Numerical Simulation Of Viscoelastic VTI Medium

After years of exploration and development,the target of seismic exploration has gradually changed from simple shallow structural oil and gas reservoir to deep hidden oil and gas reservoir,which requires more and more precision of seismic exploration,but at present,the target of seismic exploration is becoming more and more accurate.Most of the high-efficiency seismic exploration techniques are still based on the basic assumption that underground medium is elastic isotropy.However,theoretical practice shows that underground medium is not completely elastic,and there are many attenuation mechanisms.Moreover,due to the nature of the medium itself,the heterogeneity of the distribution and the diversity of the composition of the medium,the underground medium still has a wide range of anisotropy,so it is of high precision.The high accuracy inversion imaging requires a more accurate and real forward modeling model which can reflect the underground medium condition and reflect the attenuation and anisotropy of the underground medium at the same time.Based on the viscoelastic theory of the GSLS model and the VTI anisotropy theory,the approximate constant Q values are simulated in a certain band range,and the viscoelastic anisotropy properties of the medium are simulated by adding attenuation anisotropy parameters.The wave equations of elastic VTI medium and viscoelastic VTI medium are derived by introducing memory variables.The numerical simulation method of staggered grid finite difference method is used to determine the differential stability condition and loading source mode.At the same time,the characteristics of traditional perfect matching,unsplit convolution perfect matching layer and multi-axis perfect matching layer are compared.The advantage of less memory and relatively stable is that multi-axis convolution perfect matching layer is used to eliminate artificial boundary reflection.In order to verify the stability and accuracy of the numerical simulation,the uniform medium model,the three-layer medium model,the complex geological model Hess model and the BP rock mound model are introduced.By comparing and analyzing the numerical simulation results of elastic VTI medium and viscoelastic VTI medium,it is found that the viscoelastic VTI medium has both anisotropic and viscoelastic properties,and the wave field snapshot of the obtained homogeneous medium is obtained.The attenuation anisotropy can be observed in the seismic records of complex medium,that is,the attenuation of seismic waves is related to the direction of space propagation,which can guide seismic wave inversion imaging and AVO analysis to a certain extent.