自然科学版 英文版
自然科学版 英文版
自然科学版 英文版

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中南大学学报(英文版)

Journal of Central South University

Vol. 27    No. 6    June 2020

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Fracture evolution in coalbed methane reservoirs subjected to liquid nitrogen thermal shocking
YAN Hong(严红)1, 2, 3, TIAN Li-peng(田李鹏)1, 2, FENG Rui-min(冯锐敏)4, Hani MITRI3, CHEN Jun-zhi(陈俊智)1, 2, ZHANG Bo(张博)5

1. Key Laboratory of Deep Coal Resource Mining of Ministry of Education, Xuzhou 221116, China;
2. School of Mines, China University of Mining and Technology, Xuzhou 221116, China;
3. Department of Mining and Materials Engineering, McGill University, Montreal H3A 0E8, Canada;
4. Department of Chemical and Petroleum Engineering, University of Calgary, Calgary T2N 1N4, Canada;
5. Key Laboratory of Orogen and Crust Evolution, Peking University, Beijing 100871, China

Abstract:Thermal shocking effect occurs when the coalbed methane (CBM) reservoirs meet liquid nitrogen (LN2) of extremely low temperature. In this study, 3D via X-ray microcomputer tomography (μCT) and scanning electron microscope (SEM) are employed to visualize and quantify morphological evolution characteristics of fractures in coal after LN2 thermal shocking treatments. LN2 thermal shocking leads to a denser fracture network than its original state with coal porosity growth rate increasing up to 183.3%. The surface porosity of the μCT scanned layers inside the coal specimen is influenced by LN2 thermal shocking which rises from 18.76% to 215.11%, illustrating the deformation heterogeneity of coal after LN2 thermal shocking. The cracking effect of LN2 thermal shocking on the surface of low porosity is generally more effective than that of high surface porosity, indicating the applicability of LN2 thermal shocking on low-permeability CBM reservoir stimulation. The characteristics of SEM scanned coal matrix in the coal powder and the coal block after the LN2 thermal shocking presented a large amount of deep and shallow progressive scratch layers, fracture variation diversity (i.e. extension, propagation, connectivity, irregularity) on the surface of the coal block and these were the main reasons leading to the decrease of the uniaxial compressive strength of the coal specimen.

 

Key words: liquid nitrogen; thermal shocking; coalbed methane; micro fracture; 3D via X-ray microcomputed tomography

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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