Solubility of n-Butane in Athabasca Bitumen and Saturated Densities and Viscosities at Temperatures Up to 200°C

Abstract

Summary The steam- and/or solvent-based recovery processes are efficient methods for recovery of heavy and extraheavy oils. The performance of these techniques depends on the amount of solvent dissolved in the oil and the variation of oil viscosity with temperature. Thus, full understanding of the quantitative effects of the solvent on heavy-oil viscosity and phase behavior is crucial for feasibility studies, design, and prediction of field-scale processes. Phase-behavior study of bitumen diluted with heavy hydrocarbon solvents, such as butane and pentane, has gained less attention in recent years. These solvents, as good candidates for recently developed recovery methods such as expanding solvent steam-assisted gravity drainage (ES-SAGD), could provide promising oil-production rates. Thus, the aim of this research is the development of an understanding of the phase behavior of n-butane/Athabasca-bitumen mixtures. It includes both experimental and modeling studies of solubilities and saturated liquid densities and viscosities over wide ranges of temperatures (up to 200 °C) and pressures (up to 8 MPa). Experimental results indicate that the dissolved n-butane in bitumen leads to a significant oil-viscosity reduction, and the effect is more pronounced at lower temperatures and/or higher pressures. The modeling results show that the measured solubilities are adequately represented by the Peng-Robinson equation of state (EOS) with an average absolute relative deviation (AARD) of 9.7%. The saturated liquid densities are also correlated with both the EOS and the effective liquid-density approach with 0.86 and 0.55% AARDs, respectively. The viscosity data are reasonably matched with Pedersen corresponding state.