Integration of ramped temperature oxidation and combustion tube tests for kinetic modeling of heavy oil in-Situ combustion

Abstract

In-situ combustion (ISC) has been applied as a follow-up process after steam injection-based technologies to improve heavy oil recovery and lower operating costs. Comprehensive understanding of the oxidation behavior and reliable prediction of the ISC performance are of great importance in the design of a ISC process. In this work, a calibration workflow was proposed to investigate the oxidation behavior and then establish a reaction kinetics model. A Ramped Temperature Oxidation (RTO) experiment was firstly conducted to capture the detailed oxidation behavior at elevated temperature conditions. Subsequently, a Combustion Tube (CT) test was performed to further evaluate the overall performance of ISC. Based on the integration of RTO and CT results, a comprehensive reaction kinetics model was developed to predict the ISC performance within a wide temperature range, including Low Temperature Oxidation (LTO), Negative Temperature Gradient Region (NTGR), and High Temperature Oxidation (HTO) reactions. It is found that the NGTR of heavy oil with high saturate and low asphaltene exhibits a narrow temperature range. The combustion front velocity in the RTO is comparable with that in the CT. In a stable HTO region, the CO2 concentrations in the RTO experiment and CT test were kept around 17% and 14%, respectively. The existence of LTO reactions in the RTO experiment caused the deviation of CO2 concentration. With the incorporation of the reaction model into simulation, a good agreement between measured and predicted results was obtained. This demonstrates that the established reaction model is capable of capturing the key oxidation mechanisms. In addition, the proposed workflow also helps upscale the oxidation behavior from a RTO experiment to a CT test and provide benchmarks for field operations.