PRELIMINARY PHASE-DIAGRAMS FOR BITUMEN HEAVY OILS AND RELATED MIXTURES

The phase behaviour of heavy oil mixtures was studied using an X-ray i maging system. Batch phase experiments were performed at temperatures and pressures up to 725 K and 7 MPa. Complex phase behaviour such as l iquid-liquid-vapour and solid-liquid-liquid-vapour were observed and p reliminary experimental phase diagrams were constructed. This observed complex phase behaviour is consistent with thermodynamic theory and s uch phase behaviour can be modelled using the Peng-Robinson equation o f state and the tangent plane criterion. These latter points are illus trated through the phase diagram for a model reservoir fluid (ethane propane + n-butane + phenanthrene) which exhibits solid-liquid-liquid -vapour phase behaviour. Example predicted and experimental phase diag rams are presented for this model system.