In this work, we studied the phase equilibrium of the normal-hexane, water, and Mackay River bitumen ternary system at operating conditions applicable to the solvent-assisted thermal recovery process. The viscosities of the hydrocarbon-rich (oleic) and water-rich (aqueous) phases were measured at three temperatures 200, 205, and 210 °C and a pressure of 2.5 MPa. The concentration of solvent (n-C6) in the hexane/water (steam) mixture was maintained at 1 mol.% (6.85 vol.%). The proportion of bitumen in the bitumen/solvent mixture was chosen to achieve a hexane concentration of 70 mol.% (37.45 vol. %), near the maximum solubility of hexane in bitumen at test conditions. The results reveal the formation of a vapor-liquid-liquid equilibrium (VLLE) at the studied conditions. The dilution effect of hexane on viscosity reduction was found to be dominant over the temperature effect at the test conditions (T > 200 °C). The findings also indicate that solvent content of the vapor phase decreases with temperature. Trace amount of solvent (~ 100 ppm) was found in the aqueous phase. The results improve our understanding of the complex phase behavior associated with solvent-aided recovery processes.

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