Research On New High-power Composite Transducer And High Frequency Induction Logging Tool

A new type of transducer is designed,which is mainly composed by a piezoelectric ceramics crystal piles and a metal thin circular pipe.The longitudinal vibration,generated by crystal piles, transforms into radial vibration of thin circular pipe.The mechanical resonance frequency equation of the transducer is derived. The relationship between the natural frequency and geometric parameters is analyzed. When the radius of thin circular pipe is fixed, the length of both the thin circular pipe and the crystal piles reduces along with the frequency. When frequency is fixed, the length of both the thin circular pipe and the crystal piles reduces along with radius of the pipe. When the frequency and the radius are fixed,the relation of the length of the thin circular pipe and the crystal piles is decreasing progressively. The change of respective vibration characteristics of the thin circular pipe and the crystal piles before and after compounded is contrasted. When pipe’s length is twice less than the radius, the natural frequency of longitudinal vibration of the pipe after compounded reduces,and the radial frequency remains the same. When pipe’s length is 5 times longer than the radius, the natural frequency of longitudinal vibration after compounded increases. When the length is 2~5 times as long as the radius, the coupling of the longitudinal and the radial vibration of compound pipe is closer. The natural frequency is higher than that of pure crystal pile.The high-frequency array induced current logging instrument is the same with the ordinary interval transit-time logging instrument, and surveys the phase difference of two different source-detector separation profiles. Usually, because the phase has the sudden change in the stratum horizontal interface, the surveyed phase difference also has the very big change on the contact surface, and this influences actual use. In the situation which does not consider the borehole effect, phase difference which is surveyed by high-frequency induced current logging and source-detector separation exist approximate linear relationship. Its slope and the formation resistivity are the monodromy relations. In order to remove the influence that the bed boundary produces for surveying phase difference, array induced current logging instrument ,based on this slope, is designed. Linear relationship of phase and source-detector separation needs to be studied under the different frequency and different formation resistivity condition. In the scope of formation resistivity less than 110Ω*m, it has given three linear relationships, the errors that linear relationships produce is all smaller than 3%; If the relative error is smaller than 3.5% , then the relation of source-detector separation and phase difference may be described by a linear function.