A new BP report concludes that "multiple companies and work teams" are to blame for the Gulf of Mexico rig explosion and the largest oil spill in U.S. history, including the rig's owner and a company doing cement work on the well bore just before the explosion.
Key Findings
-- 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.
-- The results of the negative pressure test were incorrectly accepted by BP and Transocean, although well integrity had not been established.
-- Over a 40-minute period, the Transocean rig crew 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 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.
Source: Deepwater Horizon Accident Investigation Report
In the 193-page internal report posted Wednesday on BP's website, the British oil giant says the April 20 accident was caused by "a sequence of failures involving a number of different parties."
"It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, Halliburton and Transocean, were involved," outgoing CEO Tony Hayward said in the report.
The report was generated by a BP team led by Mark Bly, BP's head of safety and operations.
In public hearings, BP has already tried to shift some of the blame to rig owner Transocean
Ltd. and cement contractor Halliburton. BP was leasing the rig from Transocean and owned the well that blew out.
Hayward singled out Halliburton for criticism in the report, pointing to that company's "bad cement job" but he was careful to defend the basic design of the well, key aspects of which were dictated by BP.
As for the rig's owner, BP said "the Transocean rig crew 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."
A Transocean lawyer said the company had no immediate comment on the report.
While BP didn't completely absolve its own engineers, the company shot down some of the things they've been criticized for by members of Congress and others.
"Well control actions taken prior to the explosion suggest the rig crew was not sufficiently prepared to manage an escalating well control situation," the report stated.
NPR Science Correspondent Richard Harris said that from the start of the disaster, BP has "argued that there's blame to go around everywhere."
Although BP said it "did not evaluate evidence against legal standards," in the report, diluting its role in the disaster was likely part of a legal strategy by BP, Harris said.
"Basically, what BP is trying to do is come up with both a legal and a [public relations] explanation," he said. "A lot depends on whether [BP] was grossly negligent or whether this was a whole series of accidents."
BP's report is just one piece in a much larger investigation into the causes of the well explosion including the Justice Department, Coast Guard and Bureau of Ocean Energy Management, Regulation and Enforcement.
The company faces hundreds of lawsuits and billions of dollars of liabilities.
Ultimately, the blowout preventer – the fail safe that was supposed to prevent disaster – did not work. That key piece of evidence was only raised to the surface on Saturday. As of Tuesday afternoon, it had not reached a NASA facility in New Orleans where government investigators planned to analyze it, so those conclusions were not be part of BP's report.
What is known is that the blowout preventer didn't seal the well pipe at the sea bottom after an eruption of methane gas triggered the explosion.
In the report, BP acknowledged that the failure of the preventer was "probably because critical components were not working."
Members of Congress, industry experts and workers who survived the rig explosion have accused BP's engineers of cutting corners to save time and money on a project that was 43 days and more than $20 million behind schedule at the time of the blast.
