Anisotropic Velocity Model Building And Kirchhoff Migration Imaging

In recent years,the application of multi-component seismic technology in oil and gas fields and coal field exploration and development has brought many benefits to actual production.The advantage of multi-component seismic data over conventional P-wave exploration is that it has richer wavefield information.The shear wave velocity provided by the converted wave data can help to obtain the lithology and physical parameters of the strata,which is favorable for the interpretation and inversion of the reservoir.However,due to the asymmetry of the converted wave path,its time-distance curve is severely non-hyperbolic.For several years,domestic and foreign scholars have constantly proposed new travel formulas,of which the formula for industrial applications is no less than 10 species.However,the accuracy of the anisotropic velocity model can't be taken into consideration when doing various Taylor expansions and high-order approximations for the travel time formulas.At the same imaging point,the anisotropic parameter in the transverse direction must not be limited by a unique value.When seeking travel time,the accuracy of the velocity function plays a decisive role.Velocity model building,especially the speed of anisotropic model is precise in seismic data imaging has important significance.Accurate velocity model means after NMO correction of in-phase superposition of shaft,can guarantee to the greatest extent of post-stack seismic wave amplitude,phase,frequency is constant.At the same time,these parameters on the reservoir inversion middle matching,reflection coefficient calculation,and ultimately the inversion interpretation results have important influence.In this paper,the non-hyperbolic problem of converted-wave time-span curves is based on previous studies.Based on seismic weak anisotropy theory and Kirchhoff integral deviation principle,the following researches and practical work are carried out to achieve certain results and understanding:(1)On the basis of the original seismic wave anisotropy travel time formula,an anisotropic travel time formula suitable for VTI media is deduced and given.Based on this formula,a new analysis method for converted wave velocity is given.(2)Design an anisotropic migration flow and add parallel computations to the flow.The designed process is modularized and tested to obtain the optimal migration imaging key parameters.(3)Anisotropic prestack time migration imaging of multi-component seismic data was performed for the main coal seam in the 3D4 C project of Guqiao Coal Mine in Huainan.The velocity model and the anisotropic parameter model obtained by the velocity analysis in this paper can be effectively used for non-hyperbolic correction of converted-wave CIP gathers.Combined Kirchhoff prestack time migration,it can be found that the quality of the anisotropic migration profile is much higher than that of the isotropic profile.