期刊
FUEL
卷 332, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.fuel.2022.126178
关键词
Ultrasound stimulation in coal; Multi -scale pore; fracture; Enhanced CBM production; Gas sorption; CT reconstruction
This study quantitatively characterizes the damage of multi-scale pores and fractures in coal induced by power ultrasonic stimulation using gas sorption and CT image-based 3D reconstruction. The results show that ultrasound treatment can significantly improve the multi-scale structure of pores and fractures in coal, thereby enhancing coalbed methane production.
Ultrasonic physical stimulation is a promising approach of coalbed methane enhancement recovery. This study is devoted to quantitatively characterizing the damage of multi-scale pores and fractures in coal induced by power ultrasonic stimulation using the gas sorption and CT image-based 3D reconstruction. The gas sorption tests show that the ultrasound treatment (3 kW, 25 Hz, 2 h) increased the maximum N2 sorption quantities (by 75.44 %- 111.8 %), the average pore diameter by 12.15 %-20.81 %, and the pore surface area (by 30.99 %-56.02 %) in the tested coal. The mesopore volumes increase by 16.46 %-79.15 %, and the macropore volumes increase by 2.38 %-14.82 % after the ultrasound treatment, which reveals that the ultrasound implemented in this study is more efficient for structure modification in pore with scale of 2-50 nm. The CT image-based characterization shows that fracture volume increased by 8.11 %-11.81 %, and the fracture surface increased by 13.92 % -21.63 %, and the average equivalent diameter increased by 6.76 %-10.74 %, and the porosity increased by 8.1 %- 11.86 % for the tested coal subjected to ultrasound treatment. Based on the pore network model, the fracture connectivity was quantitatively analyzed, and it shows that pore throat number increased by 17.62 %-45.76 %, and the average equal radius of pore throat increased by 3.86 %-4.83 %. The proportion of connected fractures in the total fractures was increased by a maximum of 12.78 % in the tested coal after ultrasound treatment. The results show that ultrasound stimulation can significantly improve the multi-scale structure of pores and frac-tures of coal, which will promote gas desorption, diffusive and Darcian flow flux in coal seam, and enhance coalbed methane production.
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