A Study On The Performances Of Piezoelectric Transducers For Acoustic Logging And Simulation Of Acoustic Field In A Borehole

In acoustic logging engineering,piezoelectric transducer is usually used both as transmitter and receiver to stimulate a sound source and receive signals.Therefore,this paper focuses on the study of the vibration characteristics and acoustic characteristics of piezoelectric transducers,and simulates the acoustic field generated by piezoelectric transducers in wireline logging and LWD.Firstly,this paper establishes the finite element model of cylindrical piezoelectric transducer and studies the effect of size of transducer's structure on the intrinsic frequency of transducer.Then,the author of this paper studies the vibration of transducer generated by excitation voltage when there is no liquid outside the transducer and the transducer is in water respectively,and compares and analyzes the vibration of the transducer in the two cases.Secondly,this paper studies the frequency response characteristics of the transmitter transducer and the directivity and attenuation characteristics of the sound pressure generated by the transmitter,and analyzes the acoustic signal generated by the transmitter under specific pulse voltage.Besides,the sensitivity-frequency line chart and sensitivity level-frequency line chart of the receiving transducer are obtained afterwards.Simulating the process of how the transmitting transducer generates sound waves and how the receiving transducer receives sound waves results in the obtainment of the vibration response and voltage response of the receiving transducer.Finally,this paper establishes the finite element model of wireline logging and LWD respectively,and calculates the acoustic fields excited by transducers in the models of wireline logging and LWD.Additionally,the logging process in which the transmitting transducer vibrates and radiates sound waves outward,and sound waves travel through the ground and generate reflected waves,and then the acoustic signal is received by the receiving transducer is simulated.On this basis,this paper analyzes the signals received,and explores the relationship between the voltage signal received by the transducer and the sound pressure signal and displacement signal at the transducer.Eventually,the analysis indicates that the voltage signal received by the transducer reflects the radial displacement signal at the transducer.This conclusion is different from what has been known and will provide evidence for the search and analysis of logging signal.