The steel drill pipe on BP’s Macondo exploration well in the Gulf of Mexico buckled under extreme pressure and kept the blowout preventer from sealing the well during the April 2010 disaster that sank the Deepwater Horizon rig, according to a new report released Thursday.
In its report, the Chemical Safety and Hazard Investigation Board said that the blowout preventer’s blind shear ram — an emergency hydraulic device with two sharp, powerful cutting blades — probably did activate on the night of April 20, contrary to the conclusions reached by some other investigations. But the device ended up puncturing the off-center pipe, sending huge volumes of oil and gas to the surface and triggering the massive oil spill, the board said.
The blowout killed 11 members of the crew on the Deepwater Horizon and led to an 87-day long spill, the biggest in U.S. history. The Macondo well was about 50 miles off the coast of Louisiana and was drilling in waters a mile deep, making the subsequent investigations difficult.
The board said other companies operating in the Gulf of Mexico should take steps to make sure that sequence of events does not happen again. “There are a lot of changes to be made,” an official said, adding that the investigation found “a litany of flaws with the blowout preventer.”
The board also said that two separate instances of bad wiring contributed to the failure of two backup batteries on the “blue pod” and “yellow pod” designed to make sure the blowout preventer’s blind shear rams activated. It said that the yellow pod activated anyway. The report faulted the maintenance by Transocean, owner of the Deepwater Horizon.
The board is an independent federal agency charged with investigating industrial and chemical accidents. It examined the reasons for the deadly explosion that took place at BP’s Texas City refinery in 2007, and it is investigating the West Virginia storage tank leak that contaminated water supplies for thousands of people. But it is a small agency, and it hired outside consultants to assist in the Deepwater Horizon case. The board has struggled against other agencies during the BP oil spill investigation to gain access to damaged equipment, and it went to federal court to get its subpoenas enforced. Transocean has argued that offshore incidents are outside the board’s jurisdiction.
Yet the companies involved in the disaster — and plaintiffs’ lawyers — saw the report in the context of ongoing litigation over where and how much negligence might have been involved. And industry groups sought to defend drilling practices in the gulf, where drilling has returned to levels that prevailed before the spill.
“There is nothing here that hasn’t already been exhaustively addressed by regulators and the industry,” the American Petroleum Institute said in a statement. “The report appears to omit significant facts and ignores the tremendous strides made to enhance the safety of offshore operations” since the spill.
The board said it relied on information from a variety of sources, including relatively recent court cases brought by private plaintiffs about how to apportion blame for the spill. Mary Beth Mulcahy, who oversaw the board’s technical analysis, said that the agency used real time pressure data from the Deepwater Horizon.
The board issued two reports detailing engineering failures, and it plans another two reports that will probe regulatory and corporate organizational issues that might have contributed to the disaster.
While other investigators noted the bent drill pipe, most believed that it had buckled days into the spill. The board said that the pipe buckled in the opening minutes of the blowout. It blamed what it called “effective compression,” a large pressure difference between the inside and outside of a pipe. It said that condition came about when the rig operators closed the blowout preventer’s pipe rams at the wellhead, temporarily sealing the well but creating a large pressure differential.
An official with the agency said a different sequence of opening and closing rams might have prevented the blowout. But the agency warned that similar conditions could occur at other wells.
“The findings reveal that pipe buckling could occur even when a well is shut-in and apparently in a safe and stable condition,” the report said. Cheryl MacKenzie, who led the board’s investigative team, said the group had access to the “full set” of blowout preventer testing data, which she said were unavailable to other investigative organizations when their reports were completed.
The board spread blame around for the spill, saying that the blowout followed “a failure of the cementing job to temporarily seal the well.” Halliburton, a major oil services firm, was involved in the cement job. The board also said that the blowout preventer, manufactured by the British firm Cameron International, “lacked the capacity to reliably cut and seal the 65 / 8 inch drill pipe” — even if the pipe had not buckled and had been properly centered.
Manufacturers are designing new blowout preventers that would seal pipes even if they are off center.
The board also said that Transocean and BP failed to perform regular inspections of emergency systems.
Transocean has refused to cooperate with the board, saying the agency lacks jurisdiction. The agency filed suit, and a federal judge ordered Transocean to respond to its subpoenas for documents and interviews. Transocean has appealed.
The report acknowledged that the buckling of the drill pipe was difficult to detect. “This hazard could impact even the best offshore companies, those who are maintaining their blowout preventers and other equipment to a high standard,” Mulcahy said.
But the report said that “there are straightforward methods to avoid pipe buckling if you recognize it as a hazard.”
BP, which said it fully cooperated with the board, said that the agency’s “core findings” were “consistent with the conclusion of every other official investigation: that the Deepwater Horizon accident was the result of multiple causes, involving multiple parties, including Transocean.”
But BP spokesman Geoff Morrell took issue with the report’s explanation, which he said was “based on flawed assumptions” that the so-called deadman device to activate the blowout preventer had worked notwithstanding the “maintenance deficiencies.”