page_title: Oil reserves
section_title: Estimated reserves by country
hierarchical_section_title: Oil reserves / Estimated reserves by country
caption_attribution_description: English: Trends in proved oil reserves in top five countries, 1980-2013 (date from US Energy Information Administration)
context_page_description: Oil reserves denote the amount of crude oil that can be technically recovered at a cost that is financially feasible at the present price of oil. Hence reserves will change with the price, unlike oil resources, which include all oil that can be technically recovered at any price. Reserves may be for a well, a reservoir, a field, a nation, or the world. Different classifications of reserves are related to their degree of certainty.
  The total estimated amount of oil in an oil reservoir, including both producible and non-producible oil, is called oil in place. However, because of reservoir characteristics and limitations in petroleum extraction technologies, only a fraction of this oil can be brought to the surface, and it is only this producible fraction that is considered to be reserves. The ratio of reserves to the total amount of oil in a particular reservoir is called the recovery factor. Determining a recovery factor for a given field depends on several features of the operation, including method of oil recovery used and technological developments.
context_section_description: The unit bbl = barrel of oil. A sample calculation for the reserve/production ratio is for Venezuela.
  It is estimated that between 100 and 135 billion tonnes (which equals between 133 and 180 billions m³ of oil) of the world's oil reserves have been used between 1850 and the present.
caption: Trends in proved oil reserves in top five countries, 1980-2013 (date from US Energy Information Administration)
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