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BP to use containment system, top kill on gulf oil spill

Paula Dittrick
OGJ Senior Staff Writer

HOUSTON, May 10 -- Oil spill response crews on May 10 continued working on a subsea containment system to reduce the flow of oil spilled by a deepwater well in the Gulf of Mexico off Louisiana while also working on possible plans to stop the flow using a “top kill” option at the wellhead.

The cost of the response of as May 10 amounted to about $350 million, including the cost of spill response, containment, relief well drilling, commitments to the Gulf Coast states, settlements, and federal costs, BP PLC said. An estimated 5,000 b/d of oil is leaking into the gulf.

Transocean Ltd.’s Deepwater Horizon semisubmersible drilling rig sank on Apr. 22 after a fatal Apr. 20 fire and explosion (OGJ, May 3, 2010, p. 31). The semi drilled the Macondo well on Mississippi Canyon Block 252 for BP and its partners, Anadarko Petroleum Corp. and Mitsui Oil Exploration Co. Ltd. BP is the operator.

The well struck oil and associated gas with the oil being 35° gravity. Cause of the accident remains under investigation.

A containment dome deployed last week has been parked on the seabed away from the spill area in 5,000 ft of water. Efforts to place the dome over the main leak point on the damaged Deepwater Horizon riser were suspended on May 8 because of the build-up of gas hydrates.

Doug Suttles, chief operating officer of BP Exploration & Production Inc., told reporters on May 7 that the formation of gas hydrates would be the biggest technical hurdle in getting the subsea containment system to work.

A second, smaller containment dome on May 10 was being readied to lower over the main leak point, which is the Deepwater Horizon riser. The smaller dome will be connected by drill pipe and riser lines to Transocean’s Discoverer Enterprise drillship to collect and treat oil.

The subsea containment system is designed to mitigate the formation of large hydrate volumes. This operation never been done in this water depth.

“In addition, further work on the blowout preventer has positioned us to attempt a ‘top kill’ option aimed at stopping the flow of oil from the well,” BP said. “This option will be pursued in parallel with the smaller containment dome over the next 2 weeks.”

All of the techniques being attempted or evaluated to contain the flow of oil on the seabed involve significant uncertainties because they have not been tested in these conditions.

Work on the first relief well, which began drilling on May 2, continues. It is expected to take 3 months to complete to 18,000 ft TD.

Work continues to collect and disperse oil from the sea’s surface. More than 275 vessels are being used, including skimmers, tugs, barges, and recovery vessels.

The volume of dispersant applied to the spill on the surface amounts to over 315,000 gal since Apr. 20.

Intensive operations to skim oil from the surface of the water also continued. Some 90,000 bbl of an oil-water mixture has been recovered. The total length of deployed boom is now more than 1 million ft.

Contact Paula Dittrick at paulad@ogjonline.com.


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