Senior Staff Writer
Transocean Ltd. asked the US Coast Guard to revise its draft report on a joint investigation by the USCG and the Bureau of Ocean Energy Management, Regulation, and Enforcement into the Deepwater Horizon semisubmersible explosion and fire.
The April 2010 accident followed a blowout of the Macondo well off Louisiana, resulting in the deaths of 11 people and a massive oil spill in the Gulf of Mexico. The Deepwater Horizon, owned by Transocean, later sank. BP PLC operated Macondo.
A Joint Investigation Team (JIT) last year conducted numerous hearings and compiled evidence. BOEMRE and USCG are expected to release a final joint report by late July.
Transocean said, "The errors in the draft report concern four fundamental issues—sources of ignition, maintenance of the blowout preventer (BOP), functioning of emergency shutdown systems, and functioning of alarms."
The drilling contractor released a 110-page response dated June 8 that it sent to the US Department of Homeland Security and the Department of the Interior regarding the USCG draft report. Transocean acknowledged the accident provided "lessons to be learned" by operators and drilling rig crews.
"Unfortunately, with conclusions and findings that are at odds with the evidence in the record, the draft report runs the risk of undermining the Coast Guard's credibility on a very important part of its marine safety mission," Transocean said.
Transocean's response said BP's "risky decisions produced a massive failure of the well, which made ignition of the hydrocarbons inevitable." Citing a Presidential Commission finding, Transocean said it was not responsible for BP's decisions and was not consulted by BP about those decisions.
The drilling contractor also said it submitted a brief to the BOEMRE discussing events leading up to the Macondo well blowout.
Transocean said equipment maintenance on the semi was not to blame for the gas ignition. Various investigators previously said the blowout caused an enormous volume of gas to reach the semi.
"There is no evidentiary basis for concluding that equipment maintenance played any role whatsoever in causing the ignition of the huge gas cloud that was released onto the vessel," Transocean said.
The Deepwater Horizon crew properly maintained the BOP, Transocean said, adding workers followed a schedule of BOP testing, repair, monitoring, and maintenance that met or exceed standards from former Minerals Management Service, the American Petroleum Institute, and Cameron International Corp., the BOP manufacturer.
"Any suggestion that the BOP was poorly maintained or that Transocean's maintenance of the BOP contributed to the blowout is not supported by the evidence," Transocean said.
The drilling contractor said the Deepwater Horizon's engine shutdown system worked as it was supposed to work. Engines of dynamically positioned rigs are not designed to shut down automatically upon ingression of gas to engine rooms, Transocean noted.
Dynamically positioned rigs do not use automated shutdown ecause that could set a rig adrift, risking damage to the BOP and a potential disconnect from the wellhead that could result in a spill, Transocean said.
"The engines were properly set to remain in operation until shut off by human operator, or in the absence of an opportunity for such intervention, until a predetermined and undesired speed was reached, in full compliance with international standards," Transocean said.
The drilling contractor said the semi's gas and fire alarm system was fully functioning. A general alarm was sounded by human intervention after the rig's gas detectors automatically sent alarm signals to the dynamic positioning officer on the bridge.
"The Coast Guard wisely and expressly forbids the use of a system that would automatically sound the general alarm upon activation of gas or smoke detectors," Transocean said. "Such systems generate repeated false alarms, resulting both in needless injuries, and over time, failure to take the alarm seriously."