An important parameter used to determine the feasibility of miscible displacement is the minimum miscibility pressure (MMP). In oil recovery, gas injection can be a very efficient method for improving the productivity of the wells, particularly in the case when miscibility develops during the displacement process. Extensive use of carbon dioxide mixed with light hydrocarbon such as ethane and propane for this purpose has the secondary benefits of being a temporary means of sequestering these green house gases. MMP at which a gas should be injected into the reservoir in order to obtain a multicontact miscible displacement has consequently attained a very important status in enhanced oil recovery studies. MMP can be estimated from phase equilibria data using pseudo-ternary conceptualization of Benham et al. The full advantages of the use of carbon dioxide as a selective solvent can only be realized through knowledge and understanding of its phase behavior and equilibria with different hydrocarbons. In this paper binary and ternary phase equilibrium studies involving a heavy hydrocarbon such as n-eicosane, light hydrocarbon such as ethane and propane with carbon dioxide was performed. Peng-Robinson equation of state with binary interaction parameters were applied to represent vapor-liquid equilibria and to optimize the representation with minimum use of ternary parameters. The experimental data obtained was used to predict the MMP using pseudo-ternary conceptualization of Benham et al. and examine its variation with nature and amount of light hydrocarbons in the injected gas.

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