One of Alaska's most controversial offshore oil ventures, BP's Arctic Ocean Northstar field, is gearing up to drill as early as November -- and company officials say another similar project could soon follow. The Northstar is the target of fervent environmental criticism because it is the first U.S. offshore Arctic production project to use an undersea pipeline. It is leading the way for the Liberty, a nearly identical project now undergoing environmental impact scrutiny by the U.S. Army Corps of Engineers, BP officials said Tuesday. The fields, which hold between 140 million and 150 million barrels of crude oil each, could eventually help steady Alaska's falling production and ease a long decline in U.S. domestic oil output.