Report cites decisions, multiple causes for Macondo well blowout, oil spill

A final report into the April 2010 Macondo deepwater well blowout and resulting massive oil spill in the Gulf of Mexico off Louisiana identified a number of causes for the blowout, concluding that a central cause was failure of a cement barrier in the production casing string.

The report comes from a Joint Investigation Team (JIT) of the US Bureau of Ocean Energy Management, Regulation, and Enforcement and the US Coast Guard. On Apr. 22, JIT released Vol. I, which outlined the panel’s findings on five aspects of the incident under USCG jurisdiction.

The incident killed 11 people on the semisubmersible. Many lawsuits remain pending regarding the spill that has been estimated at nearly 5 million bbl of oil and that took 87 days to stop. Industry, lawmakers, and regulators have altered offshore drilling procedures and rules since the incident, and BP PLC has called itself “a changed company (OGJ Online, Apr. 14, 2011).”

The Sept. 14 Vol. II report includes findings on the causes, both direct and contributing to the blowout of the well, operated by BP, and the resulting explosion and fire on Transocean Ltd.’s Deepwater Horizon semi.

The report concludes that BP, Transocean, and Halliburton’s conduct violated federal offshore safety regulations under BOEMRE’s jurisdiction. Vol. II also includes recommendations for the continued improvement of the safety of offshore operations. Halliburton Co. was responsible for the cement work.

“The loss of life at the Macondo site on Apr. 20, 2010, and the subsequent pollution of the Gulf of Mexico through the summer of 2010 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 Deepwater Horizon,” the report said.

At the time of the blowout, the rig crew was involved in temporary abandonment activities to secure the well after drilling was completed and before the Deepwater Horizon left the site, investigation said.

“In the days leading up to Apr. 20, BP made a series of decisions that complicated cementing operations, added incremental risk, and may have contributed to the ultimate failure of the cement job,” the report said. “These decisions included:

• The use of only one cement barrier. BP did not set any additional cement or mechanical barriers in the well, even though various well conditions created difficulties for the production casing cement job.

• The location of the production casing. BP decided to set production casing in a location in the well that created additional risk of hydrocarbon influx.

• The decision to install a lockdown sleeve. BP’s decision to include the setting of a lockdown sleeve (a piece of equipment that connects and holds the production casing to the wellhead during production) as part of the temporary abandonment procedure at Macondo increased the risks associated with subsequent operations, including the displacement of mud, the negative test sequence and the setting of the surface plug.

• The production casing cement job. BP failed to perform the production casing cement job in accordance with industry‐accepted recommendations.”

Investigators concluded BP and Transocean crew members on the Deepwater Horizon “missed the opportunity to remedy the cement problems when they misinterpreted anomalies encountered during a critical test of cement barriers called a negative test, which seeks to simulate what will happen if the well is temporarily abandoned and to show whether the cement will hold against hydrocarbon flow.”

JIT noted BP and Transocean had problems in detecting a kick on Mar. 8, 2010, that went undetected for 30 min. BP did not conduct an investigation into the reasons for the delayed detection of the kick, the investigation report said.

“Ten of the 11 individuals on duty on Mar. 8, who had well control responsibilities, were also on duty on Apr. 20,” the report said.

Investigators also concluded that simultaneous rig operations complicated the crew’s well monitoring efforts and that the crew bypassed a critical flow meter once it discovered a hydrocarbon flow.

JIT concluded stronger and more comprehensive federal regulations might have reduced the likelihood of the Macondo blowout.

In the aftermath of the accident, BOEMRE already has changed some regulations involving cementing procedures and testing, blowout preventer configuration requirements and testing, well integrity testing, and other drilling operations (OGJ Online, July 20, 2011).

The report concludes with recommendations to improve the safety of offshore drilling operations, including:

• Well design. Improved well design techniques for wells with high flow potential, including increasing the use of mechanical and cement barriers, will decrease the chances of a blowout.

• Well integrity testing. Better well integrity test practices (e.g., negative test practices) will allow rig crews to identify possible well control problems in a timely manner.

• Kick detection and response. The use of more accurate kick detection devices and other technological improvements will help to ensure that rig crews can detect kicks early and maintain well control. Better training also will allow rig crews to identify situations where hydrocarbons should be diverted overboard.

• Rig engine configuration (air intake locations). Assessment and testing of safety devices, particularly on rigs where air intake locations create possible ignition sources, may decrease the likelihood of explosions and fatalities in the event of a blowout.

• Blowout preventers. Improvements in BOP stack configuration, operation, and testing will allow rig crews to be better able to handle well control events.

• Remotely-operated underwater vehicles (ROVs). Standardization of ROV intervention panels and intervention capabilities will allow for improved response during a blowout.

Contact Paula Dittrick at

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