Electrical source transient electromagnetic ground-air detection method and system

Abstract

The invention discloses an electrical source transient electromagnetic ground-air detection method and system, and relates to the technical field of geophysical exploration. The method comprises the following specific steps: arranging a transient electromagnetic transmitting device and a receiving device in a detection area; carrying out ground-air transient electromagnetic measurement at different flight height positions to obtain a transient electromagnetic data total set; preprocessing electromagnetic data in the transient electromagnetic data set to obtain preprocessed data; data interpretation is carried out on the preprocessed data, an underground electrical structure is reconstructed by using an inversion algorithm, and a resistivity distribution image of the underground geologic body is obtained to identify a low-resistance abnormal region; and based on an inversion result, expressing spatial distribution and physical property parameters of the deep geologic body by adopting a three-dimensional modeling technology. According to the invention, the deep geological target body can be accurately explored, so that the accurate and detailed geological information of the deep geological target body can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of geophysical exploration, and particularly to an electrical source transient electromagnetic ground-air detection method and system. Background Art

[0002] The transient electromagnetic method (TEM), also known as the time-domain electromagnetic method, is an electromagnetic detection method based on the principle of electromagnetic induction. It is widely used in the detection of coalfield water hazards, mineral resources, and underground resources, and is an important geophysical exploration method. The electrical source transient electromagnetic method belongs to a branch of the transient electromagnetic method. It injects electromagnetic field signals into the ground using an electrical source and collects the induced signals from underground geological bodies during the source-off period to obtain their distribution information. However, in the prior art, the processing and interpretation of transient electromagnetic field signals do not consider the terrain interference problem. Under complex terrain conditions, terrain changes will have a significant impact on the electromagnetic response signals, resulting in reduced positioning accuracy, insufficient in-depth feature extraction and analysis, limiting the accuracy and reliability of the positioning results, and being inapplicable to the underground target positioning under complex terrain conditions. Therefore, exploring new transient electromagnetic interpretation technologies has important practical significance. Summary of the Invention

[0003] The object of the present invention is to provide an electrical source transient electromagnetic ground-air detection method and system to solve the problems raised in the background art.

[0004] To achieve the above object, the present invention provides the following solutions: On the one hand, an electrical source transient electromagnetic ground-air detection method is provided, and the specific steps are as follows:

[0005] Arrange a transient electromagnetic emission device and a receiving device in the detection area;

[0006] Carry out ground-air transient electromagnetic measurements at different flight altitude positions to obtain the total set of transient electromagnetic data;

[0007] Preprocess the electromagnetic data in the total set of transient electromagnetic data to obtain preprocessed data;

[0008] Perform data interpretation on the preprocessed data, use the inversion algorithm to reconstruct the underground electrical structure, and obtain the resistivity distribution image of the underground geological body to identify the low-resistance anomaly area;

[0009] Based on the inversion results, use three-dimensional modeling technology to express the spatial distribution and physical property parameters of deep geological bodies.

[0010] By adopting the above technical solutions, the following beneficial technical effects are achieved: collecting the ground-air transient electromagnetic data at different flight altitudes increases the effective data volume, enhances the constraint of the data on the reconstruction process, and can effectively reduce the non-uniqueness problem of multi-parameter reconstruction.

[0011] Preferably, the transmitting device uses a grounded long wire or multi-wires of any shape as the transmitting source, and emits a primary electromagnetic field pulse signal into the ground through electrodes. The waveform of the transmitting current is selected as a step waveform or a pseudo-random signal to excite the secondary induced eddy current field of the underground medium and generate an electromagnetic response signal; the receiving device is a magnetic sensor carried by an unmanned aerial vehicle, a helicopter or a gyroplane, and collects the secondary induced electromagnetic field signal of the underground medium in the air.

[0012] Preferably, the specific steps for preprocessing the electromagnetic data in the total set of transient electromagnetic data are as follows:

[0013] Filter out the noise of each transient electromagnetic data;

[0014] Normalize the transient electromagnetic data after noise filtering;

[0015] Perform time series analysis on the normalized data to identify and remove outliers;

[0016] Integrate the processed data to obtain the preprocessed data.

[0017] Preferably, the specific steps for data interpretation of the preprocessed data and reconstructing the underground electrical structure using the inversion algorithm are as follows:

[0018] Set an initial model according to the preprocessed data and construct an objective function for the ground-air transient electromagnetic regularization inversion;

[0019] Set the inversion termination conditions, including: the maximum number of iterations, the minimum fitting error, use the Gauss-Newton method to iteratively calculate the model update amount, obtain a new iterative model, and optimize the solution of the Jacobian matrix;

[0020] Set various inversion parameters, adaptively calculate the regularization parameter, repeat the iteration until the termination conditions are met, output the inversion model vector, and obtain the final inversion model.

[0021] Preferably, it also includes terrain correction for the electromagnetic data in the total set of transient electromagnetic data, and the specific steps are as follows:

[0022] Find the topographic elevation data of each acquisition point in the digital elevation model of the detection area to obtain the actual elevation data. Use a high-precision GPS device to record the initial elevation data of each acquisition point. Process the actual elevation data and the initial elevation data of each acquisition point to obtain the topographic correction factor for each acquisition point. Use the topographic correction factor to correct the electromagnetic response signal to obtain the corrected electromagnetic response signal.

[0023] By adopting the above technical solution, the following beneficial technical effects are achieved: Use a high-precision GPS device to record the initial elevation data of each acquisition point, calculate the topographic correction factor, and correct the electromagnetic response signal, significantly reducing the interference of terrain changes on the signal.

