Oil shale reserves refers to oil shale resources that are economically recoverable under current economic conditions and technological abilities. Oil shale deposits range from small presently economically recoverable reserves to large presently uneconomically recoverable resources. Defining oil shale reserves is difficult, as the chemical composition of different oil shales, as well as their kerogen content and extraction technologies, vary significantly. The economic feasibility of shale oil extraction is highly dependent on the price of conventional oil; if the price of crude oil per barrel is less than the production price per barrel of shale oil, it is uneconomic.