Near surface P-wave velocity inversion with average velocity analysis method
The sensitivity of surface wave dispersion to different parameters such as P-and S-wave velocity and thickness varies greatly.In surface wave studies,the S-wave velocity and thickness can be easily estimated,but the P-wave velocity cannot be accurately obtained.In engineering and petroleum exploration,the P-wave velocity model is more important than the S-wave velocity model.A previous study has shown that Poisson's ratio is sensitive to the wavelength(W)-depth(D)relationship.Based on this observation,we proposed a procedure to estimate the P-wave velocity model.Once the dispersion curves are extracted and the S-wave model is inverted,the W-D relationship is then obtained according to the average velocity.The synthetic data test proved that direct inversion for the W-D curves cannot produce a reliable P-wave velocity model.The W-D curves are not sensitive to P-wave velocities for superficial layers,which can lead to the failure of the P-wave inversion for the entire profile.We revised the traditional inversion method and added the W/D-D information,which is more sensitive to the superficial layers for the objective function.The synthetic data tests show that the proposed method can produce accurate P-wave velocity for both superficial and deep layers.We then applied it to field data.The resulting P-wave profile is consistent with the drilling data.The results indicate that the proposed method can obtain a good P-wave profile only using the dispersion curves without the help of other information.
Average velocity analysisDispersion curvesP-wave velocity inversion
万方数据
维普
