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Investigation report blames failure of 'blowout preventer' for Gulf of Mexico oil spill

March 24, 2011 - Houston

A buckled section of drill pipe prevented a blowout preventer from properly sealing to stop last year's massive Gulf of Mexico oil spill, according to a report released by the US Interior Department and the US Coast Guard.

The report is a detailed analysis by Norwegian undersea oil-equipment experts, who spent six months investigating why the "fail-safe" device did not work.

It said that the sudden rush of gas and oil forced the pipe upward following which a thick connecting portion became stuck near the top of the blowout preventer.

"With the pipe stuck in a large rubber ring called an annular, additional forces from the blowout caused the pipe to buckle below it. That stopped the ultimate fail-safe part of the preventer - a pair of heavy-duty blades called the blind shear rams - from cutting the pipe, which was bent and out of position," the report said.

The blind shear rams were designed to be activated from control panels on the drilling rig, or by several backup means: an emergency disconnect button on the rig, an automatic cutoff if connections were lost between the rig and the blowout preventer 5,000 feet down at the sea floor, or direct manipulation by remotely operated submersibles, the Christian Science Monitor reports.

The report also said that several of the backup methods did not work as intended.

The failure of the blowout preventer allowed oil to flow unchecked into the gulf until mid-July, when the well was sealed.

Besides the "primary cause", the investigators also identified several other blowout-preventer design problems - including one questionable procedure as well as one subpar industry standard that they said should be addressed "in the design of future blowout preventers and the need for modifying current blowout preventers".

The report, however, did not assign responsibility to BP, Cameron International, which manufactured the preventer, or Transocean, which owned and maintained it along with the Deepwater Horizon rig that was drilling the well.

The oil spill had stemmed from a sea-floor oil gusher that resulted from the April 20, 2010 explosion of Deepwater Horizon, which drilled on the BP-operated Macondo Prospect.

The explosion killed 11 men working on the platform and injured 17 others.

On July 15, the leak was stopped by capping the gushing wellhead, after it had released about 4.9 million barrels, or 205.8 million gallons of crude oil.

It was estimated that 53,000 barrels per day were escaping from the well just before it was capped.

It is believed that the daily flow rate diminished over time, starting at about 62,000 barrels per day and decreasing as the reservoir of hydrocarbons feeding the gusher was gradually depleted.

On September 19, the relief well process was successfully completed and the federal government declared the well "effectively dead".

The spill caused extensive damage to marine and wildlife habitats as well as the Gulf's fishing and tourism industries.

The US Government has named BP as the responsible party, and officials have committed to holding the company accountable for all cleanup costs and other damage.

After its own internal probe, BP had admitted that it made mistakes, which led to the spill.


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