BRAVE EFFORTS to save the world's largest floating oil platform failed on Tuesday when the giant Petrobras 36 rig sank in rising seas.
The 32,000t P-36 was holed below the waterline after three explosions ripped through the semi-submersible platform last Thursday in the Roncador oilfield, 125km off the Brazilian coast.
Ten men died in the blasts, most of them firefighters and safety staff. Only one body was recovered from the structure, now resting on the seabed in 1,362m of water.
The structure was originally built speculatively as a mobile exploration rig in Italy in 1995. It was modified significantly by contractors including Amec to become a permanently moored semi-submersible platform.
Contracted to Brazillian oil conglomerate Petrobras, it finally took up position off Rio de Janeiro last year.
The steel platform deck was supported by two steel pontoons, each supporting a pair of cylindrical steel legs, and anchored with 16 polystyrene ropes, 187mm in diameter. Its operating draft was 22m.
A Petrobras spokeswoman said that the cause of the blasts was unknown but that the first major breach occurred 15m below the waterline, inundating compartments of one pontoon, with the structure developing a list of 28degrees.
After the evacuation of the remaining 175 workers, a team of more than 300 people joined by Dutch salvage specialist Smit Tak pumped in compressed air and non-explosive nitrogen in an attempt to expel water from the pontoon and level the rig.
'We had stabilised it for a time, but it must have been more badly damaged than originally thought. Once the list developed, water began coming in through ventilation openings, ' said a Smit Tak spokesman.
The platform was lost after a heavy swell developed, with Smit Tak evacuating its team before the platform went down.
As NCE went to press, fears were being expressed about the possibility of environmental damage from oil spillages.