Measurements of volumetric phase behavior of mixtures of n-decane and CO₂ at high pressures and high temperatures

The use of CO₂ as an enhanced oil recovery agent is ever increasing as CO₂ is becoming widely used for heavier oil production. The environmental burdens of CO₂ also encourage that it should be disposed of in a way that those liabilities are minimized. Hence there is a need for understanding the phase behavior of Hydrocarbon-CO₂ systems and mechanism by which the hydrocarbon rich phase is displaced. Accurate data on phase behavior of mixtures containing hydrocarbons and CO₂ will not only help in oil recovery and production but also will help in designing infrastructure for transportation and downstream separation. Solubility of CO₂ in hydrocarbons at low and moderate pressures is pretty good. This phenomenon reduces the density of the mixture and volume swelling is observed. At high pressure range there is a dramatic increase in the density of CO₂ with pressure, which can produce a complete miscibility. In some complex mixtures of hydrocarbon and CO₂ a second liquid CO₂-rich phase can also exist. Development of experimental methods and technique for measurements of volumetric properties for binary mixtures of CO₂+ n-decane will be discussed. The phase behavior properties measured include isothermal compressibility, mass density, bubble points at temperatures from (313 to 410) K and pressures up to 76 MPa (11000 psi). Our data are compared with the predictions from equation of state (EOS) models commonly used in software simulators. The accuracy of experimental data and challenges in development of the experimental technique will also be discussed.