Risky Decisions Before BP Well Blowout

The choice of a tapered string meant that the well had only two barriers to upward gas flow that could cause a blowout: cement near the bottom of the well and a seal assembly near the top. The congressmen described three flawed decisions relating to the cement, and said the company also decided not to use a device called a “lockdown sleeve” to ensure that the top seal would hold.

Among the decisions relating to the cement, the congressmen said, BP opted to use far fewer “centralizers,” devices to keep the final string of casing centered in the well hole and help assure that cement flows evenly around the outside of the casing. BP used six instead of the 21 recommended by the cement contractor, Halliburton, which warned of a potential for a “severe gas flow problem.” A BP official complained in an April 16 e-mail message that it would take 10 hours to install the recommended number. “I do not like this,” he wrote.

In addition, the congressmen wrote, BP did not fully circulate heavy drilling mud through the well — which would have taken about 12 hours — before proceeding with the cement job. The congressmen noted that the American Petroleum Institute, a trade group, recommends full circulation before cement work to reduce the possibility that the mud will contaminate the cement, which could contribute to its failure.

BP also did not order a cement bond log, a testing procedure that would have more fully evaluated the quality of the cement barrier. BP’s own engineers had run computer models suggesting that a good cement job was unlikely, and the company had a crew from Schlumberger on hand to conduct the test, which would have taken up to 12 hours.

But BP officials decided not to proceed with the test and the Schlumberger workers left the Deepwater Horizon the morning of the disaster.

New York Times