Acoustic logging while drilling (LWD), characterised by simultaneous drilling and logging, is widely used to obtain the elastic parameters of the formation around the borehole. Most published monopole acoustic LWD simulation waveforms are routinely presented as pressure. However, these pressure waveforms disagree with the voltage waveforms recorded in the experiments. Here, to find out the reason of the inconsistent of these two waveforms, both the piezoelectric effect of the transducer and the propagation of the acoustic wave are integrally calculated with the finite-element method, obtaining the voltage waveform as well as the mechanical waveforms. The quantitative comparisons between the mechanical waveforms and the voltage waveform show that the output voltage cannot represent the pressure signal, but a combination of multiple mechanical signals. Based on the piezoelectric equation and the structure of the piezoelectric transducer used in this paper, we formulate the output voltage in terms of the four mechanical quantities, i.e. the radial strain and axial stress of the transducer as well as the acoustic pressure and the radial displacement of the borehole fluid. Furthermore, the contributions of these four mechanical quantities to different wave groups are explored. Finally, the waveforms comparisons after drill collar grooving reveal that the displacement waveform before and after grooving should also be displayed when evaluating the grooving effect instead of only the pressure waveform as in previous studies.

中文翻译：

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单极声随钻测井机械响应及其与输出电压波形的关系

随钻声波测井（LWD）以同时钻井和测井为特点，广泛用于获取井眼周围地层的弹性参数。大多数已发表的单极声学 LWD 模拟波形通常以压力表示。然而，这些压力波形与实验中记录的电压波形不一致。在这里，为了找出这两种波形不一致的原因，用有限元法对换能器的压电效应和声波的传播进行了积分计算，得到了电压波形和机械波形。机械波形和电压波形的定量比较表明，输出电压不能代表压力信号，而是多个机械信号的组合。基于压电方程和本文所用压电换能器的结构，我们将输出电压用换能器的径向应变和轴向应力以及声压和径向位移四个力学量来表示。的钻孔流体。此外，探讨了这四个机械量对不同波群的贡献。最后，钻铤开槽后的波形比较表明，在评估开槽效果时，还应显示开槽前后的位移波形，而不是像以前的研究那样只显示压力波形。我们根据四个机械量制定输出电压，即换能器的径向应变和轴向应力以及井眼流体的声压和径向位移。此外，探讨了这四个机械量对不同波群的贡献。最后，钻铤开槽后的波形比较表明，在评估开槽效果时，还应显示开槽前后的位移波形，而不是像以前的研究那样只显示压力波形。我们根据四个机械量制定输出电压，即换能器的径向应变和轴向应力以及井眼流体的声压和径向位移。此外，探讨了这四个机械量对不同波群的贡献。最后，钻铤开槽后的波形比较表明，在评估开槽效果时，还应显示开槽前后的位移波形，而不是像以前的研究那样只显示压力波形。探讨了这四个机械量对不同波群的贡献。最后，钻铤开槽后的波形比较表明，在评估开槽效果时，还应显示开槽前后的位移波形，而不是像以前的研究那样只显示压力波形。探讨了这四个机械量对不同波群的贡献。最后，钻铤开槽后的波形比较表明，在评估开槽效果时，还应显示开槽前后的位移波形，而不是像以前的研究那样只显示压力波形。