The analysis on coal facies of coal seams in early Cretaceous Wujianfang coal basin, Inner Mongolia

Inner Mongolia is a very important coal-resources reserve base in China,where most of the coal seams are accumulated in the Cretaceous faulted basins.The Wujianfang coal basin is rich in coal resources,and the total explored reserves of coal is 10.77 billion tons according to the general and detailed survey of coal resources.Based on the coal petrological and chemical analysis of fifty-seven coal samples from three wells in the southeast of the coal basin,the coal quality characteristics,coal facies types and their evolution characteristics of coal seams are discussed.The results show that the studied coal seams are of low-middle high ash,high volatile matter yields,low-very low sulfur content,and high vitrinite-inertinite ratio(V/I) and tissue preservation index(TPI).The wet forest swamp is the dominant type of coal facies and the overlying water of the peat-forming swamp generally deepens towards the upper coal seam.The upper coal seams are of transgressive characteristic with increasing of water table,while the lower coal seams are of regressive characteristic with decreasing of water table.