高阶煤孔隙特征的低场核磁共振实验研究

Experimental study on pore characteristics of high rank coal by low field NMR

研究孔裂隙特征对煤层中甲烷的产出及运移具有重要的意义。为了得到高阶煤的孔裂隙特征信息,采用低场核磁共振仪对高阶煤样做低场核磁共振实验,测得煤样的T2图谱,进一步分析得到了煤样的核磁渗透率、核磁孔隙度、可动流体饱和度、束缚流体饱和度以及孔径分布等参数的实验结果,并测出煤样的工业分析参数。分析结果得出:原煤中孔隙体积与煤的挥发分含量呈正比的关系;高阶煤孔隙发育而裂隙不发育,并且在孔隙中微孔和小孔占有较大的比例而中孔和大孔占有较少的比例;煤样渗透率与煤样内小孔和大孔所占的比例成正比,与煤样内微孔所占的比例成反比等结论。

The study on the characteristics of pore and fracture is of great significance to the output and migration of methane in coal seam. In order to obtain the characteristic information of pore and fracture in high rank coal,the low field NMR experiments were carried out on the high rank coal samples by using the low field NMR apparatus,and the T2 maps of coal samples were obtained. Further analysis was made to get the experimental results of the parameters such as NMR permeability,NMR porosity,movable fluid saturation,irreducible fluid saturation and pore size distribution of coal samples. Besides,the industrial analysis parameters of coal samples were measured. The results showed that the pore volume of raw coal is proportional to the content of volatile matter in coal. The pores in high rank coal develops,while the fracture has no development.Among the pores,the micro pores and small pores occupy a large proportion,while the middle and large holes account for a small proportion. The permeability of coal sample is proportional to the proportion of small holes and large holes in the coal sample,and is inversely proportional to the proportion of micro pores in the coal sample.