Study on Oxidative Exothermic and Pyrolytic Endothermic Characteristics and Kinetics of Chang 7 Medium-Low Maturity Shale Oil Reservoir in the Southern Margin of Ordos Basin

The amount of recoverable resources by in-situ conversion technology of medium and low maturity shale oil is about (700–900) × 108 t, which is an important replacement resource for oil and gas development. Air injection technology of medium and low maturity shale oil is considered to be an efficient means to improve the recovery of this kind of reservoir. This technology realizes the thermal cracking and transformation of solid kerogen by injecting air and oxidizing organic matter to release a large amount of heat. At present, the oxidation kinetics, thermal endothermic and exothermic characteristics of medium-low maturity shale oil in Chang 7 reservoir in the southern margin of Ordos Basin have not been studied. Chang 7 reservoir was selected as a homogeneous sample, and its pyrolysis and oxidation characteristics in N2 and Air atmospheres were tested by TG/DTG/DSC, and the relevant activation energy was calculated based on Arrhenius theory. The results show that TOC content of Chang 7 shale oil sample is 21.75%. The oxidative heat release is 8.14 times of the thermal desorption heat, in which the oxidative heat release is 10300.13 J/g, and the thermal desorption heat is 1265.19 J/g. The oxidation and pyrolysis activation energies of the sample are 93.02 kJ/mol and 107.09 kJ/mol, and the pre-factor is 6.73E+09 s−1 and 2.71E+14 s−1, respectively. The research results provide basic parameters for the numerical simulation of air injection development of Chang 7 reservoir in the southern margin of Ordos Basin.