Characteristics of fissures and pores of anthracite in Jincheng by SEM

Anthracite in Jincheng is a highly metamorphic coal and its system of fissures and pores is differentfrom that of low and medium ranked coal. In order to discover their characteristics, 69 samples were collected from 18 CBM wells in Zhengzhuang in Jincheng and their fissures and pores were observed by a Scanning Electron Microscope (SEM). To the naked eyes and by SEM, the pores in the Jincheng anthracite are seen to have abundant mold pores with isolated, shallow and poor connectivity (diameters between 1∼50 μm) and few plant tissue pores, gas pores, and solution pores. Most of the fissures are filled with clay minerals or closed; while open fissures are not often visible in the Jincheng coal (aperture between 3∼10 μm). These characteristics are determined by the high rank and high vitrinite content of the coal. The existence of too many mold pores and filled fissures does not allow the migration of methane, hence hydraulic fracture stimulation will be required and is an effective method of adding and connecting fissures to enhance CBM production.