SMT seismic system is a 2D system comprising a 6000 m streamer and a seismic source optimized for the acquisition of seismic reflection and refraction.
This system can be deployed from the following ships: L’Atalante, Pourquoi pas ?, Marion Dufresne II.
Acquisition speed is 4–5 knots.
Main characteristics of the SMT system
Seismic system SMT comprises a Sercel Sentinel RD streamer with FDU spacing of 6.25 m, amounting to 960 FDUs. Data acquisition is achieved through the use of a Sercel SEAL 428 v2 acquisition system. Data is recorded in the SEG-D format.
The navigation system used is the ECOS system developed by Genavir.
The depth of the seismic streamer is controlled by ION streamer depth controllers (Compass Bird 5011-2) positioned every 300 m along the seismic streamer.
A buoy fitted with a GPS system enables the position of the streamer tail to be established.
The SMT seismic source involves the use of two 12 m flexible floaters to deploy two source lines towed from either side of the vessel.
Each floater has five fastenings points for air guns or clusters (Ggun or Bolt, cylinder volumes from 45 in3 to 520 in3).
The deployment system can adjust the depth of the guns from 5 m to 10 m.
The two source lines are integrated into 40 ft containers featuring rails and winches for stowing and deploying the lines at sea. Each line has its own umbilical for towing, supplying high-pressure air and transmitting electric signals.
The gun lines are fitted with high-pressure sensors, depth sensors and hydrophones to verify the behaviour and good working order of the impulsive sources during acquisition.
Several compressors (4 or 5 compressors, totalling 1200 m3 per hour) supply compressed air (140 bars). A lubrication and filtering system has been added to prolong the working lives of the guns. The Gunlink control system synchronizes the firing of the guns with precision.
Two configurations are possible, to achieve either reflection or refraction-type acquisitions. The configurations detailed above may be adjusted to suit the needs of the scientific objectives of the mission concerned (number of guns, type of guns, gun depth, etc.). The source lines are towed from two booms extending from either side of the ship. Their positions are established by GPS.
