Blowout preventer manufacturer questions Deepwater Horizon forensic report
Published: Friday, April 08, 2011, 12:00 PM Updated: Friday, April 08, 2011, 1:00 PM
A top executive at the company that built the Deepwater Horizon's blowout preventer expressed major doubts Friday about recent theories of why the massive subsea device failed to shut off BP's blown out Gulf oil well last year.
Those findings were released two weeks ago by Det Norske Veritas, a Norwegian company hired by federal investigators to produce what was essentially a coroner's report to help government agencies figure out what stopped the BOP from shutting off the worst oil gusher in American history.
Det Norske Veritas concluded that oil and gas shooting up through a 5.5-inch drill pipe at extremely high pressures caused the pipe to bend and knocked it off-center in the middle of the BOP. Without a centered pipe, the device couldn't use its powerful slicing rams to cut and seal the pipe shut.
The implication of those findings is that the BOP wasn't designed by Cameron to handle such intense emergency conditions.
But under questioning earlier this week, Det Norske Veritas officials acknowledged that they had no physical evidence of the pipe bending and that the elastic bowing of the pipe was simply their theory of what happened based on modeling.
On the other hand, McWhorter acknowledged that Cameron has tested its BOPs hundreds of times in accordance with industry standards and had never done so with the pipe off-center. That kind of test is not in the standards.
Still, McWhorter faulted the examiners for not presenting several other things that he believes could have gone wrong to prevent the rams from cutting properly - things that wouldn't have required the pipe to bend and would have resulted from poor maintenance of the BOP's components by the rig's owner, Transocean.
The Cameron questioned whether there could have been enough pressure to buckle the pipe, which by Det Norske Veritas' own calculations, would have required an incredible 113,000 pounds per square inch of force.
McWhorter said the examiners also ignored the possibility that the critical blind shear rams didn't work because there simply wasn't enough power to get them to close fully. He said a normal level of 1,500 psi may have initially triggered the rams instead of the much higher triggering pressures that should have been employed in an emergency.
"If that happened, it would not have been enough force to cut the pipe (even if centered)," McWhorter said. "It's possible then that the pipe was only dented, not sheared all the way through."
He said hydraulic controls may also have simply "not been up to the game that day." And he noted that the "deadman" function that is supposed to automatically close the rams and disconnect the rig from the well when hydraulics, electricity and communications are all lost can be manually armed or disarmed. He suggested it wouldn't have worked if it wasn't armed when the blowout happened, but he didn't know if it was or wasn't.
There has been no testimony or investigative findings indicating whether the "deadman" was armed on the Deepwater Horizon that day.
Investigators did find that a solenoid valve that helps trigger emergency closure of the BOP's rams worked only intermittently during later testing. That, McWhorter said, also could have yielded a partial closure of the blind shear rams even if the pipe had been properly centered.
It's been difficult for investigators to get a clear picture of why the "fail-safe" mechanisms in the BOP didn't work, or, for that matter, when various functions of the BOP activated. Specialists spent two weeks after the explosions trying to get rams and valves to work using remote-controlled submarines, which meant the BOP was not in the same position as it was on April 20, 2010, by the time it was brought to the surface in September.
Also, people opened and closed valves and rams in the BOP when it was first brought to the surface and was still out on a ship. That again moved devices before the forensic examiners had begun their review, which started when the BOP stack got to the NASA facility at Michoud in New Orleans. Videos of that tinkering on the ship were posted on YouTube last September, and a member of the technical group advising the examiners testified Friday that the rams "had been tampered with" before Det Norske Veritas began its review.
McWhorter noted that during the weeks-long intervention right after the accident, the rams "double-clutched," and he criticized Det Norske Veritas examiners for not considering those post-accident changes when they drew certain conclusions based on the location and condition of various BOP components.
The Marine Board of Investigation panel of three Coast Guard officials and three Interior Department officials completed its seventh session of hearings with McWhorter's testimony Friday. The panel must produce a final report by July 27 detailing what caused the disaster and analyzing the effectiveness of the immediate response.