During the Deepwater Horizon drilling rig explosion incident on April 20, 2010, the blowout preventer should have activated itself automatically to preclude a blowout and subsequent oil spill in the Gulf of Mexico. Underwater robots later were used to manually activate the mechanism's controls, to no avail. As of May 2010 it is unknown why it failed.[4] Chief surveyor John David Forsyth of the American Bureau of Shipping testified in hearings before the Joint Investigation[5] of the Minerals Management Service and the U.S. Coast Guard investigating the causes of the explosion that his agency last inspected the rig's blowout preventer in 2005.[6] BP representatives suggested that the preventer could have suffered a hydraulic leak.[7] X-ray imaging of the preventer conducted on May 12 and May 13, 2010 showed that the preventer's internal valves were partially closed and were restricting the flow of oil. Whether the valves closed automatically during the explosion or were shut manually by remotely operated vehicle work is unknown.[7]
The permit for the Macondo Prospect by the Minerals Management Service in 2009 did not require redundant acoustic actuation means.[8] Inasmuch as the BOPs could not be closed successfully by underwater manipulation, pending results of a complete investigation it is uncertain whether this omission was a factor in the blowout.
Documents discussed during congressional hearings June 17, 2010, suggested that a battery in the device's control pod was flat and that the rig's owner, Transocean, may have "modified" Cameron's equipment for the Macondo site which increased the risk of BOP failure, in spite of warnings from their contractor to that effect. Another hypothesis is that a junction in the drilling pipe may have been positioned in the BOP stack in such way that its shear rams had a larger thickness of material to cut through.[9]
It was later discovered that a second piece of drill pipe got into the BOP stack at some point during the Macondo incident, potentially explaining the failure of the BOP shearing mechanism.[10]
On July 10 BP began operations to install a sealing cap, also known as a capping stack, atop the failed blowout preventer stack. Based on BP's video feeds of the operation the sealing cap assembly, called Top Hat 10, includes a stack of three ram-type BOPs manufactured by Hydril (a GE Oil & Gas company), one of Cameron's chief competitors.
发表于 2010-7-14 14:09
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