WASHINGTON - President Bush calls it the most promising source of untapped oil in America and the key to greater energy independence. But how much oil is there in Alaska's Arctic National Wildlife Refuge?
Nobody knows for certain.
As a Christmas week fight raged in Congress over whether to allow drilling along the narrow coastal strip of tundra 200 miles north of the Arctic Circle, both sides are trying to use the refuge's oil estimates - as vague as they may be - to their advantage. And some of the rhetoric has little bearing on reality.
After the House gave a go-ahead to drilling as part of a defense spending bill, Democrats and moderate Republicans scrambled Monday in the Senate to try to block the measure crafted by Sen. Ted Stevens, R-Alaska, an ardent supporter of developing the refuge's oil. A Senate vote on the matter was likely by Wednesday.
"There is considerable uncertainty regarding both the size and quality of the oil resources that exist" in the refuge, according to an analysis by the Energy Information Administration, the government agency that tracks energy statistics.
Even more uncertain is how much of the oil will be worth going after. That will depend largely on the price of oil and the cost of development - including compliance with a slew of environmental restrictions likely to be imposed to protect the area's abundant wildlife.
A 1998 U.S. Geological Survey assessment still used today concluded it's almost certain there are at least 5.6 billion barrels of recoverable oil and possibly as much as 16 billion barrels (a 5 percent likelihood) beneath the refuge's 1.5 million-acre coastal plain.
The number most frequently cited is 10.4 billion barrels, the amount the report says is the "mean" - a statistical tool that simply says there's as good a chance to find less than that as there is to find more.
"There's no question there's a range of uncertainty involved that is quite large," says David Houseknecht, a government geologist involved in the 1998 study. Still, he calls it an "educated assessment" based on seismic studies conducted in the mid-1980s and an examination of adjacent geology where oil has been discovered.
The massive Prudhoe Bay oil field, which has produced 13 billion barrels since 1977 and has 3 billion left, sits 65 miles to the west and there are oil fields in Canada to the east.
"In many cases the oil is dripping out of those rocks," says Houseknecht.
But there has never been a well dug in the federal part of the refuge's coastal plain and only one well drilled in a smaller area within the refuge controlled by Alaska natives.
If that well, dug 22 years ago, indicates an oil bonanza, few know it. The results have been kept a closely held secret by the Alaska native corporation and a handful of people at two oil companies that did the drilling.
The oil numbers are "a ballpark, seat-of-the-pants estimate," concedes Roger Herrera of Arctic Power, the lobbying group that for years has tried to persuade Congress to approve oil development in the refuge. But given the adjacent geology, Herrera says, "you can logically expect" a lot of oil to be there.