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USCG, Transocean evaluate source of Gulf of Mexico oil sheen

This article was updated later on Sept. 28.

The US Coast Guard issued a notice of federal interest (NOFI) to Transocean Ltd. regarding whether the wreckage of the Deepwater Horizon semisubmersible might be the source of recent oil sheens observed in the vicinity of BP PLC's deepwater Macondo well, which was sealed following a blowout last year.

The NOFI put Transocean on notice that under the Oil Pollution Act of 1990, the company could be financially responsible for debris removal costs and damages associated with the oil sheen.

USCG suggested a series of oil sheens seen off Louisiana could indicate a release of oil from riser pipe or other debris from the Deepwater Horizon, which sank and remains on the seabed following an April 2010 explosion and fire that killed 11 people (OGJ Online, Sept. 14, 2011).

A massive oil spill resulted in the Gulf of Mexico following the blowout. Government officials estimate nearly 5 million bbl of oil was spilled before the Macondo well was capped in July 2010 and permanently sealed with cement in September 2010. The well later was plugged and abandoned with the approval and oversight of the US Bureau of Ocean Energy Management, Regulation, and Enforcement.

Video taken by a remotely operated vehicle confirmed there is no release of oil from the Macondo well or the relief well. The video was taken on Aug. 25-26, said a statement on RestoretheGulf.gov, a web site the government hosts to report updates regarding the gulf after the Macondo blowout and spill.

The video of both wellheads shows intermittent bubbles coming from cement ports at the base of the wellheads, which government officials believe are nitrogen bubbles, a residual byproduct of the nitrified foam used in setting surface casing cement.

Deepwater Horizon owner Transocean suggests that BP might be ultimately responsible for costs.

“If a volume of oil has remained in the riser, there is no question that it is oil from BP’s Macondo well,” Transocean said in an e-mail to OGJ. “As owner and operator, BP is the responsible party for all fluids that emanated from the Macondo wellhead, and BP has repeatedly acknowledged that responsibility. Transocean has accepted responsible party status for rig fluids, such as diesel fuel, consistent with the law. We take this very seriously, and we are committed to working with BP, the Coast Guard, and other parties to investigate these reports.”

BP said it continues to cooperate with USCG to investigate possible sources of the sheen, noting that the Macondo well is not leaking oil.

The Deepwater Horizon Joint Investigation Team (JIT) released its final report on Sept. 14, saying the blowout stemmed from multiple causes and decisions involving BP and contractors Transocean and Halliburton Co.

Contact Paula Dittrick at paulad@ogjonline.com.


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