Dissertation
Dissertation > Astronomy,Earth Sciences > Geology > Geology, mineral prospecting and exploration > Geophysical exploration > Underground geophysical > Borehole measurements > Ultrasonic logging

The Wave in a Fluid-Filled Borehole Excited by a Cylindrical Piezoelectric Transducer

Author WangJun
Tutor HuHengShan
School Harbin Institute of Technology
Course Solid Mechanics
Keywords sonic logging cylindrical piezoelectric transducer acoustic wave source the real axis integral
CLC P631.814
Type Master's thesis
Year 2007
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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.

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