Phase behavior of Athabasca bitumen + water mixtures at high temperature and pressure

•A method for measuring the phase behavior of bitumen + water mixtures up to the critical temperature of water is presented.•The method is validated.•P − x at constant T and P − T at constant x phase diagrams are presented.•The phase behavior type of bitumen + water mixtures is identified.

Mixtures of hydrocarbons + water exhibit complex phase behaviors, and transitions in phase behavior classification also arise as hydrocarbon composition is varied. In this work, the phase behavior of Athabasca bitumen + water mixtures is reported, in the temperature range (522.1–644.0 K) and the pressure range (4.2–35.7 MPa). Pressure–temperature (at fixed composition) and pressure–composition (at fixed temperature) phase diagrams were prepared based on observations obtained using a view cell apparatus equipped with X-ray transmission tomography. Phase boundary and phase composition accuracy and precision were validated by reproducing phase diagrams for 1-methylnaphthalene + water and toluene + water mixtures available in the literature. The Athabasca bitumen + water pseudo-binary exhibits type IIIb phase behavior, based on the van Konynenburg and Scott classification scheme, as the composition difference between the water rich and Athabasca bitumen rich liquid phases remain large and liquid–liquid–vapor phase behavior persists up to the critical temperature of water. The reported phase diagrams are expected to provide benchmark data needed to define operating conditions for hydrocarbon resource production and refining processes based on the addition or exploitation of sub critical and near critical water.

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