Cement failure, insufficient training, plan changes, inappropriate responses, and multiple other problems killed BP’s Deepwater Horizon crew of 11 and caused the spill of 5 million barrels of oil into the Gulf of Mexico in 2010, a federal investigation has found.
A Joint Investigation Team comprised of the Bureau of Ocean Energy Management, Regulation and Enforcement (formerly the Minerals Management Service or MMS) and the U.S. Guard identified a number of causes of the Macondo well blowout, detailed in a scathing, new 212-page report that pins the blame overwhelmingly on BP.
‘Poor Risk Management’
Although the direct physical cause of the blowout was the failure of a cement barrier, the report said, the loss of life and 87-day oil spill “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.”
U.S. Coast Guard
|Coast guard responders douse the blazing remnants of BP’s Deepwater Horizon rig on April 20, 2010.|
The disaster erupted about 9:50 p.m. April 20, 2010, while the crew of the Deepwater Horizon offshore rig was finishing work after drilling the Macondo exploratory well, when an undetected influx of hydrocarbons (commonly called a “kick”) “escalated to a blowout,” the report found.
“Shortly after the blowout, hydrocarbons that had flowed onto the rig floor through a mud-gas vent line ignited in two separate explosions,” the report said. ”Flowing hydrocarbons fueled a fire on the rig that continued to burn until the rig sank on April 22.”
The failure occurred in 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. That breach allowed the flow of hydrocarbons that eventually caused the blowout.
Although investigators were unable to fix a cause of the failure, they said it was probably due to:
• Swapping of cement and drilling mud (referred to as “fluid inversion”) in a casing section known as the “shoe track” near the bottom of the well;
• Contamination of the shoe track cement; or
• Pumping the cement past the well’s target location, leaving the shoe track with little or no cement (known as “over-displacement”).
The report said BP was “ultimately responsible” for the safety of operations at Macondo, although it noted responsibility by other companies as well:
• Transocean, Deepwater Horizon’s owner, was responsible for conducting safe operations and for protecting personnel onboard;
• Halliburton, a BP contractor, was responsible for the failed cement job and, through its subsidiary Sperry Sun, for monitoring the well; and
• Cameron was responsible for the design of the Deepwater Horizon blowout preventer (BOP) stack.
Decisions, Communication Criticized
Investigators detailed a series of poor decisions in March and April that eventually contributed to the disaster. The report cited, for example:
• The use of only one cement barrier, “even though various well conditions created difficulties for the production casing cement job”;
• Setting the production casing “in a location in the well that created additional risk of hydrocarbon influx”; and
• Failing to perform the production casing cement job “in accordance with industry-accepted recommendations.”
Moreover, the panel said, “BP failed to communicate these decisions and the increasing operational risks to Transocean,” so personnel aboard the rig “did not fully identify and evaluate the risks inherent in the operations that were being conducted…”
Test Anomalies Ignored
Compounding those errors, the panel said, rig crews “misinterpreted anomalies encountered during a critical test of cement barriers” on the day of the blast. The test revealed “a serious anomaly that should have alerted the rig crew to potential problems…”
Even though a second test showed the same anomaly, the crew developed an alternative explanation based on “a theory that later proved to be unfounded” and concluded erroneously that the cement barrier was sound.
“Despite a number of additional anomalies that should have signaled the existence of a kick or well flow, the crew failed to detect that the well was flowing until 9:42 p.m.,” the report said.
And “by then, it was too late.”
The rig crew had missed kicks before, the team found. A kick on March 8 went undetected for about 30 minutes, but BP did not investigate later how the crew had missed it.
Transocean personnel told BP later that the March 8 crew had “screwed up by not catching” the kick. Ten of the March 8 crew members were also on duty April 20, the report said.
Among other problems cited by investigators:
• The rig’s general alarm system was operating in a mode that did not sound automatically, leaving the crew to manually sound that alarm after about 20 individual alarms indicating maximum gas concentrations around the rig;
• The 360-ton blowout preventer stack at the top of the well failed to seal the well to contain the flow of hydrocarbons, probably due to cable and line damage caused by the explosions;
• Recurring, unaddressed well control events and delayed kick detection in the weeks before the disaster;
• Scheduling conflicts and cost overruns that had the project “significantly behind schedule” and more than $58 million over budget;
• “A number of problems” involving BP personnel, including conflicts among managers and a shakeup in the weeks before the accident that changed the roles and responsibilities of at least nine individuals at the site;
• Failure of the BP Macondo team to fully evaluate ongoing operational risks; and
• Multiple violations of federal safety regulations by BP, Transocean and Halliburton.
The panel also found room for improved drilling inspections and a variety of federal safety regarding drilling facilities.