Pore space characterization of Tamusu mudstone based on FIB/SEM

Abstract

This study focuses on characterizing the pore space in Tamusu mudstone, a preferred nuclear waste disposal host medium in China, using Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM). The investigation is conducted at the mesoscale, with a sample volume of 7.96 × 9.16 × 10.00 μm3 and voxel sizes of 5 × 5 × 10 nm3. The findings reveal that the pores in Tamusu mudstone primarily exist at the nanoscale, typically within its mineral matrix or at interfaces with non-porous minerals. At the FIB/SEM-imaged scale, the pore space in the Tamusu mudstone is mainly unconnected, with an analyzed porosity of approximately 3.5%. Pore characteristics within the specimen exhibit relative consistency within a box size of 6∼8 μm. Furthermore, the pore paths in Tamusu mudstone exhibit a preferred orientation within the bedding plane, suggesting anisotropy in pore space, possibly attributed to changes in pore path orientation and tortuosity.