AT APPROXIMATELY 9.50pm on the evening of April 20, 2010, while the crew of the Deepwater Horizon rig was finishing work after drilling the Macondo exploratory well, an undetected influx of hydrocarbons (commonly referred to as a “kick”) escalated to a blowout.
Shortly after the blowout, hydrocarbons that had flowed on to the rig floor through a mud-gas vent line ignited in two separate explosions. Flowing hydrocarbons fuelled a fire on the rig that continued to burn until the rig sank on April 22. Eleven men died on the Deepwater Horizon that evening.
Over the next 87 days, almost 5million barrels of oil were discharged from the Macondo well into the Gulf of Mexico . . . the worst offshore pollution incident ever.
Investigators affirm in their final report on the causation of the disaster 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 on to the rig, resulting in the blowout.
However, it is admitted that the precise reasons for the failure of the production casing cement job are not known.
The investigation panel assembled by the US government concluded that the failure was likely due to:
Swapping of cement and drilling mud (referred to as “fluid inversion”) in the shoe track (the section of casing near the bottom of the well)
Contamination of the shoe track cement; or
Pumping the cement past the target location in the well, leaving the shoe track with little or no cement (referred to as “over-displacement”).
The panel is in no doubt that poor risk management is central to what happened . . . 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.
But while BP’s approach lies at the heart of what happened, Transocean, Halliburtion with subsidiary Sperry Sun and Cameron also have a responsibility to bear.
The panel found that, critically, in the days leading up to April 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.
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 lock-down sleeve: BP’s decision to include the setting of a lock-down 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.
The Panel concluded that BP failed to communicate these decisions and the increasing operational risks to Transocean. As a result, BP and Transocean personnel onboard the Deepwater Horizon did not fully identify and evaluate the risks inherent in the operations that were being conducted at Macondo.
There were several possible reasons why the Deepwater Horizon crew did not detect the kick:
The rig crew had experienced problems in promptly detecting kicks. The Deepwater Horizon crew had experienced a kick on March 8, 2010, that went undetected for approximately 30 minutes. BP did not conduct an investigation into the reasons for the delayed detection of the kick. Transocean personnel admitted to BP that individuals associated with the March 8 kick had “screwed up by not catching” the kick. Ten of the 114 individuals on duty on March 8, who had well control responsibilities, were also on duty on April 20.
Simultaneous rig operations hampered the rig crew’s well monitoring abilities. The rig crew’s decision to conduct simultaneous operations during the critical negative tests – including displacement of fluids to two active mud pits and cleaning the pits in preparation to move the rig – complicated well-monitoring efforts.
The rig crew bypassed a critical flow meter. At approximately 9.10pm, the rig crew directed fluid displaced from the well overboard, which bypassed the Sperry Sun flow meter, which is a critical kick detection tool that measures outflow from the well.
Macondo was clearly an edgy well as, prior to the events of April 20, BP and Transocean experienced a number of problems while conducting drilling and temporary abandonment operations at Macondo.
These problems included:
Recurring well control events and delayed kick detection. At least three different well control events and multiple kicks occurred during operations at Macondo.
Scheduling conflicts and cost overruns. At the time of the blowout, operations at Macondo were significantly behind schedule. BP had planned for the Deepwater Horizon to move to its Nile well by March 8. In large part as a result of this delay, as of April 20, BP’s Macondo operations were more than $58million over budget.
Personnel changes and conflicts. BP experienced a number of problems involving personnel with responsibility for operations at Macondo. For example, the panel found evidence of conflict between the BP drilling and completions operations manager and the BP wells team leader and evidence of a failure to adequately delineate roles and responsibilities for key decisions.
At the time of the blowout, both BP and Transocean had extensive procedures in place regarding safe drilling operations. BP required that its drilling and completions personnel follow a “documented and auditable” risk management process.
However, the panel found no evidence that the BP Macondo team fully evaluated ongoing operational risks, nor did it find evidence that BP communicated with the Transocean rig crew about such risks.