Impact of connectivity characteristics on the permeability of three-dimensional fracture networks

Abstract

A program for rapid modelling, connectivity evaluation, and seepage simulation of a three-dimensional fracture network was developed based on COMSOL using MATLAB to accurately evaluate the seepage characteristics of a rock fracture network. A Monte Carlo algorithm was used to generate the fracture geometry parameters, and the Euler angle was introduced to establish a three-dimensional fracture model. The bounding box method was used to calculate the fracture network connectivity, and the Darcy module was used to simulate the seepage process. The fracture density, dip direction, dip angle, and length were selected as the experimental factors. Orthogonal numerical experiments were conducted to explore the primary factors controlling the connectivity, permeability, and permeability anisotropy of a three-dimensional fracture network. The results show that connectivity and permeability were primarily affected by the fracture density, length, and dip direction. Moreover, the permeability anisotropy was primarily affected by the fracture dip direction. The quantitative relationship among the connectivity index, permeability coefficient, and permeability anisotropy coefficient was determined based on numerical analysis. The results show that the permeability coefficients in various directions increased with the connectivity index and gradually stabilized. The permeability anisotropy weakened rapidly with increasing connectivity. It stabilized when the connectivity index exceeded 15. The research results have positive significance for revealing the seepage mechanism of complex three-dimensional fracture networks and for preventing and controlling water disasters in fractured rock masses.

Keywords

Three-dimensional fracture network / Connectivity / Permeability / Anisotropy / Numerical simulation

CRediT authorship contribution statement

Weijie Zhang: Writing -review & editing, Writing -original draft, Project administration, Investigation, Funding acquisition, Conceptualization. Yuanlin Bai: Writing -original draft, Visualization, Validation, Data curation. Chenghao Han: Writing -review & editing, Writing -original draft, Resources, Methodology, Formal analysis. Pengfei Wang: Visualization, Data curation, Conceptualization. Danyang Zhang: Supervision, Formal analysis. Jicheng Zhang: Writing -original draft, Software.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant No. 52304239) and Shandong Provincial Natural Science Foundation (Grant No. ZR2023QD026 and Grant No. ZR2021MD016). The authors thank the anonymous reviewers for their helpful comments and suggestions.

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