When looking at the world’s oil supply, experts talk about proven and unproven reserves. Proven reserves have been verified to a near certainty, while unproven reserves are based on geological or engineering data which still needs further exploration.

The Middle East is where the largest concentrations of proven oil reserves can be found, and Saudi Arabia alone has over 20 percent of global supplies. Iran, Iraq and Kuwait take the regions share of the world’s total to over 50 percent. Additionally, the oil in the Middle East is easy to extract and refine.

Many people would be surprised to learn that the nation with the largest proven reserves of oil is not in the Middle East, but in South America. Venezuela, with over 99 billion barrels, has slightly more oil than Saudi Arabia, and because its fields are largely untapped its oil will last far longer. However, the political situation in the country makes exploiting these vast oil reserves a thorny issue for many of the largest oil companies.

Canada also has huge reserves of oil, but 95 percent of Canadian oil is contained in tar sands. This type of oil is very expensive and environmentally damaging to extract, and is only economically viable when oil prices are high.