A new economic analysis of the National Petroleum Reserve-Alaska, released in May 2011 from the U.S. Geological Survey, estimated there were 986 million barrels of undiscovered, technically recoverable conventional oil in the reserve, down from a 2002 assessment of 10.5 billion barrels.
State of Alaska geologists strongly disagreed with USGS’ downgrade.
The revised estimates resulted from data that wasn’t available in 2002; data from exploration wells drilled in the past decade, which indicated an abrupt change from oil prone to more gas prone resources just 15 to 20 miles west of the Alpine oil field in the Colville River Delta, USGS scientists said.
Consequently, oil plays analogous to the Alpine field in NPR-A likely contain very little oil west of the area that ConocoPhillips and Anadarko Petroleum have been exploring around their Lookout and Alpine West prospects, USGS said.
Much of the agency’s new pessimism over potential NPR-A undiscovered, recoverable oil revolved mainly around a revised evaluation of the petroleum system in the Beaufortian sequence, one of four major oil-bearing rock sequences in northern Alaska.
Greatest potential near Teshekpuk Lake
USGS said the greatest potential in the Beaufortian sequence was near Teshekpuk Lake and the adjacent coastal plain, a region largely inaccessible because of environmental concerns.
And while USGS dropped its oil estimates for the Brookian, the youngest and shallowest of the region’s four rock sequences, it also commented that the greatest potential for finding new NPR-A oil exists in what are termed “stratigraphic traps” in that same Brookian sequence.
During the May 2011 meeting of the Pacific Section, American Association of Petroleum Geologists, in Anchorage, scientists from the U.S. Department of the Interior, home of USGS, said that it was possible to find huge Brookian stratigraphic traps in northeast NPR-A, in locations ideally positioned to capture oil from prolific oil source rocks at the base of the Brookian.
“These untested prospects potentially rival or exceed the size of the Alpine field discovery 15 years ago,” the scientists said.
