Characteristics of macro-nanopores in anthracite coal based on mercury injection,nitrogen adsorption and FE-SEM

The structure characteristics of coal micro / nano pore are the foundation for revealing the enrichment mecha- nism and the rule of diffusion and migration of gas in coal. Characteristics of anthracite samples from Xinjing coal mine in Yangquan were fully studied based on various experimental techniques including argon ion polishing-field emission scanning electron microscopy(FE-SEM),low temperature nitrogen adsorption and high pressure mercury injection in this paper. The results show that pores in nanoscale with the complex morphology of tested samples are widely devel- oped. As determined through the direct observation with FE-SEM,phyteral cell residual pore,vitrinite matrix pore, junction formed by ultramicroscopic maceral,clay mineral pore,quartz intragranular pore,pore between components and micro-fractures were identified,which then constituted the coal interconnected pore system. The main reservoir space is in nanometer scale with an average pore diameter of 39. 31 nm,more than 80% of the reservoir space is under 100 nm and concentrated in 10-40 nm range. The fractal dimension of nanopores is between 2. 72 -2. 90,indicating distinct heterogeneity characteristics. The quantitative characterization showed that the nanopores developed well and the carbonaceous nanopore take an absolute advantage among all kinds of pore types,the macropores and mesopores have a certain degree while the microfissure is not,which brings about the high adsorption ability and poor penetration ability of coal reservoir.