To target drilling positions and enable the riser to re-enter the DART, Eidesvik Subsea is using a remote operated vehicle (ROV) fitted with a camera. The ROV descends attached to a tethering management system but once at depth it undocks and swims off powered by a vertical thruster at both ends and four vectorised thrusters to give a full range of movements.
The system offers a significant advantage over a camera fitted inside the drill string which would have provided a limited top down view. Eidesvik Subsea offshore manager Steinar Holte says: 'It gives a side on view that we wouldn't get with a down-the-hole camera. It's especially useful here as the seabed is so uneven. It looks like something volcanic.' Seacore exploration division technical manager Stewart Frazer adds: 'It's worse than undulating, it's precipitous.
It's full of gullies, cliffs and indentationsà it's forbidding.' The ROV is also equipped with two mechanical arms.
A fi ve function grabber can grip and hold, while a more dextrous seven function manipulator can screw and unscrew, operate valves and hatches and attach wires.
'Off the coast of Denmark we used one of these to pick up a 55 seater passenger plane that had crashed into the sea. We got 90% of it, ' says Holte.