The Study of Multi-Scale Specific Surface Area in Shale Rock with Fracture-Micropore-Nanopore

The specific surface area is an important parameter to characterize pore structure and adsorption properties, however, it difficult calculate accurately in shale rock due its multiscale structure. In this paper, the representative 3D gray images of a microfracture sample, micropore subsample nanopore were obtained with computed tomography (CT) scanning focused ion beam-scanning electron microscopy (FIB-SEM) scanning. multi-threshold segmentation algorithm improved maximum inter-class variance method was introduced construct platform multi-scale digital rock. Then, based on fracture, rocks, corresponding network models extracted obtain different-scale structures, respectively. Finally, at different scales, percentage, matrix percentage calculated It found that areas both microfractures micropores are small, their 2~3 orders magnitude smaller than nanopores, formation mainly contributed by nanopores. This paper provides effective has influence characteristics swelling properties matrix.