A strategy for enhanced hydrogen generation: The effect of varying atmospheres on in-situ gasification in heavy oil reservoirs

In-situ generation of hydrogen, typically produced as syngas with COx and CH4, from hydrocarbon reservoirs presents a novel and cost-efficient approach to clean energy development. Creating atmospheric conditions conducive to hydrogen production can significantly enhance hydrogen generation efficiency and demonstrate high commercial attractiveness. In this study, kinetic cell (KC) experiments were conducted to explore the reaction pathways and mechanisms responsible for hydrogen generation through in-situ heavy oil gasification under atmospheric conditions of nitrogen and air. The results indicate that hydrogen is generated through pyrolysis and coke dehydrogenation reaction processes in a nitrogen atmosphere. The coke dehydrogenation process contributes over 60% of the total hydrogen production when temperature varies in the range of 500-650 degrees C. However, the cracking process contributes all the hydrogen production under an air atmosphere condition, corresponding to a temperature range of 300-500 degrees C. Furthermore, a mixed atmosphere (nitrogen and air) significantly enhances the hydrogen conversion rate of heavy oil, which is 83.53% higher than a pure-air atmosphere and 45.05% higher than a nitrogen-only atmosphere. In the optimal experiment, a maximum hydrogen concentration of 1.29% is achieved with the highest hydrogen generation efficiency of 27.39%. A substantial hydrogen conversion rate from heavy oil is calculated as 179.39 mL/g. This study underscores the potential of mixed atmospheres to improve hydrogen generation during the in-situ heavy oil gasification process, which provides deep insights into creating atmospheric conditions conducive to hydrogen production.