OREANDA-NEWS. US regulators today permitted Shell to start drilling for oil off the north coast of Alaska, giving the company its first chance to see if the $6bn it has invested so far on arctic exploration will pay off.

Shell now has just over 40 days to finish drilling its Burger J exploratory well in the Chukchi sea. The company started drilling the top of the well on 30 July, but the Interior Department's Bureau of Safety and Environmental Enforcement (BSEE) in an earlier permit prevented drilling into oil-bearing rock until an icebreaker carrying a spill-control device arrived in Alaska.

Shell said it was looking forward to "evaluating what could potentially become a national energy resource base" but left open the possibility that it might not finish the well before the close of the arctic drilling season on 28 September. It said drilling crews on the Transocean Polar Pioneer continue to make progress on the well.

"It is possible we will complete a well this summer, but we are not attaching a timeline to the number of feet drilled," Shell said. "Safe, efficient operations will ultimately determine the progress we make."

BSEE in its decision today agreed to modify a permit for the Burger J well to remove the drilling restrictions and allow the company to drill to oil-bearing zones. Shell requested the revision on 6 August when icebreaker MV Fennica, which is carrying the capping stack that would collect oil during a blowout but was damaged in early July, was close to reaching the drilling site.

Shell did not to ask BSEE to modify a separate drilling permit for its Burger V well, meaning the restrictions that prevented the company from drilling into oil-bearing zones there will continue. Shell pulled back from an initial goal to complete two wells this year after US regulators rejected its plan to simultaneously drill the wells.

The Burger prospect is in about 140 feet of water and is located about 70 miles northwest of a small city of Wainwright, Alaska. Shell attempted to drill the same prospect in 2012 but could not get government permission to drill into oil-bearing zones because of damage to its oil-containment system.

BSEE director Brian Salerno said the agency would "monitor their work around the clock to ensure the utmost safety and environmental stewardship." Safety inspectors with the agency have been on the two drilling ships around the clock to provide continuous oversight.

Environmentalists have opposed Shell's plans to drill in the arctic. League of Conservation Voters president Gene Karpinski said he was "deeply disappointed" with the US administration's decision, which he said was at odds with efforts to limit greenhouse gas emissions.