London — It took only a minute or two for the huge "floatel" Alexander Kielland in the Ekofisk offshore oil field to tip over, but it will require weeks of investigation to be sure why the North Sea's worst disaster happened.
With 123 dead, the calamity that overtook the huge accommodation platform when one of its five supporting steel legs collapsed without warning has stunned the North Sea oil industry. If, as many suspect, the fault was from metal fatigue, literally dozens of rigs of a similar type currently operating could be very risky.
An official investigation is due to open in Norway March 31, but theories already abound about possible design faults in the semisubmersible rig's pontoon-tipped support legs.
Within the oil industry it is thought that a tall 200-ton derrick atop the platform may have contributed to the tragedy by causing the rig to turn upsidedown rapidly, trapping scores of offshore workers inside the floatel's residential and cinema complex.
Aside from doubts about the Alexander Kielland's steel components, some safety experts believe the initial trouble may have been caused by a fatigue failure in the drilling rig connected to the floatel platform by a narrow catwalk. Workers on the floatel crossed the catwalk to operate the drilling rig.
Some experts are claiming that complete metal fatigue tests have never been carried out on the giant hollow legs on which rigs of the Alexander Kielland type stand above the stormy, freezing waters of the North Sea. Much of the technology involved derives from the aerospace industry in which aluminum, not steel, was the building material used.
According to an industry source, the legs are between nine and 12 feet in diameter but made of steel less than one inch thick. The legs are welded to the platform itself, and it could be that poor welding standards contributed to the tragedy. According to one theory, a leg of the rig simply buckled, and with the derrick on the deck making it top-heavy, the entire craft turned turtle.
One disturbing aspect of the tragedy is that it happened only three days before the Alexander Kielland was due to be withdrawn from service for modification. There appear to be doubts also about the use to which rigs of this type are currently being put.
If platforms are solely involved in drilling, when dangerous weather is forecast anchors are pulled up and the craft is allowed to drift with the swell. But floatels linked up with drilling rigs lack this degree of maneuverability.
While the investigation proceeds, the rig's operators, Phillips Petroleum, face the problem of removing the Alexander Kielland from the scene of the tragedy. Hopes are slim that the rig, now upside down with four of its five flotation pontoons poking through the surface of the sea, can be righted.
Norwegian oil industry experts say additional flotation collars will be fitted and pumped full of compressed air. The rig would then be towed to safer waters in Norway.
But the ocean through which it must pass is turbulent, and there is a clear threat of the disabled rig breaking free and perhaps colliding with other rigs and platforms.
The Ekofisk field where the Alexander Kielland was operating is a notorious trouble spot. It is where North Sea oil was first discovered. Three years ago the Ekofisk Bravo well blew out and poured oil into the North Sea for eight days before it could be capped.
Some critics of the rig construction industry are saying the main reason is economy, but engineers reply that if calculations are correct, steel of thin gauge ought to be able to withstand the strains and stresses of being buffeted in the tempestuous waters of the North Sea.
Public reaction appears to be that the rescue rate of 89 out of 212 is too low, but within the industry it is being said that it is remarkably high. The waters where the disaster happened were around 43 degrees F. and not as stormy as they had been a few hours earlier.