This paper will describe the analyses performed to determine the raw oil path, pressurized at 10 kgf/cm2, to reach the Emergency Drainage Tank and the detailed plastic structural analysis, considering geometric and material non-linearity's together with the steel characteristics. These analyses revealed that, in fact, the first main event in P-36 accident was the mechanical rupture of the Emergency Drainage Tank due to internal overpressure. With the tank rupture, equipment and piping on column floor were damaged, causing the flooding of platform's pontoons and column with water, raw oil and gas that ignited and exploded causing the second event, now a real explosion.
The P-36 semi-submersible production platform was the first production module of Roncador Field, located 130 km off the northeastern coast of the state of Rio de Janeiro, Brazil. The Floating Production Unit was stationed over 1,360 m water depth, in ultra-deep waters at Campos Basin. P-36 was a semi-submersible, equipped with a production plant able to process and treat 180,000 bopd, compress 7.2 million Nm3/d of gas and inject 24,000 m3 of water. In the night of 15 March 2001, two main events, initially reported as explosions, took place at the aft-starboard column. The first one occurred at 0:22 AM and the second 17 min later. At the time of the accident, P-36 was producing 84,000 bopd and 1.3 million Nm3/d of gas. The platform evacuation started at 01:45 AM and the complete abandonment occurred at 6 AM. The Inquiry Commission, established by PETROBRAS to determine the causes of the accident, assembled a timeline, crossing data obtained from crew reports about the ongoing operations; fire-fighters reports from actions taken after the first main event and data collected from Fire and Gas System and Emergency Shut Down procedure.