While mature oil reservoirs and aquifers are considered to be good potential candidates for CO2 sequestration, we proposed and investigated an alternative which combines CO2 sequestration and CO2 EOR at the very start of production in a gas condensate reservoir. First, we established a co-simulation workflow with a combination of compositional reservoir simulation and synthetic seismic simulation. Next, we conducted compositional reservoir simulation and synthetic seismic simulation in a five-spot well pattern to investigate whether seismic data can monitor the CO2 front and gas condensate bank with CO2 injected from the very beginning of well production. Then, we compared the compositional simulation results with the seismic simulation results. Although the density contrast among reservoir gas, injected CO2, and condensate is lower than the density contrast in the case of CO2 sequestration in aquifers, the seismic signal may have the potential to capture this smaller difference, monitor the CO2 injection front, and locate the condensate zone, depending on the temperature, pressure and phase properties. When no adequate data are available for reservoir characterization at an early period of production, the seismic data is the only direct measurement of inter-well properties. It may be very valuable for reservoir characterization and for the evaluation of the condensate block. It can serve as the basis for time-lapse monitoring. We compare production by natural depletion with production by CO2 EOR and sequestration started at the very beginning of well production. It shows that the latter will speed up the recovery process and increase the recovery rate while simultaneously storing a large amount of CO2 in the reservoir. (C) 2014 Elsevier Ltd. All rights reserved.