液态CO2溶浸煤体孔裂隙演化特征的实验研究

Experimental study on variations of pore-fissure in coal-rock leached by liquid CO

为研究煤层在液态CO2溶浸作用下煤体孔裂隙的演化特征,设计液态CO2溶浸实验系统,选取3种不同煤质的煤样,干燥后对其进行液态CO2溶浸实验,在一定压力温度下溶浸30 min,通过扫描电镜和核磁共振测试方法对溶浸前后的煤样进行观测,基于分形理论和T2谱分布方法定量地对煤体孔裂隙进行分析,分形理论分析得出:3种煤样分形维数均为增大趋势,且直线拟合系数均大于0.967;T2谱分布分析得出经液态CO2溶浸后,吸附孔T2谱面积增长率分别为15.9%,38.1%,29.1%;渗流孔增长率分别为11.9%,55.7%,61.1%;全孔T2谱面积分别增加24.7%,54.6%,56.1%.结合渗透率理论模型计算1/3焦煤、气煤和褐煤渗透率分别提高了5.56%,13.79%和14.80%.液态CO2溶浸可有效促进煤体裂隙发育,有利于提高煤体的渗透性。

In order to study the evolution characteristics of coal pore-fissure under the treatment of liquid CO2(L-CO2),the experimental system of liquid CO2leaching was designed.Three kinds of coal samples with different coal quality were selected,after drying the experiment was carried out at a certain pressure and temperature for 30 min treatment.The coal samples before and after liquid CO2 treatment were observed by means of scanning electron microscope and nuclear magnetic resonance.According to the analysis of fractal theory and T2 spectrum,the paper quantitatively analyzed the pore-fissure of coal body.The fractal theory analysis shows an increasing trend in the fractal dimension of three kinds of coal samples,and the linear fitting coefficient is greater than 0.967.T2 spectrum analysis indicates that the area growth rate of adsorption pore T2 spectrum are 15.9%,38.1%and 29.1%,and the seepage pore growth rate are 11.9%,55.7%and 61.1%respectively.The total pore T2 spectrum area grows by 24.7%,54.6%and 56.1%respectively.Calculation based on permeability theory model obtains the permeability of 1/3 coking coal,gas coal and lignite rise by 5.56%,13.79%and 14.80%separately.The relationship between permeability increment and coal rank after leaching indicates that the lignite is superior to gas coal,and the gas coal is superior to 1/3 coking coal,which is consistent with the analysis of effective porosity.The results of experiment show that the liquid CO2 leaching can effectively promote the development of coal fractures,possible to improve the permeability of coal.