Density of mistures of heavy oil and solvents
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2012
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Abstract
The design of solvent-based and solvent-assisted heavy oil and bitumen recovery processes requires the accurate prediction of the physical properties of heavy oil mixed with solvents. In particular, density is a critical parameter for gravity drainage and gravity separation based processes. It has proven challenging to accurately predict the density of these mixtures, particularly when the solvent is a dissolved gas. The objective of this thesis is to develop a straightforward method to predict the density of heavy oils or bitumens diluted with liquid solvents and dissolved gases. Most mixtures of heavy oil and solvents are well below their critical point, and therefore liquid phase density prediction methods are appropriate. Excess volume based mixing rules were investigated with a binary interaction parameter used to relate the excess volume to the composition of the mixture. The mixing rules were tested on literature data for binary mixtures of hydrocarbons. The binary interaction parameters were found to correlate to the normalized difference in the molar volumes of the binary pairs. To apply these mixing rules to a liquid containing a dissolved gas, the effective liquid density of the dissolved gas is required. However, while effective liquid densities have been used to estimate petroleum densities, values have only been developed for a very limited range of conditions. Nor have these values been rigorously tested. In this thesis, the effective liquid densities of light n-alkanes were determined by linearly extrapolating the molar volumes of higher n-alkane (C7 and up) versus their molecular weight. The extrapolated molar volumes were converted to the mass density and correlated to temperature and pressure. The correlation was validated on density data on n-alkane binary mixtures from the literature and from this thesis. Densities were measured with an Anton Paar density meter from room temperature to l 75°C and from 10 to 40 MPa for ethane, propane, and n-butane as the dissolved gas and n-decane, toluene, and cyclooctane as the heavier liquid component. The effective liquid densities applied with regular solution mixing rules (zero excess volume) predicted the densities of these mixtures with an average absolute relative deviation (AARD) less than 1 %. Finally, the mixing rules and effective densities were tested on diluted bitumens. Densities were measured from room temperature to 175 ° C and from 0.1 to 10 MPa for bitumen/propane (this project), and bitumen/ethane, bitumen/ n-butane, and bitumen/n-heptane (as part of another project, Motahhari, 2012). The regular solution mixing rules (zero excess volume) predicted the mixture densities with an AARD less than 1 %. The AARD was reduced to less than 0.15% with fitted excess volume mixing rules. The binary interaction parameters were correlated to the normalized molar volume difference with a quadratic expression. The AARD with the correlated parameters was less than 0.4%. Overall, the excess volume mixing rules with the correlated interaction parameters predict the density of diluted bitumens to almost within experimental error as long as the mixture is subcritical and the component densities are known at the conditions of interest. The proposed method is suitable for hand calculations and could be implemented in a simulator with an appropriate database of component densities.
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Bibliography: p. 105-113
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Citation
Saryazdi, F. (2012). Density of mistures of heavy oil and solvents (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/5041