Royal Dutch Shell halted drilling in the Chukchi Sea on Monday, one day after it began, because of sea ice moving toward the company's drill ship off Alaska.
Shell Alaska spokesman Curtis Smith tells The Associated Press that drilling was stopped for safety reasons.
"As a precautionary measure and in accordance with our approved Chukchi Sea Ice Management Plan, Shell has made the decision to temporarily move off the Burger-A well to avoid potentially encroaching sea ice," he said by email. "Once the ice moves on, the Noble Discoverer will re-connect to anchors and continue drilling."
That could be a couple of days or more, Smith said.
The company's Burger Prospect is 70 miles off the northwest coast of Alaska.
Shell officials on Sunday began monitoring a piece of ice measuring 30 miles by 12 miles from 105 miles away, Smith said. The decision to halt drilling was made Sunday. At noon Monday, the drill ship was still detaching from anchors. Smith said he did not know how far away the ice was at that time.
Drilling had begun at 4:30 a.m. Sunday.
The oil giant was given permission last month to begin preliminary work on an exploratory well. The company is authorized to drill pilot holes that do not descend into oil reservoirs.
Shell has spent upward of $4.5 billion for Arctic Ocean drilling but had been thwarted from drilling by environmental lawsuits, regulatory requirements and short open-water drilling seasons.
Shell Alaska vice president Pete Slaiby on Sunday called the beginning of drilling historic. He said it was the first time a drill bit had touched the sea floor in the U.S. Chukchi Sea in more than two decades.
Drilling is bitterly opposed by environmental groups that say oil companies have not demonstrated they can clean up a spill in ice-choked water. They say a spill of the magnitude of the Deepwater Horizon blowout in the Gulf of Mexico would be catastrophic in a region hammered by climate warming and home to endangered or threatened marine mammals such as bowhead whales, polar bear and walrus.