Catalytic effects of Al2O3 nano-particles on thermal cracking of heavy oil during in-situ combustion process

In-situ combustion (ISC) is regarded as one of the most promising and economic alternative in the development of heavy oil reservoir. Maintaining high temperature oxidation (HTO) reaction with a high cracking efficiency at relatively low fuel consumption is deemed particularly crucial for the success of ISC process. In this work, Al2O3 nano-particles as a catalyst for achieving this during ISC is investigated in three parts. First, kinetic cell experiments with ramped temperature oxidation (RTO) process were conducted on the heaviest fraction of crude oil (residue) to obtain the apparent activation energy (Ea) fingerprints for oil-oxygen reactions with and without Al2O3. Second, thermogravimetric analysis-mass spectrometry-differential scanning calorimetry (TGA-MS-DSC) was used to detect pyrolysis products from the residue and characterize its dynamic change during the process, with SEM and EDS employed to observe the morphology and verify the condition of nano-particles afterwards. Third, combustion tube experiments were performed on the whole crude to analyze the distinction between combustion behavior with and without Al2O3. The results showed addition of Al2O3 catalyst resulted in: Ea decreased and oscillated visibly, temperature of fire front increased by 60.3–83.6 °C, speed of propagation was enhanced by 37.3%, residual coke remains in the quartz sand at the end of combustion tube experiment decreased by 24.8%, production efficiency increased by 13–64% with the reduction of COx production (12.3%) and oxygen consumption (26.9%). This shows a higher ultimate oil recovery is possible with higher upgraded oil percentage during a catalyst-assisted ISC process, which bodes well for future field application. •Nano-Al2O3 induces a lower value of Ea with more vibrative fingerprint.•Totally 12.3% COx productions and 26.9% O2 consumption are reduced in combustion tube experiments with Nano-Al2O3.•Light components generations are verified by the tests of TGA-MS-DSC.•Evaporation of light components makes the cracking process endothermic.•The enhanced production efficiency is verified by the combustion tube experiments assisted by Nano-Al2O3.