The U.S. Department of Interior’s (DOI ’s) Bureau of Ocean Energy Management, Regulation and Enforcement (Bureau) and the U.S. Coast Guard have issued a 217-page report on the Deepwater Horizon oil rig explosion and resulting oil spill in the Gulf of Mexico. The September 14, 2011, report concludes that “a central cause of the [well] blowout was failure of a cement barrier in the production casing string, a high-strength steel pipe set in a well to ensure well integrity and to allow future production.” According to the report, the failure allowed hydrocarbons to flow up the wellbore, through the riser and onto the rig, resulting in the blowout. The report concludes that the precise reasons for the failure of the cement barrier are unknown.

Based on the investigation, the report alleges that numerous parties, including the rig operator, rig owner and several contractors, were to blame for the accident. The report recommends the issuance of rules on specific well- and blowout-prevention operations, revisions of incident-reporting regulations and enhanced well-control training. It also recommends the development of a standardized negative test procedure for wells and review of current procedures for analyzing well-activity reports.