The Peak Oil theory basically states that the majority of our oil producing fields have reached maximum extraction capacity and are currently on the decline for production while at the same time consumption for oil is growing each year. Based off this current trajectory the reserves of oil will continue to deplete and the price of oil will continue to rise.

It is said that there isn't that much oil left to discover and that the majority of the largest producing oil fields, such as those in Saudi Arabia, have been almost tapped dry. In order to keep up with current demand more oil fields will need to be discovered otherwise we will continue a yearly oil deficit until it becomes a crisis.