Theoretical study on nonlinear seepage mechanism in fractal dendritic fracture network of low permeability coal with water injection

• Published in: Journal of non-Newtonian fluid mechanics Vol. 333; p. 105327
• Main Authors: Liu, Zhen, Dong, Shuai, Yang, He, Yang, Wenzhi, Zhu, Muyao
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2024
• Subjects: Coal seam water injection; Dust reduction; Fractal theory; Fractal tree-like bifurcation network; Nonlinear seepage; Threshold pressure gradient; Fractal tree-like bifurcation network; Coal seam water injection; Fractal theory; Dust reduction; Threshold pressure gradient; Nonlinear seepage
• ISSN: 0377-0257
• DOI: 10.1016/j.jnnfm.2024.105327

•The fractal tree bifurcation network model is constructed.•The relationship between the TPG and the nonlinear permeability is established.•The main controlling factors affecting the nonlinear seepage process are clarified. Coal seam water injection technology is adopted by many mines as an effective means of dust reduction in coal mines. There is a threshold pressure gradient phenomenon in the process of water injection in low permeability coal seam, which makes the flow of pressure water in the fracture structure of coal body present nonlinear seepage characteristics. To reveal the theoretical relationship between the structural parameters of coal and the nonlinear seepage characteristics, firstly, the Bingham fluid constitutive equation is used to describe the non-Newtonian behavior in low-permeability coal. Combined with the fractal tree-like bifurcation fracture network model, a mathematical analytical model of threshold pressure gradient is established. Secondly, the model was verified by high-pressure water invasion and radial seepage experiments, and the sensitivity of the model was analyzed. The results show that the error between the theoretical calculation value and the experimental measurement value is between 8.65 % and 42.4 %, which verifies the validity of the model. The above research results can provide a theoretical basis for improving the water injection effect of low permeability coal seam.