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Inversion of shear velocity profile in a cased borehole

The theoretical model in this study is constructed with a fluid-filled well-bonded cased borehole with a radially layered formation outside. The thickness and shear velocity of each layer are different from that of others, and it may not be inverted from flexural dispersion data easily. In A parametric exponential profile controlled by three parameters to express the radial variations of the formation shear velocity approximately are used, and the objective function for inverting the three parameters based on the modified perturbation method is established. Reasonable inverted results demonstrate the validity of the radial profiling methodology. After analysis of effect of factors on the inverted results, we have obtained preliminary conclusions.