【作者】 王军；

【导师】 胡恒山；

【作者基本信息】 哈尔滨工业大学 ， 固体力学， 2007， 硕士

【摘要】 声波测井是一种重要的测井方法,在油田勘探和开采、工程物探等许多领域有着广泛的应用。声源的特性对声波测井的结果有着很重要的影响。以往的文章主要考虑了传播媒质对接收的声波信号的影响,而很少考虑声源对接收的声波信号的影响,典型的做法是采用未知声源强度的点膨胀声源来模拟测井声场。考虑到测井采用柱状换能器发射声波的实际情况,本文研究在给定激励电压脉冲作用下柱状薄管换能器的辐射声场和井孔响应。利用辐射阻抗的谐振条件,分析了圆柱压电换能器的暂态响应。在考虑周围介质耦合作用的情况下,根据留数定理,导出了圆柱形压电换能器的机电方程,建立了其等效电路,求解了时域、频域的传递函数,从而得到了在电信号激励下柱状换能器表面振动位移的时域和频域函数。利用波数实轴积分法和快速傅立叶变换法,计算了柱源模型下弹性介质的井孔声场,绘出了声场的时域波形图,并且分析和讨论了不同介质中的波形的差异。与前人采用假设声源强度只能求出波场的相对幅度不同,本文求出了在给定激励电压下的测井声场幅度。换能器辐射的声信号受到电压驱动信号和换能器自身特性的影响,在换能器物理特性的基础上,通过调整换能器的几何尺寸,改变周围耦合液体的参数,选择合适的电压脉冲信号,可使换能器在测井过程中辐射出满足特殊需要的声波信号。这对设计特定要求的换能器是很有意义的。更多还原

【Abstract】 Acoustic well-logging is a widely used method in oil and gas exploration. The characteristics of acoustic wave source have an important influence on the acoustic well-logs. The former papers mainly research the influence of the media, the typical method adopts the point source of an unknown intensity to calculate the sound field in the borehole. Considering the practical circs, this paper research the radiated field of the cylindrical piezoelectric transducer and the borehole response.This paper analyses the transient response of cylindrical piezoelectric transducer, develops its equivalent circuit and determines the relation between the applied electric signal and the radiated acoustic signal. By using the residue principle, the transient functions of the temporal and frequency domains for the transducer are determined analytically for any electrical driving signal.The integral along the real wave-number axis and frequency axis are calculated .The waveform is plotted in the time domain. Several different waveforms are compared and discussed in different media. The sound field is different from the supposed point source, the exact intensity is got.The radiating signals depend on both the type of the exciting voltage and the characteristics of the piezoelectric transducer, according to physical characteristics of the transducer choosing proper piezoelectric material, the suitable geometry of the transducer and the surrounding coupling fluid can improve the quality of the transmitted acoustic signal, and also make the transducer satisfy special purposes. The results are significant for designing the piezoelectric transducer.更多还原