Characterization Of Athabasca Bitumen For Gas Solubility Calculations

Abstract

Abstract The solubility of five pure gases, namely N2 CO, CH4, CO2 and C2H2, in Athabasca (GCOS) bitumen is calculated using the Peng-Robinson EOS and with the use of the literature bitumen characterizations and a new ‘3PC’ characterization. The calculated gas solubilities are compared with the published data over a temperature range of 20 °C to 110 °C and pressures up to 10 MPa. The best over-all match of the gas-solubility data is obtained with the ‘3PC’ scheme which models the bitumen as a mixture of three pseudocompoments. Optimized values of the binary interaction parameter for use in the Peng-Robinson EOS are also provided. Introduction The objective of this paper is to evaluate bitumen characterizations for calculating the solubility of five gases, namely N2, CO, CH4, CO, and C2 H6, in Athabasca bitumen by use of the Peng-Rpbinson(l) equation of state (EOS). Bitumen is a highly complex mixture of light, medium and heavy organic compounds. Hence, it is not reasonable to model the bitumen as a single pseudocomponent even for use in simple calculations. Three bitumen characterization schemes for Athabasca (GCOS) bitumen are considered in this paper. The first scheme of Mehrotra et al.(2), with the bitumen-split suggested originally by Bishnoi et al.(3), consisted of five pseudocomponents. The second scheme of Johnson et al.(4), consisting of four pseudocomponents, had been used for predicting the viscosity of gas-free and gas-saturated Athabasca bitumen by use of a corresponding states method. A third scheme consisting of three pseudocomponents (termed the ‘3PC’ scheme) was developed in the present study. For all pseudocomponents in each of the above mentioned schemes, the critical properties and acentric factor were estimated from the Kesler-Lee(5) correlations, which have been shown to produce satisfactory results for the solubility of CO2, in Athabasca and Peace River bitumens(2). The literature on the measurement and prediction of thermodynamic properties of light hydrocarbons/gas systems is extensive. However, the literature specifically related to the properties of Alberta bitumen/gas systems is still very limited.