An important clarification:
The 600+ billion barrels is an estimate of undiscovered oil (note the additional estimated reserves of other hydrocarbons). This is a critical clarification, and one which the Scientific American article does not make all that clear. From other sources, I have read that overall oil reserves, including both estimated undiscovered sources and already-discovered reserves, top out at over a trillion barrels.
Socialists seize on perceived resource shortages as a pretense for instigating massive controls over the citizens of the world, which is why they encourage more pessimism on these issues.
Maybe we should see Success_Machine's math on this.