Despite efforts to right P-36, the rig capsized and sank in waters approximately 4,300 feet deep off the coast of Brazil.
The Petrobras rig, P-36, was 120 miles northeast of Rio de Janeiro on March 15 in the oil-rich Campo Basin when three explosions occurred in one of the rig supports. The first explosion on the semi-submersible oil platform occurred shortly after midnight. Another, stronger blast hit 20 minutes later after firefighters were fighting the fire from the first explosion. A third explosion followed.
The cause of the explosions has not been determined, but investigators suspected a build-up of gas in the support. One worker was killed and nine others were missing and presumed dead in the wake of the blasts. Approximately 175 people were on the rig at the time of the first explosion, but survivors were transferred to a nearby platform. A firefighting team of 25 was left aboard the rig.
The explosions in the rig support caused it to begin to fill with water, and P-36 began to list. Petrobras, Brazil’s national oil company, immediately went to work to try to recover the missing workers and save the 40-story rig, considered a national asset. The P-36 rig, which cost $350 million to build, was insured for $500 million. P-36 had the potential to produce 180,000 barrels of crude oil per day, but since starting operations last year, it was producing approximately 80,000 barrels of crude oil per day, or 5 percent of Brazil’s total daily output of the country’s booming oil industry.
The other major concern was the threat of a major oil spill if P-36 sank. P-36 had 250,000 gallons of diesel and 62,500 gallons of crude oil stored on the rig in addition to oil that was in piping that was bringing the oil to the rig from the ocean floor. In order to contain the potential spill, Petrobras brought in ships with containment booms and stationed them around the listing rig.
For five days, experts from Brazil and around the world fought to keep the rig afloat. A team of 350 navy divers, engineers and foreign consultants worked around the clock to try to save the rig. They came up with a plan to inject nitrogen and compressed air into flooded compartments to try to displace the water that was causing the rig to list. These efforts were initially partly successful in slowing the list and even in partly righting the rig, according to Petrobras. However, high winds and seas hampered the operation. Despite the best efforts of the team, P-36 continued to list. On March 20, the rig suddenly shifted, listing approximately 30Â°. This put the platform’s damaged side completely underway and made it impossible to continue repair and salvage work.
The team was withdrawn, and P-36 continued to list until it capsized and sank in waters that are approximately 4,300 feet deep. Salvage of the rig is said to be virtually impossible because of the depth of the water. Petrobras is expected to erect a temporary rig while a replacement for P-36 is under construction for approximately two years.
The P-36 sinking is the latest in a series of deadly incidents for Petrobras. The company has had two major oil spills and a series of accidents in which 81 workers died in the last three years.
The 13 vessels that were on station to contain the spill were not able to use containment booms because of rough seas. However, the chance of oil reaching shore was thought to be slight due to the rig’s 75-mile distance from the Brazilian coast.