【作者】 郑贵强；

【导师】 唐书恒； 潘哲军；

【作者基本信息】 中国地质大学(北京) ， 矿产普查与勘探， 2012， 博士

【摘要】 为对高、中、低煤阶的不同煤样进行实验和数值模拟研究，分别在沁水盆地晋城矿区和长治矿区，以及新疆准噶尔盆地铁厂沟煤矿进行采样。重点研究不同煤阶煤的吸附、扩散和渗流特征及变化规律，以及在ECBM过程中渗透率的动态变化和预测。本次研究共使用四种气体，分别为：H_e，N₂，CH₄和CO₂，对于每种气体，测试条件为三到四个不同孔隙压力（一般为1MPa，2.5MPa，4MPa和6MPa）和五个不同有效应力（1MPa，2MPa，3MPa，4MPa和5MPa）及三个不同温度（35℃，40℃和45℃）。测定煤样的吸附量并绘制等温吸附曲线，测定扩散率随时间的变化并绘制其变化曲线，测定其渗透率并绘制渗透率变化曲线，同时进行膨胀量计算和压汞及低温液氮实验，分析实验现象与煤岩特征及孔径分布的定性或定量关系。对三组煤样的吸附性能研究发现，同一煤样对不同气体的吸附能力不同。不同煤阶的煤样对同一气体的吸附能力也不同，基本上呈现随煤阶的增加吸附能力也相应增加的趋势。通过扩散实验和压汞及低温液氮实验研究发现，高煤阶煤以微孔为主，扩散和吸附所需的平衡时间长。中煤阶煤以中孔为主，而低煤阶煤样以中孔为主，也含有部分大孔。数值模拟的结果显示：本次实验所研究的煤样，均可使用双孔模型进行模拟研究。对渗透率的实验研究发现，有效应力和孔隙压力对渗透率有重要的影响，使用的测试气体的类型对于渗透率也有重要影响。割理的压缩系数与渗透率数值关系密切，通过对其研究发现，割理的压缩系数与有效应力、孔隙压力和测试气体的类型有关。随着孔隙压力的增加，割理的压缩系数先降低然后又缓慢的增加。通过膨胀量计算和绘制动态渗透率预测曲线图发现，在ECBM过程中，渗透率随CO₂的摩尔分数的变化，呈现一定的变化规律：先急剧降低，后缓慢的降低，在保持某一固定的数值后，再缓慢的升高。动态渗透率预测曲线对于注气提高煤层气的采收率的过程有重要的指导意义。更多还原

【Abstract】 Three typical different-ranked Chinese coal samples, JCC-1, CZ-1and TCG-1takenfrom Jinchen area，Changzhi area of Qinshui Basin and Junggar Basin of Xinjiang area,respectively, were used to study the adsorption, diffusivity and permeability and theirchanging laws. Moreover, the dynamic permeability change and the prediction ofpermeability during ECBM process were also studied.In this study, four types of gases, H_e，N₂，CH₄and CO₂, were used to do theexperiment. For each type of gas, the adsorption amount, diffusivity and permeability weremeasured under the condition of three or four different pore pressure steps（Generally,1MPa，2.5MPa，4MPa and6MPa）and five different effective stres（s1MPa，2MPa，3MPa，4MPa and5MPa）and three different temperatures（35℃，40℃and45℃）. The adsorptionamount was measured and the adsorption isothermals were obtained. The diffusivity andthe changing curves with time were drawn; and the permeability was tested and its relativecurves were also plotted in this study. Meanwhile, by means of swelling calculation and theexperiment of mercury injection and low temperature liquid nitrogen adsorption experiment,the analysis about the experiment phenomenon and its relationship with coal rank and porestructure distribution was performed.Through studying the adsorption characteristics, the following conclusions can bemade: for the same coal sample, the adsorptive capacity for different gas is different.Meanwhile, for the same gas, the adsorptive capacity for different ranked coal is alsodifferent. The capacity increases with the increasing of coal rank from low to high.Studying on the diffusivity and using experiment of mercury injection experiment and lowtemperature liquid nitrogen experiment, it is found that micropore makes up the majority ofthe pore space for the high rank coal. While for the middle-ranked coal, mesopore is themajority; for the low-ranked coal, mesopore is still the majority but macropore is also animportant part of the structure. According to the modeling result, bidisperse model is bestdiscripbing diffusion for all the three different ranked Chinese coal.Studying on the permeability for the three coals found that effective stress and porepressure both have significant effect on permeability. Moreover, the gas type also hasimportant effect on permeability. Permeability and cleat compressibility have very closerelationship. Cleat compressibility is related to effective stress, pore pressure and gas type.Combined with result of swelling calculation and depicting the dynamic permeability prediction curve, it is found that during the ECBM process, permeability presents certainrules with the changing of CO₂molar fraction: it first declines dramatically, then declinesslowly, and then keeps a certain value, finally rises slowly. The dynamic permeabilityprediction curves have significant guidance to the coalbed methane production duringECBM process.更多还原