Studying The Inversion Of Shear Radial Profile In The Cased Well

Understanding the radial slowness changes around the borehole is significant to assess the borehole stability,determine the optimal completion,access the mud filtrate invasion depth and select the perforation position(avoid producing sand).In recent years,many researchers at home and abroad study a number of radial slowness profile inversion methods outside the borehole for the open well.Because the existence of casing and cement increases the heterogeneity around the borehole in the cased well;and applying these methods of the open well to the cased well can't get good results.So we need to improve these methods to adapt to the case of the cased well.In this paper,we study a new dispersion method-Phase Moveout method.The method is a data-driven and nonparametric algorithm.Compared to WSS method,the new method has a high slowness resolution and accuracy.Compared to APES method,the computation speed is fast.It proves the advantages of this method by processing the simulated data and measured data.In addition,we discuss the influence of the casing parameters,such as the casing radius,casing velocity and cement thickness to the wave curve in the cased well.It helps to improve the inversion accuracy using this method to the constrained inversion by improving the accuracy of dispersion analysis results.Applying the improved constrained inversion method to process the simulated data,and the results show that the relative error is controlled within 2.5%.The good results also prove that the inversion method is an effective method to inverse the shear radial profile.