| Coal is the main body of energy in our country,but with the continuous increase of coal mining depth,the frequency of mine geological disasters increase obviously,mine geological safeguard becomes more and more difficult.In order to achieve effective geological safeguard,this time,taking the 2 mining area of Buertai Coal mine in Shendong mining area as an example,integrated multiple pre-stack and poststack seismic inversion methods,focused on the main mining seam and the top and bottom sandstone,identified the transverse variation of coalbed thickness,predicted the fracture density and direction plane distribution,and evaluated the water richness of the sandstone roof of the coalbed.The relevant results can not only be used to support the efficient mining of coalbed,but also can guide the prevention and control of mine geological disaster,which has significant economic value and social significance.As a typical organic sedimentary rock,the thickness of coalbed varies horizontally under the influence of sedimentary environment and tectonic movement.If the horizon variation of coalbed thickness is not learned accurately before mining,the mining equipment may be damaged by cutting the hard roof or floor surrounding rock during mining.In order to effectively predict the thickness of coalbed,the log constrained impedance inversion method is used to invert the wave impedance data body of the study area.Combined with the interpretation horizon,the difference of wave impedance between coalbed and surrounding rock,and the thickness of coalbed interpreted by logging,the cokriging interpolation method is used to predict the thickness plane distribution of main coalbed in the study area,such as 12# coal,22# coal and 42top# coal.The prediction results show that t in the study area the 12# coal is thicker in the middle of the study area and thinner in the southeast.The 22# coal is thicker in the northwest of the study area and thinner in the east.The 42 top # coal is thicker in the southeast of the study area and thinner in the northwest.Geostatistical inversion is a new method to predict formation thickness compared with logging constrained inversion.In order to study the effect of coalbed thickness prediction,a comparative analysis is carried out based on the forward model.Through forward and inversion analysis of the geological model of wedge-shaped coalbed and sandstone interlayer,it is found that geostatistical inversion reflects the characteristics of thin coalbed obviously,and can predict the transverse change of coalbed thickness more accurately.On the basis of forward modeling,geostatistical inversion is carried out for the actual study area,and corresponding wave impedance data and probability data are obtained.According to the coal thickness interpretation method of logging constrained wave impedance inversion,the coal thickness interpretation of geostatistical inversion data is carried out.By comparing and analyzing the coalbed thickness interpreted by the two inversion methods,it is found that geostatistical inversion has advantages in horizontal continuity and vertical resolution,and can better predict the transverse change of coalbed thickness.In order to predict the water richness of the sandstone on the top and floor of coalbed,the roof sandstone above the 22# coalbed and the floor sandstone below the 52# coal in the study area are inversion based on AVO.Firstly,AVO processing such as residual time difference correction and macro element superposition is carried out to obtain high quality AVO track sets.Secondly,the P and G attributes are obtained according to the AVO response,and the water content of sandstone is analyzed by using the P-G intersection diagram.Finally,combined with AVO inversion properties such as pseudo-Poisson’s ratio and S-wave reflectance,the water-bearing plane distribution of top and bottom sandstone is predicted.The prediction results show that the roof sandstone above 22# coalbed has strong water content in the west and northeast of the study area,while the water content in the southeast is relatively weak.On the other hand,the fissure zone is an important drainage channel of mine water,which is important for mine water control.Therefore,AVAz azimuth anisotropy inversion is carried out for 42# coal which has the best seismic data quality in the study area with the method of azimuth AVO.In the inversion,the wide azimuth prestack seismic data were divided into 6 subregions according to 0-180° azimuth,and the reflected wave amplitude with medium offset was selected as the input parameter.Nonlinear equation method was used as the inversion method.The inversion results show that the fracture density is developed in the northwest and southeast of the study area,which is the main drainage channel of mine water.The fracture density in the middle of the study area is relatively low and it is not easy to conduct water.The general direction of fracture development in the study area is NEE.Have a more obvious change in middle of the study area,it is related to Yanshan movement geological structure.In a word,the thickness of main coalbed,water content and conductivity of top and bottom sandstone in the study area are discussed by comprehensive application of logging constrained wave impedance inversion,geostatistics inversion,AVO attribute inversion and azimuthal AVO inversion,etc.Relevant results can not only be directly used to support coalbed mining,but also can be used to prevent and control water damage of mine sandstone,which is of great significance for mine geological guarantee.There are 62 figures,4 tables and 110 references in this thesis. |
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