Texture-Dependent Thermal Properties of Sandstone Rocks Examined by Scanning Electron Microscopy for Thermal Energy Storage Applications

Abstract

Abstract Sedimentary rocks are widely used as geological reservoirs and as host rocks for geothermal energy systems. The thermal properties of sedimentary rocks, such as thermal conductivity, thermal diffusivity, and volumetric specific heat, play a critical role in their suitability for these applications. This study examined the thermal properties of 30 different sandstone rock samples using scanning electron microscopy (SEM) analysis. The SEM images of rock samples with different thermal properties were compared to analyze how textural properties influence thermal properties. Our results suggest that the thermal properties of sedimentary rocks are highly dependent on their texture. Specifically, we found that rocks with a higher degree of roughness, tend to exhibit lower thermal conductivity and thermal diffusivity. The presence of pores and cracks impacted the thermal properties of the sandstone rocks examined. The average surface roughness extracted from images showed a strong negative correlation with thermal conductivity and diffusivity (−0.59 and −0.6, respectively) obtained experimentally, while pore, cracks, and voids area have a less apparent negative correlation (−0.18 and −0.17) likely due to their complex effect on heat transfer. The size, shape, and distribution of voids affect heat transfer, with interconnected voids providing networks for heat flow, and smaller voids trapping heat more effectively. The texture of sedimentary rocks plays a critical role in determining their thermal properties. This knowledge can be used to optimize the understanding of the potential of sandstone reservoirs in applications, such as geothermal energy or thermal energy storage.