A comprehensive study on pore topology of Lower Indian Gondwana shale using pore-scale 2D scan electron micrographs

The characterization of the microstructure of low permeability rock like shale is important for the assessment of its hydrocarbon potential and the designing of a hydraulic fracking program. The present study attempts to characterize the pore microstructure of the Indian Gondwana shale. High-resolution scan electron microscopy (SEM) images have been used to capture the pores and matrix skeleton of shale samples collected from different boreholes. The topological complexity of the pore is quantified by estimating the 2D fractal dimension (FD) using the box-counting technique. The FD varies from 1.89 to 1.98, suggesting that the pore topology is highly complex. The microstructure of Gondwana shale has been segmented using the watershed image segmentation technique. The throats are precisely located in between the pores. The modelled porosity varies from 0.7 to 5.1%. The average pore diameter ranges from 62 nm to 2.5 mu m, and the average throat size varies from 3 to 635 nm. The coordination number for Gondwana shale has been estimated for the very first time, suggesting a well-developed pore network. The modelled parameters are compared with the laboratory-measured data and found to be in good agreement.