Quantitative Calculation and Correction of the Influence of Microannulus on Acoustic Amplitude Log

In order to eliminate the effect of microannulus on acoustic amplitude logging,improve the accuracy of cementing quality evaluation,on the basis of analyzing propagation characteristics of acoustic wave in media,various interface layered medium models for good cementation and cementation with microannulus were built,the received acoustic intensity of acoustic amplitude logging in these two cases was derived,and acoustic amplitude ratio expression was obtained.The expression quantifies the effect of microannulus on acoustic amplitude logging and can be used to correct the acoustic amplitude logging curve.Actual application showed that,after correction,highest relative sound amplitude decreased from 57%-59% to 36%-38%,and the cement quality evaluation turned from poor to average.It can be seen that microannulus has significant impact on the results of acoustic amplitude logging evaluation,causing error in evaluation of cementing quality,so its correction is necessary for improving the accuracy of cementing quality assessment.