Kinetic modelling of thermal cracking and low temperature oxidation reactions

Two kinetic models were developed to describe thermal cracking and low temperature oxidation (LTO) reactions of Athabasca bitumen for the in situ combustion process. These unified kinetic models can describe the compositional changes in the Athabasca bitumen under thermal cracking or LTO. Bitumen composition was expressed in terms of the pseudo-components maltenes, asphaltenes, and coke. Oxidation reactions occurring in the low temperature range (less than 300 degrees C) are complex with two primary oxidation reaction modes: oxygen addition and bond scission. For Athabasca bitumen, oxygen addition reactions are generally dominant in the low temperature range (less than 300 degrees C) however bond scission or carbon oxide forming reactions occur to some extent at reaction temperatures greater than approximately 150 degrees C. The variation in the oxygen uptake rate with time at a given temperature is accounted for through rate equation describing the change in composition of the oil and the rate of oxygen uptake at the temperature of interest for each of the pseudo-components. The oxidation model for the low temperature range that was developed in this work accounts for both oxygen addition and bond scission modes of reaction. It is capable of predicting the effect of temperature, pressure, oxygen concentration, and time on bitumen composition and oxygen uptake rates.