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Acoustic method of through-tubing cement bond evaluation based on Mie resonances


Without presence of tubing, cement bonds behind casing has proven able to be evaluated by acoustic methods such as sonic cement bond logging, the ultrasonic pulse-echo method, and the pitch-catch method. However, there is no reported acoustic method effective to estimating cement bonds through tubing. Through-tubing cement bond evaluation becomes a challenge because of the unwanted strong interference of tubing.

Here, we propose a novel acoustic method for through-tubing cement bond evaluation based on low-frequency Mie resonances excited by cylindrical wavefronts. Physically, the phenomenal Mie and the companied anti- resonances can be explained by the coupling Duffing model. This model shows that the change of cement impedance can be characterized by the response change of Mie resonances. The amplitude of Mie resonances at low frequencies has an appreciable response even though there exists tubing. Then, the response is qualitatively captured by the change of the electrical input power fed to the cylindrical transducer, based on the principle of acoustic Purcell effect. Therefore, by measuring the electrical input power or terminal resistance, cement bonds can be evaluated through tubing. Last but not least, our proposed method has the capability of not only evaluating cement bonds but also estimating the quantity of casings and the eccentering of tubing based on the azimuthal profile of Mie resonances.