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基于压汞法对黔西青龙矿构造煤孔隙结构特征的研究

Study on pore structure characteristics of tectonic coal in Qinglong Coal Mine in Western Guizhou based on mercury injection

  • 摘要: 煤与瓦斯突出地区基本都有构造煤的发育,构造煤的孔隙结构是瓦斯吸附、扩散和渗流的重要影响因素。为了研究不同类型构造煤孔隙的发育特征,以青龙煤矿构造煤为研究对象,基于压汞法表征其孔隙结构特征,并结合分形维数对孔隙进行定量表征,详细分析了青龙煤矿构造煤孔隙结构的复杂特征。结果表明:①构造煤类型主要有碎裂煤、片状煤、碎斑煤、鳞片煤和揉皱煤,孔隙发育微孔和大孔,不同类型的构造煤在显微尺度上表现出了明显的差异性,脆性变形与韧性变形之间特征显著;②碎裂煤微孔和大孔孔隙形态以半封闭孔和开放孔为主;片状煤微孔和大孔孔隙均发育半封闭孔和开放孔;碎斑煤微孔和过渡孔孔隙形态以半封闭孔为主;鳞片煤微孔形态以半封闭孔为主,大孔孔隙形态以开放孔和细瓶颈孔为主;揉皱煤中微孔和大孔孔隙形态均以半封闭孔和细瓶颈孔为主;③当进汞压力处在低压段(0.01~0.69 MPa)时,在脆性变形阶段,分维值变化规律为碎斑煤>片状煤>碎裂煤,韧性变形阶段,分维值变化规律为揉皱煤>鳞片煤;当进汞压力处在高压段(0.31~8.84 MPa)时,脆性变形阶段碎裂煤分维值最大,韧性变形阶段揉皱煤的分维值高于鳞片煤。构造煤在高压段的分维值整体比低压段高,高压段下的煤体变形程度更复杂,渗流孔复杂程度高,孔隙结构具有较强的非均质性。

     

    Abstract: Tectonic coal is basically developed in coal and gas outburst areas. The pore structure of tectonic coal is an important factor influencing gas adsorption, diffusion and seepage. In order to study the development characteristics of different types of tectonic coal pores, taking the collected coal-rocks from the Qinglong Coal Mine as the research object, based on the mercury intrusion experiment to characterize the pore structure characteristics and combined with the fractal dimension to quantitatively characterize the pores, and analyze the complex characteristics of the pore structure of the Qinglong Coal Mine. The results shows: ①Tectonic coal types mainly include cataclastic structural coal, schistose structural coal, mortar structural coal, scaly structural coal and wrinkle structural coal, and with micropores and macropores developed in coals; the difference between brittle deformation and ductile deformation is significant. ②The micropores and macropores of cataclastic structural coal are dominated by semi-closed pores and open pores; the micropores and macropores of schistose structural coal have semi-closed pores and open pores; the micropores and transition pores of mortar structural coal are mainly semi-closed pores; the micropore morphology of scaly structural coal are mainly semi-closed pores, and the macropores pore morphology are mainly open pores and narrow-necked pores; the micropores and macropores in wrinkle structural coal are dominated by semi-closed pores and narrow bottle pores; ③When the mercury inlet pressure is in the low pressure section (0.01-0.69 MPa), in the stage of brittle deformation, the fractal dimension value changes; while in the brittle deformation stage, the fractal dimension changes law as mortar structural coal>schistose structural coal>cataclastic structural coal; while in the ductile deformation stage, the fractal dimension change law is wrinkle structural coal>scaly structural coal; when the mercury injection pressure is in the high pressure section (0.31-8.84 MPa), and the fractal dimension value of the crumpled coal in the ductile deformation stage is higher than that of the scaly coal. The fractal dimension of tectonic coal in the high-pressure section is generally higher than that in the low-pressure section, the degree of coal deformation under the high-pressure section is more complex, the seepage pores are more complex, and the pore structure has strong heterogeneity. The research results are of great significance for evaluating the recoverability of coalbed methane and revealing the risk of coal and gas outbursts.

     

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