Halliburton Co. acknowledged that it skipped a critical test on the final formulation of cement used to seal BP's oil well before it blew out catastrophically in the Gulf of Mexico.
The company, which was BP's cementing contractor, came under increased scrutiny when investigators from the president's oil spill commission revealed Thursday that tests performed by the company before the deadly blowout showed the cement to be unstable.
Halliburton in a statement issued late Thursday night said it did not conduct a stability test on the final mix of cement after a last-minute change by BP added more of a certain ingredient. Earlier statements by the company had said tests showed the cement to be stable.
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, the largest offshore oil spill in U.S. history.
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 criticized.