The US Bureau of Safety and Environmental Enforcement is looking into why the traveling block on board Transocean’s semi-submersible Deepwater Nautilus plummeted to the rig floor while drilling a development well on the Glider field in the deep-water US Gulf of Mexico.
Shell told Upstream the incident occurred “late in the afternoon" on 9 June when the rig "experienced a failure of the draw works – the large winch-like piece of equipment that assists in maneuvering drilling pipe and casing in and out of the well within the derrick".
"This unexpected failure allowed the traveling block , which is connected to the draw works, to fall to the drill floor while crews were in the process of extracting drill pipe from a recently drilled well about 100 miles off the coast of Louisiana," Shell said.
"There were no injuries and the well remains secure."
BSEE said inspectors were to board the rig as soon as weather permits in Green Canyon Block 248, which is located some 100 miles south of Fourchon, Louisiana.
BSEE added that there was no pollution: "The project is limited to drilling; no production was affected by the incident."
Transocean did not comment and referred all queries to Shell, which has the rig under contract through August 2017 for about $533,000 a day.
No possible causes have yet been disclosed for why the draw works failed.
BSEE defined the traveling block as a "large piece of equipment" that supports the top drive which rotates the drill pipe.
BSEE expects to divulge more information when it becomes available.