Investigation of the Flow Properties of CBM Based on Stochastic Fracture Network Modeling

• Published in: Materials Vol. 12; no. 15; p. 2387
• Main Authors: Zhang, Bo, Li, Yong, Fantuzzi, Nicholas, Zhao, Yuan, Liu, Yan-Bao, Peng, Bo, Chen, Jie
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26.07.2019; MDPI
• Subjects: Coal; Coalbed methane; Domains; dual-porosity and dual-permeability media; Finite element method; fracture geometric parameters; Fractures; Gas flow; Geology; Households; Investigations; Monte Carlo method; Natural gas prices; Permeability; Porous media; Researchers; Seepage; Simulation; stochastic fracture network; Theory; Transport properties; United States > US; China; coalbed methane; dual-porosity and dual-permeability media; Monte Carlo method; stochastic fracture network; finite element method; fracture geometric parameters
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma12152387

Coal contains a large number of fractures, whose characteristics are difficult to describe in detail, while their spatial distribution patterns may follow some macroscopic statistical laws. In this paper, several fracture geometric parameters (FGPs) were used to describe a fracture, and the coal seam was represented by a two-dimensional stochastic fracture network (SFN) which was generated and processed through a series of methods in MATLAB. Then, the processed SFN image was able to be imported into COMSOL Multiphysics and converted to a computational domain through the image function. In this way, the influences of different FGPs and their distribution patterns on the permeability of the coal seam were studied, and a finite element model to investigate gas flow properties in the coal seam was carried out. The results show that the permeability of the coal seam increased with the rising of fracture density, length, aperture, and with the decrease of the angle between the fracture orientation and the gas pressure gradient. It has also been found that large-sized fractures have a more significant contribution to coal reservoir permeability. Additionally, a numerical simulation of CBM extraction was carried out to show the potential of the proposed approach in the application of tackling practical engineering problems. According to the results, not only the connectivity of fractures but also variations of gas pressure and velocity can be displayed explicitly, which is consistent well with the actual situation.