scholarly journals Double Trapezoidal Wave Transmitting System with Controllable Turn-Off Edge

2020 ◽  
Vol 10 (21) ◽  
pp. 7932
Author(s):  
Yuan Jiang ◽  
Yanju Ji ◽  
Yibing Yu ◽  
Shipeng Wang ◽  
Yuan Wang
Keyword(s):  
Polarization Effect ◽  
Induced Polarization ◽  
Emission Current ◽  
Wire Loop ◽  
Transient Electromagnetic ◽  
Charging Time ◽  
The Earth ◽  
Electromagnetic Measurement ◽  
Induced Polarization Effect ◽  
Off Time

For time domain transient electromagnetic measurement, the negative sign often appears in the polarization region, which contains the induced polarization information. It is considered that the polarization effect is caused by the capacitance charge of the earth. Extending the turn-off time of the emission current means increasing the charging time, and reducing the charging voltage, which makes the polarization effect easier to observe. Therefore, a double trapezoidal wave transmitting system with a controllable turn-off edge is designed in this paper. In the process of current transmitting, the turn-off time can be controlled by changing the clamping voltage depending on the passive clamping technology. By cutting into the absorption resistance, the current oscillation can be eliminated under the condition of ensuring linearity. To verify the effectiveness of the system, we designed a polarized wire loop based on the filament model simulating the polarized earth. Comparing the response of the wire loop, the emission current with short and long turn-off times contributes to inducing the induction and polarization fields respectively. The double trapezoidal wave transmitting system with a controllable turn-off edge is suitable for measuring the induced polarization effect.

A non-linear induced polarization effect on transient electromagnetic soundings

2016 ◽  
Vol 133 ◽  
pp. 16-24 ◽  
Author(s):  
Valeriya Yu. Hallbauer-Zadorozhnaya ◽  
Giovanni Santarato ◽  
Nasser Abu Zeid ◽  
Samuel Bignardi
Keyword(s):  
Polarization Effect ◽  
Induced Polarization ◽  
Transient Electromagnetic ◽  
Electromagnetic Soundings ◽  
Non Linear ◽  
Induced Polarization Effect

Electrical-prospecting method for hydrocarbon search using the induced-polarization effect

Geophysics ◽  
2006 ◽  
Vol 71 (4) ◽  
pp. G179-G189 ◽  
Author(s):  
Sofia Davydycheva ◽  
Nikolai Rykhlinski ◽  
Peter Legeido
Keyword(s):  
Polarization Effect ◽  
Induced Polarization ◽  
Controlled Source ◽  
3D Environment ◽  
Electrical Prospecting ◽  
Displacement Currents ◽  
Source Excitation ◽  
Induced Polarization Effect ◽  
Hydrocarbon Deposits ◽  
Regions Of Russia

We propose a method of surface and marine electrical prospecting using controlled-source excitation. The method is designed to detect hydrocarbon deposits at depths of a few kilometers and to map their boundaries. The technique is based on imaging the induced-polarization (IP) parameters of the geologic formation. We use the fact that, because of the imaginary part of the electric conductivity, polarized media support wave propagation processes whose nature is similar to displacement currents induced by the dielectric permittivity. However, unlike displacement currents, these processes reveal themselves at much lower frequencies and, therefore, at greater depths. It is established that the ratio of the second and the first differences of the electric potential does not decay after the current turn-off in polarized media, whereas it decays quickly if the IP effect is absent. Thus, the IP response can be observed directly and separated from the electromagnetic (EM) response. We use a vertical focusing of the electric current to decrease the effect of laterally adjacent formations to apply a 1D layered model in a 3D environment. This method obtained promising results in several regions of Russia.

Induced polarization effect on grounded-wire transient electromagnetic data from transverse electric and magnetic fields

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. E111-E120 ◽  
Author(s):  
Nan-Nan Zhou ◽  
Lei Kangxin ◽  
Guoqiang Xue ◽  
Wen Chen
Keyword(s):  
Transverse Electric ◽  
Transverse Magnetic ◽  
Induced Polarization ◽  
Double Line ◽  
Electromagnetic Data ◽  
Transient Electromagnetic ◽  
Electric And Magnetic Fields ◽  
The Difference ◽  
Polarizable Body ◽  
Induced Polarization Effect

Transient electromagnetic (TEM) data can be seriously distorted by induced polarization (IP) phenomena when a polarizable body is present. The TEM field generated by a grounded-wire source contains transverse electric (TE) and transverse magnetic (TM) modes. The IP effect is most commonly studied with the TEM total field, rather than considering the difference between TE and TM fields. To investigate the effect of IP phenomena on the TE and TM fields, we have performed a detailed analysis on IP-distorted TEM data based on numerical and field examples. We first compare the IP effect on the TE and TM fields when polarizable bodies with different polarizable parameters are present. The TM field is more severely affected by the IP effect than the TE field. Compared to a single grounded-wire source, a double-line grounded-wire source can generate a larger TM field in the horizontal electric field. We compare the IP effect on TEM data from single- and double-line grounded-wire TEM configurations, and find that the data from the double-line configuration have a higher TM/TE ratio and are more severely affected by IP phenomena than in the single-line case. Thus, it would be easier to identify and extract the IP response from field data acquired with a double-line grounded-wire source configuration. These results have been verified by a field survey of the Kalatongke copper-nickel ore district, which has predominantly layered geology, in Xinjiang, China.

Study of transient electromagnetic method measurements using a superconducting quantum interference device as B sensor receiver in polarizable survey area

Geophysics ◽  
2018 ◽  
Vol 83 (2) ◽  
pp. E111-E116 ◽  
Author(s):  
Shangyu Du ◽  
Yi Zhang ◽  
Yifeng Pei ◽  
Kun Jiang ◽  
Liangliang Rong ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Electromagnetic Method ◽  
Transient Electromagnetic Method ◽  
Primary Field ◽  
Survey Area ◽  
Superconducting Quantum Interference Device ◽  
Sign Reversal ◽  
Wire Loop ◽  
Transient Electromagnetic ◽  
Off Time

Time-domain transient electromagnetic method (TEM) measurements sometimes exhibit a sign reversal in the secondary field during the off-time, which is usually attributed to the induced-polarization (IP) effect. In contrast with the conventional IP method, which uses a current source, TEM with an ungrounded transmitting loop operates using a pure voltage source, which is induced by the primary field switching on and off. We performed TEM measurements in a resistive survey area showing an IP effect, and we used a low-temperature superconducting quantum interference device (LT-SQUID) with sensitivity of [Formula: see text] as a magnetic field sensor. A sign reversal in all of our measurements was observed; furthermore, the negative amplitude reached [Formula: see text]. In-depth analysis with an extended version of a wire-filament circuit reveals that the large negative signal may be due to discharging of in-ground capacitance, an IP effect. The conduction response of the ground can be restored by subtracting the fitted discharging response (negative valued) from the observed data. To verify this operation, we compared TEM measurements with and without wire-loop targets, which can induce a conduction field with a known decay time constant during the off-time. The extracted conduction responses of the wire-loop targets match the expected ones well. This research reveals that the primary field switch-off must always be included when interpreting TEM data with sign reversal and an LT-SQUID may be a good alternative sensor for studying the IP effect in TEM.

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