Tests 'warned of problem with cement' before disastrous BP oil well blowout

It was the first finding from the commission looking into the causes of the April 20 explosion that killed 11 workers and led to the largest offshore oil spill in US history.

And it appears to conflict with statements made by cementing contractor Halliburton, which has said its tests showed the cement mix was stable. The company has instead blamed BP’s well design and operations for the disaster.

The cement mix’s failure to prevent oil and gas from entering the well has been identified by BP and others as one of the causes of the accident.

BP and Halliburton decided to use a foam slurry created by injecting nitrogen into cement to secure the bottom of the well, a decision outside experts have criticised.

The panel said that of four tests done in February and April by Halliburton, only one – the last – showed the mix would hold. But the results of that single successful test were not shared with BP and may not have reached Halliburton before the cement was pumped, according to a letter sent to commissioners by chief investigative counsel Fred Bartlit.

BP had at the time of the blowout the results of only one of the tests – a February analysis sent by Halliburton in a March 8 email that indicated the cement could fail.

The slurry tested in that case was a slightly different blend and assumed a slightly different well design, but there was no indication that Halliburton flagged the problem for BP, or that BP had concerns, the letter said.

“Halliburton (and perhaps BP) should have considered redesigning the foam slurry before pumping it at the Macondo well,” Mr Bartlit wrote.

Independent tests conducted for the commission by Chevron on a nearly identical mixture were also released yesterday. The results concluded that the cement mix was unstable.