Report says trapped drill pipe thwarted ‘blowout preventer’ in BP disaster

A federal investigation into why a failsafe subsea device didn’t block BP’s runaway Macondo oil well last year concludes a piece of trapped drill pipe prevented the blowout preventer from deploying properly.

The Interior Department released a detailed forensic study Wednesday (available here) as part of its joint probe of last year’s disaster with the U.S. Coast Guard.

The report calls for new industry studies to prevent such malfunctions.

The report notes that so-called blind shear rams (BSRs) on the massive blowout preventer were unable to close around a piece of pipe that became trapped during the accident.

“As the BSRs were closed, the drill pipe was positioned such that the outside corner of the upper BSR blade contacted the drill pipe slightly off center of the drill pipe cross section. A portion of the drill pipe was outside of the BSR shearing blade surfaces. As the BSRs closed, this portion of the drill pipe cross became trapped between the ram block faces, preventing the blocks from fully closing and sealing,” states the report prepared by the company Det Norske Veritas.

Interior’s Bureau of Ocean Energy Management, Regulation and Enforcement and the Coast Guard are jointly probing the disaster. They will consider the forensic report at public hearings in Louisiana the week of April 4.

The blowout prompted the April 20 explosion of the Deepwater Horizon rig, killing 11 workers and setting in motion the months-long spill of an estimated 4.1 million barrels oil into Gulf of Mexico waters.

The blowout preventer was raised from the sea floor in September, and the forensic probe was undertaken at a NASA facility in New Orleans.

The lengthy report reconstructs why the pipe was able to become trapped in a manner that prevented the BSRs from successfully deploying.

The report calls for industry study of factors that lead to the “elastic buckling” of drill pipe that prevented the BSRs from closing fully and sealing off the well and several other issues, as well.

“It is recommended the industry examine and study the ability of the shear rams to complete their intended function of completely cutting tubulars regardless of their position within the wellbore, and sealing the well. The findings of these studies should be considered and addressed in the design of future Blowout Preventers and the need for modifying current Blowout Preventers to address these findings."

The blowout preventer was manufactured by Cameron International and was used on Transocean Ltd’s Deepwater Horizon rig, which BP had contracted for drilling the Macondo well.