随钻多极子声波测井仪接收换能器的数值模拟

接收换能器是随钻多极声波测井仪的关键器件,其性能直接影响测量信号的质量。利用有限元法分析了边界条件、金属基片厚度以及封装方式对随钻多极子声波测井仪叠片型接收换能器振动模态和接收灵敏度的影响。模拟结果表明,两端钳定边界条件下换能器一阶伸缩振动模态的谐振频率最高,声波测井工作频率范围内接收灵敏度曲线最平缓、起伏最小,接收灵敏度较高,是随钻多极子声波测井仪最适合的一种机械安装方式。中间金属基片厚度对接收换能器灵敏度有一定影响,接收灵敏度随着金属基片厚度的增加而略有升高,且频率为3 kHz附近的灵敏度跳跃点往高频移动、起伏变大。采用充满硅油的长方体壳体对接收换能器封装,接收灵敏度比无壳体有较大差异,灵敏度曲线在多个频率点存在跳变,工作频段内起伏变大。数值模拟结果对随钻多极子声波测井仪接收换能器设计、制作及正确安装起到良好的指导作用。

Numerical Simulation of Transducer of LWD Multipole Acoustic Logging Tool

As a key part of a LWD multipole acoustic logging tool, the performance of the transducer directly affects the quality of logging data. This study analyzed how boundary conditions, the thickness of metal substrate and sealing method affect the vibration and sensitivity of the laminated transducer of a LWD acoustic logging tool by finite element method. The simulation results show that the clamped boundary at both ends is the most suitable mechanical installation for a LWD acoustic logging tool, because the resonant frequency of the first-order stretching vibration is the highest for the transducer, the sensitivity curve is the smoothest and the least undulating, and the receiving sensitivity is relatively high. It is also found that the thickness of the intermediate metal substrate has a certain effect on the sensitivity of the transducer. The sensitivity rises slightly with the increase of the thickness of the metal substrate, and the sensitivity jump point near 3 kHz moves to high frequency and the fluctuation increases. When a rectangular shell filled with silicone oil is used to seal the transducer, its receiving sensitivity is quite different from that without the shell, the sensitivity curve jumps at several frequency points, and the fluctuation in the working frequency band becomes larger. The results of numerical simulation play a good guiding role in the design, fabrication and installation of the transducer of a LWD multipole acoustic logging tool.