The Kulluk and Noble Discoverer and support ships are headed first to Dutch Harbor. Once open water allows, the rigs will move to the Beaufort and Chukchi seas for offshore drilling.
Shell Oil prepared the ships in Seattle to explore for oil and natural gas. New oil discoveries could feed the trans-Alaska pipeline.
Coast Guard vessels escorted the blue and white vessels through Seattle's Elliott Bay, maintaining a 500-yard safety zone.
Environmental groups, including Greenpeace, oppose the drilling because they fear an oil spill in ice-choked ocean waters.
The Kulluk is headed to the Beaufort Sea off Alaska's north coast, the Noble Discoverer to the Chukchi Sea off the state's northwest coast.
Meanwhile, Greenpeace is sending its own ship to the Arctic to monitor and study Shell Oil's work.
"We're on our way up to Alaska's pristine waters with hundreds of thousands of others to draw a line in the ice and say 'no further.' This is now one of the defining environmental battles of our age," said Jackie Dragon, Greenpeace's senior oceans campaigner, in a statement issued from on board the Esperanza.
The 72-meter ice class vessel is traveling with scientists and submarines and an observational drone to document what happens at the drill sites, Greenpeace said.
Secretary of the Interior Ken Salazar said he will announce on Thursday the proposed final offshore oil and gas leasing program for 2012-2017. Salazar said Tuesday that the leasing plan will include targeted Arctic waters of Alaska's northern coast, including potential lease sales in the Chukchi Sea in 2016 and the Beaufort Sea in 2017. Until then, federal regulators will continue to work to gather information on safety and environmental considerations, he said.
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