Anadarko Petroleum says its holdings in the foothills of Alaska's Brooks Range may contain up to 10 trillion cubic feet of natural gas. The preliminary estimate, which it has been presenting for several months, covers three Colville River prospects near the village of Umiat. The estimate does not include data from exploration wells Anadarko drilled this year. The exploration program was the first in northern Alaska to explicitly target natural gas. Alaska does not yet have a pipeline to deliver gas from the region.