Bitumen Characterization and Pseudocomponents Determination for Equation of State Modeling

Abstract

The phase behavior and thermodynamic properties of heavy oil and bitumen are of crucial importance for their in situ recovery, pipeline transportation, and upgrading; however, bitumen is a complex mixture of organic compounds whose chemical structures are not well understood. Therefore, bitumen is commonly characterized as a mixture of pseudocomponents derived from experimental data. This manuscript is intended to characterize and define the thermodynamic properties of Alberta bitumens. It has been undertaken three specific objectives: the first is the characterization of the bitumen as a mixture of pseudocomponents. The second objective is calculation of the gas solubility of gas-saturated bitumens by using an equation of state (EOS). The final objective is the selection of a set of pseudocomponents that would be applicable for different types of bitumen; in other words, the pursuit of a universal set of pseudocomponents for an EOS, independent of bitumen type. Varying numbers of pseudocomponents have been tested against the experimental data in the literature for bitumen from different fields (Athabasca, Wabasca, Peace River, and Cold Lake) with four different solvents (CH4, C2H6, CO2, and N2). The results show that the Lee−Kesler correlation (Lee, B. I.; Kesler, M. G. AIChE J. 1975, 21, 510−527) has produced considerably better results than the other correlations; it also appears that the Lee−Kesler correlation is appropriate for bitumen/solvent systems to determine the critical properties of the pseudocomponents.