CSB on Deepwater Horizon: Pipe Buckling Caused Blowout Preventer Failure
A new Deepwater Horizon disaster report, released on June 5, found that the blowout preventer (BOP), designed to shut off the flow of oil and gas from the Macondo well, "failed to seal the well because drill pipe buckled for reasons the offshore drilling industry remains largely unaware of."
The U.S. Chemical Safety Board (CSB) released the new, two-volume draft investigation report, the result of an independent examination at the request of Congress on the technical reasons behind the April 20, 2010, incident and to find opportunities for possible improvements to industry standards. Volumes three and four are set for release later this year.
Cementing repairs were designed to seal the well temporarily. Later pressure tests falsely indicated a proper seal that, combined with the BOP failure, ultimately led to the disaster that killed 11.
Early investigations assumed the drill pipe buckled days after the initial blowout, but the CSB determined the buckling likely happened within minutes.
CSB investigators concluded the BOP's blind shear ram (BSR)—an emergency hydraulic device intended to seal an out-of-control well—likely did activate on the night of the accident, days earlier than other investigations found. But the shear ram was likely kept from functioning properly because of the buckled pipe; instead, the shear ram punctured the pipe, sending huge, additional volumes of oil and gas surging toward the surface, contributing to the 87-day-long release into the Gulf, the report found.
Further, the new buckling mechanism—called "effective compression," which occurs when there is a large pressure difference between the inside and outside of a pipe—could still contribute, under certain conditions, to the malfunction of other blowout preventers deployed on all offshore drilling rigs.
According to Dr. Mary Beth Mulcahy, who oversaw the CSB's technical analysis, "The findings reveal that pipe buckling could occur even when a well is shut in and apparently in a safe and stable condition. 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."
The Deepwater Horizon crew did perform regular tests and inspections on the BOP components but not on the BOP's emergency systems, compromising the emergency systems before the BOP was even deployed, the report determined.
"Better understanding of [the] buckling phenomenon can lead to improvements in equipment design, well control procedures, training and adoption of more rigorous management methods, each of which could ultimately lessen the likelihood of buckled drill pipe across the BSR of a BOP, as occurred at Macondo," volume two of the report states.
