OGJ Senior Staff Writer
HOUSTON, May 3 -- Transocean Ltd.’s semisubmersible Development Drilling III started drilling a relief well on May 2 to stem the source of a crude oil leak from a BP PLC well off Louisiana, a BP spokesman said.
The relief well is expected to take 2-3 months to complete, Doug Suttles, chief operating officer of BP Exploration & Production Inc., told reporters during a May 3 news conference in Roberts, La.
The relief well will be drilled to 18,000 ft, which is the same depth as the first well from which oil is leaking. Heavy drilling fluids, and ultimately cement, will be used to stop the flow through the first well, which is leaking an estimated 5,000 b/d, Suttles said.
Transocean’s Deepwater Horizon semisubmersible drilled the Macondo well on Mississippi Canyon Block 252 in 4,992 ft of water. An Apr. 20 explosion and fire left 11 crew members missing and presumed dead. The Deepwater Horizon sank on Apr. 22.
Cause of the accident remains under investigation by various companies and government agencies. As of May 3, spill response officials said they had yet to confirm if oil had reached the coast. Weather prevented the use of low-flying aircraft to check on this.
Subsea containment system
Suttles expects a subsea containment system could be installed and operating in about 7 days. Pressure at this water depth is 2,500 psi, he said. “There are a number of challenges,” because such a system never has been used at this water depth, he said.
The system is designed to collect oil and gas, which then will be pumped to Transocean’s Discoverer Enterprise drillship. The system involves a metal structure that will be set on top of the end of the riser about 600 ft from the wellhead.
A fact sheet said the subsea container will be connected to a riser through which oil will flow to the Discoverer Enterprise. Once on the Discoverer Enterprise, oil will be separated from water and gas.
The Discoverer Enterprise is capable of processing 15,000 b/d of oil and storing 139,000 bbl. A support barge will be deployed. The barge can hold 137,000 bbl, the fact sheet said.
Spill response officials estimate the subsea containment system could collect as much as 85% of oil rising from the seafloor.
Meanwhile, Suttles said efforts continue to activate a blowout preventer. In addition, BP is working to put a shutoff valve over the top of the drill pipe.
Nine remotely operated vehicles are being used, Suttles said, adding the ROVS are being used to monitor the leaks, to activate the BOP, to install the valve on the drill pipe, and to spray chemical dispersants into the oil at the seabed level.
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BP drilling relief well to stem source of gulf oil spill