Traditionally, marine seismic sources have been towed in front of the two innermost streamers of a streamer spread. Spreading out multiple sources in front of a streamer spread can improve both spatial sampling and the near offset coverage without sacrificing 3D survey efficiency.
This is especially relevant for shallow water areas with relatively shallow targets, where good near offset coverage is required for high-resolution imaging of the shallow overburden, robust AVO analysis for shallow exploration targets, or effective removal of multiple energy.
PGS is one of several companies that have plans to take part in a growing market for geophysical services that are needed ahead of offshore wind power developments. However, conventional streamer data is not good enough to bring out details in the layers directly below the seabed, and the seismic company has therefore seen it necessary to invest in another type of technology.
CO2 storage development projects and site characterization efforts for future offshore wind farms have increased the need for high-resolution imaging and characterization of the near-surface, and thus the demand for cost-effective high-integrity 3D seismic acquisition solutions. PGS outlined the high potential of the surveying method for the energy transition in a publication in 2021. In 2022 the Northern Endurance CCS seismic survey deployed a wide-tow quad source.
From 2023, the multi-source wide-tow method is complementing the P-Cable for ultra-high resolution 3D site surveys for offshore wind farms.
NEXT 2024
Luca Limonta in PGS will give the talk Integrated 3D acquisition and processing technology to accelerate the development of offshore wind at the New Energy X Subsurface (NEXT) 2024 conference in Bergen.
Bergen, January 24 – 25. 2024
Why is it a game-changer?
The concept was launched as an alternative to the marine survey design method commonly used to improve near-offset coverage, i.e., the reduction of the streamer spread width (number of streamers) to minimize the distance between the sources in the center and the outermost streamers.
Reducing the streamer spread width also meant reducing the sail line separation, and consequently, lower survey efficiency and higher cost. Wide-tow multi-sources have overcome the efficiency trade-off and, at the same time, have increased data quality.
PGS’ wide-tow multi-source concept was launched as a single vessel operation with multiple sources spread out as wide as operationally feasible reducing cost, risk, and environmental footprint compared to dual vessel operations or traditional solutions.
History and Track Record
PGS conducted its first field trials with wide-tow sources in 2016 and proposed wide-tow triple-source solutions to operators in Norway in 2016, 2017, and 2018. The method was described first time publicly at the SEG conference in 2017 with a focus on exploration in the Barents Sea.
PGS finally acquired its first two commercial surveys with wide-tow multi-sources in 2019. Industry acceptance of the multi-source wide-tow method was rapid. By the end of 2022, the method was successfully utilized in 15 surveys: 8 seismic surveys on the Norwegian Continental Shelf (North Sea, Norwegian Sea, Barents Sea), 4 surveys offshore UK, and 3 outside Europe.
Wide-tow multi-sources have also been a key design element of the GeoStreamer X multi-azimuth campaigns in the Viking Graben and the Norwegian Sea. In addition, the method has been adopted by other seismic contractors and/or operators for seismic surveys in recent years.
Another 5 projects with wide-tow multi-sources was either ongoing or planned offshore Norway and UK in 2023, i.e., the method is rapidly becoming the new standard.
The project was nominated for the Exploration Innovation Prize 2023.