关键词: 煤, 孔隙度, 渗透率, 煤层气, 地质控制, 华北

Abstract:

The low porosity and low permeability of coal reservoirs have brought about a big problem for the exploration and exploitation of coalbed methane in China. Based on the coal proximate, coal maceral composition and low-temperature N2 adsorption analyses, microfracture analysis by fluorescence microscope, helium porosity and air permeability analyses, this study investigated the geological control of porosity and permeability of coals in Hedong, Weibei, Yangquan, Jincheng, Datong and Huainan.Huaibei coalfields. The results showed that coal porosity ranged from 2% to 10%, and strongly related to the coalification degree. The porosity reached a minimum value when Ro,r  was about 1.2%. The filling and mineralization of pores by minerals were proven to decrease the coal porosity. Coal permeability is commonly less than 5×10-3μm2, and shows an exponential increment relationship with porosity. The anthracite porosity is commonly less than 6%, which dominated by the micro and meso-pores porosity. The anthracite permeability mainly related to the development of micro and macro-fractures, while the permeability of bituminous and sub-bituminous coals related not only to the fractures but also to the pores.

Key words: coal, porosity, permeability, coalbed methane, geological control, North China