摘要
声电频谱测井的频谱包含实部和虚部,其测井的主要目的之一是获得探头响应的虚部.因为虚部包含着更多的地层参数信息或者与地层参数具有直接的关系.例如感应测井响应的虚部在一阶近似的情况下与地层的电导率成正比;声波测井的传播速度信息在相位上表现,所测量的时差是相位差,也是虚部;井下超声换能器的辐射阻抗与地层参数有关,也包含虚部.用稳态的正弦波或者方波激发时,虚部的信息包含在所测量波形的相位中,虚部的测量就是这些波形幅度和相位的测量,即原始测量信号仍然是正弦波,但是经过探头和地层以后,其幅度和相位会发生比较大的变化,特别是在探头或者响应的谐振频率处,其变化更加剧烈.本文研究用采集到的正弦波处理虚部的方法.包括测量电路:一般测量电路和桥式测量电路,模拟测量方法和数字测量方法等.其中模拟测量方法借助于模拟乘法器和滤波完成虚部的测量,数字测量方法需要借助于信号处理方法获得虚部.模拟测量方法中因为有低通滤波器,因此只对一定频率段有效(大于5kHz),数字方法则可以从很低的频率开始,对大多数频率段有效.桥式测量电路可以增加原始信号的幅度,提高虚部的测量精度.
The spectrum of acoustoelectric spectrum logging includes real part and imaginary part.The imaginary part tends to contain more information about stratum parameters or be directly related to the stratum parameters,so one of the main purposes of logging is to obtain the imaginary part of probe response.For example,the imaginary part of induction logging response is proportional to the conductivity of stratum in the case of first-order approximation. Information about propagation velocity of acoustic logging is shown in phase and the phase difference measured is imaginary part.Radiation impedance of ultrasonic transducer in downhole is related to stratum parameters which also includes imaginary part.Phase of the waveform measured contains the Information about imaginary part when excited by steady-state sine or square wave.Measuring imaginary part is to measure amplitude and phase of the waveform.It means that original signal is still sine wave,but the amplitude and phase will change greatly after the effect of probe.They change more drastically at resonance frequency of the probe or response.In this paper,we use sine wave collected to process imaginary part.The main content includes ordinary measuring circuit and bridge measuring circuit,analog measurement method and digital measurement method.Analog measurement method completes measurement of imaginary part by means of analog multiplier and filter.In another method,a signal processing method is used.Due to low-pass filter,analog measuring method is suitable for use in a certain frequency range（5kHz）.While digital measuring method is suitable for most frequency range and can be used at a very low frequency.The bridge measurement circuit can increase the amplitude of original signal and improve the measurement accuracy of imaginary part.
出处
《地球物理学进展》
CSCD
北大核心
2015年第6期2749-2755,共7页
Progress in Geophysics
基金
国家自然科学基金(2012B2-0029)项目资助
关键词
虚部
相位
幅度
频率
乘法
测量
imaginary part
phase
amplitude
frequency
multiplication
measurement
