Experimental Study on the Influence of Effective Stress on the Adsorption–Desorption Behavior of Tectonically Deformed Coal Compared with Primary Undeformed Coal in Huainan Coalfield, China

Kun Zhang, Shuxun Sang (), Mengya Ma, Xiaozhi Zhou and Changjiang Liu
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Kun Zhang: State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science and Technology, Huainan 232001, China
Shuxun Sang: Jiangsu Key Laboratory of Coal-Based Greenhouse Gas Control and Utilization, Low Carbon Energy Institute, China University of Mining and Technology, Xuzhou 221008, China
Mengya Ma: School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China
Xiaozhi Zhou: Jiangsu Key Laboratory of Coal-Based Greenhouse Gas Control and Utilization, Low Carbon Energy Institute, China University of Mining and Technology, Xuzhou 221008, China
Changjiang Liu: School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China

Energies, 2022, vol. 15, issue 18, 1-19

Abstract: In order to explore the influences of effective stress change on gas adsorption–desorption behaviors, primary undeformed coal (PUC) and tectonically deformed coal (TDC) from the same coal seam were used for adsorption–desorption experiments under different effective stress conditions. Experimental results showed that gas adsorption and desorption behaviors were controlled by the coal core structure and the pore-fissure connectivity under effective stress. The coal matrixes and fissures were compressed together under effective stress to reduce connectivity, and it was difficult for gas to absorb and desorb as the stress increased in primary undeformed coal. The loose structure of tectonically deformed coal cores can help gas to fully contact with the coal matrix, resulting in higher adsorption gas volumes. The support of coal particles in tectonically deformed coal cores weakens the compression of intergranular pores when effective stress increases, which in this study manifested in the fact that while the volumetric strain of the coal matrix change rapidly under low effective stress, but the adsorbed gas volume did not decrease significantly. The reduction in effective stress induced the rapid elastic recovery of the coal matrix and the expansion of cracks, and increased desorption gas volumes. The stress reduction significantly increased the initial gas volume of the tectonically deformed coal, while promoting slow and continuous gas desorption in primary undeformed coal. Therefore, the promotion effect of the reservoir pressure reduction on gas desorption and coal connectivity enhancement can help to improve coalbed methane recovery in primary undeformed coal and tectonically deformed coal reservoirs.

Keywords: tectonically deformed coal; effective stress; adsorption–desorption behavior; strain response (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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