张连昆,王月芳,张晓雨,等. 循环微波改性对无烟煤渗透率的影响[J]. 煤矿安全,2024,55(6):30−39. doi: 10.13347/j.cnki.mkaq.20231225
    引用本文: 张连昆,王月芳,张晓雨,等. 循环微波改性对无烟煤渗透率的影响[J]. 煤矿安全,2024,55(6):30−39. doi: 10.13347/j.cnki.mkaq.20231225
    ZHANG Liankun, WANG Yuefang, ZHANG Xiaoyu, et al. Effect on permeability of anthracite subjected to cyclical microwave modification[J]. Safety in Coal Mines, 2024, 55(6): 30−39. doi: 10.13347/j.cnki.mkaq.20231225
    Citation: ZHANG Liankun, WANG Yuefang, ZHANG Xiaoyu, et al. Effect on permeability of anthracite subjected to cyclical microwave modification[J]. Safety in Coal Mines, 2024, 55(6): 30−39. doi: 10.13347/j.cnki.mkaq.20231225

    循环微波改性对无烟煤渗透率的影响

    Effect on permeability of anthracite subjected to cyclical microwave modification

    • 摘要: 微波增透是提高煤层气抽采效率的潜在可行性储层改造技术之一。采用微波炉对沁水盆地晋城地区15号无烟煤样进行3次循环微波改性实验,通过自主研发的固气耦合渗流平台测试了自然煤样及每次改性后煤样的气体渗透率;经显微CT扫描及图像处理技术表征煤样的孔隙属性,并基于分形理论探讨了改性前后煤样孔裂隙网络的复杂程度。研究结果表明:无烟煤样气体渗透率循环次数增加而增大,3次循环后增加了8.8倍,微波辐射引起无烟煤孔裂隙的扩展和连通是气体渗透率增大的根本原因;3次循环后煤样总孔隙率由3.48%增大至6.19%,其中,连通孔裂隙占比由27.0%升高至77.4%,而孤立孔占比由73.0%降低至22.6%;连通孔裂隙的孔数量、孔体积、孔表面积和喉道数量、喉道表面积及孔喉配位数随循环次数的增加而增大,而最大喉道长度有所减小,证实了微波改性对孔隙的“扩展、连通”作用;煤样3处典型截面孔裂隙二维分形维数都随循环次数增加而增大,3次循环后分别由1.25、1.16、1.09增大至1.46、1.54、1.37;循环微波改性会使煤样内孔裂隙网络(气体渗流通道)发育得更为复杂。

       

      Abstract: Increasing the permeability via microwaves is one of the potential feasible reservoir modification technologies to improve the efficiency of coalbed methane extraction. The microwave oven is used to conduct 3 cycles of microwave modification experiments on No.15 anthracite in Jincheng area of Qinshui Basin. The gas permeability of anthracite samples before and after each modification is tested using a self-built solid-gas coupling seepage platform. The pore properties are tested by micro CT scanning combined with image processing technology. In addition, the complexity index of pore-fracture network of coal samples before and after modification is discussed based on fractal theory. The results show that the gas permeability of anthracite sample increases with the increase of cycle times, and increases by 8.8 times after 3 cycles. The expansion and connection of pores/fractures in anthracite caused by microwave radiation is the fundamental reason for the increase of gas permeability. After three cycles, the total porosity of anthracite samples increases from 3.48% to 6.19%, in which the proportion of connected pores and fractures increases from 27.0% to 77.4%, and the proportion of isolated pores decreases from 73.0% to 22.6%. The pore number, pore volume, pore surface area and throat number, throat surface area and pore-throat coordination number of connected pores/fractures increase with the increase of cycle times, while the maximum throat length decreases, which confirms the “expansion and connection” effect of microwave modification on pores/fractures in anthracite. The two-dimensional fractal dimensions of pores/fractures of three typical sections in anthracite samples increase with the increase of cycle times, and increase from 1.25, 1.16, and 1.09 to 1.46, 1.54, and 1.37 respectively after three cycles, which clarifies that the cyclical microwave modification will make the pore-fracture network (gas seepage channel) in coal samples more complex.

       

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