The change of fracture conductivity caused by coal fines with different particle sizes displaced by single-phase water
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ORIGINAL PAPER
The change of fracture conductivity caused by coal fines with different particle sizes displaced by single-phase water Xiaoming Ni 1,2 & Quanzhong Li 2 & Zheng Zhao 1
&
Zedong Liu 3 & Wenlong Han 4
Received: 12 August 2020 / Accepted: 14 November 2020 # Saudi Society for Geosciences 2020
Abstract Ascertaining the change of fracture conductivity caused by coal fines with different particle sizes displaced by single-phase water can provide a theoretical basis for studying the migration characteristics of coal fines in coal fractures. A single-phase water displacement device was used to measure the effects of changes in parameters such as the displacement time, the mass concentration of coal fines in the output fluid and the cumulative water yield when the coal fines were driven by single-phase water with six different particle sizes. The changes of permeability and fracture conductivity of resin–coal core samples caused by mixtures of water and coal fines with different particle sizes were calculated and analyzed. The results demonstrated that, with the decrease of the particle size of coal fines, the required time for the fracture to be completely sealed in the resin–coal core sample and the mass concentration of coal fines in the output fluid are increasing; the grinding effect of coal fines with particle size < 80 mesh on the crack wall surface is obvious, and coal fines with particle size > 200 mesh can pass through the cracks, and the cumulative water yield is higher when these two kinds of coal fines are displaced. The fracture conductivity of resin–coal core sample caused by coal fines with different particle sizes displaced by single-phase water shows the same characteristics of “slowly rising–rapidly rising–reaching a peak and starting to decrease–reducing to zero”. In the displacement process of fines at < 80 mesh and > 200 mesh, the fracture conductivity increases rapidly in the early stage and decreases slowly in the later stage. In the displacement process of 80–100 mesh coal fines, the fracture conductivity increases slowly in the early stage and decreases rapidly in the later stage. Keywords Coal fines with different particle sizes . Conductivity . Permeability . Coal fine concentration . Fractures
Introduction Pulverised coal produced in the drainage of coalbed methane (CBM) from wells can block fracture channels in coal and influence the output of water, thus finally affecting gas production from CBM wells (Shi et al. 2018; Gao et al. 2018). Responsible Editor: Santanu Banerjee * Zheng Zhao [email protected] 1
School of Energy Science and Engineering, Henan Polytechnic University, 454000 Jiaozuo, China
2
Mining Engineering department, Shanxi Institute of Engineering and technology, 045000 Yangquan, China
3
SHCCIG Yubei Coal Industry Co., Ltd., Shaanxi 719000 Yulin, China
4
China University of Mining and Technology, Beijing 100083, China
Ascertaining the change of fracture conductivity caused by coal fines can provide a foundation for the study of its migratory character
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