Capstone — DAS-enabled hybrid survey
Learning objectives
- Describe the OBN + well-DAS + surface-DAS hybrid pattern
- Compute total channel count across all three technologies
- Compare per-channel cost for each technology
- Recognise PGS Apollon / Equinor Johan Sverdrup as leading examples
Modern reservoir-surveillance programmes combine sparse conventional OBN, permanent well-DAS on monitoring wells, and trenched surface-DAS along critical transects. The aggregate channel count far exceeds any single technology’s reach; the per-channel cost is lower than any 100% conventional design. The hybrid has become the default for offshore producing fields.
The three technologies and their strengths
- Conventional OBN: broad 3D coverage, full azimuth, established imaging workflow. Per-channel cost ≈ $8 k installed; best for the framework image.
- Well-DAS: 3000+ channels per well fibre at 1 m spacing, behind-casing install cemented for decades. Per-well install ≈ role="main" aria-label="Lesson content" tabindex="-1"50 k one-time. Strong near-wellbore vertical imaging.
- Surface-DAS: 1000+ channels per km of trenched fibre. role="main" aria-label="Lesson content" tabindex="-1"5 k/km one-time install. Strong along-line sampling for ground roll, refractions, ambient-noise.
Real deployments
PGS Apollon (North Sea, 2022) — hybrid OBN + streamer + trenched DAS PSDM programme. Aramco Ghawar passive DAS with 4C reference receivers (2020–ongoing). Equinor Johan Sverdrup permanent OBN PRM with well-DAS on every monitoring well (2019–ongoing). Shell Ormen Lange pipeline-DAS + OBN (2021–2023). Each leverages existing or cheaply-installable fibre to augment a conventional patch.
Closing thought
The hybrid pattern resolves a long-standing tension between channel count (always wanted more) and cost (always capped). The DAS / conventional split lets you spend conventional dollars on azimuth and framework, DAS dollars on along-line density. The combined geometry is more flexible than any single-technology design, and cheaper per useful channel.
References
- Mougenot, D. (2013). MEMS-based 3C accelerometers for land seismic acquisition. The Leading Edge, 32(4), 388–396.
- Vermeer, G. J. O. (2002). 3-D Seismic Survey Design. SEG Geophysical References 12.
- Berg, E., Svenning, B., Martin, J. (2010). OBN technology — recent developments. EAGE Workshop on Permanent Reservoir Monitoring.
- Cordsen, A., Galbraith, M., Peirce, J. (2000). Planning Land 3-D Seismic Surveys. SEG Geophysical Developments 9.