Interim Report on Causes of the Deepwater Horizon Oil Rig Blowout and Ways to Prevent Such Events (2010) / Chapter Skim
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Letter Report
Letter Report
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that was part of the drilling operation at the Macondo well nor to interview representatives of Cameron (manufacturer of the recovered BOP) or Transocean [owner and operator of the Deepwater Horizon mobile offshore drilling unit (MODU)
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As indicated in the committee's statement of task, this interim consensus report is provided to inform the ongoing activities of the MBI, the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling2 and other formal investigations. The committee's final report, due in June 2011, will present its overall findings regarding the causes of the Deepwater Horizon MODU explosion, fire, and oil spill and recommended approaches for minimizing the likelihood that similar events will occur in the future.
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4. Other decisions noted by the committee that may have contributed to the Macondo well accident are as follows: • Changing key supervisory personnel on the Deepwater Horizon MODU just prior to critical temporary abandonment procedures (Section VI)
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However, the committee will be looking into reports (such as testimony provided at the MBI hearings) that various alarms and safety systems on the Deepwater Horizon MODU failed to operate as intended, potentially affecting the time available for personnel to evacuate (Section V)
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This results in a very narrow range of safe operating pressures in the open-hole section during cementing. To stay in this range during cementing operations, the mud weight must be high enough to prevent inflow from the sands at relatively high pore pressure, but not so high that it could accidentally 5 BP, Deepwater Horizon Accident Investigation Report, Sept.
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As stated in the first few sentences about cement design in Section 2.1 of the BP Deepwater Horizon Accident Investigation Report, "The narrow pore pressure and fracture gradient conditions in the Macondo well … [were] a challenge for the BP and Halliburton personnel involved .
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2000. 13 MBI hearing, July 22, 2010, testimony of John Guide, Wells Team Leader, BP.
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17 MBI hearing, August 24, 2010, testimony of Nathaniel Chaisson, Cementer, Halliburton. 18 A cement bond log is a report of the cement thickness in a well bore obtained from using an imaging tool.
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caused by hydrostatic pressure differences between the dense cement and drilling mud on the outside of the casing and the less dense displacement fluid on the inside. The float collar also acts as the landing point for the cementing plugs used during the job.
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Well-Monitoring Services There were several clear failures in the monitoring of the Macondo well that appear to have ultimately contributed to the blowout and explosion on the Deepwater Horizon MODU. Because detection of hydrocarbons, especially gas entering a well, is critical for maintaining safe operations, this report focuses on monitoring failures immediately prior to the first explosion on April 20, 2010.
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Full returns were cited as the reason BP did not run a cement bond log after cementing, which could have helped reveal that cementing operations had not gone as planned.26 However, there appears to have been no monitoring system in place that could have confirmed that this was actually occurring during cementing operations.27 In fact, data presented during the MBI hearings appear to indicate that during cementing operations, about 80 barrels more cement and spacers were pumped into the well than mud was flowing out of the well.28 Such losses would be consistent with accidental hydraulic fracturing during cementing, as discussed above. While much of this difference may be the result of compression of the nitrogen in the cement,29 losses during cementing still appear to have occurred.
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Blowout Preventer The BOP is relied on as a critical component for preventing uncontrolled hydrocarbon flows and avoiding a catastrophic blowout of a well. Various attempts were made to activate BOP functions on the Deepwater Horizon MODU, and there are indications that one of the annular preventers and perhaps a variable bore ram did operate to some degree, once actuated.
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Once the uncontrolled flow of hydrocarbons had enveloped the deck of the rig on April 20, ignition was most likely, given the large volume of gas, the multitude of ignition sources on the rig, moderate temperature, and limited wind conditions. Testimony provided at the MBI hearings indicated, however, that various alarms and safety systems on the rig failed to operate as intended, potentially affecting the time available for personnel to evacuate.
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Delegation of Decision-Making Authorities Witnesses at the MBI hearings exhibited a variety of perspectives with regard to the assignment of responsibility aboard the Deepwater Horizon MODU. Testimony suggested that decision making was a "team process" involving personnel from various companies, or that the offshore installation manager (OIM)
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Standards for Education, Training, and Professional Certification As described in testimony of witnesses at the MBI hearings, standards for education, training, and professional certification of private-sector decision-making personnel involved in drilling operations are relatively minimal compared with other safety-critical industries. Personnel on the Deepwater Horizon MODU were mostly trained on the job, and this training was supplemented with limited short courses (such as 1 week of well control school every few years)
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As the flag state for the Deepwater Horizon MODU, the Republic of the Marshall Islands had oversight 39 U.S. Department of the Interior Outer Continental Shelf Safety Oversight Board, Report to Secretary of the Interior Ken Salazar, Sept.
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The safety case44 strategies required by the United Kingdom Health and Safety Executive,45 the National Offshore Petroleum Safety Authority in Australia,46 and other authorities illustrate the application of a systems approach. The committee will assess the extent to which there are gaps, redundancies, and substantial uncertainties concerning the responsibilities of multiple regulatory agencies and classification societies overseeing deepwater drilling operations.
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Department of the Interior Outer Continental Shelf Safety Oversight Board Report to Secretary of the Interior Ken Salazar. September 1, 2010.
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That report will provide the committee's overall findings regarding the causes of the Deepwater Horizon incident and recommend approaches for minimizing the likelihood of similar events occurring in the future. Sincerely, Donald C
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