Transocean semi sinks into gulf; search for missing 11 continues

Transocean Ltd.’s Deepwater Horizon semisubmersible drilling rig sank about 41 miles off Louisiana on Mississippi Canyon Block 252 on Apr. 22, and the search continued for 11 people missing since an Apr. 20 explosion and fire on the rig.

Paula Dittrick
Senior Staff Writer

HOUSTON, Apr. 22 -- Transocean Ltd.’s Deepwater Horizon semisubmersible drilling rig sank about 41 miles off Louisiana on Mississippi Canyon Block 252 on Apr. 22, and the search continued for 11 people missing since an Apr. 20 explosion and fire on the rig (OGJ Online, Apr. 21, 2010).

The semi was on contract to BP for an exploration well in 4,992 ft of water near Rigel gas field. The well, which struck crude oil and associated gas, was being temporarily plugged when the accident happened, said David Rainey, BP vice-president of Gulf of Mexico operations.

“We don’t know what’s going on below the surface of the water,” US Coast Guard Rear Admiral Mary Landry in a news conference from New Orleans. “We don’t know if there is any oil coming from the seabed.” Landry is commander of the USCG 8th District.

Landry said a “rainbow sheen with a dark center” indicating crude oil was visible on Apr. 22. Officials estimate it measures about 1 mile by 5 miles as of Apr. 22. The fire was extinguished when the semi settled below the surface of the water.

Authorities said oil containment equipment such as booms and skimmers were en route to the scene in case of a potential oil spill. Rainey said it was impossible yet to estimate the size of any potential spill.

Landry said no oil had reached any coast. Permits have been obtained to use dispersants to try and prevent oil from going ashore if an oil spill materializes, authorities said.

The well had reached a TD of more than 18,000 ft. Casing had been run and cementing operations were being done when the accident happened, Rainey said. Workers were in the process leading up to displacing the riser with seawater and setting a surface plug.

Cause of the accident will be investigated as a cooperative effort between the US Minerals Management Service and USCG.

Transocean said it would cooperate with that investigation and also will conduct its own investigation.

USCG reported two pipelines in the area, unrelated to the drilling rig, already had been shut down as a precaution. There was no determination at of midafternoon on Apr. 22 about whether any oil was flowing from the subsurface.

Adrian Rose, Transocean vice-president of quality, health, safety, and the environment, said 9 Transocean employees were missing along with 2 employees from service providers.

Another 115 workers evacuated the rig successfully with most of them using life boats to get to nearby supply vessels. Two lifeboats had been found, but there was no one in those boats, Landry said.

She said 23 total sorties had been completed by air and surface assets covering more than 3,000 sq miles as of midday Apr. 22. Landry said the search would continue for at least another 12 hr.

Contact Paula Dittrick at paulad@ogjonline.com.

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