Large Power Supply Hydrological Instrument Transient Electromagnetic System For Shallow Detection

Large Power Supply hydrological instrument Transient Electromagnetic System for Shallow Detection

Prodict Description

WTEM-1/GPS is newly developed product with all functions of Transient Electromagnetic method. It is full of the advantages of same products home and abroad, and characterized with large transmitter power, high reliability, strong anti-interference (sky electricity, 50 or 60 Hz industrial electricity), light and of low power cost. The WTEM-1J/GPS TEM exploration system receiver could be applied together with the large power transmitter WTEM-1D for deep exploration, also could be applied together with small power transmitter WTEM-1X for shallow exploration.

Exploration Principles

Basic principle
Electromagnetic induction phenomenon: When the current in the transmitting coil changes suddenly, a primary magnetic field that changes rapidly with time will be generated in the surrounding space. According to the law of electromagnetic induction, this primary magnetic field will induce eddy currents in the underground conductive medium, and the eddy currents will generate secondary magnetic fields.
Receiving secondary magnetic field: After the primary magnetic field disappears, the underground eddy current will gradually decay due to heat loss and other reasons, and the secondary magnetic field it generates will also decay accordingly. The receiving coil of the transient electromagnetic instrument receives the signal of the change of the secondary magnetic field over time in this process.
Working process
Transmitting stage: The transmitter sends a pulse current to the underground through the transmitting coil. The current usually has a certain frequency and waveform, and common ones are step waves and square waves. The size and waveform of the transmitting current will affect the intensity and distribution of the primary magnetic field, and then affect the excitation effect of the underground eddy current.
Transition stage: At the moment after the transmitting current is cut off, the primary magnetic field disappears rapidly, the eddy current in the underground medium begins to decay, and a secondary magnetic field is generated at the same time. This stage is the key period for the generation and change of transient electromagnetic signals. The receiving coil begins to receive the secondary magnetic field signal at this time.
Receiving stage: The receiving coil converts the received secondary magnetic field signal into an electrical signal, which is amplified by the preamplifier and transmitted to the receiver for processing. The receiver performs operations such as sampling, filtering, and digitization on the signal, and records the attenuation curve of the secondary magnetic field over time.
Geological information acquisition
Conductivity differences reflect: Different geological bodies have different conductivity. For example, good conductors (such as metal ore bodies, groundwater, etc.) have strong conductivity for eddy currents, which will produce a strong secondary magnetic field and decay relatively slowly; while insulators or low-conductivity geological bodies produce weaker secondary magnetic fields and decay faster. By analyzing the intensity, attenuation characteristics and other parameters of the secondary magnetic field, the conductivity distribution of the underground geological body can be inferred.
Principle of depth detection: The propagation depth of transient electromagnetic signals is related to time. The early signals mainly reflect the information of shallow geological bodies. As time goes by, the late signals contain more information about deep geological bodies. By analyzing and processing signals in different time windows, the detection of geological bodies at different depths underground can be achieved.
Data processing and interpretation
Data processing: The collected transient electromagnetic data needs to undergo a series of processing, including noise removal, correction, deconvolution, etc., to improve the quality and resolution of the data. Then, the measured secondary magnetic field response is converted into a distribution model of underground resistivity by inversion calculation of the processed data.
Geological interpretation: Based on the resistivity model obtained by inversion, combined with the geological background and known geological data, the underground geological structure and geological body distribution are interpreted and inferred. For example, identifying geological structures such as faults, folds, and stratigraphic interfaces, and looking for potential ore bodies, groundwater and other resources.

Application

Configuration is selectable for different geological problems, such as quick survey, stereo mapping, deep mine finding, and shallow detection. It is mainly used for metal mine, coal mine, oil and gas field, geothermic field, and hydro- and engineering geology survey.

Transient Electromagnetic Method Configuration

1.Transmitter: It is the core component that generates and transmits electromagnetic signals. It can provide enough energy to stimulate the underground medium to generate secondary electromagnetic fields. Its power, frequency and other parameters can be adjusted according to different detection needs.
2.Transmitter coil: Generally, a multi-turn ring coil is used to convert the current generated by the transmitter into a magnetic field and transmit it underground. The size, number of turns and shape of the transmitting coil will affect the intensity and distribution of the transmitted magnetic field.

3.Receiver: used to receive the secondary electromagnetic field signal generated by electromagnetic induction in the underground medium. It has the characteristics of high sensitivity, wide bandwidth and low noise, and can accurately capture weak electromagnetic signals and convert them into digital signals for processing.
4.Preamplifier: connected between the receiving coil and the receiver, used to amplify weak electromagnetic signals and improve the signal-to-noise ratio for subsequent processing and analysis.

Product Details: