Study on Key Layer of Water Prevention and Control in Ordos Basin Jurassic Coalfield Based on Sedimentary Water Control Theory

In order to make clear the key layer of water control in Jurassic coalfield of Ordos Basin, we research the relationship between coal seam and aquifer from the aspects of geological structure, stratum deposition, paleogeographic evolution, rich water of aquifer, etc. The results showed that the roof and floor of the deep buried coal seam in Ordos Basin mainly develops two regional aquifers of Anding formation and 3-1 coal seam; Anding formation has large thickness and continuous distribution, and it is far away from the main coal seam of Yan’an formation; 3-1 coal seam is the regional main coal seam with large thickness and mudstone development in the roof and floor of the coal seam, which forms an impermeable layer with good water retention. Three tectonic uplift and erosion events occurred in Mesozoic era, and formed three unconformity interfaces including unconformity interface of Anding formation and Zhidan group (including Zhidan group sandstone), unconformity interface of Yan’an formation and Zhiluo formation (including Qilizhen sandstone), unconformity interface of Yanchang formation and Yan’an formation (including Baota sandstone). In addition, the paleo interlayer oxidation zone and Zhenwudong sandtone were also important aquifers for threating mine safety.