There is no single universal scale used to determine this available amount of fossil fuel. This leads to some confusion. The text prefers the US Geological Survey approach. Recoverable resource assumes the level of effort required for extraction is not much greater than the present nominal effort used for extraction.
All resources are finite .
However, if the rate of use of the resource is small, it is for all practical purposes infinite . It is more likely a result of one not initially counting the resource because it was not economically convenient to extract. He predicted a peak of 7 mbd in US oil production in 1954. The peak actually came in 1970 at 9.4 mbd. However, predictions and reality began to match with the Hubbert curves .