|
The Deepwater Horizon investigation included several investigations and commissions, among others reports by National Incident Commander Thad Allen, United States Coast Guard, National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, Bureau of Ocean Energy Management, Regulation and Enforcement, National Academy of Engineering, National Research Council, Government Accountability Office, National Oil Spill Commission, and Chemical Safety and Hazard Investigation Board.〔 ==April 2010 Coast Guard and Mineral Management Services investigation == On 22 April 2010, the United States Coast Guard and the Minerals Management Service launched an investigation of the possible causes of the Deepwater Horizon explosion; they obtained and analyzed the blowout preventer, a crucial piece of evidence as to the cause of the explosion and spill. In a 23 December letter, the U.S. Chemical Safety Board asked the Bureau of Ocean Energy Management, Regulation and Enforcement (formerly called the Minerals Management Service) to discontinue its investigation of the blowout preventer, which began 16 November at a NASA facility near New Orleans, until dealing with conflicts of interest. The board said Transocean and Cameron International, maker of the blowout preventer, had more access than the board did, and that Det Norske Veritas, which led the testing, should be removed or monitored more closely. Transocean said the board's "accusations are totally unfounded." On 8 December, Joe Keith, a senior Halliburton manager, said to the U.S. Coast Guard-Interior Department panel in Houston that he left his post aboard Transocean’s rig to smoke a cigarette on the night of the April disaster in the Gulf. While he was away from his monitors, charts entered into evidence showed that pressure data indicated the well was filling up with explosive natural gas and crude. Halliburton shares immediately fell on the New York Stock Exchange when news of his testimony emerged. On 23 March 2011, BOEMRE and the Coast Guard published the forensic examination report prepared by U.S. Det Norske Veritas (DNV) Columbus, the contractor that performed the examination.〔(【引用サイトリンク】FORENSIC EXAMINATION OF DEEPWATER HORIZON BLOWOUT PREVENTER-Final Report )〕 The report concluded that the primary cause of failure was that the blind shear rams failed to fully close and seal due to a portion of drill pipe trapped between the shearing blocks. This happened because the drill pipe elastically buckled within the wellbore due to forces induced on the drill pipe during loss of well control, consequently, drill pipe in process of shearing was deformed outside the shearing blade surfaces, and, consequently, the blind shearing rams were not able to move the entire pipe cross section into the shearing surfaces of the blades. Therefore, oil continued to flow through the drill pipe trapped between the ram block faces and subsequently through the gaps between the ram blocks. Since the pipe buckled when well control was lost, the blind shear rams would have failed to function as planned no matter when they were made active.〔See page 5 of (【引用サイトリンク】FORENSIC EXAMINATION OF DEEPWATER HORIZON BLOWOUT PREVENTER-Final Report: Volume 1 )〕 In September 2011, BOEMRE and the Coast Guard published its final investigative report on the accident. In essence, that report states that the main cause was the defective cement job, and Halliburton, BP and Transocean were, in different ways, responsible for the accident.〔(Gulf oil spill report: BP ultimately responsible in Gulf spill - CSMonitor.com )〕 The report consists of two volumes. Volume I contains the report of the US Coast Guard. That volume states that, although the events leading to the sinking of Deepwater Horizon were set into motion by the failure to prevent a well blowout, the investigation revealed numerous systems deficiencies, and acts and omissions by Transocean and its Deepwater Horizon crew, that had an adverse impact on the ability to prevent or limit the magnitude of the disaster. These included poor maintenance of electrical equipment that may have ignited the explosion, bypassing of gas alarms and automatic shutdown systems that could prevent an explosion, and lack of training of personnel on when and how to shut down engines and disconnect the MODU from the well to avoid a gas explosion and mitigate the damage from an explosion and fire. These deficiencies indicate that Transocean’s failure to have an effective safety management system and instill a culture that emphasizes and ensures safety contributed to this disaster. This investigation also revealed that the oversight and regulation of Deepwater Horizon by its flag state, the Republic of the Marshall Islands (RMI), was ineffective in preventing this casualty. By delegating all of its inspection activities to “recognized organizations,” without itself conducting on board oversight surveys, the RMI effectively abdicated its vessel inspection responsibilities. Volume II of the report cited above contains the report of the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE). That volume states that a central cause of the 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. The failure of the cement barrier allowed hydrocarbons to flow up the wellbore, through the riser and onto the rig, resulting in the blowout. The loss of life and the subsequent pollution of the Gulf of Mexico were the result of poor risk management, last‐minute changes to plans, failure to observe and respond to critical indicators, inadequate well control response, and insufficient emergency bridge response training by companies and individuals responsible for drilling at the Macondo well and for the operation of the drilling platform. BP, as the designated operator under BOEMRE regulations, was ultimately responsible for conducting operations at Macondo in a way that ensured the safety and protection of personnel, equipment, natural resources, and the environment. Transocean, the owner of the Deepwater Horizon, was responsible for conducting safe operations and for protecting personnel on board. Halliburton, as a contractor to BP, was responsible for conducting the cement job, and, through its subsidiary (Sperry Sun), had certain responsibilities for monitoring the well. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Deepwater Horizon investigation」の詳細全文を読む スポンサード リンク
|