The calculation of oil reserves (estimate ultimate recovery, EUR) is required for reservoir management. It is important to differentiate between oil reserves and oil resources. The latter is roughly defined as the sum of recoverable and unrecoverable volumes of oil in place; whereas, the oil reserves can be defined as those amounts of oil anticipated to be commercially recoverable from a given date under defined conditions. However, there is always uncertainty when making reserve estimates, and the main source of uncertainty is the lack of available geological data. Depending on the quantity and quality of the available data, different methods are used for the evaluation of the EUR.

A number of essentially straight-line extrapolation techniques (production data analysis) have been proposed to estimate the EUR for oil and gas wells. Thus, a detailed analysis of past performance of oil and water production data is required in order to predict the future performance of the oil and gas wells. This work utilized seven straight-line extrapolation techniques to estimate and compare the values of EUR of three oil wells from the same reservoir. The comparison shows very similar estimated EUR.

Keywords

EUR, WOR, reserve, X-plot, production data analysis, decline curve analysis