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THE UNTHINKABLE HAPPENED on March 20, 2001. P-36, a semi-submersible drilling rig owned and operated by Brazil's Petrobras sank in Guanabara Bay, off Rio de Janeiro.
Five days earlier the 30,000-tonne rig was rocked by an explosion that killed 11 men and threw the government-owned company into turmoil. One year later, as promised, top Petrobras executives faced the offshore oil industry to tell what went wrong, how the company and community reacted, and what will be done to prevent another tragedy.
Petrobras rendered its account during the 2002 Offshore Technologies Conference in Houston. On March 14, 2001, the rig was working in the prolific Roncador Field in the Campos Basin, at a water depth of 4,460 feet and was producing 84,000 barrels per day of oil and 45 million cubic feet per day of gas. The trouble started at 00:22 hours March 15. An abnormal thumping sound was heard. A fire alarm sounded inside the starboard aft column. An explosion inside the column occurred 17 minutes later. At 01:45 hours evacuation of the rig began. At 06:00 hours, the decision was made to abandon the platform. On March 20 at 11:41 hours, the platform sank, taking 2.5 minutes to reach the ocean floor where it turned upside down.
The narrative understates the chaos and confusion on the platform in its last hours. At the time of the incident, 175 workers were aboard, 7,550 barrels of diesel oil were in the tanks, and there were 944 barrels of petroleum in the production equipment. The sinking destroyed a huge investment for Brazil. The US$485 million rig was built in Italy in 1994, and underwent a complete, two-year refit in Canada at the Levis shipyard of Industries Davie Inc. near Quebec City after Petrobras bought it in 1997.
The investigation concluded: "The accident occurred due to a series of factors that in isolation would have had very litde impact. Additionally, if just one of those factors had not been present, the accident would not have been nearly as serious."
The events included a rupture of an emergency drain storage tank in the starboard aft column of the platform,...