In the steam-based recovery processes, the coinjected gas can dissolve and diffuse into bitumen or heavy oil for viscosity reduction. The equilibrium concentration and solubility of methane are governed by the complex interaction with the bitumen. Thus, it is necessary to know the quantitative effects of gas dissolution on bitumen viscosity, density, and phase behavior at elevated temperatures in which steam-based processes are applied.
Thus, this study aims at providing necessary experimental data for methane/Athabasca bitumen over a wide range of temperatures and pressures (up to 190°C and 10 MPa); that is, conditions that approach the temperatures at in-situ steam processes. Our previously designed phase-behavior experimental apparatus was used to measure the solubility of methane in Athabasca bitumen and its corresponding saturated-phase properties. Then, the measured solubility and density data were modeled with the Peng-Robinson equation of state (EOS) (Robinson and Peng 1978).
The results indicate that the effect of temperature on the solubility profile of the methane/Athabasca-bitumen mixture is negligible at high temperatures and there is a distinct difference in the solubility data at 50°C compared with other isotherms (100, 150, and 190°C). Therefore, a reduction in viscosity at higher temperatures is much lower compared with a similar reduction at low temperature (50°C). There is a linear relationship between the methane-saturated viscosity and pressure for all temperatures in a semilog plot. The EOS modeling results also show that temperature-dependent binary-interaction parameters and volume-translation values should be considered to match density and solubility data.