No single fault to blame for Deepwater Horizon disaster

BP's internal investigation has concluded that a sequence of failures involving multiple parties led to the Deepwater Horizon explosion and oil spill.

The report, published nearly five months after the explosion of the Macondo well drilling rig in the Gulf of Mexico, has concluded that a series of factors, rather than a single cause, led to the loss of 11 lives and one of the largest environmental disasters in recent US history.

The report states that decisions made by "multiple companies and work teams" contributed to the accident, along with a sequence of technical and human failures.  The report was led by BP's Head of Safety and Operations, Mark Bly, with a 50-strong team of in-house and external experts.

According to BP's own statement, the report concluded 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;
• 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 recognise 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.

Organisations named in the report as being at fault included BP themselves, Haliburton, who provided the cement, and Transocean who were responsible for management and operation of the rig itself.

BP's outgoing CEO, Tony Hayward, stated: "Based on the report, it would appear unlikely that the well design contributed to the incident, as the investigation found that the hydrocarbons flowed up the production casing through the bottom of the well".

Commenting on the disaster, which profoundly affected communities and the environment along the Gulf Coast, incoming CEO, Bob Dudley, added: "“We have said from the beginning that 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."

A total of 25 recommendations have been made to prevent a similar tragedy and BP stated that a number of the report's findings and recommendations are likely to have an impact on the oil industry in general.