A “complex and interlinked” series of events involving mechanical failures and human judgments led to the Gulf of Mexico oil disaster, a report by oil company BP said yesterday.
The internal inquiry, led by company head of safety and operations, Mark Bly, found BP was responsible in part for the tragedy, but also placed some blame on rig owner Transocean and cement contractor Halliburton.
The explosion on April 20 killed 11 workers and caused an estimated 4.9million barrels of oil to gush into the gulf – the largest offshore spill in history.
Commenting on the findings, outgoing chief executive Tony Hayward, who was forced to stand down in the wake of the disaster, said: “The investigation report provides critical new information on the causes of this terrible accident.
“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.”
The four-month probe found shoddy cement work at the bottom of the Deepwater Horizon well failed to hold gas and oil in its reservoir, which leaked into the casing. BP and Transocean employees then incorrectly accepted negative pressure readings in the crucial minutes before the explosion – meaning they did not spot the gas leak, the inquiry found.
Further mechanical failures then allowed gas to be vented directly on to the rig – rather than being diverted overboard – where it ignited. The rig’s blowout preventer, a protective valve, should have sealed the well but it failed.
Based on its key findings, the investigation team has proposed 25 recommendations designed to prevent such an incident.
The recommendations are directed at strengthening blowout preventers, well control, pressure-testing for wells, emergency systems, cement testing and rig audit and verification, as well as personnel competence.
Accepting full responsibility for the disaster could lead to BP being found guilty of gross negligence and fined up to £13billion, so it was always likely to maintain its stance that other parties were involved. It is not the first time that blame has been shared – with BP, Transocean and Halliburton all pointing the finger at each other at a US Congress meeting in May.
This report is not the final word on the causes of the explosion, as several divisions of the US government, including the Justice Department, Coast Guard and Bureau of Ocean Energy Management, Regulation and Enforcement are also investigating.
In addition, the failed blowout preventer was raised from the water only on Saturday and awaits further analysis.
Swiss-based company Transocean attacked the BP investigation in a strongly-worded statement. It said: “This is a self-serving report that attempts to conceal the critical factor that set the stage for the Macondo (well) incident: BP’s fatally-flawed well design.
“In both its design and construction, BP made a series of cost-saving decisions that increased risk – in some cases, severely.”
The firm said its own investigation was ongoing and would be concluded once “critical information” requested from BP had been received.
Halliburton claimed there were “substantial omissions and inaccuracies” in BP’s report. The group added it was “confident that all the work it performed with respect to the Macondo well was completed in accordance with BP’s specifications for its well construction plan and instructions, and that it is fully indemnified under its contract for any of the allegations contained in the report”.
BP has already spent £5.2billion trying to contain the disaster and has forecast that it will eventually cost the group more than $32billion (about £20.9billion).
The crisis cost former chief executive Mr Hayward his job after a series of PR blunders and he will make way in October for fellow board member Bob Dudley.