Sorry--this is a relatively new pet peeve of mine. I first learned of the concept of peak oil last June from Richard Heinberg, speaking at the Midwest Renewable Energy Fair. I read his book and a couple of others on the subject, and it has become a frequent topic on this blog. As Heinberg explained it, and the name implies, peak oil describes the time of maximum oil production for a well, a field, a nation or a planet. Since the production curves for these entities frequently resemble bell curves, some suggest that peak oil occurs when half of the oil is gone. This is certainly possible in some cases, but there is no reason whatsoever that it has to be the case (nor could we ever really know even if it was). So it really bugs me when so-called experts on the subject claim that "peak production" and "half gone" are identical. The latest culprit is Michael Klare, author of Resource Wars
, one of the first books I read after 9/11 to try and figure out what was really happening. Here's a paragraph from Klare's recent article on TomDispatch
Where one stands on this critical issue depends on one's estimate of how much petroleum the Earth originally possessed. Those like Deffeyes, who contend that peak oil will arrive soon, believe that our petroleum inheritance amounted to roughly 2,000 billion barrels when commercial oil drilling first commenced in 1859. Since we have already consumed approximately 950 billion barrels and are now burning some 30 billion barrels each year, in this scenario the halfway point of total world extraction -- and so the moment of peak production -- should be just a year or two away. By contrast, those who hold that peak oil is safely in the distance claim that the world's total inheritance is closer to 3,000 billion barrels. This more optimistic figure would include the 950 billion barrels already consumed, "proven" reserves of approximately 1,150 billion barrels, and as-yet-undiscovered fields believed to hold another 900 billion barrels. This latter amount, it should be noted, represents the equivalent of all the known oil in the Middle East, Asia, and Africa combined.
To be fair, Klare does say earlier in the article that peak oil occurs "usually when half of the total amount of oil has been extracted," so at least he's hinting that they're not identical concepts. But to claim that the halfway point of total world extraction will be (has been?) the "moment" of peak production pretty clearly indicates that he believes they are identical concepts.
But they aren't. The total amount of oil that existed in the world before commercial drilling began in 1859 was strictly a matter of two things--geology and definitions (sweet crude, sour crude, oil sands, etc.--how much counts as "oil?"). While impossible to accurately estimate, the actual amount according to any particular definition was fixed and finite. Peak oil, however, depends on geology, definitions, technology, economics, politics and probably lots of other things. Where is the oil located, who controls it, how hard is it to get, how much money will they get for it? The interaction of all of these things and more will determine how much oil gets pumped out of the ground in a given year, and will also determine in which year the most oil gets pumped. The fact that the amount of oil is finite guarantees that there will be a peak year, but there is no reason at all that it has to coincide with the "half-gone" date, even if we had a clue as to when that would be, which we don't.
If I had to, I would guess that we'll reach peak oil any day now, but that probably well under half of the oil will be gone by then. It's just that most of what's left is too hard to get, or of too poor quality, ever to justify its extraction economically. There is an absolute limit--if oil takes more energy to get than it has in it, it won't be extracted.
PS: Here are a couple of analogies to explain why "peak extraction" and "half gone" are different. Consider a bowl of spaghetti sitting in front of me when I'm hungry. Peak extraction will occur almost immediately, but it will be a little while before the spaghetti is half gone. Or consider manned planetary exploration. This activity, like US oil production, peaked in the early 1970's (counting the moon as a planet). New technology may someday create a new peak when other planets and moons in the solar system are explored, and possibly even a planet or two outside the solar system. Unless Einstein was wrong, however, peak planetary exploration will occur long before half of all planets in the universe, or even the Milky Way, are explored.
World oil doesn't match either scenario closely, but I think it is probably closer to the second one than the first. Higher oil prices will make some old fields and some new exploration economical, but they will also make alternatives, including conservation, more attractive. What remains, no matter how much there is, will not be worth getting.