Since the beginning of the use of oil in the second industrial revolution about a century and a half ago, it's projected that we have used more than half of the Earth's supply of oil. Now at current rate of usage in the U.S. it wouldn't be a problem. However, the United States isn't the only country. Oil consumption in Asia, particularly in China has far exceeded that which was consumed by other nations during the industrial age. At current rate of usage, the available oil in the world will run out some 50-70 years from now. So yes, the U.S. has massive reserves of oil, but many countries don't and they need that oil just as much. And while natural gas can be used effectively as power, it doesn't replace oil. We use oil for so much more than power. The plastic components used to make these computers we're typing on, the health products we use on our bodies and even the clothes on our backs are made from or with oil products.