US OIL services giant Halliburton has acknowledged it skipped a key test on the cement mix pumped into BP’s Gulf of Mexico well after BP changed the formula shortly before the explosion.
A commission set up by US President Barack Obama pointed to unstable cement that Halliburton poured into BP’s Macondo well to secure the casing on the sea floor as a cause of the April 20 explosion.
Halliburton said it was reviewing results of a government probe which said the firm knew the mix was faulty.
In a statement released late on Thursday, Halliburton acknowledged that after four internal tests were conducted on the cement slurry to be used to seal the well casing, BP ordered a change in the mixture’s formula, from eight gallons of retarder per 100 sacks of cement to nine gallons per 100 sacks.
“Tests, including thickening time and compressive strength, were performed on the nine gallon formulation and were shared with BP before the cementing job had begun,” Halliburton said.
“A foam stability test was not conducted on the nine gallon formulation.”
After the disaster, the commission had scientists conduct stability tests on cement made from what they believed were the same compounds as the slurry used on the BP well, but found it was unstable.
Halliburton said: “Halliburton believes that significant differences between its internal cement tests and the commission’s test results may be due to differences in the cement materials tested.
“The commission tested off-the-shelf cement and additives, whereas Halliburton tested the unique blend of cement and additives that existed on the rig at the time Halliburton’s tests were conducted.”
Two Halliburton tests of a nitrogen foam mixture were conducted in February and one at the beginning of April, just days before the rig exploded. But a review of the three tests by the commission determined none of them found the cement to be stable.
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