TGS uses steerable source technology to enhance seismic acquisition accuracy, improve 4D survey repeatability, and support flexible survey geometries in all conditions.

Steerable Sources - Fig3
A standard TGS source array equipped with source steering units mounted on each float. Two relative GPS (RGPS) towers are installed per float, with a near-field hydrophone and seven depth sensors along each source keel. Combined with the TGS eBird system for streamer steering and depth control, this setup ensures high-precision, repeatable source and receiver positioning.

Solutions for Flexible Survey Geometries

All TGS seismic vessels are equipped with steerable source sub-arrays, which reduce lateral deviations and improve control over source positioning. This results in more accurate acquisition geometry for 4D baseline and monitor surveys.

TGS combines this with GeoStreamer® technology, which uses collocated hydrophones and velocity sensors to eliminate free-surface ghost reflections. The deep-towed, low-drag streamer design reduces surface noise, improves weather robustness, and captures a broad frequency range. This enables high-resolution imaging, reliable 4D reservoir monitoring, and improved reservoir characterization at all depths.

Advantages of Steerable Sources

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Maintains uniform sub-array separation for a consistent source wavefield across all shots

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Enables precise, independent steering of each sub-array—ideal for 4D monitoring and CCS surveys

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Improves source-position control during wide-tow, multi-source acquisition

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Supports up to six sources with total lateral separation of less than 450 meters

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Increases acquisition efficiency and enhances near-surface imaging resolution

Highly Repeatable 4D Monitoring Survey Geometry

Steerable source systems help maintain accurate acquisition geometry in variable current conditions, improving survey efficiency and 4D repeatability. Each sub-array adjusts to follow pre-plot source lines, while the vessel maintains optimal streamer positioning. Lateral source corrections of up to ±4 meters are possible, with mean lateral deviations typically less than ±2 meters.

Adjustable wings on each sub-array are automatically controlled to maintain both lateral position and separation. GPS and acoustic sensors track each sub-array’s position in real time, and onboard systems compare this against the planned source trajectory. Any deviation is used to compute wing angle adjustments, ensuring the source remains aligned with the target path.

The graph shows a comparison of source positions with and without active steering.

Steerable Sources -Fig1
An illustration of the lateral source positioning error with active source steering (dark blue curve) and without source steering (light blue curve).
Steerable Sources - Fig2
4D monitor survey shot positions color-coded by the crossline source position error from the 4D baseline shot positions.

Maximizing 4D Survey Accuracy

Consistent source positioning is critical for reliable 4D seismic monitoring. Steerable source systems reduce lateral and inline positioning errors, improving repeatability across baseline and monitor surveys, even in complex environmental conditions.

In a 2014 field trial, an early prototype demonstrated average lateral-source-position errors well below 5 meters. Today’s systems are more advanced, with over 90% of radial shot positions typically within 3 meters of target across modern TGS 4D projects.

 

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