Research On Full Wave Exploration Model Of Transient Electromagnetic Low Resistance Anomalies

The electrical signals used in conventional electrical exploration are usually the response signals after the voltage or current stabilizes at DC.Since the potential signal is unstable when the voltage of the transmitting electrode is turned on,its function is often ignored.At the moment when the signal is turned on,there is not only the current propagation but also the electromagnetic field propagation.Compared with the current conduction propagation,the electromagnetic field carries the conductivity information of the formation medium.In this paper,the full-wave waveform is comprehensively analyzed,and the transient response and steady-state response data are combined to carry out experimental research on low-resistance abnormal bodies.Firstly,Maxwell equations are analyzed,and the propagation law of electromagnetic field and propagation velocity in medium are deduced.Secondly,the propagation laws of uniform infinite medium and two-layer medium are calculated respectively,and the electric field distribution excited by point electrode is deduced.A mature theory is adopted for data processing,and finite difference iterative calculation is used for simulation.The transient response and steady-state response in the collected waveform data are respectively plotted as potential contour maps for comparative analysis.For full-wave waveforms,electrodes of different sizes are used to carry out experimental collection and analyze the relationship between waveform morphological changes and electrodes.For the transient response form,the equivalent circuit model is used to simulate the transmission and reception waveforms.In terms of the selection of media materials for the signal acquisition system,the emission system and the experimental model,continuous improvement and adjustment have been made in the experiment.First of all,the signal acquisition system collects from 8 channels to 32 channels,and finally 64 channels to make the collected signals more comprehensive.Secondly,the transmitting system transmits from low power to high power,which increases the range of potential amplitude.Then there are the selection of electrode materials and the materials in the experimental model.The electrodes range from aluminum materials prone to electrochemistry to relatively stable copper electrodes.The experimental environment also ranges from water body experiments to sand model experiments.However,the sampling frequency was also adjusted during the whole experiment.The sampling frequencies of 100 Hz,1000Hz and 4000 Hz were adopted respectively,and the transient response and steady-state response provided by the emission waveform were collected during the on and off switching of the experiment.This provides a theoretical and experimental basis for the use of transient response data in actual electrical detection.