A new method for evaluating the pore structure complexity of digital rocks based on the relative value of fractal dimension. (July 2022) - Li, Xiaobin
Abstract: Natural porous media have extremely complex pore structures, which greatly affect the material properties. However, it remains a challenge to characterize the pore structure complexity accurately. Fractal geometry is one of the effective tools for this task, which allows for quantitative analysis. In this paper, a new method is proposed for evaluating the pore structure complexity of digital rock models by using the relative value of box-counting fractal dimension. The proposed method transforms the judgment criterion from the comparison of the absolute value to the comparison of the relative value in the fractal dimension by establishing an intermediate fractal reference model. Firstly, the digital core model with progressively changing porosity and pore structure is reconstructed using a numerical modeling means, and three kinds of fractal dimensions of the model are estimated by the box-counting algorithm. Meanwhile, the relationship curve between fractal dimension and porosity is employed as the fractal reference model. Then, the fractal dimensions of the study samples and the reference model are mapped to the same coordinate system. By comparing their relative positional relationship, the pore structure complexity of samples is effectively evaluated and classified. Finally, CT samples are taken as a concrete example to illustrate the application of the proposed method. The correctness and availability of this method are verified through the comprehensive analysis of digital images, pore structure, porosity, and permeability. The constructed method provides a reference for a more accurate evaluation and classification of the complexity of pore space in digital rock physics. Highlights: A new method for evaluating the pore structure complexity of digital rocks is proposed. The degree and law of the influence of porosity and pore structure on the fractal dimension are analyzed. The interface fractal dimension is an effective parameter in evaluating the pore structure complexity.