How to drill from the JOIDES Resolution?
the drill bit is lowered directly on the sea floor at the start of the drilling process: it’s the technique of the riserless drilling.
the drill string is made up by stands (= 3 drill pipes connected together ).
The drill string is lowered to the sea floor.
First challenge :
The boat is rising and falling with the swell ( sometimes more than 5 meters) and it could make difficult to keep the bit at the good depth.
In riserless drilling weight is kept on the drill bit by a “heave compensator”.
So the JOIDES is able to drill in waves as high as 4 meters.
To keep the ship exactly above the drill site against the wind and the currents.
In order to keep the JOIDES in the good horizontal position, a dynamic positioning system is used making possible for her to stay in the good place :
An acoustic transponder is lowered on the sea floor.
The ship sends sonar signals to the transponder
the transponder answers and its signal is read by a computer’s system
which manages 12 thrusters working to keep the ship in place .
(read more in: http://www.planetseed.com/fr/node/15303)