CSB reports unrecognized pipe buckling contributed to Macondo oil spill

This story was updated June 5.

An incident similar to the 2010 deepwater Macondo well blowout and resulting oil spill still could occur, the US Chemical Safety Board reported June 5 in releasing its investigation findings into the 2010 incident.

CSB called for better safety management by oil companies and regulators concerning drilling equipment, and CSB investigators identified a type of pipe buckling that they called effective compression.

The blowout preventer (BOP) on the Deepwater Horizon semisubmersible drilling rig on Apr. 20, 2010, failed to seal the well because of this buckling, CSB said in a two-volume draft investigation report released June 5.

The report concluded that, under certain conditions, the effective compression phenomenon could compromise the proper functioning of other BOPs being used worldwide.

“Although both regulators and the industry itself have made significant progress since the 2010 calamity, more must be done to ensure the correct functioning of [BOPs] and other safety-critical elements,” said Rafael Moure-Eraso, CSB chairperson.

The Macondo blowout caused explosions and a fire on the Deepwater Horizon semi, killing 11 people. The semi later sank, leaving the Macondo well spewing oil and gas into Gulf of Mexico waters off Louisiana for 87 days.

The CSB report said pipe buckling likely occurred during the first minutes of the blowout and that the BOP’s blind shear ram attempted to cut the pipe, but the pipe buckling prevented the shear ram from cleanly cutting and sealing the pipe.

“The shear ram actually punctured the buckled, off-center pipe, sending huge additional volumes of oil and gas surging toward the surface,” the report said.

Miswiring, batteries failures

CSB reported two instances of miswiring and two backup battery failures affected the electronic and hydraulic controls for the BOP’s blind shear ram.

A comprehensive examination of a full set of BOP testing data was made available to the CSB team that was unavailable to other investigative organizations. The blowout followed a failure of the cementing job to temporarily seal the well, and a series of pressure tests were misinterpreted, the report said.

CSB Investigator Cheryl MacKenzie noted Macondo was a high-pressure well, which likely contributed to how the drill pipe buckled and moved off-center within the BOP, preventing the well from being sealed.

Effective compression occurs when there is a large pressure difference between the inside and outside of a pipe, MacKenzie said.

“The CSB’s model differs from other buckling theories that have been presented over the years but for which insufficient supporting evidence has been produced,” said CSB investigator Mary Beth Mulcahy, who oversaw the technical analysis. “The CSB’s conclusions are based on real-time pressure data from the Deepwater Horizon and calculations about the behavior of the drill pipe under extreme conditions. 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.”

CSB reports ‘safety gaps’

CSB’s investigation found the Deepwater Horizon crew regularly tested and inspected BOP components necessary for daily drilling operations, neither Transocean nor BP performed regular inspections or testing to identify latent failures of the BOP’s emergency systems.

“Safety-critical BOP systems responsible for shearing drill pipe in emergency situations and safely sealing an out-of-control well were compromised before the BOP was even deployed to the Macondo wellhead,” the report said.

The report also noted that the BOP lacked the capacity to reliably cut and seal the 6-5/8-in. drill pipe used during most of the Macondo drilling before Apr. 20.

Despite the multiple maintenance problems found in the Deepwater Horizon BOP, CSB investigators ultimately concluded the blind shear ram likely did close, and the drill pipe could have been successfully sealed but for the pipe buckling.

The draft report, subject to board approval, makes numerous recommendations to the US Department of Interior’s Bureau of Safety and Environmental Enforcement (BSEE), the federal organization established following the Macondo accident to oversee offshore safety.

These recommendations call on BSEE to require drilling operators to effectively manage technical, operational, and organizational safety-critical elements to help reduce major-accident risk to an acceptably low level.

“Although blowout preventers are just one of the important barriers for avoiding a major offshore accident, the specific findings from the investigation about this BOP’s unreliability illustrate how the current system of regulations and standards can be improved to make offshore operations safer,” MacKenzie said.

The report also proposes the American Petroleum Institute revise API Standard 53, Blowout Prevention Equipment Systems for Drilling Wells, and provide new guidance for management of safety-critical elements in general.

Moure-Eraso said, “Drilling continues to extend to new depths, and operations in increasingly challenging environments, such as the Arctic, are being planned…. To maintain a leadership position, the US should adopt rigorous management methods that go beyond current industry best practices.”

Two forthcoming volumes of the CSB’s Macondo investigation report are planned to address additional regulatory matters as well as organizational and human factors safety issues raised by the accident.

CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB does not issue citations or fines but makes safety recommendations.

The American Petroleum Institute later reacted strongly about the report. API spokesman Brian Straessle said, “There is nothing here that hasn’t already been exhaustively addressed by regulators and the industry. We are still reviewing the parts that CSB has decided to release, but the report appears to omit significant facts and ignores the tremendous strides made to enhance the safety of offshore operations. As the co-chairs of the Presidential Oil Spill Commission recently said, offshore drilling is safer today because industry and the government have enhanced spill prevention, containment and response, implemented new standards and rules, and focused on strong safety culture.”

Contact Paula Dittrick at paulad@ogjonline.com.

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