A practical optimization approach has been coupled with a commercial reservoir simulator to evaluate the optimal number and locations of infill wells in a conceptual sector of the Main Pay in South Rumaila Oil Field in Iraq. This field, of 58-years of production, has 40 producing wells. There is also an edge water drive from the infinite active aquifer at the east and west flanks. The water drive from the west flank is more than 20 times the drive from the east flank. Therefore, twenty injection wells have been drilled located at the east flank to maintain and balance the reservoir pressure.

After achieving the reliable history matching and running the simulator for a future period until 31 December 2020, the optimization approach has been implemented via spreadsheet considering the aspects of Net Present Value as objective function. The Net Present Value (NPV) is a function of economic variables representing costs and revenues. The revenue is directly proportional to the cumulative oil production that has been predicted by the reservoir model for the entire field. The costs include capital (CAPEX) and operational (OPEX) expenditures. There are ten assigned location of wells taken as a premise to be production wells. These 10 locations have been ranked according to the highest value of permeability and oil saturation spatial distribution in the reservoir in order to be evaluated considering achieving the highest NPV. The optimal number of infill wells was three, six, and ten when the NPV is calculated by the end of 2015, 2017, and 2022, respectively and all the wells at the three cases located at the crest of the reservoir. These optimal wells don't have the maximum cumulative oil production; however, they have the maximum Net Present Value especially at the first two prediction cases.

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