Combining streamers and nodes is an option in congested survey areas, for very shallow water, where offsets >20 km are required to augment FWI velocity model building, or where converted-wave data would be beneficial for subsurface characterization.
- Shallow image resolution is optimized courtesy of the streamer data
- OBN data may enhance FWI model building where ultra-long offsets are beneficial. The improved velocity model may improve seismic image quality in complex salt provinces
- Converted wave OBN data may enable PP-PS subsurface characterization
- OBN deployment can improve 3D seismic coverage where obstructions create holes in towed streamer data
Hybrid towed+node surveys, involving the deployment of an OBN array either during towed-streamer acquisition or afterward, can provide additional subsurface information essential for understanding highly complex areas.
Because the source vessel is decoupled from OBN receivers, the maximum offsets recorded can be as large as logistically reasonable and as large as the signal-to-noise (SNR) of recorded diving wave events allow. The OBN spacing is typically not dense enough to enable standalone OBN imaging.
Simultaneous Node and Streamer Acquisition
A project for Lundin Energy Norway (and partners in PL1083) in the Barents Sea in 2021 involved an innovative solution, with an ultra-wide Hexa-source configuration towed behind the Sanco Swift on top of a massive, high-density 3D GeoStreamer spread towed by the Ramform Hyperion, and a unique simultaneous node deployment.
The survey area covered 3 812 sq. km in a source-over-streamer operation. The GeoStreamer spread, towed behind the Ramform Hyperion (image below), comprised 18 streamers with 75-meter separation, each 8025 m in length – setting a world record for the quantity of towed streamers, 144.45 km. The Sanco Swift’s ultra-wide hexa-source (see image below) was also a record-breaker, at 437.5 m, this is the widest source spread ever towed.
Ramform Hyperion towing an 18 x 75 m x 8 025 m GeoStreamer spread.
A substantial portion of the survey area was also covered with a sparse grid of approximately 1 000 ocean bottom nodes, the first survey to use automated free-dropped nodes. To deploy the nodes onto the seabed, PGS designed a conveyor belt system installed on a support vessel, which provided greater efficiency and lower HSE exposure than other node deployment solutions. The nodes were safely retrieved from the seafloor using an ROV, with 100% node recovery.
Sanco Swift towing a 437.5- meter -wide-tow hexa-source.
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