A practical method to obtain kinetic data from TGA (thermogravimetric analysis) experiments to build an air injection model for enhanced oil recovery

Abstract

To build an air injection model for enhanced oil recovery, it is necessary to obtain the kinetic data from thermal experiments. For TGA (thermogravimetry analysis) experiments, fitting the weight loss data using different forms of the Arrhenius Equation is practiced to obtain a single set of kinetic data which are used for the whole temperature range. The problem is that the kinetic data changes with the test temperature, oil composition, etc. Therefore, the obtained kinetic data do not represent the actual physics. This paper presents a detailed practical method to obtain kinetic data from TGA experiments to build an air injection model. The air injection model contains two parts. One part is to define fluid pseudo-components and their physical properties. The other part is to define oxidation reaction and the corresponding kinetic data. In order to validate the air injection model, both air purging TGA experiments and nitrogen purging TGA experiments are conducted. The fluid model (pseudo-components and their properties) is validated by matching model results with the nitrogen purging TGA experiments. Then, the kinetic data are obtained by matching the model results with the air purging TGA experiments.To verify the above approach to build an air injection model, TGA experiments using a pure hydrocarbon C20 and a Wolfcamp crude oil were conducted. The pure hydrocarbon C20 is used to verify the approach. Then seven oxidation reactions of seven pseudo components are utilized to define the air injection model for the Wolfcamp crude oil. The selection of the pseudo components was validated with the nitrogen purging TGA experiments and the oxidation reactions were validated with the air purging TGA experiments. The result shows that the combination of isomerization reactions and oxygen addition reactions can perfectly simulate a light oil air injection process in the low temperature region. This paper shows that an air injection model can be built using the kinetic data by analyzing TGA experiments.