Engineering validation and numerical simulation of oxidative pyrolysis model for oil Shale: Based on the Fuyu pilot project

The autothermic pyrolysis in situ conversion process (ATS) is an efficient oil shale recovery method, whose core principle involves injecting ambient-temperature oxygen-containing gas into a locally preheated formation. This gas reacts with residual organic matter generated from kerogen pyrolysis through an exothermic oxidation reaction, supplying heat for kerogen cracking into oil and gas. Focusing on the Fuyu oil shale block, this study integrated geological and production data from an ATS pilot test with an oxidative pyrolysis model to build a matched numerical model. Simulation results indicate that 1.99% kerogen conversion in 170 days causes low recovery, and injection rate significantly affects cumulative oil production. Therefore, it is systematically further analyzed how injection rate, O2 concentration, and injection mode affect oil production, thereby optimizing process parameters. Additionally, ATS performance under 50-m well spacing was predicted. Results indicate that increasing air injection rate and O2 concentration simultaneously boosts cumulative oil production and kerogen-specific oil yield, with an optimum at 21% O2. Excessively high O2, however, generates intense exothermic zones near the wellbore, converting produced oil to carbon oxides and reducing recovery efficiency. Intermittent injection (20 days of injection followed by 10 days of shut-in) enables the redistribution of heat and oxygen, with an oil yield per unit kerogen that is 1.72 times higher than that of continuous gas injection. ATS demonstrates high applicability for 50-m well spacing, with an effective recovery factor of 19.2%. This research guides lab-to-field oxidative pyrolysis model optimization for deep reservoir in situ recovery parameter matching.