Petrobras 36 (P-36) was at the time the largest floating semi-submersible

Semi-submersible

A semi-submersible is a specialised marine vessel with good stability and seakeeping characteristics. The semi-submersible vessel design is commonly used in a number of specific offshore roles such as for offshore drilling rigs, safety vessels, oil production platforms and heavy lift cranes.The...

 oil platform

Oil platform

An oil platform, also referred to as an offshore platform or, somewhat incorrectly, oil rig, is a lаrge structure with facilities to drill wells, to extract and process oil and natural gas, and to temporarily store product until it can be brought to shore for refining and marketing...

 in the world prior to its sinking on 20 March 2001. It was owned by Petrobras

Petrobras

Petróleo Brasileiro or Petrobras is a semi-public Brazilian multinational energy corporation headquartered in Rio de Janeiro, Brazil. It is the largest company in Latin America by market capitalization and revenue, and the largest company headquartered in the Southern Hemisphere by market...

, a semi-public Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

ian oil

Petroleum

Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 company headquartered in Rio de Janeiro

Rio de Janeiro

Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...

. The cost of the platform was US$350 million (currently US$).

The vessel was built at the Fincantieri

Fincantieri

Fincantieri - Cantieri Navali Italiani S.p.A. is a shipbuilding company based in Trieste, Italy. It was formed in 1959 and is the largest shipbuilder in the Mediterranean, and one of the largest in Europe...

 shipyard in Genoa

Genoa

Genoa |Ligurian]] Zena ; Latin and, archaically, English Genua) is a city and an important seaport in northern Italy, the capital of the Province of Genoa and of the region of Liguria....

, Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 in 1995 as a drilling rig

Drilling rig

A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...

. She was owned then by Società Armamento Navi Appoggio S.p.A. The 33000 tonnes (36,376.3 ST) rig was converted in Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 to the world's largest oil production platform.

P-36 was operating for Petrobras on the Roncador Oil Field

Roncador Oil Field

Roncador oil field is a large oil and gas field located in the Campos Basin, off the coast of Brazil, northeast from Rio de Janeiro. It covers an 111 km2 area and reaches depths between --History:...

, 130 kilometres (80.8 mi) off the Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

ian coast, producing about 84000 barrels (13,354.9 m³) of crude per day.

Accident

In the early hours of March 15, 2001 there were two explosions in the aft starboard column at or around the emergency drain tank. The first explosion was caused by an overpressure event, the second by ignition of leaking hydrocarbon vapor. At the time there were 175 people on the rig; 11 were killed. Following the explosions, the rig developed a 16° list, sufficient to allow down-flooding from the submerged fairlead boxes.

Marine salvage

Marine salvage

Marine salvage is the process of rescuing a ship, its cargo, or other property from peril. Salvage encompasses rescue towing, refloating a sunken or grounded vessel, or patching or repairing a ship...

 teams tried over the weekend to save the platform by pumping nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 and compressed air

Compressed air

Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....

 into the tanks to expel the water, but they abandoned the rig after bad weather.

The platform sank five days after the explosions (March 20), in 1200 m (3,937 ft) of water with an estimated 1500 tonne of crude oil remaining on board.

External links

• BBC article
• Sinking of the Petrobras P-36 Photographs of the platform's sinking.
• SustainAbility case study Costs of the sinking.
• Petrobras Oil Rig Project with images on the P-36
• Article in Offshore Sinking Sequence of P36