Conservation group Oceana became the second such organization to intervene in the consideration of Shell's leases offshore Alaska on environmental grounds.

Shell is appealing to the U.S. federal government to ensure leases for exploration activity in the Beufort and Chukchi Seas expire as expected. In September, the company found evidence of oil and natural gas in its Burger exploration well located in the area, but not enough to warrant further activity.

Federal leases expire at the end of their terms unless operators are engaged in drilling or related activity. Shell's leases would start to expire by next year.

Oceana, in a 12-page motion to appeal to the U.S. Department of Interior emailed to UPI, said if the federal government's move to cancel the leases is reversed, Shell would obviously re-examine the Arctic waters with a renewed drilling campaign.

"The most obvious risk from these activities is a large oil spill, like the one that resulted from the Deepwater Horizon rig exploding and sinking in the Gulf of Mexico," the organization said in its filing.

Earlier this week, Earthjustice, working on behalf of eight conservation groups, filed to intervene in decisions before the Department of Interior regarding Shell's leases, calling the Arctic region "ground zero for climate change."

Earthjustice added that, so far, Shell has been unable to display it has an adequate response plan should a major oil spill occur offshore Alaska.

Shell's early efforts off the coast of Alaska were plagued by equipment issues. The company in July discovered a small breach in the hull of MV Fennica, chartered to carry the safety equipment to the Chukchi Sea. A drill ship slated for offshore Alaska, Noble Discoverer, suffered a series of setbacks during a 2012 campaign off the coast of Alaska.

The company said the lack of exploration success, high costs and a challenging regulatory regime meant it was time to abandon the Alaska program for the foreseeable future.

"Shell's recent public announcement that it will not engage in further exploration drilling on its Beaufort and Chukchi leases 'for the foreseeable future' does not affect the conclusion that Oceana's interests would be adversely affected by a reversal," Oceana's filing read.