SARA-based kinetics model for simulating heat release during crude oil combustion

This study presented the development of a reaction kinetics scheme based on saturates-aromatics-resins-asphaltenes (SARA) fractions to represent the complicated chemical reactions occurring during high-pressure differential scanning calorimetry (HP-DSC) tests. The heat release characteristics during heavy crude oil combustion were analyzed from a set of HP-DSC results. On the basis of this analysis, an improved reaction kinetics model, including low-temperature oxidation (LTO) reactions of SARA fractions, cracking of oxidized asphaltenes, and coke combustion, was established. Following that, this model was incorporated into Computer Modeling Group STARS to simulate the HP-DSC results. Both activation energy and frequency factor of each reaction were continuously tuned until the correct kinetics parameters were obtained by matching the simulation data with the HP-DSC experimental data. The experimental results indicated that the heavy crude oil experienced greater heat release due to LTO rather than high-temperature oxidation at 5 MPa, which differed from the results observed at atmospheric pressure. The simulation results showed that the energy required to activate the oxidation reactions in the HP-DSC experiments was similar to that in the numerical simulation. However, the oil sample was subjected to higher molecular collision frequency in the HP-DSC experiments than in the numerical simulation. Therefore, more attention should be given to adjusting frequency factor when determining the oxidation kinetics parameters in the numerical model. Overall, the SARA-based oxidation kinetics model successfully simulated the exothermic characteristics of the heavy oil during heating.