保德煤矿复杂结构煤层物性及孔隙渗流特征研究

    The study on physical properties and pore seepage characteristics of complex-structured coal seam in Baode Coal Mine

    • 摘要: 针对保德煤矿复杂结构煤层瓦斯抽采难题,本研究通过现场观测与采样,结合室内实验分析,采用煤岩手标本宏观特征描述、工业分析、显微组分分析、XRD测试,以及低温液氮吸附、低场核磁共振和工业CT扫描等多种实验手段,全面表征了煤岩的物理性质和流体渗流特性。研究结果表明,8号煤层具有典型的复杂结构特征,通常夹矸层数为5~8层,最多可达11层。煤体结构以原生结构煤为主,构造裂隙和内生裂隙发育程度较低。显微组分分析显示,镜质组平均含量为28.88%,黏土矿物平均含量为24.53%,其中,高岭石为主要黏土矿物组分。孔隙结构特征方面,煤样以小孔为主,中孔次之,微孔占比相对较少,孔径主要分布在0.01~0.16 μm区间,其中,0.025~0.10 μm区间占比最大;煤岩孔隙度平均值为5.75%;煤岩中连通型孔-裂隙发育程度较低,导致煤层渗透性较差,流体在煤岩中的流动能力较弱。鉴于此,建议在8号煤层中实施大规模水力压裂技术,对煤层和致密的多夹矸层进行破碎性改造,增加煤层的渗透性,加速全层瓦斯的解吸和渗流速度,提高煤层瓦斯抽采效率。研究成果对于解决保德煤矿瓦斯抽采难题提供了实验数据和理论支撑。

       

      Abstract: In response to the challenges of gas drainage in the complex-structured coal seams of the Bode Coal Mine, this study conducts field observations and sampling, combined with laboratory experiments, and utilizes multiple experimental methods such as macroscopic characterization of coal-rock hand specimens, industrial analysis, microscopic component analysis, XRD testing, low-temperature liquid nitrogen adsorption, low-field nuclear magnetic resonance (NMR), and industrial CT scanning. These methods are employed to comprehensively characterize the physical properties and fluid flow characteristics of the coal-rock. The results indicates that the No.8 coal seam exhibits typical complex structural features, with an average of 5-8 intercalated shale layers, and up to 11 layers in some areas. The coal structure is primarily composed of primary structural coal, with relatively low development of tectonic fractures and intrinsic fractures. Microscopic component analysis reveals that the average content of vitrinite is 28.88%, and the average content of clay minerals is 24.53%, with kaolinite being the predominant clay mineral component. In terms of pore structure characteristics, the coal samples are dominated by small pores, followed by medium pores, with fewer micro-pores, and pore sizes are primarily distributed in the range of 0.01-0.6 μm, with the largest proportion in the 0.025-0.10 μm interval. The average porosity of the coal-rock is 5.75%. The connectivity of pores and fractures in the coal-rock is relatively poor, resulting in low permeability of the coal seam and weak fluid flow capacity. Based on these findings, it is recommended to implement large-scale hydraulic fracturing technology in the No.8 coal seam to enhance fragmentation of the coal seam and dense intercalated shale layers, thereby increasing permeability, accelerating gas desorption and seepage, and improving gas drainage efficiency. The research findings provide experimental data and theoretical support for addressing gas drainage challenges at the Bode Coal Mine.

       

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