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US investigators examining the Deepwater Horizon disaster have warned that the failure of the safety systems that led to the explosion and oil spill in the Gulf of Mexico could reoccur and that the oil and gas industry is “largely unaware” of why it happened.
The US Chemical Safety Board’s (CSB) final report on the Deepwater Horizon disaster has concluded that the blowout preventer (BOP), which should have shut-off the well to stop oil and gas escaping from the Macondo well, failed to do so because the drill pipe had previously buckled. According the CSB, this meant the BOP’s shearing ram, a hydraulic device that horizontally cuts across the pipe, actually punctured the buckled, off-centre pipe, instead of sealing it off.
The blowout in 2010 caused the deaths of 11 crew members and the serious injuries of 17 others on board the Deepwater Horizon and the largest oil spill in US history. Heavy fines have been issued to BP and Transocean, the offshore rig’s operator and owner. BP pleaded guilty to manslaughter and other criminal charges and has racked up more than £16 billion in spill-related expenses, including clean-up costs, compensation for businesses and individuals, and £2.6 billion in criminal penalties. BP also still faces fines of up to £11 billion for an ongoing civil legal action under the US’ Clean Water Act.
The CSB report differs from previous investigations into the incident, which assumed that the drill pipe buckled days after the blowout had occurred and that defective emergency systems meant the BOP was only triggered remotely two days after the blowout.
Instead, the report concludes that the BOP did trigger automatically when it was supposed to and that the Deepwater Horizon crew “likely” caused the drill pipe to buckle when they closed rams on the BOP pipe at the wellhead to temporarily seal the well. This closure enabled a “large pressure differential” to build-up between the inside and outside of the steel drill pipe, causing “effective compression” that led to the buckling and the ineffective operation of the last resort blind shear ram.
Dr Mary Beth Mulcahy, the CSB investigator that oversaw the technical analysis, said: “Our conclusions are based on real-time pressure data from the Deepwater Horizon and calculations about the behaviour of the drill pipe under extreme conditions. The pipe buckling – unlikely to be detected by the drilling crew – could render the BOP inoperable in an emergency.
“This hazard could impact even the best offshore companies, those who are maintaining their blowout preventers and other equipment to a high standard. However, there are straightforward methods to avoid pipe buckling if you recognise it as a hazard.”
Similarly to the UK’s Health and Safety Executive, the CSB examines equipment and plant after an accident to determine the reasons for incidents and makes recommendations to industry to prevent their reoccurrence.
Cheryl MacKenzie, CSB lead investigator, said: “Although there have been regulatory improvements since the accident, the effective management of safety critical elements has yet to be established. This results in potential safety gaps in US offshore operations and leaves open the possibility of another similar catastrophic accident.”