re: What do you think the world would be like if it ran out of oil?

I'm assuming you mean "recoverable oil", since in every oil field, a large percentage of oil is left behind when the field is abandoned due to the rock and petrophysical properties not allowing 100% recovery factor.

Oil reserves (recoverable oil) are dependent on the oil price. If oil is $50/barrel, a company may have, say, 100 million barrels of reserves in its fields. If oil goes to $75/barrel, their reserves may now have increased to 200 million barrels, since the amount of oil that is economical to recover has increased due to an increase in oil price. The amount of oil in the rock hasn't changed, but the amount of recoverable reserves has.

If oil prices keep going up, then reserves will keep getting added. The world will never run out of oil.