Seismic ship Vyacheslav Tikhonov
Initially, dynamite was the sound source for marine seismic exploration.
Due to its obvious danger, pneumatic guns were later used as a source. The accumulation of seismic data is a mapping of the underwater structure in the constant search for hydrocarbons. At first, the data form was two-dimensional.
The data was obtained using a single hose streamer (or, simply, an oblique, it is also a streamer, from the English “streamer”) and one signal source.
A new method for three-dimensional mapping was later developed. To do this, they strive to install as many braid streamers as possible, to cover a large area as much as possible. The vessel under consideration “Vyacheslav Tikhonov” has 8 braids for data collection (this is not the maximum number, there are vessels with a large number of braids).
The data collection method can be compared with a very large echo sounder. An audio signal is sent by the airgun down to the seabed, and then the towed cable registers the reflected signals that are recorded.
Seismic ship at work
The length of one braid on the ship “Vyacheslav Tikhonov” has a length of 6,000 meters (namely meters, not cable and other marine units). Putting braids in working condition and selecting them at the end of measurements is not a quick matter, it takes several days. At the same time, as during measurements, the vessel must follow a strictly defined piece with a fixed speed (in this mode, the working speed is about 5 knots).
Because it’s quite difficult and tiring for a person to maintain such a clear course and speed; a dynamic positioning system (DP) is installed on the vessel, which allows you to perform this task automatically.
Navigators mainly monitor the navigation situation, establish communication with ships to ensure safe discrepancies, etc. The turning radius in the measurement mode is several miles, so that the braids do not mess up. The crew heading is set from the seismological laboratory on the ship.
Also, to ensure safe discrepancies with other vessels, to prevent damage to towed streamers (by the way, the cost of one streamer with all equipment is about $ 2 million) and other auxiliary tasks, two tracking vessels work in tandem with the vessel (in English – chase boats).
There is also one auxiliary vessel for the supply of supplies and crew, for bunkering and other auxiliary tasks.
To successfully complete these tasks, the research vessel must maintain reliable and constant communication with the tracking vessels, and inform them in a timely manner of its plans.
As mentioned above, turning in the measurement mode is a rather difficult task. With a distance of 800 meters between the outer braids, the turning radius should be at least 4,000 meters, increasing to 5,000 meters in bad weather. When turning with a radius of 5 km, the turning speed should be 3 degrees per minute. It should be noted that the weather and sea conditions strongly influence the turning trajectory. When turning, navigators are guided by the position of paravanes – towed braid taps.