Solubility of water in bitumen

Liquid/liquid-vapor (L/LV) and aqueous-liquid/aqueous-liquid-vapor (AL/ALV) boundaries of pseudo-binary mixtures of bitumen and water were measured using the isothermal stepwise volume expansion method at conditions relevant to in situ heavy oil operations (temperatures from 180 to 280 °C and pressures from 1.5 to 5 MPa). The L/AL boundary was determined from the intersection of the L/LV and AL/ALV boundaries. An activity coefficient model of the pseudo-binary system was used to check the self-consistency of the L/LV measurements. The Advanced Peng Robinson equation of state, which has a distinct alpha function for water, was used to model the VLE and VLLE data. For this model, the oil was characterized into pseudo-components based on a SimDist assay and the specific gravity and asphaltene content of the oil. Temperature dependent binary interaction parameters between bitumen pseudo-components and water were tuned such that the model fit the measurements to within the experimental error. Isothermal pressure-composition phase diagrams were generated for the pseudo-binary mixtures at each temperature. Finally, a straightforward correlation for the solubility limit of water in bitumen as a function of temperature was developed using the data in this study and from the literature. The average deviation of the correlation was 0.5 wt % below 340 °C.