Fractal Characterization on Three-dimensional Fracture Tortuosity in Coal based on CT Scanning

This paper proposed a method for the fractal characterization of the three-dimensional (3D) fracture tortuosity (DT3) in coal based on CT scanning experiment. The methodology was deduced in detail, and the values of DT3 of four coal samples were calculated by the rigorous derivation equation established by Feng and Yu. The values of DT3 by the proposed method fit the relation of DT3 versus the fractal dimension for 3D fracture number Df3, and the relation of DT3 versus the 3D fracture porosity, indicating the rationality and accuracy of the proposed method on estimation of the DT3. The results show that the proposed DT3 can comprehensively character the fractal characteristics of fractures tortuosity in 3D space. It is worth to further study for establishing an analytical fractal equation for fluid mass transfer in 3D fractures of porous media based on the DT3.