针对我国煤层气储层渗透性差、采收率低的难题,利用自制三轴渗透仪进行CO2在常规与超临界2种状态下的煤样增透试验.在宏观增透试验基础上进行微观成像试验,利用分形理论、图像处理、Matlab编程等数据处理方法,提取增透后煤样微观孔隙特征,计算表面孔隙率,得到盒维数分析图及孔隙分布分形维数,定量分析CO2作用后煤微观结构的发育程度.宏观增透试验结果表明:超临界CO2作用后,煤样渗透率较常规CO2作用后提高了十几倍,增透效果明显;微观成像结果显示,煤孔隙分布具有明显的分性特征,超临界CO2作用后,煤孔隙分布的分形维数及表面孔隙率均大于常规CO2作用后的煤样,孔隙分布定量计算结果与扫描电镜结果是一致的.微观试验结果说明超临界CO2有效促进了煤微观孔隙的发育.宏微观试验相结合,证实了超临界CO2对改善低渗透煤层的渗透性有良好的作用.%According to the poor permeability and low recovery rate of the coalbed methane reservoir in China,a self made triaxial permeameter was applied to the permeability experiment on CO2 under both conventional and supercritical conditions.Based on the experiment of the macro permeability improvement,a micro image experiment was conducted.The fractal theory,image processing,Matlab programming and other data processing method were applied to pick up the micro pore features of the coal samples after the permeability improved and to calculatc the surface porosity.The box dimension analysis pictnre and the pore distribution fractal dimension were obtained.The development degree of the coal micro structure after the CO2 functioned was quantitatively analyzed.The macro permeability improved experiment results showed that after the supercritical CO2 functioned,the permeability was increased by over ten times than the conventional CO2 and the permeability improved effect was obvious.The micro image results showed that the coal porosity distribution had obvious features.After the supercritical CO2 functioned,the fractal dimension of the coal pore distribution and the surface porosity were both higher than the coal samples after the conventional CO2 functioned.The pore distribution quantitative calculation results were the same to the results of the scanning electron microscope.The micro experiment results showed that the supercritical CO2 could effectively promote the development of the coal micro pore.The micro and macro experiments combined showed that the supercritical CO2 would have excellent role to improve the permeability of the low permeable seam.
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