Adsorption capacity and its pore structure of coals with different coal body structure
MENG Zhao-ping;LIU Shan-shan;WANG Bao-yu;TIAN Yong-dong;WU Jie;College of Geosciences and Surveying Engineering,China University of Mining and Technologgingy ( Beijing);Key Laboratory of Geologgingical Hazards on Three Gorges Reservoir Area,Ministry of Education,China Three Gorges University;Shanxi Lanyan CBM Group Co.,Ltd.;
Adsorption capacity of coals is a main reservoir parameter to determine the amount of gas-bearing and exploitive potential in coal seams. To determine the adsorption capacity of coal to methane under different temperatures and pressures related to coal body structures,isothermal adsorption experiments were conducted with four high-rank coal samples of different coal body structures,which were selected from No. 3 Shanxi Formation( Permian) coal seam of Zhaozhuang coal mine in south-eastern Qinshui basin. To reveal the control mechanism of porous structure to CBM( coal bed methane) adsorption from microcosmic level,low-temp liquid nitrogen adsorption-desorption experiments on various coal body structure coals were conducted. The results show that coal adsorption to methane is in accordance with Langmuir equation. Saturated adsorption volume increases with the increase of coal deformation degree while decreases with the temperature increase. Pore specific surface area and pore volume increase with the increase of deformation degree in coal body. Wherein,pore volume is mainly dominated by mesopores while pore specific surface area islargely contributed by adsorption pores. Mylonitized coal has the maximum size of pore specific surface area and pore volume under various pore diameters,which is followed by the granulated coal,calaclastic coal and intact coal. The rule concluded is in consistent with that of isothermal adsorption test,indicating that CBM content is higher in area with greater deformed coals under the same geological conditions.