It is from a book called 'The Skeptical Environmentalist' by Bjorn Lomborg which came out in 2001. I no longer have the book but it was referenced and I checked it at the time...his graph showed current proven reserves (as at time of writing...lots more oil has been discovered since) up the Y axis and oil used on the X axis. I cannot remember the exact numbers now but at the usage rates at the time of writing it was something like 3000-5000yrs of 'oil' left in the ground...if memory serves the higher figure was including oil shale/tar sand 'oil equivalent' that, again as at 2001, could be profitably extracted at US$30/bbl...and is actually flowing from Canada to the US as we speak...very fecking profitably.
I highly recommend the book...it covers many other areas besides energy in a factual, detailed, referenced manner...as opposed to the emotional crap put out by the far left of the environmental movement.
Current high oil prices are not a result of scarcity per se but of demand outstripping supply caused by oil companies lack of infrastructure spending. This artificial suppy constraint is good for probably US$45/bbl which corrected for inflation is not a lot more than oil was worth in the 50s/60s etc...the rest is security 'concerns'...i.e. 'the market' speculating the price up and down for their own ends.
To suggest this situation will not correct itself in time is to deny history and how a market functions. They are building more infrastructure and they are finding more oil as the current high prices spur companies to look for it which they were not doing when it was $20/bbl. The current high prices ARE pushing the world towards recession...despite the protestations to the contrary by fecking politicians.
The biggest worry oil producers currently have is to 'manage' things so the price doesn't fall off a cliff but instead is 'massaged' lower to maintain their profits on the one hand while not driving the world into recession on the other...or force to much research into alternatives.
To touch on the TEL thing for a minute. Yes it is expensive and yes only one company still makes it and yes it isn't very nice stuff.
But there is so little of it in a liter of avgas it only contributes about 3 cents/liter to the cost. That one company in the UK has no thoughts about stopping production and if the environmental movement in the EU/UK causes to much grief I am sure they'd simply move production somewhere else...and finally the **** they put in UL fuel to raise the octane up to useabe figures, even for cars, is MUCH nastier stuff than TEL.
The real reason the EPA banned TEL in 1974 in The Clean Air Act was because it ruins catalitc converters that were required to fix the smog issues caused by cars burning fuel made by refiners that wanted to do the minimum amount of refining they could get away with to produce the petrol. They could have refined it more, at a cost of course, but didn't want to because they feared the higher cost would constrain demand so they passed the problem onto the consumer in a different way...one that didn't make them look like the 'bad guy'.
After they banned it from car fuel the EPA essentially lost interest and passed the responsibility for the issue of avgas onto the FAA..within the US context the FAA decides whether it is a problem...and so far they have not showed any signs of doing so.