Shale Microstructure Extraction Based on Micro-CT and Permeability Inversion

A shale rock sample was scanned by micro-CT technology, tomographic images of the rock sample were obtained, and the three-dimensional structure was reconstructed by Avizo software. The uneven three-dimensional space structure inside the rock sample was composed of fractures, branch fractures and pores. Sample 1 has a porosity of 6–8% due to fractures, the porosity of sample 2 is between 4 and 5%. A self-written MATLAB program extracts the pore and fracture structure data from the scanned image and imports the data into COMSOL software to calculate the permeability of the rock sample by inversion. The macroscopic permeability of a rock sample is a comprehensive manifestation of the microelements of the rock sample. The greater the porosity of a rock sample, the greater its corresponding permeability. During the percolation process, medium exchange occurs frequently between the matrix and the pores and cracks. The permeability increases with increasing pore pressure and decreases with increasing confining pressure.