"Peak oil primer
What is peak oil?
Peak oil is the simplest label for the problem of energy resource depletion, or more specifically, the peak in global oil production. Oil is a finite, non-renewable resource, one that has powered phenomenal economic and population growth over the last century and a half. The rate of oil 'production', meaning extraction and refining (currently about 85 million barrels/day), has grown almost every year of the last century. Once we have used up about half of the original reserves, oil production becomes ever more likely stop growing and begin a terminal decline, hence 'peak'. The peak in oil production does not signify 'running out of oil', but it does mean the end of cheap oil, as we switch from a buyers' to a sellers' market. For economies leveraged on ever increasing quantities of cheap oil, the consequences may be dire. Without significant successful cultural reform, severe economic and social consequences seem inevitable. "
This a good source to learn more:
Peak oil primer and links | Energy Bulletin