National scientific academies criticize Macondo well procedures

Nov. 22, 2010
Numerous technical and operation breakdowns that contributed to the Macondo well accident and subsequent crude oil spill in the deepwater Gulf of Mexico suggest there was no suitable approach for managing the inherent risks, uncertainties, and dangers associated with deepwater drilling, a National Academy of Engineering and National Research Council joint committee said in an interim report on Nov. 17.

Nick Snow
Washington Editor

Numerous technical and operation breakdowns that contributed to the Macondo well accident and subsequent crude oil spill in the deepwater Gulf of Mexico suggest there was no suitable approach for managing the inherent risks, uncertainties, and dangers associated with deepwater drilling, a National Academy of Engineering and National Research Council joint committee said in an interim report on Nov. 17.

BP PLC, Macondo's operator, and its offshore drilling contractor and service and supply companies failed to learn from previous "near misses," the interim report said. It also suggested that there were not sufficient checks and balances for critical decisions affecting the schedule for abandoning the exploratory well and for considering safety.

"Important decisions made to proceed toward well abandonment despite several indications of potential hazard suggest an insufficient consideration of risks," said Donald Winter, former US Navy secretary, professor of engineering practice at the University of Michigan, and chairman of the study committee.

"It's also important to note that these flawed decisions were not identified or corrected by BP and its service contractors, or by the oversight process employed by the US Minerals Management Service and other regulatory agencies," Winter said.

US Interior Sec. Ken Salazar, who requested the study, and Bureau of Offshore Energy Management, Regulation, and Enforcement Director Michael R. Bromwich welcomed the interim report from the two National Academies of Science divisions. Salazar said it would guide efforts by BOEMRE, the restructured MMS, to improve offshore oil and gas operations and safety, and assist other ongoing investigations.

'Important questions'

"The interim report by the NAE and NRC team raises important questions they will be exploring further in their ongoing review" said Bromwich. "Their work will help guide our continuing efforts to strengthen standards and oversight and underscores the importance of our ongoing efforts to build a strong and independent agency with the resources, training, and expertise to provide aggressive oversight of offshore oil and gas operations."

The joint committee said it expects to complete its work by June 2011. It said it may not be possible to definitively establish which mechanisms caused the well to blow out and Transocean Ltd.'s semisubmersible Deepwater Horizon drilling rig to explode on Apr. 20, given the deaths of 11 witnesses on board, the loss of the rig and important records, and the difficulty in obtaining reliable forensic information at the Macondo well's depth.

"In addition, no information is available yet from the recovered blowout preventer," the report stated. "Nonetheless, the committee believes it has been able to develop a good understanding of a number of key factors and decisions that may have contributed to the blowout of the well, including engineering, testing, and maintenance procedures; operational oversight; regulatory procedures; and personnel training and certification."

A spokeswoman for the BOEMRE-US Coast Guard joint investigation said on Nov. 16 that the static testing phase of the Deepwater Horizon's recovered BOP's forensic test has begun at the National Aeronautics and Space Administration's Michoud facility in New Orleans. Det Norske Veritas personnel are conducting the examination in consultation with experts from Cameron International Corp., the BOP's manufacturer; Transocean; BP; and experts representing the US Department of Justice; the US Chemical Safety Board; and plaintiffs in multidistrict litigation in New Orleans, she said.

The scientific academies' interim report concluded that the accident apparently was precipitated by the decision to proceed with temporary abandonment of the Macondo well despite indications from several repeated well integrity tests that the cementing process following the installation of a long-string production casing failed to provide an effective barrier to hydrocarbon flow.

Compounding actions

That decision's impact was compounded by delays in recognizing that hydrocarbons were flowing into the well and riser, and by a failure to take timely and aggressive well-control actions, it continued. "Furthermore, failures and/or limitations of the BOP, when it was actuated, inhibited its effectiveness in controlling the well," it said.

