Investigators determining the cause of the Deepwater Horizon oil disaster have lent support to BP’s view that the cement used to seal the well was faulty.
“Unstable” foam cement
Cement experts at energy giant Chevron have conducted tests on a sample of the nitrogen foam cement injected to prevent hydrocarbons entering the well, and were unable to generate stable foam cement.
Chevron is carrying out tests on behalf of the National Commission on the BP Deepwater Horizon Spill and Offshore Drilling appointed by President Obama to find the cause of the explosion, which killed 11 and led to the largest offshore oil spill in history.
Contractor Halliburton, which recommended and supplied the cement at Deepwater, provided Chevron with samples of cement and additive materials used at the well. Although these materials did not come from the specific batches used at Deepwater, they were in all other ways identical in composition to the slurry used there.
The commission also found that only one in four tests that Halliburton ran on slurry designs before the cement job was carried out indicated that it would be stable, and the positive results may not have been known at the time of pumping.
In a letter to fellow commissioners, chief counsel Fred Bartlit wrote: “Halliburton may not have had – and BP did not have – the results of that test before the evening of 19 April [a day before the explosion], meaning that the cement job may have been pumped without any lab results indicating that the foam cement slurry would be stable.
“Halliburton and BP both had results showing that a very similar foam slurry design would be unstable, but neither acted upon the data.”
“Halliburton and BP both had results in March showing that a very similar foam slurry design to the one actually pumped at the…well would be unstable, but neither acted upon the data.”
Halliburton has claimed that the foam used in the first two tests, which were carried out two months prior to the explosion, was not similar to the one actually used and that the third test – carried out just a week before the disaster – was irrelevant as its laboratory “did not use the correct amount of cement blend”.
Further test ordered
The contractor also said that the results of Chevron tests, which found the foam was unstable, could be due to “differences in the cement materials tested”.
Further tests have been ordered by US district judge Carl Barbier, who is overseeing the lawsuits filed after the explosion, using the exact batch used by drillers in hours before the blast.