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声、电频谱测井直接测量声和电探头频谱的实部和虚部.通常情况下,实部信号幅度比较大,与地层参数的关系不密切;虚部的信号比较小,与地层声、电参数关系密切.测量时,换能器在井下,地面(或者井下电路)发射频率可调的正弦波或者方波电压于声、电探头,测量其电压和电流波形,处理其幅度和相位可得到探头的阻抗或导纳的实部和虚部.由于位于井下的探头的辐射声阻抗和电阻抗都与地层参数有关,因此,通过测量换能器的阻抗或导纳随频率的变化关系可获得地层的声电参数.与现有的测井方法测量一个频率(感应测井)或者瞬态声波波形(主频附近)不同,声电频谱测井对频率进行扫描,获得一定频率段的频谱.具体的频率区间根据井眼条件和所测量的地层参数以及探头结构确定.声电频谱测井理论建立井眼条件下频谱的实部和虚部与地层参数之间的关系,测井资料处理则利用这些关系从测量的频谱曲线获得所测量地层的声、电参数.该方法可以在裸眼井和套管井中进行,并且还可以像最早的电极测井那样,直接在地面完成测量,井下只放置探头,不设置电路.这时声电频谱测井通过电缆输入到井下探头的是正弦波或者方波,电缆对测量结果影响比较大.本文首先给出声电频谱测井的现场实验结果,然后讨论电缆的频谱特征以及对测量结果的影响.电缆的频谱峰在探头阻抗发生变化的时候变化比较小,容易从频谱测量结果中区分出来.
Acoustic and electrical spectrum logging directly measures the real and imaginary parts of the acoustic and electric probe spectrums.In general, the real part of the signal amplitude is relatively large, and the relationship between the formation parameters is not close; the imaginary part of the signal is relatively small, and the sound of the formation, Electrical parameters are closely related to the measurement. The transducers transmit sinusoidal or square-wave voltage with adjustable frequency downhole and ground (or downhole circuit) to the acoustic and electric probes to measure the voltage and current waveforms and process their amplitude and phase. Obtain the real part and the imaginary part of the impedance or admittance of the probe.As the acoustic impedance and the electrical impedance of the probe located underground are related to the formation parameters, Get the acoustic parameters of the formation.Comparing with the existing logging method to measure a frequency (inductive logging) or transient acoustic waveform (near the main frequency), the acousto-electric spectrum logging scans the frequency to obtain the spectrum of a certain frequency band Specific frequency intervals are determined based on wellbore conditions and measured formation parameters and the structure of the probe Acousto-electric spectrum logging theory Establishes the relationship between the real and imaginary parts of the spectrum and formation parameters in wellbore conditions, Processing then uses these relationships to derive the acoustic and electrical parameters of the measured formation from the measured spectral curves.The method can be performed in openhole and cased wells and can also be measured directly on the ground as in the earliest electrode logging, Only the probe is placed, no circuit is set, then acoustic-electric spectrum logging through the cable into the downhole probe is a sine wave or a square wave, the cable has a greater impact on the measurement results.This paper first gives field experiment results of acoustic-electric spectrum logging , And then discuss the cable’s spectral characteristics and the impact on the measurement results.The cable’s spectral peak changes little when the impedance of the probe changes and is easy to distinguish from the spectrum measurement results.