低渗透煤层孔隙结构的分形特征及力学性质研究

发布时间：2018-03-07 09:47

本文选题：低渗透煤层　切入点：孔隙结构　出处：《西安科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文针对新疆低渗透煤层水压致裂工程中存在的问题,在低温氮吸附和扫描电镜实验基础上,基于分形理论研究了低渗透煤层B1~B6煤的孔隙分形特征;根据微观孔隙扫描电镜实验,采用多点统计法构建了三维孔隙模型;主要研究了孔隙分维数与孔隙结构、微观孔隙结构特征及其物理力学性质之间的关系;可将研究结果应用于新疆低渗透煤层B1~B6水压致裂工程中,对于压裂液损失、瓦斯释放等科研课题具有重要的价值和意义。本文主要内容如下:(1)总结了孔隙分形的常用模型、量测方法的适用范围,分析得到孔隙分布维数值在1~2之间,孔隙体积、比表面积、表面分形维数值在2~3之间。(2)通过低温氮吸附试验及扫描电镜实验,测定B1~B6煤样的孔隙结构参数并分析了其结构特征;根据孔隙SEM实验,建立了孔隙度为1.86%、3.7%、7.4%、11.2%的圆柱三维重构模型;(3)采用孔隙分维数表达式计算了B1~B6煤样的孔隙体积、比表面积、表面、孔隙分布分维数值;分析了孔隙结构参数与分维数的关系,结果表明孔隙体积、比表面积、表面分维数能够较好地表征孔隙结构的非均质性和复杂程度;采用灰色关联度理论对各孔隙分维数的影响因素进行了分析。(4)实验测定了B1~B6煤样的孔隙度及渗透率,研究了煤体孔隙结构与宏观物性之间的关系,确定孔隙分布分维数可以用来计算孔隙介质的渗透率,综合分析了各煤样对气体的吸附能力;数值模拟了不同孔隙度下模型的单轴压缩过程,分析了模型破裂的应力分布情况,研究了孔隙度与抗压强度及分形维数的关系。
[Abstract]:Aiming at the problems existing in hydraulic fracturing engineering of low permeability coal seam in Xinjiang, based on the experiments of low temperature nitrogen adsorption and scanning electron microscope, the fractal characteristics of porosity of coal bed B1 / B6 in low permeability coal seam are studied based on fractal theory. According to the microscopic pore scanning electron microscope experiment, the three-dimensional pore model was constructed by multi-point statistics, and the relationship between pore fractal dimension and pore structure, micro-pore structure and its physical and mechanical properties was studied. The results can be applied to the hydraulic fracturing engineering of low permeability coal bed in Xinjiang, which has important value and significance for fracturing fluid loss, gas release, etc. The main contents of this paper are as follows: 1) summarize the commonly used pore fractal models. The scope of application of the measurement method, the analysis of the pore distribution dimension between 1 and 2, pore volume, specific surface area, surface fractal dimension values in the range of 2 ~ 3.) through low temperature nitrogen adsorption test and scanning electron microscope experiment, The pore structure parameters of B _ 1 / B _ 6 coal sample were measured and its structural characteristics were analyzed. Based on the pore SEM experiment, a cylindrical three-dimensional reconstruction model with porosity of 1.86 ~ 3.7g / 7.4% was established. The pore volume and specific surface area of B _ 1 / B _ 6 coal sample were calculated by using the expression of pore fractal dimension, and the pore volume and specific surface area of B _ (1) B _ (6) coal sample were calculated by using the expression of pore fractal dimension. The relationship between pore structure parameters and fractal dimension is analyzed. The results show that pore volume, specific surface area and surface fractal dimension can well characterize the heterogeneity and complexity of pore structure. The influence factors of pore fractal dimension were analyzed by grey correlation degree theory. The porosity and permeability of coal samples were measured by experiments, and the relationship between pore structure and macroscopic physical properties of coal was studied. The fractal dimension of pore distribution can be used to calculate the permeability of porous media, the adsorption ability of coal samples to gas is analyzed comprehensively, the uniaxial compression process of models with different porosity is numerically simulated, and the stress distribution of model rupture is analyzed. The relationship between porosity and compressive strength and fractal dimension is studied.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD712

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