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RPR is measured in time units and is usually presented in years.

For the green fields the RPR assumes the ratio of initial recoverable reserves over the initial production rate.

Although RPR is expressed in time units it does not represent the actual lifetime of the field because production rate is not constant over time.

Usually production rate is declining thus leading to a much longer production time than estimated by RPR.

But in many other cases the initial production rate of the green field is being increased over time due to increase in drilling and advanced completions which lead to contraction if the field lifetime comparing to RPR estimate.

See Also

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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petroleum Geology /  Petroleum Reservoir / Recoverable Hydrocarbon Reserves