Binary Interaction Coefficients Of The Modified Soave-Redlich-Kwong Equation Of State For Bitumen-Containing Systems At In-Situ Conditions
Authors: Fu C.T. , Puttagunta R. 
Published: March 2010

Many equations of state which can represent the vapour-liquid equilibrium (VLE) properties of hydrocarbon systems are available in the literature. However, the binary interaction coefficient values for these equations rarely appear and are seldom correlated. The objective of this study is to develop a good correlation for the binary interaction coefficients of the modified Soave-Redlich-Kwong (SRK) equation of state for representing the VLE properties of bitumen-containing systems at in-situ conditions. The pseudo-binary systems included in this investigation are : carbon dioxide – Athabasca bitumen, carbon dioxide – Cold Lake bitumen, nitrogen – Athabasca bitumen, methane – Athabasca bitumen, methane – Cold Lake bitumen, and ethane – Athabasca bitumen. These systems are particularly important to petroleum engineers in the study and design of recovery processes and in the development of numerical simulators.

The binary interaction coefficients of the modified SRK equation of state were determined for each isotherm on the basis of the binary experimental measurements and were then correlated with temperature. Measured VLE compositions of bitumen containing systems were compared with values predicted by the equation using the newly developed correlations. Good agreement was obtained.

Introduction

Vapour-liquid equilibrium (VLE) properties of bitumen containing mixtures at in-situ conditions are important to the study of the recovery of bitumen from oil sands, the development of numerical simulators, and the application of various flooding processes in enhanced oil recovery. However, only limited experimental data for these systems have been reported in the literature, perhaps because the experimental measurements are time-consuming and expensive; problems then arise when VLE properties are needed for applications. One way to solve this problem is to predict VLE properties at the desired conditions using a theoretical approach. The purpose of this investigation is to improve the accuracy of the presently available method for making these predictions.

Vapour-liquid equilibrium properties can be predicted and represented by many methods. One of the most popular methods uses an equation of state. A cubic equation of state is usually chosen because of its relative simplicity and high degree of accuracy in VLE predictions. In this study, the modified Soave-Redlich-Kwong (SRK) equation of state(1–3) was chosen to represent and predict the VLE properties of bitumen-containing systems. Excellent results can he calculated if the required critical properties of the components in the mixture, and the binary interaction coefficients of the equation of state are available. Although the modified SRK equation has been studied and applied in the natural gas and petroleum industries for many years, the binary interaction coefficients or the equation for oil sands bitumen-containing systems have not been thoroughly evaluated and correlated with temperature.

The specific objective of this study is to evaluate the binary interaction coefficients of the modified SRK equation from the binary experimental data available in the literature and from the data measured in this laboratory for oil sands bitumen-containing systems, to correlate these values with temperature, and to use these correlated values to predict the VLE properties of the systems at other conditions.