In-situ observation and modeling approach to evolution of pore-fracture structure in coal

• Published in: International journal of mining science and technology Vol. 33; no. 3; pp. 265 - 274
• Main Authors: Zhou, Hongwei, Liu, Zelin, Zhao, Jiawei, Chen, Bocen, Li, Xiangnan, Zhong, Jiangcheng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2023; Elsevier
• Subjects: Compressibility; Fractional derivative; Nuclear magnetic resonance imaging; Pore-fracture structure; Stress sensitivity; Stress sensitivity; Compressibility; Pore-fracture structure; Nuclear magnetic resonance imaging; Fractional derivative
• ISSN: 2095-2686
• DOI: 10.1016/j.ijmst.2023.01.001

The characterisation of the pore-fracture structure (PFS) and its evolution in coal during mining are essential for preventing gas outbursts and improving gas extraction efficiency. In this study, the evolution of the PFS in coal samples under the condition of mining stress was directly captured in situ by combination of the mechanical testing system with high-precision visualisation nuclear magnetic resonance equipment. A fractional derivative model was established to describe the relationship between stress and porosity based on experimental results of the PFS under different stress states. The results showed that with an increase in the deviatoric stress, the adsorption pore content increases rapidly initially and then increases slowly or remains unchanged; the seepage pore and fracture (SPF) content decreases initially and then increases. The SPF compressibility coefficient decreases with an increase in the deviatoric stress. The fractional derivative model can accurately describe the stress sensitivity of the SPFs at the pre-peak stage, thus providing a new approach for accurately characterising the seepage characteristics of coal reservoirs.