Study on the temperature field in coal-rock mass and the temporal and spatial evolution of overburden damage in the tar-rich coal pyrolysis zone

Abstract

Tar-rich coal is a type of coal resource that produces oil and gas through low-temperature pyrolysis. In-situ pyrolysis is crucial for reducing global carbon emissions, protecting the ecological environment, and improving engineering safety and benefits. In this study, a physical simulation test system was constructed for the in-situ pyrolysis of tar-rich coal to monitor the change of formation temperature during tar-rich coal pyrolysis in real time. Furthermore, the fracture development characteristics of overlying strata caused by temperature field changes were analyzed. The results demonstrated that as the heating time increased, the horizontal temperature field of each layer evolved into the high-temperature center. Moreover, the vertical temperature field transitioned from a low temperature in the middle and high temperatures on both sides to a symmetrical distribution of higher temperatures in the middle than on both sides. The fracture development degree was considerably higher in the middle and lower parts of the same stratum. Horizontal and vertical cracks were observed in the middle of the mudstone layer, and the broken rocks were larger. Furthermore, the fracture degree of rock mass on both sides was higher than that in the middle part, with the separation from the rock being relatively smooth.