Sea is certainly choppy! The platforms are obviously built very well though. Has there ever been any proper danger you know of to a rig with regard to damage caused by weather? Presumably they will be made with a pretty large margin of safety over even the worst you could expect.

Google " ocean ranger " there was a documentary on about it a couple of years back. ( not the north sea I know but it shows you the dangers )

Seen some structural damage but nothing too serious, seen some proper damage to rigs in the Gulf of Mexico though, don't know if they are built to a lesser spec or not. Give it a google and see what you come up with.

One totally upended off Newfoundland early eighties , i think i remember it on the news

That was the ocean ranger one I was refering to.