An enormous Shell Oil offshore drilling rig ran aground on an island in the Gulf of Alaska on Monday night after it broke free from tow ships in rough seas, officials said.
The rig, the Kulluk, which was used for test drilling in the Arctic last summer, is carrying about 139,000 gallons of diesel fuel and 12,000 gallons of lubricating oil and hydraulic fluid, the officials said.
A Coast Guard helicopter flew over the rig after the grounding at 8:48 p.m. and “detected no visible sheen,” said Darci Sinclair, a spokeswoman for a unified command of officials from Shell, Alaskan state agencies and other groups that has been directing the response since the troubles with the rig began last Thursday.
Ms. Sinclair said that more overflights were planned after daybreak on Tuesday, and that the unified command would be monitoring the fuel situation as it planned further actions. “The focus will be around salvage,” she said.
The 266-foot diameter rig ran aground on the east coast of Sitkalidak Island, an uninhabited island that is separated by the Sitkalidak Strait from the far larger Kodiak Island to the west. The nearest town, Old Harbor, is across the strait on Kodiak Island; it has a population of about 200 people.
Ms. Sinclair said the coast where the Kulluk ran aground has a combination of rocky and sandy terrain.
Earlier Monday, a Shell spokesman had said that the rig had been brought under control after towlines were reconnected to two ships during a break in what had been several days of extremely rough seas and high winds.
But late Monday afternoon the line from one of the ships, the Aiviq, became separated. Then several hours later, the other ship, the Alert, was ordered to disconnect its towline, out of concern for the safety of the ship’s nine-person crew. At the time, Ms. Sinclair said, swells were as high as 35 feet and winds were gusting up to 65 miles an hour.
The Kulluk, one of two rigs that Shell used to drill test wells off the North Slope of Alaska as part of the company’s ambitious and expensive effort to open Arctic waters to oil production, was being towed by the Aiviq to a Seattle shipyard for off-season maintenance when the towline initially separated during a storm on Thursday.
The Aiviq then lost power, and other support ships and a Coast Guard cutter were brought in to help with engine repairs and to reconnect towlines to the Kulluk, which does not have its own propulsion system. The 18 workers aboard the rig were evacuated by Coast Guard helicopters on Saturday.
Over the weekend, support crews struggled in 25-foot swells to reconnect towlines, succeeding several times. But each time the lines separated again, leaving the rig in danger of drifting toward land.
The Kulluk, which was built in Japan in 1983 and upgraded over the past six years at a cost of $292 million, is designed for icy conditions in the Arctic. It can drill in up to 400 feet of water and up to 20,000 feet deep. During drilling season it carries a crew of about 140 people, Mr. Smith said.
Shell has spent six years and more than $4 billion in its effort to drill in Arctic waters, one of the last untapped oil-producing regions in the United States. But the effort has faced regulatory hurdles and opposition from American Indian and environmental groups.
Last summer, the Kulluk drilled a shallow test well in the Beaufort Sea while another rig drilled a similar hole in the Chukchi Sea to the west.
But Shell announced in September that it would be forced to delay further drilling until this year after a specialized piece of equipment designed to contain oil from a spill was damaged in a testing accident.
The episode was one of a number of setbacks for the Arctic drilling program last year.
Shell now says it hopes to drill five exploratory wells in the region during the 2013 drilling season, which begins in mid-July.
