Offshore drilling moratorium: US cites blowout preventers' weak spot
The Obama administration on Monday cited control systems on subsea blowout preventers as one reason for its offshore drilling moratorium. But more than a year before the BP oil spill, authorities learned that balky control systems were the most common cause of blowout preventer failure.
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Because the newer systems "have electrical and electronic components in the water; leaks are more likely to have significant consequences in these systems," the report warned. After noting that hydraulic fluid may leak to the sea in some circumstances, the report states: "Leaks in electrical systems can be expected to render them inoperative."Skip to next paragraph
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It was not the first such warning. A smaller 1999 study of BOP reliability in the Gulf had warned that "a single leakage can jeopardize complete BOP control."
But the big new 2009 study, funded by the industry and the MMS, was focused on finding ways to cut the cost of BOP safety testing – with potential savings of about $193 million annually, the study's prospectus estimated.
In fact, the study authors – West Engineering Services, a Texas consulting firm specializing in BOP technology – did recommend that the MMS relax its standards concerning how often to test several subsea BOP components. The study, for instance, recommended a reduced schedule for pressure testing of some BOP valves, from at least once every 14 days to once every 35 days. It recommended testing the shear ram valve just once in 77 days instead of once in 30 days. (See related story.)
Emphasis on testing control systems
But because control systems were found to be the part of the BOP most susceptible to failure, the report recommended no change to rules for testing control systems: at least once a week.
"It is important to understand and focus on the fact that control system failures are the most likely category of failures on subsea BOP equipment," the authors wrote. "Even though control systems seem to have the larger margin of failures, due to redundancy there were not any cases where a control system failure would have compromised the well control abilities."
While the control system failure rates may be accurate, the study's conclusions are questionable, some industry veterans say.
Leaks of hydraulic fluid in deep water are the bane of BOP control systems and need more, not less, oversight, says Robert Bea, an engineer at the University of California at Berkeley who was a chief engineer for Shell Oil for 18 years and an expert reviewer for President Obama's recent 30-day safety study on offshore drilling.
The BOP hydraulic lines of the Deepwater Horizon were leaking, according to the drill logs, he says.
"It's like the brakes on your car. Those brakes get mushy when there's a leak," Dr. Bea says. "At some point they just won't work. With a BOP, you don't need much of a leak for that control system's hydraulics to fail."
The complexity of newer BOP control systems makes them vulnerable, says another BOP engineer who asked not to be named because he is still active in the industry. "The biggest problem with a BOP is the control system," he says. "If a BOP has maybe 50 parts, then its control system has 500 parts. Many of them are vulnerable to water leaks."
As part of the Deepwater Horizon's last line of defense, a “dead man’s switch” in the BOP unit was supposed to trigger the shear ram, if both electrical and hydraulic communications with the rig were lost. But this system failed, too.
"We already know one of the battery pods [providing power to the BOP control system] was dead," Bea says. "The other one was functional. But you have this system designed for redundancy, and because of neglected maintenance it is no longer redundant. It's like going parachuting, but without a backup chute. We were relying on this BOP like a parachute – and when it came time, the backup didn't work."