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

Abstract

Sedimentary rocks are widely used as geological reservoirs and as host rocks for geother-mal energy systems. The thermal properties of sedimentary rocks, such as thermal conduc-tivity, thermal diffusivity, and volumetric specific heat, play a critical role in their suitabilityfor these applications. This study examined the thermal properties of 30 different sandstonerock samples using scanning electron microscopy (SEM) analysis. The SEM images of rocksamples with different thermal properties were compared to analyze how textural propertiesinfluence thermal properties. Our results suggest that the thermal properties of sedimentaryrocks are highly dependent on their texture. Specifically, we found that rocks with a higherdegree of roughness, tend to exhibit lower thermal conductivity and thermal diffusivity. Thepresence of pores and cracks impacted the thermal properties of the sandstone rocks exam-ined. The average surface roughness extracted from images showed a strong negative cor-relation with thermal conductivity and diffusivity (-0.59 and-0.6, respectively) obtainedexperimentally, while pore, cracks, and voids area have a less apparent negative correla-tion (-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 networksfor heatflow, and smaller voids trapping heat more effectively. The texture of sedimentaryrocks plays a critical role in determining their thermal properties. This knowledge can beused to optimize the understanding of the potential of sandstone reservoirs in applications,such as geothermal energy or thermal energy storage.