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Final Deepwater Horizon JIT report out BOEMRE, USGC joint investigative team cites faulty cement job in Gulf of Mexico blowout; says BP exercised poor risk management Kristen Nelson Petroleum News
A joint investigation team of the Bureau of Ocean Energy Management, Regulation and Enforcement and the United States Coast Guard released its final report Sept. 14, finding a central cause of the April 20, 2010, blowout on the Deepwater Horizon rig in the Gulf of Mexico was failure of a cement barrier in the production casing string.
A blowout occurred on the Deepwater Horizon following an undetected kick, or influx of hydrocarbons, on the evening of April 20, 2010, followed by two explosions. Eleven men died on the Deepwater Horizon; the rig continued to burn and sank on April 22; oil flowed from the Macondo well into the Gulf of Mexico for 87 days.
The joint investigation team said the precise reasons for the failure to the production casing job are not known, but identified three likely causes: fluid inversion — swapping of cement and drilling mud in the section of casing near the bottom of the well known as the shoe track; contamination of the shoe track cement; or pumping cement past the target location in the well, leaving the shoe track with little or no cement.
Poor risk management But behind that cement barrier failure were human actions.
The loss of life at the Macondo site, and subsequent discharge of almost 5 million barrels of oil, “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 concluded.
BP, as the designated operator at the well, “was ultimately responsible for conducting operations at Macondo in a way that ensured the safety and protection of personnel, equipment, natural resources, and the environment,” the report said.
Transocean, owner of the Deepwater Horizon, was responsible for the safety of operations and personnel.
Halliburton was responsible for the cement job and though its subsidiary Sperry Sun had certain responsibilities for monitoring the well.
Cameron was responsible for design of the blowout preventer stack used on the well.
Decisions complicated cementing The report said BP made a series of decisions in the days leading up to April 20 “that complicated cementing operations, added incremental risk, and may have contributed to the ultimate failure of the cement job.”
BP used only one cement barrier “even though various well conditions created difficulties for the production casing cement job.” The report also cited BP’s decision on where to set production casing, choosing a location that the report found “created additional risk of hydrocarbon influx.” BP decided to install a lock-down sleeve as part of the temporary abandonment procedure at Macondo, which the report said “increased the risks associated with subsequent operations.”
As for the production casing cement job, the report said BP failed to perform that job in accordance with industry-accepted recommendations.
The report also said that “BP failed to communicate these decisions and the increasing operational risks to Transocean,” and as a result BP and Transocean personnel onboard the Deepwater Horizon on April 20, 2010, “did not fully identify and evaluate the risks inherent in the operations that were being conducted at Macondo.”
Anomalies misinterpreted On April 20, BP and Transocean personnel “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 occur at the well after it is temporarily abandoned and to show whether cement barrier(s) will hold against hydrocarbon flow.”
There was “a serious anomaly” in an initial test on the production casing cement job, which the report said should have alerted the rig crew to problems with the cement barrier or with the test. The report said that after discussion and more testing, the rig crew explained away a pressure differential encountered in the test as a “bladder effect,” a theory which proved unfounded.
By 7:45 p.m. on April 20, the report said, “the rig crew most likely concluded that the production casing cement barrier was sound.”
“The cement in the shoe track barrier, however, had in fact failed, and hydrocarbons began to flow from the Macondo reservoir into the well.”
The report said there were “a number of additional anomalies” that should have alerted the rig crew to the kick or well flow, but “the crew failed to detect that the well was flowing until 9:42 p.m. By then it was too late — the well was blowing drilling mud up into the derrick and onto the rig floor.”
Problems with kicks The report said the rig crew had previous problems in promptly detecting kicks, citing a March 8, 2010, kick that went undetected for some 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 11 individuals on duty on March 8, who had well control responsibilities, were also on duty on April 20.”
The report also said that simultaneous rig operations hampered well monitoring, including displacement of fluids in two active mud pits and cleaning the pits in preparation for moving the rig.
A change in direction of fluids from the well, made about 9:10 p.m., meant the Sperry Sun flow meter was bypassed; the report described that flow meter as “a critical kick detection tool that measures outflow from the well.”
The blowout preventer failed to seal the well, and the report says the explosions likely damaged the Deepwater Horizon’s lines, rendering the rig’s crew unable to activate the blowout preventer. The report said the blind shear ram should have sealed the well, and a forensic examination of the BOP stack “revealed that elastic buckling of the drill pipe had forced the drill pipe up against the side of the wellbore and outside the cutting surface of the BSR blades.”
Earlier problems Prior to April 20, BP and Transocean had a number of problems with drilling and temporary abandonment operations at Macondo, including recurring well control events and delayed kick detection; scheduling conflicts and cost overruns; and personnel changes and conflicts.
BP and Transocean both had extensive procedures in place for safe drilling operations.
While BP required drilling and completions personnel to follow a “documented and auditable risk management process,” the report said 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.”
Transocean had documented safety programs in place at the time of the blowout, the report said. But there was “evidence that Transocean personnel questioned whether the Deepwater Horizon crew was adequately prepared to independently identify hazards associated with drilling and other operations.”
The report also said that there was a Transocean “stop work” policy in place obligating each employee “to interrupt an operation to prevent an incident from occurring,” and said there were a number of reasons a member of the rig crew could have invoked the stop work authority, but “no individual on the Deepwater Horizon did so on April 20.”
Violation of federal regulations The report said BP and in some cases its contractors violated several federal regulations.
It also said that while there is no evidence that Minerals Management Service regulations in place on April 20, 2010, were a cause of the blowout, “stronger and more comprehensive federal regulations might have reduced the likelihood of the Macondo blowout.”
The report recommends additional changes to federal regulations and improving the safety of offshore drilling operations, including: well design; well integrity testing; kick detection and response; rig engine configuration (air intake locations); blowout preventers; and remotely operated vehicles.
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