No abstract

At temperatures close to the critical temperature of carbon dioxide, some crude oils form three phases when mixed with CO 2 . The objective of this work was to investigate whether the three-phase behaviour of CO 2 -crude oil mixtures can be predicted with the Soave-Redlich-Kwong equation of state. In the description of the C 7+ -fraction, a previously described characterization method was applied. In this characterization procedure, the critical properties and the acentric factor of single carbon number groups within the plus fraction are estimated on the basis of measurable physical properties. By comparison of experimental and calculated data, it is shown that no, or very little tuning of the EOS parameters is necessary to obtain representative predictions of three-phase regions. In addition it is demonstrated how too severe tuning leads to very erroneous results in the simulation of phase diagrams. Finally, it is shown how the described method fails to predict the three-phase region of a very heavy oil with a small three-phase region at the given temperature.