中高煤阶煤瓦斯吸附能力差异性的低场核磁共振实验研究

Research on the pore fracture characteristics and the adsorption ability difference of mid-high rank coal, has important strategic significance to improve the effect of low permeability coal seam through modification, CBM resource evaluation and development level, and to promote China's economic development and national energy security. This project intends to develop saturated water of coal samples by 1H NMR(nuclear magnetic resonance) experiment, testing hole fracture parameters by different rank coal sample, and study on the pore fracture characteristic and change rule of different metamorphic grade of coal; Test of different sizes mid-high rank coal samples under different saturated degree, adsorption pressure, different storage conditions, such as confining pressure and temperature of the gas adsorption capacity and adsorption isotherm, analyzing the influence characteristic of the metamorphic grade, coal body structure, porosity, industrial parameters and storage conditions on the absorption ability of the coal gas. With the study of the mid-high rank coal gas adsorption rule, it can be find out of main factors that controlled the adsorption capacity of mid-high rank coal. According to the experimental data and theoretical analysis, the gas adsorption desorption kinetics model about multiple pore fissure structure coal can be established to analyze and validate the mid-high rank coal seam gas adsorption characteristics and change rules.

研究中高煤阶煤体孔裂隙特征及瓦斯吸附能力差异性，对提高低渗煤层增透改性效果、煤层气资源评价与开发水平，推动我国经济发展和国家能源安全有着重要的战略意义。本项目拟通过开展饱和水下的煤样1H核磁共振实验，测试不同煤阶煤样孔裂隙参数，研究不同变质程度中、高煤阶煤的孔裂隙发育特征及变化规律；测试不同尺度的中-高煤阶煤样在不同饱水程度、不同吸附压力、不同围压及温度等储存条件下的瓦斯吸附量及吸附等温线，分析变质程度、孔隙特征、煤体结构、煤层显微组分、矿物成分及储存条件对煤的瓦斯吸附能力的影响，研究中-高煤阶煤的瓦斯吸附规律，查明中、高煤阶煤吸附能力差异性的主控因素；并依据实验数据及理论分析，建立多重孔裂隙结构煤体瓦斯吸附动力学模型，分析并验证中高煤阶煤层瓦斯吸附特性及变化规律。

研究中高煤阶煤体孔裂隙特征及瓦斯吸附能力差异性，对提高低渗煤层增透改性效果、煤层气资源评价与开发水平，推动我国经济发展和国家能源安全有着重要的战略意义。项目采集了山西王台铺矿、王庄矿、河南赵固一矿、赵固二矿、九里山矿、平顶山矿等典型矿区的中高阶煤为研究对象，在现有低场核磁共振实验系统基础上，通过改造外围压力加载、温度控制系统及气样计量装置，并结合IS-100气体等温解吸吸附仪，研究了不同变质程度中、高煤阶煤的孔裂隙发育特征，得到了围压、温度及冷浸加载等因素对中高阶煤孔隙结构的影响规律；分析了不同含水率、瓦斯压力、围压及温度等相关影响因素变化条件下瓦斯吸附量及吸附等温线，得到了影响中、高煤阶煤的瓦斯吸附规律及吸附能力差异的主控因素；建立了多重孔裂隙结构煤体瓦斯吸附动力学模型，分析并验证了中高煤阶煤层瓦斯吸附特性及变化规律。结果表明，中阶煤大多属于低渗透性煤，部分高阶煤样渗透性较好，渗透性越好的煤样可动流动饱和度越大；高阶煤核磁孔隙度均值在6.0%以上，从孔径分布看高阶煤小孔最为发育、微孔次之，高阶煤微孔比例越大，煤样的束缚流体饱和度增大，小孔比例的越大，可动流体饱和度增大。随着加载围压的增大，煤样孔隙体积减小，孔隙度逐渐降低，呈幂函数形式衰减，在加载压力小于4MPa的时煤样孔隙度衰减较快，当压力高于4MPa时，衰减量减小，并趋于平缓。液氮冷浸对中高阶煤样孔裂隙体积增大有较好的促进作用，冷浸时间30min左右时增透作用最为明显；液氮冷浸循环次数有利于促进煤层孔裂隙扩展，甚至可使煤层形成大的连通裂隙，提高瓦斯抽采效率。水分、围压均会使煤的吸附能力降低，瓦斯压力促进煤对瓦斯的吸附，随着变质程度增大，煤体吸附瓦斯能力增强。项目研究成果对进一步揭示中高阶煤的瓦斯赋存、吸附解吸规律及运移机理等具有重要的借鉴意义。