Evolution Characteristics of Pyrolysis Gas and Kinetic Analysis of Marine-Continental Transitional Shale from Shanxi Formation in the Ordos Basin

In this study pyrolysis behaviors, pyrolysis gas evolution and kinetic parameter distribution of marine-continental transitional shale from Shanxi Formation in the Ordos Basin were investigated. To analyze the pyrolysis of kerogen from marine-continental transitional shale of Shanxi Formation at different heating rates TG-FTIR-MS combined technology was used. The weight loss and the evolution of pyrolysis gases of kerogen samples under different heating rates were studied, and the kinetic parameters were calculated. The results showed that the weight loss of kerogen at heating rates of 5, 15 and 25°C/min were 28.08, 25.46 and 26.58 wt %, respectively. With the increase of the pyrolysis temperature, the pyrolysis gases such as H2O, CO2, CO, CH4 and H2 are successively released. The whole pyrolysis process can be divided into six stages: drying, slow pyrolysis, first fast pyrolysis, second fast pyrolysis, fast polycondensation and slow polycondensation. Among them, in the two fast pyrolysis stages (393.4–589.4°C), the weight loss rate of kerogen was larger. With the increase of conversion rate, the activation energy increases, indicating that the energy required for the fracture of different functional groups is different, and the difficulty of the reaction is also different.