BP says series of complex events caused rig explosion

On Wednesday, September 8, British Petroleum (BP) issued an internal investigation report indicating that no single factor caused the April 20, Macondo well tragedy.

According to the release, a sequence of failures involving a number of different parties led to the explosion and fire, which killed 11 people and caused widespread pollution in the Gulf of Mexico earlier this year.

The report concludes that decisions made by “multiple companies and work teams” contributed to the accident which purportedly arose from “a complex and interlinked series of mechanical failures, human judgments, engineering design, operational implementation, and team interfaces”.

The report, based on a four-month investigation led by Mark Bly, BP’s Head of Safety and Operations and conducted independently by a team of over 50 technical and other specialists drawn from inside BP and externally, found that:

The cement and shoe track barriers, and in particular the cement slurry that was used at the bottom of the Macondo well failed to contain hydrocarbons within the reservoir, as they were designed to do, and allowed gas and liquids to flow up the production casing.

BP and Transocean incorrectly accepted the results of the negative pressure test, although well integrity had not been established.

Over a 40-minute period, the Transocean rig crews failed to recognize and act on the influx of hydrocarbons into the well until the hydrocarbons were in the riser and rapidly flowing to the surface.

After the well flow reached the rig, it was routed to a mud-gas separator, causing gas to be vented directly on to the rig rather than being diverted overboard.

The flow of gas into the engine rooms through the ventilation system created a potential for ignition, which the rig’s fire and gas system did not prevent.

Even after the explosion and fire had disabled its crew-operated controls, the rig’s blowout preventer on the seabed should have activated automatically to seal the well. However, it failed to operate, probably because critical components were not working.

“This was a tragic accident that resulted in the loss of 11 lives and impacted the communities and the environment along the Gulf Coast region. It will be incumbent on everyone at BP to embrace and implement the changes necessary to ensure that a tragedy like this can never happen again.”

BP said the report was based on information available to the investigating team. It noted that additional relevant information might be forthcoming.