BP has published its internal investigation report into the Deepwater Horizon rig disaster in the Gulf of Mexico on 20 April 2010.
Largely, that it was the well cement’s fault, and thus Halliburton’s a little bit, for not testing the cement properly before placement. Although BP’s workers are in the frame too. As the report puts it:
It did not appear that Halliburton conducted all relevant lab tests on the final cement slurry prior to proceeding with cement placement. The investigation team saw no evidence that the BP Macondo well team confirmed that all relevant lab test results had been obtained and considered by the Halliburton in-house cementing engineer before cement placement proceeded.
Based on CSI Technologies’ lab results and analysis, the investigation team concluded that the nitrified foam cement slurry used in the Macondo well probably would have experienced nitrogen breakout, nitrogen migration and incorrect cement density, which would explain the failure to achieve zonal isolation of hydrocarbons. Nitrogen breakout and migration would have also contaminated the shoe track cement and may have caused the shoe track cement barrier to fail.
And here’s the Macondo explosion neatly illustrated in one easy to understand graphic — eight grey Swiss cheese slices of failure:
Plus an insightful timeline of events:
Finally, this is what outgoing chief executive Tony Hayward had to say about the report:
Commenting on the report, which he commissioned immediately after the Macondo explosion, BP’s outgoing chief executive Tony Hayward said: “The investigation report provides critical new information on the causes of this terrible accident. It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy.
Multiple parties, including BP, Halliburton and Transocean, were involved. “To put it simply, there was a bad cement job and a failure of the shoe track barrier at the bottom of the well, which let hydrocarbons from the reservoir into the production casing.
The negative pressure test was accepted when it should not have been, there were failures in well control procedures and in the blow-out preventer; and the rig’s fire and gas system did not prevent ignition. “Based on the report, it would appear unlikely that the well design contributed to the incident, as the investigation found that the hydrocarbons flowed up the production casing through the bottom of the well,” Hayward said.