CO2 injection is one of the most frequently used gas injection EOR methods which its applicability grows very fast because of its abundance, greenhouse effect, easily achievement of miscibility condition and so forth. In this study a compositional simulator has been used to determine the reservoir management and production strategies in order to optimize oil recovery from an Iranian undersaturated reservoir. Due to decline of reservoir production rate, this reservoir is candidate for an enhanced oil recovery (EOR) process. Consequently, three possible scenarios have been used, including: (1) Natural depletion, (2) CO2 injection and (3) Water flooding. A series of numerical compositional slim tube simulations were performed to measure the minimum miscibility pressure (MMP) of separator gas, CO2, N2, methane and enriched gas. The results of slim tube simulation show that among these gases CO2 has the minimum MMP which is about 1000 psi below the current reservoir pressure. Available huge CO2 resource in the vicinity of this field along with high reservoir pressure which is more than the MMP of the CO2 increases the feasibility of miscible CO2 injection in this field.

Full field simulation results show that among the performed scenarios, CO2 injection is the best method to produce this reservoir. This production strategy has resulted in better performance and higher oil recovery and therefore good economics.

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