The complicated nature of combustion reactions makes the performance prediction of in-situ combustion difficult. This study proposes a solution to better understand the complex chemical reaction schemes through systematically conducted Thermogravimetric Analysis and Differential Scanning Calorimetry (TGA/DSC) experiments.
In this study, results from combustion tube experiments (CTE) are integrated with kinetic and analytical modeling. The SARA (Saturates, Aromatics, Resins, and Asphaltenes) fractions of a bitumen sample were subjected to TGA/DSC experiments under air injection at a constant heating rate. Heat flow curves (DSC curves) were used to determine kinetic parameters by using Reaction Kinetic Models (Arrhenius Model, Coats-Redfern Model, Horowitz-Metzger Model, and Ingraham-Marrier Model).
The kinetic analyses conducted on separate SARA fractions and on bulk crude oil samples provided valuable information: asphaltenes require the largest activation energy but generate the greatest amount of heat upon combustion. Saturates provide large amounts of heat, which proves their ignition feature. Aromatics and Resins play an important role on asphaltene cracking, in addition to supplying large amounts of heat to asphaltenes upon burning.
In-situ combustion is a very promising enhanced oil recovery method which can yield high oil recovery. However, the unknowns associated to chemical reactions inhibit the prediction of combustion performance. This study provides a unique solution to find the correct and simple reaction kinetics by integrating reaction kinetic experiments with several kinetic analysis methods.