Design of Inter-Well CO2EOR Pilot Test in Offshore Field

Abstract

CO2EOR has much advantage not only in enhancing oil recovery but also in CO2 storage. It is, however, necessary to confirm or estimate the technical, operational and economic uncertainties by pilot test for applying CO2EOR to actual oil fields. This paper describes the methods and the procedures to design an inter-well CO2EOR pilot test. As a result of subsurface study, the number of pilot wells is determined to be 1 injection well and 2 production wells in order to estimate CO2 areal sweep efficiency in the minimum cost. To confirm the effect of CO2EOR, well interval, cumulative CO2 injection volume and duration were determined to be 300 m, 2,000 tonnes and 2 weeks, respectively. The oil production rate begins to increase 1 month after the beginning of the pilot test, and the gas production rate and the vapor phase CO2 mole fraction also begins to increase at the same time. Then, the oil production rate reaches the peak after 1.5 months from the beginning, and the effect of CO2EOR is confirmed clearly. If oil saturation is high in the target reservoir, it will be difficult for confirming the oil bank clearly. In such case, pre-water injection before CO2 injection is found to be an effective countermeasure. As a result of surface study, a CO2 procurement method and a new platform were designed through the process optimization study. Manufactured CO2 was selected as CO2 source for the pilot test. The packed manufactured CO2 into tank containers are transported to the injection site by trucks and supply vessels. Moreover, CO2 impact study was conducted, and it is found that we can manage the potential risks related to corrosion and scale formation by using suitable countermeasure such as CRA's and inhibitors. Finally, based on the result of corrosion and scale formation studies, the operation guidelines were prepared. When the CO2EOR pilot test will be planned in any oil field, it will be possible to make the test design with the similar procedure to this study.