BP's had an unlucky run, and those figures on H&S inadequacies are misleading, look at the fine $87million, thats peanuts, you could buy a footballer for that, and oil companies could (and did) buy entire football clubs and invest enough to win the champions league on a whim!
Checkout the explosion on the gas storage/reinjection platform in the north sea a few years back, (47/3B?), the thing was blown sky high yet there wasnt a single H&S violation recoreded. Sometimes things really are just freak accidents.
Theres a rig sunk off venezuella at the moment, very similar circumstances and equipment. They were just lucky and the valve worked. Its barely made the news outside industry magazines.