Xi’an Research Institute,China Coal Technology and Engineering Group Corp.,Xi’an ,China

In order to find out the main reasons for the difference of gas bearing property of Jurassic coal seam in the northern and southern Ordos Basin,based on the gas content and gas saturation of coal seam in the basin,from the four aspects of the coal seam's gas generating capacity,tectonic movement,hydrogeological conditions and lithologic characteristics of roof and floor of coal seam,the analysis and research are carried out.The results show that Jurassic coal seam is intact in the northern part of the basin,but has poor gas content,the southern part is incomplete but has good gas content.The degree of thermal evolution of the coal seam in the south is higher than that in the north,and the gas intensity is strong,the mineralization degree of formation water in the southern part of the basin is higher than that in the northern part of the basin,and the dynamic condition of groundwater is weak,which is favorable for the enrichment and preservation of coalbed methane.The roof and floor of the main coal seam in the north and south of the basin is mainly mudstone,and the influence of them on coalbed methane is almost the same.The comprehensive analysis shows that the main factors affecting the gas-bearing difference of the Jurassic coal seam in the northern and southern Ordos Basin are hydrogeological conditions,tectonic movement and vitality.