dedicated acquisition remains the benchmark for high-fidelity reservoir surveillance, opportunistic 4D can provide meaningful early insights at significantly lower cost. This makes it a practical screening solution for assessing the feasibility and expected impact of seismic monitoring before committing to a full dedicated program.
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