The influence of the salinity of groundwater in coal measures on low rank coalbed methane in the south margin of Junggar basin

Groundwater salinity of coal-series is one of important factors affecting the generation, migration and accumulation of low rank coal bed gas. Taking south of Junggar Basin in Xinjiang as the study area, it is divided into eight hydrogeological units. Distribution characteristics of groundwater salinity of coal-series and the influence on methanogen's living in the study area are researched. Taking 1000 m depth as example, methane solubility of groundwater in coal-series in each hydrogeological unit was estimated. Capacity for transporting methane was analysed and assessed. Through the analysis of distribution of groundwater salinity, the chloride concentration of groundwater in coal-series and regional geological structures, the flow direction of groundwater in coal-series can be found. Taking Liuhuanggou hydrogeological unit as example relationship between salinity and enrichment of coalbed methane is discussed. The Research results show that the salinity distribution has the characteristics of north-south sub-zone and east-west subsection. Houxia hydrogeological unit, south of Manas river-Hutubi River hydrogeological unit, south of Liuhuanggou hydrogeological unit, west of Fukang hydrogeological unit promote the survival and methane generation of methanogens. Capacity for transporting methane of Houxia hydrogeological unit is strong. The runoff of surface water can influence the flow direction of groundwater. The center of high salinity and depression of low water level is the accumulation area of low-rank coal-bed methane in Liuhuanggou hydrogeological unit.