"We have known for some time that the cement used to secure the production casing and isolate the hydrocarbon zone at the bottom of the Macondo well must have failed in some manner, " the letter said, noting that BP used a "nitrogen foam cement" recommended and supplied by Halliburton.
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The location of hydrocarbon zones is critical information required prior to performing cementing services and achieving desired cement placement, Halliburton said.
FORBES: Halliburton Sues BP for Defamation, Misrepresentation