Compositional Simulation of a Chemically Unconventional Oil Flooded by CO2

CO2 flooding is considered as one of the most effective EOR processes when the miscibility can be achieved under reservoir conditions. The key point in this connection is the understanding and reproducing of the phase interactions between CO2 and reservoir oil. A challenging compositional simulation was performed to investigate the feasibility of CO2 flooding in a field in northern Germany having chemically unconventional oil. The usual steps of PVT simulation were applied. The grouping of the components was performed based on the chemical structure as well as on the distribution of K-values from CO2-oil flash experiments. Good agreements with the experiments were obtained at the end of the regression of the selected EOS parameters. The calibrated PVT set was further used to simulate the core flood experiments. Good matches with measured oil-water production were obtained after the fine tuning by parachor values of the pesudo components. A fully miscible process could not be achieved. On the other hand, the simulation using separator oil composition (lower C1 content) indicated the miscible/partially miscible displacement process with recoveries up to 70% of the remaining oil in place which fits well with observed results.