Pore structure of low-permeability coal and its deformation characteristics during the adsorption-desorption of CH4/N2
Pengfei Ji1
Haifei Lin2
Xiangguo Kong2
Shugang Li2
Biao Hu1
Pei Wang1
Di He1
Songrui Yang1
1.College of Safety Science and Engineering,School of Safety Science and Engineering,Xi'an University of Science and Technology,58,Yanta Mid.Rd.,Xi'an 710054,Shaanxi,China;Western Engineering Research Centre of Mine Gas Intelligent Drainage for Coal Industry,Xi'an 710054,Shaanxi,China2.College of Safety Science and Engineering,School of Safety Science and Engineering,Xi'an University of Science and Technology,58,Yanta Mid.Rd.,Xi'an 710054,Shaanxi,China;Key Laboratory of Western Mine Exploitation and Hazard Prevention Ministry of Education,Xi'an University of Science and Technology,Xi'an 710054,Shaanxi,China;Western Engineering Research Centre of Mine Gas Intelligent Drainage for Coal Industry,Xi'an 710054,Shaanxi,China
摘要：The pore structure of coal plays a key role in controlling the storage and migration of CH4/N2.The pore structure of coal is an important indicator to measure the gas extraction capability and the gas displacement effect of N2 injection.The deforma-tion characteristic of coal during adsorption-desorption of CH4/N2 is an important factor affecting CH4 pumpability and N2 injectability.The pore structure characteristics of low-permeability coal were obtained by fluid intrusion method and pho-toelectric radiation technology.The multistage and connectivity of coal pores were analyzed.Subsequently,a simultaneous test experiment of CH4/N2 adsorption-desorption and coal deformation was carried out.The deformation characteristics of coal were clarified and a coal strain model was constructed.Finally,the applicability of low-permeability coal to N2 injec-tion for CH4 displacement technology was investigated.The results show that the micropores and transition pores of coal samples are relatively developed.The pore morphology of coal is dominated by semi-open pores.The pore structure of coal is highly complex and heterogeneous.Transition pores,mesopores and macropores of coal have good connectivity,while micropores have poor connectivity.Under constant triaxial stress,the adsorption capacity of the coal for CH4 is greater than that for N2,and the deformation capacity of the coal for CH4 adsorption is greater than that for N2 adsorption.The axial strain,circumferential strain,and volumetric strain during the entire process of CH4 and N2 adsorption/desorption in the coal can be divided into three stages.Coal adsorption-desorption deformation has the characteristics of anisotropy and gas-difference.A strain model for the adsorption-desorption of CH4/N2 from coal was established by considering the expansion stress of adsorbed gas on the coal matrix,the compression stress of free gas on the coal matrix,and the expansion stress of free gas on micropore fractures.N2 has good injectability in low-permeability coal seams and has the dual functions of improving coal seam permeability and enhancing gas flow,which can significantly improve the effectiveness of low-permeability coal seam gas control and promote the efficient utilization of gas resources.
机标关键词：permeabilitycharacteristicsstructureadsorptioncoaldeformationdesorptionduring
论文发表日期：2023-08-28
在线出版日期：2025-08-15（本平台首次上网日期，不代表文献的发表时间）
页数：21( 107-127 )
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