中文摘要：

本文针对地层横波慢度径向分层模型,分析了地层横波慢度的径向非均匀性对弯曲波频散的影响.基于径向非均匀与均匀模型之间弯曲波频散的差异,结合微扰法和Backus-Gilbert（BG）理论建立了反演横波慢度径向分布的方程,求取了地层横波慢度的径向分布.在无噪声和参数误差时,反演结果较好地反映了实际地层横波慢度的径向分布,当井孔流体或井外地层纵波慢度的选取误差在10%内变化时,反演结果基本保持不变;存在信噪比（SNR）为20dB（信号的功率为噪声的100倍）或10dB（信号的功率为噪声的10倍）噪声时,反演结果没有发生明显的改变,其相对误差基本控制在10%以内,可见噪声对反演结果的影响不大.以上反演结果说明,本文采用的结合微扰法和BG理论的反演方法来估测地层横波慢度的径向分布时,具有很好的鲁棒性,可以被用于现场了解井壁周围的地层性质.

英文摘要：

The effect of shear wave slowness′s radial heterogeneities on dipole flexural mode dispersions is analyzed for shear wave slowness′s radially layered model. Perturbation method and Backus-Gilbert（BG） theory are used for the inversion of shear wave slowness radial variations based on the difference of flexural wave dispersions between radially heterogeneous and homogeneous formations. When there is no noise and error of other parameters, the radial variations of the inverted shear wave slowness agree very well with the assumed radial profile. When the choice of slowness for the borehole fluid or formation compressional wave has a deviation from the true value within 10 percent, the inverted radial variations of shear wave slowness almost remains unchanged. When there exists noise with SNR （Signal Noise Ratio） of 20 dB or 10 dB, the relative error of the inversion results is within 10 percent, which means the impact of noise on the inversion results is little. From the inversion results described above, the technique which combines perturbation method and BG theory for the inversion of shear wave slowness′s radial variations is robust, and can be utilized for understanding formation properties around borehole wall on the spot.