The Analysis Of Seismic Reflection Interpretation And Anisotropy In Thin Interbeds

There are many thin or interbedded reservoirs and coal seams in oil and gas fields and coal fields in China.In this paper,according to the thin interlayer model with different impedance difference,the seismic data of tight sandstone gas in hangjinqi area of ordos basin and guqiao mine in huainan,anhui are taken as examples,the seismic interpretation of thin interbed and the anisotropy of long-wavelength equivalent VTI are studied.The thin interbedding of sand and shale in the xiashihezi formation of Permian is a typical thin interbedding with weak impedance difference.affected by the strong reflection of the underlying shanxi formation and Taiyuan Formation coal seam,the reflection amplitude of sand body is relatively weak,it is almost impossible to see the visible seismic reflection.Horizon calibration is difficult by conventional methods of synthetic seismogram.The accuracy of synthetic seismogram calibration is improved by using thin layer reflectivity method and weakening the strong reflection of coal seams.Based on the post-stack 3D seismic structure interpretation of guqiao coal mine in Huainan,we explored the existence of the collapse column in the study area,the suspected collapse column on the seismic section is identified by coherence,variance and other seismic attributes.At the same time,we analyzed the energy relationship between the overlying coal seam and the underlying limestone in the coal seam with strong impedance difference,testing the weakening treatment of 1 coal reflection.However,it is found that the weakening treatment of this single coal seam cannot provide useful help for the identification of structures such as collapse column under strong reflection shield of coal seam.It may be necessary to consider weakening the reflection of multiple coal seams later.The characteristics of VTI anisotropy coefficient is analyzed by using logging curve.On the premise of consistent thickness,the equivalent VTI anisotropy development rules of the thin interlayer stratification model divided by different sampling intervals were compared.The overall performance is: the anisotropic coefficient increases with the increase of sampling interval in the weak impedance difference model,while the anisotropy coefficient decreases with the increase of the sampling interval in the strong impedance difference model,the law of the models is opposite;The weak impedance thin interlayer presents as the weak anisotropic equivalent VTI medium,and the strong impedance thin interlayer presents as the strong anisotropic VTI medium;The equivalent VTI anisotropy coefficient of 13-1 coal is generally greater than 11-2 coal in the coal seam stratum of Guqiao Coal Mine.