Summary The phase behavior of heavy-oil/propane mixtures was mapped from temperatures ranging from 20 to 180°C and pressures up to 10 MPa. Both vapor/liquid (VL1) and liquid/liquid (L1L2) regions were observed. Saturation pressures (VL1 boundary) were measured in a Jefri 100-cm3 pressure/volume/temperature (PVT) -cell and blind-cell apparatus. The propane content at which a light propane-rich phase and a heavy bitumen-rich (or pitch) phase formed (L1/L1L2 boundary) was visually determined with a high-pressure microscope (HPM) while titrating propane into the bitumen. High-pressure and high-temperature yield data were measured using a blind-cell apparatus. Here, yield is defined as the mass of the indicated component(s) in the pitch phase divided by the mass of bitumen in the feed. A procedure was developed and used to measure propane-rich-phase and pitch-phase compositions in a PVT cell. Pressure/temperature and pressure/composition phase diagrams were constructed from the saturation-pressure and pitch-phase-onset data. High-pressure micrographs demonstrated that, at lower temperatures and propane contents, the pitch phase appeared as glassy particles, whereas at higher propane contents and temperatures, it appeared as a liquid phase. Ternary diagrams were also constructed to present phase-composition data. The ability of a volume-translated Peng-Robinson cubic equation of state (CEOS) (Peng and Robinson 1976) to match the experimental measurements was explored. Two sets of binary-interaction parameters were tested: temperature-dependent binary-interaction parameters (SvdW) and composition-dependent binary-interaction parameters (CDvdW). Models derived from both types of binary-interaction parameters matched the saturation pressures and the L1L2 boundaries at one pressure but could not match the pressure dependency of the L1L2 boundary or the measured L1L2 phase compositions. The SvdW model could not match the yield data, whereas the CDvdW model matched yields at temperatures up to 90°C.

The phase behavior of propane diluted bitumen was mapped from temperatures between 20 and 180°C and pressures up to 10 MPa. Both vapor-liquid (VL) and liquid-liquid (LL) regions were observed. High pressure micrographs demonstrated that the heavy phase (a pitch phase) transitioned from a glass to a liquid state with increased temperature and feed propane content. Pressure-temperature and pressure-composition phase diagrams were constructed from saturation pressure and pitch phase onset data. The amount and composition of the heavy phase was also measured. Solvent-free pitch yields as high as 70 wt% of the bitumen were observed. Pseudoternary diagrams were also constructed to observe the partitioning of the species between the phases. Finally, the ability of a cubic equation-of-state with two forms of mixing rules were explored to model the data. The results can be used in the design of in situ and surface processes involving the addition of propane to bitumen.