Pyrolysis characteristics of organic-rich shale from the Chang 7 member of Triassic Yanhe Profile in Ordos Basin

A set of thick, black organic shale is developed at the bottom of the Chang 7 accumulation, an important oil-producing section of the Triassic Yanchang Formation in Ordos Basin. In this paper, the thermogravimetric (TG) behaviour of different organic-rich shale layers is studied in an argon environment. Changes in activation energy (E) are analysed by the Coats-Redfern kinetic method, and thermodynamic characteristics at different temperature stages are clarified. The TG curve of Chang 7 shale decreases between 400 and 650°C, which is the main temperature range of organic matter pyrolysis. Meanwhile, the pyrolysis rate reaches a maximum at about 500°C. In the low-temperature stage, E is low and increases with the temperature. At a temperature of about 650°C and conversion rate of about 0.8, the E reaches a maximum. The organic carbon content in layers Y4 and Y5 are higher, while the E is relatively low. © 2021, Saudi Society for Geosciences.