This is highly debatable. The variety of energy sources technologically available to us today is wide ranging and can easily replace all known oil energy reserves multiple times. It is simply a matter of implementation and on what time scale that is open to debate. All the economic issues surrounding this debate are a great ball and chain inhibiting humanity from a more rapid implementation of a shift from our extreme reliance on fossil fuels. When I say economic issues, I recognize these are primarily cultural issues as our entire monetary market system is a creation of a certain traditionally derived and extremely outdated cultural prejudice.