Just one day after it began, Royal Dutch Shell plc on Monday halted drilling in Alaska's Chukchi Sea for safety reasons as sea ice began moving toward a drillship.

The Noble Discoverer, one of the two drillships leased by Shell for its historic Alaska drilling campaign, had begun digging a top hole of the Burger prospect about 4:30 a.m. Sunday. The Burger prospect is about 70 miles off the northwest Alaska coast. It is the first time a drillbit had touched the sea floor in the U.S. Chukchi Sea in more than 20 years, according to Shell.

However, company officials began monitoring a piece of ice on Sunday that had been about 105 miles away that measured 30 miles by 12 miles, according to Shell Alaska spokesman Curtis Smith. After the wind shifted, management made a decision to halt drilling.

"As a precautionary measure and in accordance with our approved Chukchi Sea ice management plan, Shell has made the decision to temporary move off the Burger-A well to avoid potentially encroaching sea ice," said Smith. At noon local time Monday the drillship still was detaching from anchors.

"Part of working in ice is having the ability to temporarily relocate," said Shell. "Once the ice moves on, the Noble Discoverer will reconnect to anchors and continue drilling. Shell uses a combination of satellite images, radar and on-site reconnaissance to monitor ice movement. Once the ice no longer is considered a hazard, Shell plans to resume the drilling."

The Obama administration late last month gave Shell the OK to begin "limited" drilling in the Chukchi Sea (see Daily GPI, Aug. 31). The limited drilling allows the company to create a mudline cellar, which is needed to place a blowout preventer in the event of a failed well. Shell also was approved to begin drilling to set casing pipes to a depth of about 1,400 feet below the sea floor. Permits to drill into Chukchi's hydrocarbon-bearing zones was not to be allowed until Shell's oil spill containment system has received a final OK from the U.S. Coast Guard.

Last Friday Shell received U.S. Environmental Protection Agency (EPA) air permits to operate the Noble drillship and support vessels in the Chukchi Sea with temporary lower emissions limits. Shell would have to reapply for more stringent EPA air permits in 2013, the agency said. Shell was given a deadline to drill until Sept. 24 by the Department of Interior; the producer has asked for an extension (see Daily GPI, Aug. 29).

Shell also has Interior permission to drill with restrictions until Oct. 31 in Alaska's Beaufort Sea. The Kulluk, a separate drillship, is anchored away from the Beaufort drill site, according to Shell. Operations are not allowed to begin until Inupiat Eskimo whalers complete their fall hunt. The Kulluk and six support vessels are destined for the Sivulliq prospect, which is about 20 miles off the northern Alaska coast.

The company had planned to drill up to five wells in both areas this summer, but it has since reduced that number to two, one in each offshore area.

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