| Piezoelectric transducers are the core components of acoustic logging,which transmit and receive acoustic signals,and their performance directly affects the logging results.In recent years,people have mainly focused on the performance of piezoelectric transducers under ideal conditions and the impact of changes in structural parameters on their vibration characteristics,as well as simulating the wellbore wave field under ideal models.However,due to various factors such as production processing,later installation,and downhole wear,the structure of the transducer is not ideal.The vibration and excited sound field of the transducer in a non ideal state should be different from that in an ideal state.The difference between transducers deviating from the ideal state and ideal transducers,as well as the impact of non ideal transducers on the logging sound field,urgently needs to be studied.This article provides a detailed study of the vibration characteristics of transducers under various states and their corresponding wellbore sound fields.The results provide a theoretical basis for improving the quality of logging data,analyzing the sources of errors,and processing errors.The following are the main research contents and results.The first part studies the impact of changes in the structure of monopole acoustic transducers on the vibration characteristics of transducers in both ideal and non ideal states.Based on the COMSOL multi physical field simulation software,starting from the ideal cylindrical piezoelectric transducer,the influence of changes in the thickness of piezoelectric ceramics and fiberglass on the vibration performance of monopole piezoelectric transducers was studied.Then,non ideal ’frustum shaped’ piezoelectric transducers and ’hourglass shaped’piezoelectric transducers were simulated,and the influence of changes in structural parameters on the vibration characteristics of the transducer was studied,Finally,comparing the vibration characteristics of ideal and non ideal transducers,it was found that the size of the ’frustum shaped’ transducer model is equivalent to that of a cylindrical transducer.This model has little effect on the vibration characteristics of the transducer,and there is a good linear relationship between the variation of resonant frequency as the size changes.When the size of the’hourglass type’ transducer is equivalent to that of a cylindrical transducer,its resonant frequency is relatively high,and there is no obvious linear relationship between its resonant frequency and size.In addition,the variation trend of the magnitude of radial point displacement between the two is the same,but there is a slight difference in numerical value,and the maximum peak value shifts back.The second part studies the resonance frequency and sound source directionality of the dipole acoustic transducer skeleton model in normal and tilted states.A framework model of a dipole acoustic logging transducer was established based on COMSOL finite element simulation software.The influence of changes in piezoelectric crystal thickness on the resonant frequency of the transducer was analyzed,and the changes in resonant frequency with different degrees of skeleton tilt were summarized.Finally,draw a conclusion;As the skeleton tilts more severely,the resonant frequency decreases.Subsequently,the directionality of the sound source in infinite water was simulated and analyzed,and the general pattern of horizontal directionality of dipole acoustic transducers was found,as well as the reasons for the irregular directionality.And the directionality of the sound source in the case of skeletal tilt was also studied,and it was found that small-scale tilt has little effect on the directionality of the horizontal sound source.The third part analyzes the impact of transducers on the wellbore wave field in both ideal and non ideal states.The acoustic logging model was established based on COMSOL multi-physical field simulation software,and the formation wave field was studied using ideal cylindrical acoustic transducers and non ideal ’frustum shaped’ acoustic transducers,respectively.Simulated the process of single transmitter dual receiver acoustic cable logging,emitting transducers to radiate sound waves outward.The sound waves passed through the formation and were finally received by the receiving transducers.Specific analysis was conducted on the received signal waveform.Through comparison,it was found that the’circular shaped’ acoustic logging transducer has almost no effect on the full wave waveform of the logging. |
