The complexity of pore networks and compositional heterogeneities in shale significantly influences shale gas flow behavior. Thermal treatment in shale reservoirs has enhanced pore connectivity and facilitated gas flow. This study investigates the evolution of pore morphometry and chemical variations in immature Raniganj shale with increasing temperature. By integrating multiple advanced techniques, we aim to improve the precision of two-dimensional/three-dimensional (2D/3D) pore morphometry and mineralogical analysis. Qualitative and quantitative analyses of pore morphometry and surface morphology are conducted on shale samples subjected to temperatures ranging from ambient to 400 °C, using atomic force microscopy (AFM), low-pressure nitrogen (N 2 ) adsorption, and field emission scanning electron microscopy (FE-SEM). Parameters such as surface roughness, fractal dimension, porosity, microcracks, absorbed gas volume, specific surface area, and thermal damage-induced surface area show significant increases, indicating the formation of new macro-and microcracks and the development of pore network connections with pre-existing cracks. The pore size distribution (PSD) reveals a rise in the mesopore and macropore ranges. This research integrates thermogravimetric analysis (TGA), X-ray diffraction (XRD), Rock-Eval pyrolysis, and Fourier transform infrared spectroscopy (FTIR) to analyze the mineralogical and chemical properties of shale and assess the impact of temperature on these attributes. The results indicate that the shale samples are clay-rich and contain significant organic content. The continuous reduction in total organic carbon (TOC) concentration and the breakdown of organic matter above 200 °C can be attributed to hydrocarbon release during devolatilization. Additionally, the observed decline in P-wave velocity and contact angle from 100 to 400 °C suggests an increase in pore volume and the hydrophilic behavior of shale with temperature. The findings of this study provide fundamental insights into the role of thermal environments in enhancing gas recovery from shale formations. They can further improve gas recovery and CO 2 storage in shale reservoirs.
