The displacement efficiency of oil by CO 2 is highly pressure dependent. Miscible displacement efficiency is achieved only at pressures greater than a certain minimum. This minimum miscibility pressure (MMP) is a function of temperature and of composition of the injection gas. This paper examines the effect on MMP of up to 55 mol % impurities in the COrrich injection gas. We developed a correlation of these data_based on the mole average pseudocritical temperature (TeM) of the gas and the MMP of pure CO 2 with the same oil at the same conditions. In general, we found that increasing the TcM of the gas lowered the MMP and decreasing the TeM increased the MMP. Injection gases with the same reM but with very different compositions were found to have the same M}1P. Various correlating parameters were tried, but the TeM was found to be the most suitable. This correlation is compared with others in the literature and found to be superior in the case when the drive gas contained both light and intermediate components.The correlation indicates that miscibility in a field-wide CO 2 flood may be maintained by a reinjection of impure CO 2 streams if sufficient intermediate hydrocarbons are present in the produced gas to offse.t the effects of lighter gases. Because CO 2 cleanup is a major cost in field-wide CO 2 flooding, reduction or complete elimination of produced-gas cleanup will have a positive impact on process economics. The operational and regulatory aspects of injecting an impure CO 2 stream, however, must be considered to optimize the recycling scheme.

Gas-liquid equilibrium data are determined for mixtures ofCOz 4toluene at five temperatures from 120 to 270 OC and for mixtures of CO, + m-xylene at four temperatures from 190 to 310 O C . The pressures were up to 50 atm for both systems.

Compositions of saturated equilibrium liquid and vapor phases are determined In a flow apparatus for mixtures of methane and n-decane at 150, 240, 270, 290, and 310 OC, for methane and benzene at 150, 190, and 230 OC, and for methane and toluene at 150, 190, 230, and 270 OC. Pressures extend to near the crltlcals of the mixtures starting from 20 atrn or from somewhat above the vapor pressure of the solvent Whichever is higher.

Compositions of saturated vapor and liquid at equilibrium were experimentally determined at four temperatures from 190 to 310 °C for carbon dioxide + n-decane and from 190 to 390 °C for carbon dioxide + n-hexadecane.Measurements were made at four pressures from 20 to 50 atm at each temperature for both systems.

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