Key elements and framework model of groundwater system in Jurassic coal measures of Ordos Basin

Groundwater is often closely associated with coal resources,and directly restricts their rational development and long-term extraction planning. Ordos Basin is an important energy basin in China. The exploration practice for several decades shows that Jurassic coal measures has not only five sets of minable coal seams,but also is associated with abundant sandstone-type uranium deposits,sandstone-type kaolin,quartz sand and other mineral resources. Based on the previous knowledge and experience about Ordos Basin,it is considered that the supply source and transport channel of groundwater are the key elements of the groundwater system structure of Jurassic coal measures. Among them,the potential groundwater recharge sources include three sets of groundwater reservoirs ( the bottom aquifer of Zhiluo formation,the Luohe formation aquifer and the luohandong formation aquifer of Lower Cretaceous) and surface water system. The groundwater transport channel includes four types of regional scale framework sandstone body,unconformity interface,fracture system and artificial mining fracture system. The “water disaster” encountered in the mineral resources development of coal measures is usually the passive exposure or destruction of the original groundwater system,which is caused by human factors connecting the groundwater source and the artificial working surface. Focusing on the safe development of mineral resources of Jurassic coal measures,on the one hand,it is necessary to understand the basic characteristics and distribution laws of the key elements of groundwater system,and on the other hand,it is necessary to reveal the spatial distribution relationship between the key elements of groundwater system and mineral resources. On this basis,a framework model of groundwater in coal measures should be built so as to provide a sedimentology hydrogeology basis for the coal measures resource development and mine water disaster prevention and control.In Ordos Basin,due to the difference of tectonic background,the types of groundwater source,transport channel,coal measures occurrence and mineral type combination are different in different areas,and the groundwater framework model is also different in different areas,so it needs to be treated differently and studied in depth.