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Correction Coefficient of Acoustic Logging Influenced by Micro-annulus

Hao Ming, Ai Chi, Wang Shujiang

Abstract



Since the existing of micro-annulus, the acoustic logging waves haven’t shear-coupled between cement mantle and casing, which makes the acoustic amplitude of casing wave higher during the examination of cement job quality and shows that the degree of cementation is bad. In this paper, through establishing the propagation models of logging acoustic wave with or without micro-annulus, the expression of head wave amplitude, the influence on acoustic logging bore log by micro-annulus has been quantified. The study results shows: with increase of the characteristic impedance of the medium inside the micro-annular, acoustic coupling rate of the interface between the casing and the micro-annular improves; when the characteristic impedance of the medium inside the micro-annular reaches the characteristic impedance of cement loop, the acoustic amplitude correction coefficient is1.



Keywords


acoustic logging, micro-annulus, acoustic amplitude, correction coefficient.

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