| The Ximeng Shengli Coalfield in this study is located in the middle and eastern part of Inner Mongolia Plateau.The coal-bearing strata in this area are lower Damoguaihe Formation(K1d)and upper Yimin Formation(K1y)of the Lower Cretaceous of the Mesozoic.There are five coal seams that can be mined.Because the lower coal seams are often under the overlying thick coal seams,it has been found in the previous three-dimensional seismic exploration that the thick coal seams have strong reflection characteristics.It forms a strong shielding effect on the coal seam below.Because of the shielding effect of overlying coal seam,the reflected wave energy becomes weaker in deep coal seam,which brings great difficulty to seismic data processing and interpretation.In view of these problems,based on the analysis of geological and seismic conditions,this study focuses on the pre-preparation work of seismic data processing,lithology analysis and logging curve standardization.After obtaining high-quality basic results,the conventional interpretation of multi-group coal seam seismic data in the study area is combined with sparse pulse impedance inversion and seismic attribute technology to predict coal seam thickness.Interpretation of geological structures.Firstly,based on the large number of coal seams in this area,how to improve the resolution and processing accuracy is the key and difficult point of the three-dimensional processing in this area.So a lot of work has been done on the original seismic data processing.Before stack,three-dimensional surface consistent amplitude compensation,three-dimensional surface consistent deconvolution,constant velocity scanning,three-dimensional DMO are mainly used.After migration,dominant frequency deconvolution is used to compensate the frequency.Compensation.On the premise of denoising and guaranteeing signal-to-noise ratio,the resolution of seismic data is improved to the greatest extent,and the main frequency range of effective wave in each coal seam reaches 70-80 Hz.The quality of the result section has been greatly improved.Finally,high-quality three-dimensional seismic data volume has been obtained.The reflected wave signal-to-noise ratio of each coal group in the data volume is high,energy is strong,and the geological structure response is clear.Secondly,the geological data of the whole area are analyzed,and the physical characteristics of coal and rock in this area are summarized.The density of coal seam is generally 1.2-1.4 g/m~3,the velocity of P-wave is about 1800 m/s,and the average density of surrounding rock is 2.2 g/m~3,and the average velocity of P-wave is 2300m/s.According to the physical characteristics of the whole area,the multivariate fitting of logging data is carried out,and the functional response relationship between the calculated curve and the reference curve is established.By fitting the measured data,the fitting coefficients suitable for this area are calculated,and the standardized logging data are obtained.Finally,in view of the characteristics of complex structure,well-developed faults and many cutting relationships among them,the structure of the whole area is identified by using variance attribute technology,which lays a good foundation for the next wave impedance inversion stratigraphic framework modeling.By using the constrained sparse pulse inversion method and a series of parameter analysis,the high quality wave impedance volume is obtained,and the variation of coal seam thickness in most areas of the region is well ascertained,but there are still some thin coal seams with multiple solutions in some individual areas.Considering that seismic attributes technology can well reflect the characteristics of thin coal,the seismic attributes with the highest sensitivity to the thickness of thin coal are selected in this study.Coal seam thickness in thin coal seam area is well predicted by multi-attribute fusion combined with BP artificial neural network technology,and regional supplementary interpretation of weak reflection area of thin coal in wave impedance inversion is made.Through the complementary integration of advantages and disadvantages of the two methods,the final prediction results of coal seam thickness are obtained,which explains the change of coal seam thickness in the whole area,and more effectively delineates the thin seam areas of each group of coal.The natural thickness of No.4coal ranges from 0.62m to 37.71m,showing a trend of thinning in the South and thinning in the north on the whole.The thinning coal area with thickness less than 1.3m mainly develops near A13-K3 borehole;the natural thickness of No.5 coal ranges from 1.63m to 55.8m,showing a trend of thinning in the South and thinning in the north on the whole;and the natural thickness of No.6 coal ranges from 1.19m to50.96 m,showing a trend of thinning in the South and thinning in the north on the whole,with thickness less than 1.3m.The lower thin coal area mainly develops near borehole 18-K0,and the natural thickness of No.7 coal is between 0.49m and 7.6m,which shows the change trend of Southwest thin and northeast thick.The thin coal area with thickness less than 1.3m mainly develops near borehole A13-K6.Forty-nine faults were interpreted,of which 45 were newly discovered.Finally,the correctness and high precision of the work are verified by the verification of drilling.Through this study,conventional seismic interpretation technology combines wave impedance inversion technology and seismic attribute technology,breaking through the limitation of single interpretation method.The three methods can complement each other in each step of the whole interpretation process,and mutually prove each other's strengths.Especially in the study area with complex geological conditions,they are feasible and effective comprehensive interpretation methods. |
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