During the period 2001 – 2011, there was a clear reduction in the number of acute crude oil spills to sea on the Norwegian shelf. Following a steep decline at the beginning of the period, the number of spills has remained at a stable level in the years 2004–2011.
The volume of crude oil in the sea as a result of acute spills has varied. The majority of the spills, 98 percent in the North Sea and 95 percent in the Norwegian Sea, can be placed in the lowest spill category (0-10 tonnes). There was one crude oil spill in the Barents Sea during the period 2001-2011. This spill was in the lowest category in 2001.
There were 34 acute crude oil spills to sea in 2011 – 24 and in the North Sea and ten the Norwegian Sea, the Petroleum Safety Authority Norway’s web site reads.
Given that this time period is relatively short (ten years) and that major spills have occurred, a general consideration might be that, while large spills are rarer, they do occur. It is also not impossible that larger and even rarer spills could occur unless extensive work is carried out to prevent this.
The report also analyses development over time of near-misses that could have led to acute spills if more barriers had failed. For the Norwegian shelf overall, there is a reduction in the number of near-misses during the period.
Despite the reduction in the number of near-misses on the Norwegian shelf, the relative risk indicator for potential number of acute spills shows a significant increase. This is related to the risk for acute spills related to leaks in and damage to flexible risers and subsea installations.
Flexible risers are a type of pipeline developed for vertical transportation from the seafloor to production and drilling facilities atop the water's surface, as well as from the facility to the seafloor,
Leaks in and damage to flexible risers are an unsolved problem area which will require continued focus in coming years. Eight serious cases of damage to flexible risers were reported in 2011, in addition to two leaks, according to the Petroleum Safety Authority Norway.