The report said that the April 20, 2010, blowout, which killed 11 workers and set off the worst offshore oil spill in U.S. history, resulted in part from the removal of drilling mud, which helped keep the well's flow under control, during a key pressure test without applying a replacement barrier.
Also, the report said the crew deviated from standard well-control and well-abandonment protocols by testing for pressure during the removal of the drilling mud, instead of prior to it—an operation that resulted in drilling pipe being present in the blowout preventer at the time of the blowout, keeping it from closing properly to contain the outburst.Electrical power failed at the time of the explosion, preventing fire-suppression systems from activating, but the size and speed of the blast was such that any attempts at controlling it would have been futile, the report concluded.
At the time of the explosion, the rig was drilling a deep-water well in the U.S. Gulf of Mexico for BP PLC. The Marshall Islands Maritime Administrator's 216-page document doesn't say whether well operator BP, rig owner Transocean or cement-job provider Halliburton Co. were ultimately responsible for the disaster.
Previous U.S. reports, including one released in April by the U.S. Coast Guard, have included scathing critiques of the companies and the oil industry. The disaster has resulted in an overhaul of U.S. drilling regulations.U.S. government reviews of the disaster have also criticized the Marshall Islands' oversight of the vessel. In its reports, the Marshall Islands says it last inspected the Deepwater Horizon in 2009, when it found it to be in compliance with regulations. However, the inspection, conducted through contractors, found some issues requiring attention—namely, engine-room components dirty with oil.
The Marshall Islands Maritime Administrator acknowledged in the report that there needs to be better coordination regarding inspections between the U.S. and the Marshall Islands.