A joint agency investigative report released on Wednesday of the April 2010 Macondo well blowout and fatal explosion aboard the Deepwater Horizon rig spread the blame for the disaster among BP plc, Transocean, Halliburton and Cameron International Corp., but BP got the brunt of it.

“BP, as the designated operator under BOEMRE [Bureau of Ocean Energy Management, Regulation and Enforcement] regulations, was ultimately responsible for conducting operations at [the Macondo well] in a way that ensured the safety and protection of personnel, equipment, natural resources and the environment. Transocean, the owner of the Deepwater Horizon, was responsible for conducting safe operations and for protecting personnel onboard. Halliburton, as a contractor to BP, was responsible for conducting the cement job, and, through its subsidiary (Sperry Sun), had certain responsibilities for monitoring the well. Cameron [International Corp.] was responsible for the design of the Deepwater Horizon blowout preventer (BOP) stack,” said the BOEM and the U.S. Coast Guard in their 217-page report.

The report’s spreading of blame is welcome news for UK-based BP and could lessen its chances of being found grossly negligent for the rig disaster when it goes to court in February, according to an article in the Wall Street Journal.

The joint panel determined that a “central cause of the [Macondo well] 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 onto the rig, resulting in the blowout.”

The loss of the lives of the 11 crew members aboard the Deepwater Horizon rig and the subsequent oil spill in the Gulf of Mexico “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.

In the days leading up to the April 20, 2010 Macondo blowout and rig explosion, “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.” Those decisions included:

The BOEM-Coast Guard 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 on the evening of April 20, 2010 did not fully identify and evaluate the risks inherent in the operations that were being conducted at Macondo,” it said.

“On April 20, BP and Transocean personnel onboard 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 occur at the well after it is temporarily abandoned and to show whether cement barriers will hold against hydrocarbon flow.”

The initial negative test conducted by rig crew “showed a pressure differential between the drill pipe and the kill line, which is a high-pressure pipe leading from the BOP stack to the rig pumps. This was a serious anomaly that should have alerted the rig crew to potential problems with the cement barriers,” the report said.

The crew, which performed a second negative test on the kill line, explained the pressure differential away as a “‘bladder effect,’ a theory that later proved to be unfounded…After observing for 30 minutes that there was no flow from the kill line, the rig crew concluded that the negative test was successful. At this point, 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. 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. [CST]. By then it was too late — the well was blowing drilling mud up into the derrick and onto the rig floor,” the report said.

The panel learned that there had been problems on the Deepwater Horizon rig prior to April 20, 2010. “The Deepwater Horizon crew had experienced a kick [well flow] on March 8, 2010 that went undetected for approximately 30 minutes…Transocean personnel admitted to BP that individuals associated with the March 8 kick had ‘screwed up by not catching’ the kick,” it noted. Ten of the 11 crew members who lost their lives on April 20 were on duty on March 8. Their chief responsibilities involved well control, according to the report.

The report said BP, Transocean and Halliburton violated several federal regulations, including:

Although the joint panel found no evidence that Interior Department regulations in effect at the time were lax and led to the disaster, it said “stronger and more comprehensive federal regulations might have reduced the likelihood of the Macondo blowout.” The report concluded that regulations in place at the time “could be enhanced in a number of areas, including cementing procedures and testing; BOP configuration and testing; well integrity testing; and other drilling operations.” It also called for the drilling inspection program to be improved. BOEM already has put a number of these initiatives into effect.

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