A continuous phase equilibrium (CPE) apparatus was used to obtain composition, density, and viscosity for a West Texas recombined crude oil during the injection of high-pressure carbon dioxide (CO2). CO2 was continuously injected at constant pressure and flow rate. The system is maintained at constant pressure during CO2 injection by controling the production rate. Compositions, densities, and vi the produced fluids were determined at system pres, and temperature, providing continuous monitoring of fluid properties produced at outlets at both the top and bottom of the CPE apparatus.

The tests were run using both pure and impure CO2 at 105°F and pressures ranging from below to well above the minimum miscibility pressure (MMP). The solubility of the injected CO2 in the oil-rich phase was found to have little dependence on pressure, while the solubility of hydrocarbons in the CO2-rich phase increased with increasing pressure. Impurities in the injected CO2 did not significantly affect trends in composition, density, and viscosity of each phase. This work reports density, viscosity, component condensation and vaporization, and equilibrium constants for systems of CO2 and a West Texas crude oil at various reservoir conditions. Information from this work is required to tune models that simulate dynamic phase behavior in CO2 displacement tests, for both laboratory and field applications.

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