Oil and gas reserves and resource quantification

Oil and gas reserves and resource quantification refers to the process of estimating the quantities of hydrocarbons present in subsurface accumulations and assessing the portion that can be economically recovered. In the petroleum industry, a distinction is made between resources, which represent the total estimated volume of hydrocarbons in place, and reserves, which are the quantities expected to be commercially recoverable under existing economic, technological, and regulatory conditions.

Source: Wikipedia — Oil and gas reserves and resource quantification (CC BY-SA 4.0)