WASHINGTON — Houston-based Halliburton knew that the cement it was using to seal BP's Deepwater Horizon oil well was likely to be unstable, but it didn't tell BP or act on the information itself before the well blew up on April 20, the staff of the presidential commission investigating the disaster reported Thursday.
In a letter to the commission's seven members, the staff said the failure of the cement was a key factor in the blowout, which resulted in millions of barrels of crude oil escaping into the Gulf of Mexico in a torrent that went largely unchecked for three months.
But the staff also took pains to point out that unstable cement wasn't the sole factor — or even the most crucial one — in the well's failure. That blame, the letter said, belongs to BP and Transocean, the company that BP had hired to drill the well.
"Industry experts inform us that cementing failures are not uncommon even in the best of circumstances," the letter said. "Because it may be anticipated that a particular cement job may be faulty, the oil industry has developed tests... to identify cementing failures.
"BP and/or Transocean personnel misinterpreted or chose not to conduct such tests at the Macondo well."
The letter added to evidence that safety procedures that are intended to head off such accidents were ignored or overlooked. BP acknowledged in a September report that its internal investigation had found that cementing tests were misinterpreted or were not run.
In its letter Thursday, the commission staff expressed concern that similar oversights were widespread in the offshore drilling industry.
Oil-drilling companies use cement to seal an exploratory well like the Deepwater Horizon as the last step before assigning a drilling rig to another location. Once the seal is in place, technicians remove heavy drilling mud from the well and replace it with lighter seawater. It was during that step that hydrocarbons surged up the Deepwater Horizon drill pipe and enveloped the rig in a cloud of methane. The ensuing explosion killed 11 workers and set off the largest accidental oil spill in history.
Chevron's test results
The letter, signed by commission counsel Fred H. Bartlit Jr. and two other staff members, came two days after Chevron reported the results of efforts it made, using materials provided by Halliburton, to duplicate Halliburton's cementing mixture. In every instance, Chevron reported, the procedures it followed failed to produce stable cement.
"We were unable to generate stable foam from any of the tests," Chevron's cementing team leader, Craig Gardner, told the commission in a letter.
Chevron conducted the tests "as a public service" at the request of the commission, Bartlit wrote in his letter. "Halliburton agreed that the Chevron lab was highly qualified for the work," the letter said.
The Chevron results should have come as no surprise to Halliburton or BP, Bartlit's letter suggested. He said that when the Chevron results came in, the commission asked Halliburton for its internal test results, which Halliburton provided. Those documents showed that at least three of four tests Halliburton conducted had found that the cement would fail, the commission staff letter said.
"The first two tests were conducted in February 2010," the letter said. "Both tests indicated the foam slurry design was unstable."
Halliburton did pass the data from one of the February tests to BP on March 8 in a technical report. But Halliburton didn't highlight the significance of the test and there was no indication that "BP personnel raised any questions about it," the letter said.
Another test conducted in April had similar results, but "it appears that Halliburton never provided the data to BP," the letter said.
A fourth test, conducted after Halliburton changed its testing procedures just days before the explosion, showed that the cement mixture would be stable, but it was unclear whether the testing had been completed before the cement was poured. The results of that test were not provided to BP until after the well exploded, the letter said.