This, a quote from OPEC Secretary General His Eminence Abdalla Salem El-Badri (thats his official title, not me being a suck up).
"Estimates from the US Geological Survey of ultimately recoverable reserves have practically doubled since the early 1980s, from just under 1.7 trillion barrels to over 3.3 trillion barrels -- while cumulative production, during the same period, has been less than one-third of this increase."
Global recoverable reserves have increased in the last 20 years... in fact doubled, despite the fact that we produced around 600 billion barrels during that time frame. Another way to look at it is such... 1.7 trillion barrels, of which we produced 600 billion barrels, leaving a remaining 1.1 trillion barrels... a flat line 37 years of future production. Of course, it doesn't work that way, this being more difficult to extract, perhaps, globally. In any case, in the last 20 years, we added 2.2 trillion new barrels to the mix, more than the total recoverable reserves in the mid 1980's.