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.

Second challenge:

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)