A dense acoustic network positioning system links locations along each streamer to the precise location of the vessel, each source sub-array and each paravane, for every shot.
This acoustic positioning network is integrated with GPS units mounted on the vessel, each paravane, each source sub-array (two GPS towers per sub-array), and the rear of each streamer. The collective streamer positioning (SPOS) system is interfaced onboard each PGS vessel with a navigation command and control system and is used to control both the depth and lateral control devices mounted along each streamer and the gun steering system (GSS) mounted on each source sub-array.
The figure below shows a real 4D monitor survey vessel pre-plot, where the color scale represents the average lateral source position error controlled by the source-steering management system. The inline source position error is influenced by the source firing time error at each baseline shot position and is usually small. For PGS 4D surveys, more than 90% of radial shot-position errors are typically less than 4m.
The PGS source steering system can move each sub-array laterally to ± 40 m from the natural towing position, with a mean lateral source position error from the target trajectory of less than ± 2 m.
Integrated Streamer Steering
In GeoStreamer spreads, eBird steering and depth control devices are built into the streamer body and enable maximum lateral steering of ±3. Our barnacle mitigation and prevention solutions ensure that multisensor 4D data is recorded with minimal drag and mechanical noise.
4D monitor survey shot positions color-coded by the crossline source position error from the 4D baseline shot positions.
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