Experimental and numerical study of air injection in light oil reservoirs

AIP (Air injection process) can offer unique economic and technical opportunities for enhanced oil recovery in light oil reservoirs. The complicated reaction mechanisms among crude oil, rock, and air make AIP different than conventional EOR (enhanced oil recovery) methods. Till now, the mechanisms of AIP are still under controversy. In our study, we firstly implemented thermal experiments to investigate the thermal-oxidative characteristics of a light oil sample. Then, a practical workflow was proposed to obtain the oxidation kinetic data by validating the simulation model with the thermal experi-ments, and a method was proposed to build a comprehensive kinetic model by combining thermal experiments and simulation. Based on the proposed method, a kinetic model was built for a light oil sample, and the LTO (low temperature oxidation) induced spontane-ous ignition feasibility was investigated. The Frank-Kamenetskii theory was introduced to build the screening criteria for AIP in terms of spontaneous ignition feasibility. The results indicated that this light oil is not feasible to achieve spontaneous ignition due to its insuf-ficient reactivity. In addition, a more general screening study was performed based on typical kinetic data values of crude oil, where activation energy varies from 20 kJ/mole to 70 kJ/mole and frequency factor varies from 0.1 s-1 to 105 s-1, and possible reservoir condi-tions with temperature from 70oC to 140oC and reservoir thickness from 1 m to 30 m. The results revealed that in order to achieve the spontaneous ignition, the activation energy of the crude oil should be lower than 60 kJ/mole and the frequency factor of the crude oil should be higher than 2 s-1.