On March 20, the Department of the Interior released the final Deepwater Horizon autopsy report, Forensic Examination of Deepwater Horizon Blowout Preventor. You can view the entire document here, in this very large .pdf file. This report is full of great photos and illustrations, so it’s worth the time to download it and look. All illustrations in this section are taken from the report linked here.

To save time, they replaced the drilling mud meant to supply backpressure in the pipes with seawater — and it turned out the sea water couldn’t hold back the oil. They attempted to deploy a blowout preventor, which failed miserably.

A network of shearing rams is normally in place, ready to cut and crimp the pipe so that the oil flow stops. At Deepwater Horizon, though, the pipe wasn’t centered correctly with respect to the shearing blade. When they deployed the shearing ram, the pipe didn’t get properly cut or sealed. Another shearing ram that would have been in place was not deployable, although it wouldn’t have made a difference: it would have suffered the same failure as the first, because the pipe was off-center there, as well.

This created the leak that spilled for months.

The shearing ram should work like this:

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By design, the pipe is in the center and it gets crimped as above. What happened in the Deepwater Horizon case was that the pipe was off-center as shown below, so the apparatus failed to properly cut and crimp the pipe. The diagram below is from a view rotated 90 degrees from the one above:

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In the initial configuration, the pipe was not centered, and is shown at the bottom as the shearing ram closed. Below are photos of the actual pipe where the blowout prevention apparatus failed to seal it:

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Frontline produced a documentary about Deepwater Horizon called The Spill, which chronicles BP’s record of cutting costs at safety’s expense, and their yet unfulfilled promises to change their culture.

British Petroleum has a track record of trying to take on too much too fast. In 2005, they had a refinery explosion in Texas, largely because they were cutting costs by using outdated infrastructure. In 2006, they spilled over 200,000 gallons of oil on the Alaskan north slope at Prudhoe Bay, because they were using outdated and corroded pipes. They are a company built on undelivered promises to improve their safety record — and still they drill on.

As BP took increasingly big risks to find oil and extract it, the company left behind a trail of mounting problems: deadly accidents, disastrous spills, countless safety violations. Each time, BP acknowledged the wider flaws in its culture and promised to do better. The FRONTLINE/ProPublica investigation shows that the rhetoric was empty. From the refineries to the oil fields to the Gulf of Mexico, BP workers understood that profits came first.

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