基于micro-CT扫描的孔裂隙结构表征及渗流模拟

    Characterization of pore-fracture structure and seepage simulation based on micro-CT scanning

    • 摘要: 以羊场湾不粘煤为研究对象,基于micro-CT扫描实验和Avizo处理软件,对煤中孔裂隙、矿物质以及煤基质进行精确提取与分割,并通过三维重构技术,得到了连通孔裂隙模型;在此基础上,进一步建立了具有孔裂隙形态学拓扑结构的等效孔隙网络模型,统计分析了煤中孔喉结构参数,包括孔隙半径、孔隙体积、喉道半径、喉道长度以及配位数;基于孔隙尺度的渗流模拟,实现了孔裂隙空间单相水的可视化渗流过程,并计算了3个方向的绝对渗透率。研究结果表明:羊场湾不粘煤中以片状孔隙群和大尺度互相垂直的裂隙发育为主,平均孔隙半径和喉道半径分别为106、27.79 μm,平均配位数为3.45;在单相水渗流过程中,孔裂隙空间内的渗流速度明显高于流入流出端,3个方向的渗透率表现出明显的各向异性,其中y方向的绝对渗透率数值最大,x方向的渗透率最小。

       

      Abstract: Taking the non-stick coal from Yangchangwan Coal Mine as the research object, based on the micro-CT scanning experiment and Avizo processing software, the pore-fracture, minerals and coal matrix of the coal are accurately extracted and segmented. Through the three-dimensional reconstruction technology, the connected pores and fracture models are obtained. On this basis, an equivalent pore network model(PNM)with the morphological topological structure of pores and fractures was further established, and the pore-throat structure parameters in the coal were statistically analyzed, including pore radius, pore volume, throat radius, throat length, and coordination number. Based on the pore-scale seepage simulation, the visualization seepage of single-phase water in the pore-fracture space was realized, and the absolute permeability in three directions was calculated. The results show that the Yangchangwan non-stick coal is dominated by flaky pore clusters and large-scale vertical fractures. The average pore radius and throat radius is 106 μm and 27.79 μm, respectively, and the average coordination number is 3.45. In the process of single-phase water seepage, the seepage velocity in the pore-fracture space is higher than that of the outlet and inlet, and the permeability in the three directions shows obvious anisotropy. Among them, the absolute permeability value in the y direction is the largest, and in the x direction is the smallest.

       

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