Study and application of high-precision direct inversion method of P-to-S-wave velocity ratio based on elastic impedance
As an important parameter for describing geological properties,P-to-S-wave velocity ratio can effectively distinguish lithology and identify reservoirs.However,conventional methods usually use AVO technology to invert P-wave and S-wave velocities,and then indirectly calculate P-to-S-wave velocity ratio.The indirect calculations may result in the insufficient accuracy of extracting P-to-S-wave velocity ratio and lead to cumulative errors in the calculation results.To overcome this issue,this study first derives the direct relationship between reflection coefficients and P-to-S-wave velocity ratio,and establishes the Linear Elastic Impedance(LEI)equation for P-to-S-wave velocity ratio based on the derived relationship.Then,two typical AVO sand-shale models are used to verify the forward accuracy of the LEI equation.Further research shows that P-to-S-wave velocity ratio is very sensitive to k-values.So,a pre-stack inversion algorithm with multiple constraints based on the LEI equation is proposed.Results from testing on the Marmousi2 model and field data from the Chuanxi fold-XC structure indicate that the proposed method effectively improves the accuracy of P-to-S-wave velocity ratio inversion and provides a method for extracting P-to-S-wave velocity ratio parameters from pre-stack seismic data.
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