A dramatic impact hit the Norwegian headlines in the summer of 2009, when well stimulation vessel Big Orange XVIII ran into the Ekofisk 2/4 W platform at a speed of almost 10 knots.
Extensive damage was caused, and the PSA’s investigation found that the incident, under slightly changed circumstances, could have developed into a major accident.
But this event was by no means unique. Collisions have been occurring on the NCS ever since the oil industry arrived in Norway during the mid-1960s.
In 1966, for instance, the Ocean Traveler rig almost sank after supply ship Smit Lloyd 8 holed one of its columns several times when discharging because of a strong current and high waves.
A total of 115 collisions between installations and visiting vessels with work on the field have been reported since 1982, and no less than 26 between 2001 and 2010.
None of these incidents have caused loss of human life or personal injury, but the material damage has been extensive in some cases.
The investigation of the Big Orange XVIII incident showed that important lessons had not been learnt after a similar event in June 2005, when supply ship Ocean Carrier hit a bridge on Ekofisk.
Both cases involved inadequate routines for handing command of the ship from one officer to another.
And although collisions occur for a variety of reasons, some key features recur. These incidents are often the result of poor organisation of work and responsibilities, deficient training of the personnel involved, or the failure of technical equipment.
Facilities on the NCS are dimensioned to withstand collisions of a certain size, but a number of such incidents have involved impact energies above the design values.
The PSA has got to grips with this issue, and believes that a significant improvement in vessel operation is needed along with better methods for assessing loads on installations and their strength.
Paying greater attention to education and organisational aspects will also be important, along with a reduction in the technical failure rate. However, the PSA sees no need to amend the regulations.
The trend is good for collisions between petroleum installations and vessels not working on the field, with a decline in the number of incidents. That partly reflects good monitoring. Two traffic management stations, one on the Ekofisk and the other at Sandsli outside Bergen, cover most of the NCS. Some fixed installations and mobile units are also responsible for keeping track of passing maritime traffic.