Study On Spatial Occurrence Form And Lithological Interpretation Method Of N2 Lateritic Layer

N2 lateritic layer of Neogene is the key water-resisting layer to the Jurassic coalfield exploration in western China,its lithological distribution and stability is great important for the safety of the coal resource safe and green mining,the sustainable development of regional economy.For this purpose,this thesis will use the seismic numerical simulation technology to understand reflection wave's propagation characteristics of N2 lateritic layer.In 3D seismic exploration,Due to the shallow seismic wave information is not concerned,in order to understand the seismic reflection wave characteristics of the N2 lateritic layer,according to the actual geological data,the seismic numerical model is established,and the rock physics parameters are determined,seismic numerical simulation using wave equation finite difference numerical method is applied.According to the results of numerical simulation,the reflected waves lineups of the N2 lateritic layer's top and bottom can be well identified,its energy intensity is related to overlying Quaternary loess layer thickness and its ownthickness.Traditional geological methods mainly rely on the borehole data to determine the spatial distribution of the N2 lateritic layer.Although the longitudinal resolution of the drilling data is very high,but the number is too small and the cost is high,which inevitably affects the determination of the spatial distribution of the N2 lateritic layer.The Three-dimensional seismic data has intensive information,seismic information can study the stratigraphic structure and lithology changes from the plane and threedimensional perspective.Three dimensional seismic inversion technique can determine the spatial information of N2 lateritic layer.The change of porosity and apparent resistivity can reflect the change of aquosity,it will easily cause uncertainty of interpretation results to evaluate rock's aquosity based on single wave impedance information,using probabilistic neural network inversion technology,based on the idea of seismic attribute fusion,to predict rock porosity and apparent resistivity,combined with wave impedance information of rock stratum,the rock's aquosity is evaluated.Yingjun No.2 field coal bearing strata are covered with Cenozoic strata,belongs to concealed coalfield.In addition to the Quaternary,the cretaceous gravel layer is the main aquifer.Using the method of logging fusion,fuse density and natural gamma curve,pseudo density curve can identifyN2 lateritic layer top and bottom interface,multi-parameter lithology inversion can be done,get the pseudo wave impedance data volume,to determine the spatial position of the N2 lateritic layer.By using the porosity curve and apparent resistivity curve,the probability neural network inversion is carried out,get the porosity data volume,apparent resistivity data volume.According to the three kinds of lithological data,the lithology information of N2 lateritic layer,Cretaceous gravel aquifer and coal seam roof rock has been extracted.Analysis founds that,in the southwest three strata's lithology is most stable,in the northwest and northeast,N2 lateritic layer is most unstable,Cretaceous gravel aquifer and the coal seam roof strata is the most unstable part in the northwestern,water inrush possibility should be higher in the coal mining process.This paper attempts to apply the lithology seismic inversion technology ininterpretationof shallow N2 laterite layer,and evaluate the main coal seam overburden water stability,provides the base geological data for prevention of water irruption in the coal mining process.