BP has said no single factor was responsible for the Gulf of Mexico oil spill, with blame instead attributed to “a sequence of failures involving a number of different parties”.

Some 4.9 million barrels of oil leaked into the Gulf following an explosion on the Deepwater Horizon oil rig in April this year, which also claimed 11 lives.

The well was capped on July 15th with an operation to permanently seal it due to take place in the next few weeks.

In a report released by BP today, the oil giant argues decisions made by “multiple companies and work teams” contributed to the accident, which it says arose from “a complex and interlinked series of mechanical failures, human judgments, engineering design, operational implementation and team interfaces”.

BP’s incoming chief executive Bob Dudley said: “We have said from the beginning the explosion on the Deepwater Horizon was a shared responsibility among many entities.

“This report makes that conclusion even clearer, presenting a detailed analysis of the facts and recommendations for improvement both for BP and the other parties involved.

“We have accepted all the recommendations and are examining how best to implement them across our drilling operations worldwide.”

Report Findings

The report – based on a four-month investigation led by Mark Bly, BP’s head of safety and operations – outlined what had caused the explosion.

Initially the cement and shoe track barriers 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.

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

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

As 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 then created a potential for ignition which the rig’s fire and gas system did not prevent.

Even after explosion and fire had disabled its crew-operated controls, the rig’s blow-out preventer on the sea-bed should have activated automatically to seal the well. But 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,” said Mr Dudley.

“We deeply regret this event. We have sought throughout to step up to our responsibilities.

“We are determined to learn the lessons for the future and we will be undertaking a broad-scale review to further improve the safety of our operations. We will invest whatever it takes to achieve that.

“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.”

Ongoing Investigation

Today’s report is just the latest step in the ongoing investigation into the accident.

BP added additional relevant information may be forthcoming, for example, when Halliburton’s samples of the cement used in the well are released for testing and when the rig’s blow-out preventer is fully examined now that it has been recovered from the sea-bed.

There is also likely to be additional information from the multiple ongoing US government investigations.

The full report can be found here.