I think the current way that oil reserves are being reported is doing a disservice to the public. We're told that there may be as much as 100 billion barrels of extractable oil along the continental shelf of the United States, 90 billion barrels in the Arctic, 2-4 billion barrels in the Arctic National Wildlife Refuge, but how much oil is this, really, in terms we can more easily understand? I'll give you a simple bit of math to do yourself below the fold.
The unspoken assumption here, of course, is that we should be spending our time and effort extracting oil rather than developing renewable energy technologies. Why this is a political debate rather than a bonehead obvious common-sense answer is I guess because we're all just plain crazy.
Over the next 20 years, our daily consumption of oil in the US under "business as usual" projections, will be about 20 million barrels per day. So the 2-4 billion barrels in ANWR? That's 2-4 billion reserves divided by 0.02 billion barrels used per day = 100-300 days, which is 3-8 months of supply for the United States only. Or you could call it 0.4 - 0.8 years.
World consumption over the next 20 years will be about 100 million barrels per day or 0.1 billion barrels per day. So if the Arctic reserves being argued about by Russia and Canada are extracted that's 90 billion barrels divided by 0.1 billion per day = 900 days or about 3 years.
So here's a simple conversion. When you are given a headline with X billion barrels of oil, do the following:
Number of years it will take for the US to consume that oil = X / 5.
Number of years it will take for the world to consume that oil = X / 30.
The total estimated world reserves are about 1000 billion barrels with maybe as much as 2000 billion more yet to be discovered, depending upon your assumptions of geology and how much you are willing to pay to extract that oil from the ground. I'll let you do the math to see how long that will last.