These failures and missed hazard indications were not isolated incidents, the report said. "Numerous decisions to proceed toward abandonment despite indications of hazard, such as the results of repeated negative-pressure tests, suggest an insufficient consideration of risk and a lack of operating discipline," it said. "The decisions also raise questions about the adequacy of operating knowledge on the part of key personnel. The net effect of these decisions was to reduce the available margins of safety that take into account complexities of the hydrocarbon reservoirs and well geology discovered through drilling and the subsequent changes in the execution of the well plan."

Other decisions may have contributed to the accident, including changing key supervisory personnel on the Deepwater Horizon just prior to critical temporary abandonment procedures; attempting to cement the multiple hydrocarbon and brine zones in the well's deepest part in a single operational step despite the zones' markedly different fluid pressures, and the small difference in the cement's density needed to prevent inflow from its density at which an undesirable hydraulic fracture might be created in a low-pressure zone; and choosing to use a long-string production casing in a deep, high-pressure well instead of a cement liner over the well's uncased section.

Deciding that only six centralizers would be needed despite modeling results to the contrary; limiting bottoms-up drilling mud circulation prior to cementing, which increased the possibility that debris in the well would contaminate the cement; not running a bond log after cementing to assess the cement's integrity despite anomalous results of repeated negative-pressure tests; not incorporating a float shoe at the bottom of the casing as an additional hydrocarbon flow barrier; and proceeding to remove the mud from the well without installing the lockdown sleeve on the production casing wellhead seals to ensure that pressure buildup could not shift the seals also may have led to the blowout and subsequent explosion, according to the report.

Checks and balances

"Available evidence suggests there were insufficient checks and balances for decisions involving both the schedule to complete well abandonment procedures and considerations for well safety," it said. "The decisions mentioned above were not identified or corrected by the operating management processes and procedures of BP or those of their contractors or by the oversight processes employed by MMS or other regulators."

It noted that there are conflicting views among experts familiar with the incident regarding the type and volume of the cement which was used to prepare for the well's temporary abandonment, as well as the adequacy of the time provided for the cement to cure. "These factors could have had a material impact on the integrity of the well," the report said.

It noted that the BOP did not control, or recapture control of, the well once personnel at the site realized that hydrocarbons were flowing into the well. Both the emergency disconnect system designed to separate the lower marine riser from the rest of the BOP and automatic sequencers controlling the shear ram and disconnect also failed to operate, it said.

"Given the large quantity of gas released onto the [mobile offshore drilling unit] and the limited wind conditions, ignition was most likely," the report said. "However, the committee will be looking into reports (such as testimony provided at the Marine Board of Inquiry hearings) that various alarms and safety systems on the Deepwater Horizon failed to operate as intended, potentially affecting the time available for personnel to evacuate."

It said the various failures mentioned show there was not a suitable approach for anticipating and managing inherent risks, uncertainties, and dangers associated with deepwater drilling, and a failure to learn from previous near misses.

No systems approach

"Of particular concern is an apparent lack of a systems approach that would integrate the multiplicity of factors potentially affecting the safety of the well, monitor the overall margins of safety, and assess the various decisions from perspectives of well integrity and safety," it said. "The 'safety case' strategy required for drilling operations in the North Sea and elsewhere is one example of such a systems approach."

BP, Transocean, Weatherford, and Halliburton Co., which provided the Macondo well's cementing services, did not respond immediately to the interim report's findings. National Ocean Industries Association Pres. Randall B. Luthi, who was MMS director from July 2007 through January 2009, did.

"The interim report corroborates the findings of earlier investigations into the potential causes of the Deepwater Horizon accident," Luthi said, adding, "With the blowout preventer currently being examined and other investigations still under way, technological failure cannot be completely ruled out at this point. However, today's findings and previous reports point to human error and a series of questionable decisions as being the leading contributing factor to the accident."

Luthi added, "This is precisely why it is so important to find the root cause of the accident, before mandating wide-scale legislative or administrative fixes that may not have any direct correlation to the cause. The good news is that industry has conducted its own investigations and reviews, and through the use of task forces has already begun to implement improved safety procedures and preparedness and response systems to help prevent and respond to any future such incidents."

He maintained, "With the safety measures already in place or under way, it is important to concentrate on getting permits for exploration under way to secure American jobs and energy security."

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