Remaining oil production after water flooding, water cut, flow characteristics and injectivity of supercritical CO2 and water play an important role in the modeling and reservoir performance prediction for a CO2 miscible WAG injection process. Six cyclic WAG displacements of supercritical CO2/live crude oil in watered-out carbonate composite cores were performed to study the performance of supercritical CO2 WAG process at reservoir conditions in great detail. The water cut during supercritical CO2 WAG process, endpoint relative permeability to oil in the miscible zone, Krom, oil bank, Kro, and to water, Krw for the water injection cycle, and injectivity for all supercritical CO2 WAG injection cycles are presented in this paper. The viscosity of supercritical CO2/live crude oil, µom in miscible zone is predicted using a Genetic Algorithm-based model and parameters of a live crude oil to calculate the endpoint relative permeability to oil, Krom, in miscible zone.

Based on supercritical CO2 core flooding data and performance of the water cut, injectivity and endpoint relative permeability for supercritical CO2 WAG process, the results indicate: 1) the oil bank and miscible zone were built up when supercritical CO2 was injected in the 1st and 2nd cycle and oil mobility was improved significantly. The remaining oil after initial water flooding was recovered mostly after the 2nd-water injection cycle and water cut dropped quickly in the 1st-water and 2nd supercritical CO2 injection cycles; 2) endpoint relative permeability, Krom in the miscible zone was higher than that of oil-endpoint relative permeability, Kro in the oil bank, and maximum value was observed at critical cycle (2nd cycle). There was a significant difference in water-endpoint relative permeability, Krw between supercritical CO2 and water injection. Krw- endpoint relative permeabilities of water injection were greater than the values of the supercritical CO2 injection. Krom and Kro endpoint relative permeability decreases quickly after the 2nd cycle of supercritical CO2 and water injection; 3) water injectivity was higher than values for supercritical CO2 injection, but the differential between water and supercritical CO2 injection was a little; 4) The viscosity of supercritical CO2/live crude oil in the miscible zone can be predicted using a Genetic Algorithm-based model, which was approximately half of the live oil viscosity in the oil bank for this study.

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