Reserves-to-production ratio

The Reserves-to-production ratio (RPR or R/P) is the remaining amount of a non-renewable resource, expressed in time. While applicable to all natural resources, the RPR is most commonly applied to fossil fuels, particularly petroleum and natural gas. The reserve portion (numerator) of the ratio is the amount of a resource known to exist in an area and to be economically recoverable (proved reserves). The production portion (denominator) of the ratio is the amount of resource produced in one year at the current rate.

RPR = (amount of known resource) / (amount used per year)

This ratio is used by companies and government agencies in forecasting the future availability of a resource to determine project life, future income, employment, etc., and to determine whether more exploration must be undertaken to ensure continued supply of the resource. Annual production of a resource can usually be calculated to quite an accurate number. However, reserve quantities can only be estimated to varying degrees of accuracy, depending on the availability of information and on the methods used to evaluate them.

A simplistic interpretation of the ratio has led to many false predictions of imminent "running out of oil" since the early years of the oil industry in the 1800s. This has been especially true in the United States, where the ratio of proved reserves-to-production has been between 8 years and 17 years since 1920. Many have mistakenly interpreted the result as the number of years before the oil supply is exhausted. Such analyses do not take into account future reserve growth.

The reserves-to-production ratio is the most widely quoted of the key indicators used in the oil and gas industry. It has a certain strategic significance for companies, which try to keep the value reasonably constant at approximately 10 years. A ratio which falls too low indicates a company in poor health. For a country or region, a value which falls too low can be a warning of impending scarcity. Globally, the RPR for petroleum varies from 8 years in the North Sea to 80 years in the Middle East. The former is typical of a region undergoing a steep production decline, the latter a region which will be continuing to produce oil well into the future.

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