[0024] Preferably, when the receiving device performs data acquisition, the flight altitude of the helicopter or drone is 30 - 150 meters under the condition of ensuring flight safety.

[0025] By adopting the above technical solution, the following beneficial technical effects are achieved: The receiving device is carried by a drone or helicopter, and the flight altitude is generally 30 - 150 meters, covering the detection area while ensuring safety.

[0026] On the other hand, a transient electromagnetic ground-air detection system for electrical sources is provided, including an equipment layout module, a data acquisition module, a data preprocessing module, an inversion module, and a 3D modeling module; wherein,

[0027] The equipment layout module is used to arrange a transient electromagnetic emission device and a receiving device in the detection area;

[0028] The data acquisition module is used to conduct ground-air transient electromagnetic measurements at different flight altitude positions to obtain the total set of transient electromagnetic data;

[0029] The data preprocessing module is used to preprocess the electromagnetic data in the total set of transient electromagnetic data to obtain preprocessed data;

[0030] The inversion module is used to interpret the preprocessed data, use the inversion algorithm to reconstruct the underground electrical structure, and obtain the resistivity distribution image of the underground geological body to identify the low-resistance anomaly area;

[0031] The 3D modeling module is used to express the spatial distribution and physical property parameters of the deep geological body based on the inversion results using 3D modeling technology.

[0032] According to the specific embodiments provided by the present invention, the following technical effects are disclosed: it is possible to accurately explore deep geological target bodies, thereby obtaining accurate and detailed geological information of deep geological target bodies; based on the Gauss-Newton method, iterative inversion of ground-air transient electromagnetic is realized, and the final inversion model conforming to the detected geological structure is obtained, which greatly improves the efficiency and accuracy of ground-air transient electromagnetic inversion in turn. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 is the flowchart of the method of the present invention;

[0035] Figure 2 is the schematic diagram of the electrical source transient electromagnetic device of the present invention;

[0036] Figure 3 is the system structure diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0038] The electrical source transient electromagnetic ground-air detection method is a deep geological detection technology that combines ground emission and air reception. Its core lies in using a long wire source to emit transient electromagnetic fields, collecting data by a receiving device carried by an unmanned aerial vehicle or a helicopter, and realizing high-resolution imaging by combining advanced data processing technologies.

[0039] The embodiment of the present invention provides an electrical source transient electromagnetic ground-air detection method, as Figure 1 shown, the specific steps are as follows:

[0040] S1. Arrange a transient electromagnetic emission device and a receiving device in the detection area;

[0041] S2. Conduct ground-air transient electromagnetic measurements at different flight altitude positions to obtain a total set of transient electromagnetic data;

[0042] S3. Preprocess the electromagnetic data in the total set of transient electromagnetic data to obtain preprocessed data;

[0043] S4. Perform data interpretation on the preprocessed data, use the inversion algorithm to reconstruct the underground electrical structure, and obtain the resistivity distribution image of the underground geological body to identify the low-resistance anomaly area;

[0044] S5. Based on the inversion results, use 3D modeling technology to express the spatial distribution and physical property parameters of the deep geological body.

[0045] Further, as Figure 2 shown, in step S1, the transmitting device uses a grounded long wire or multi-wires of any shape as the transmitting source, and emits a primary electromagnetic field pulse signal into the ground through the electrodes. The transmitting current waveform selects a step waveform or a pseudo-random signal to excite the secondary induced eddy current field of the underground medium and generate an electromagnetic response signal; the receiving device is a magnetic sensor carried by a drone or a helicopter or a gyrocopter to collect the secondary induced electromagnetic field signal of the underground medium in the air. In this embodiment, a grounded long wire is used as the transmitting source, with a length usually of 1 - 4 kilometers and a transmitting power of not less than 10 kilowatts to generate a strong electromagnetic pulse signal. The advantage of the electrical source is that its vertical current diffusion speed is faster than that of the loop source, and it can excite electromagnetic fields in both TE and TM polarization modes, enhancing the detection ability for high-resistivity bodies; the receiving device is carried by a drone or a helicopter, with a flight altitude generally of 30 - 150 meters to ensure safety while covering the detection area, and the flight range is usually controlled within 3 times the scale of the electrical source to optimize the signal reception efficiency.

[0046] In step S2, collecting the ground-air transient electromagnetic data at different flight altitudes increases the amount of effective data, enhances the constraint of the data on the reconstruction process, and can effectively reduce the non-uniqueness problem of multi-parameter reconstruction.

[0047] Further, the specific steps for preprocessing the electromagnetic data in the total set of transient electromagnetic data in step S3 are:

[0048] S31. Filter the noise from each transient electromagnetic data;

[0049] S32. Perform normalization processing on the transient electromagnetic data after noise filtering;

[0050] S33. Perform time series analysis on the normalized data to identify and remove outliers;

[0051] S34. Integrate the processed data to obtain the preprocessed data.

[0052] Further, the specific steps for performing data interpretation on the preprocessed data and using the inversion algorithm to reconstruct the underground electrical structure are:

[0053] S41. Set the initial model according to the preprocessed data and construct the objective function for the ground-air transient electromagnetic regularization inversion;

[0054] S42. Set the inversion termination conditions, including: the maximum number of iterations and the minimum fitting error, use the Gauss-Newton method to iteratively calculate the model update amount, obtain a new iterative model, and optimize the solution of the Jacobian matrix;

[0055] S43. Set various inversion parameters, adaptively calculate the regularization parameter, repeat the iteration until the termination condition is met, output the inversion model vector, and obtain the final inversion model.

[0056] Furthermore, it also includes terrain correction for the electromagnetic data in the transient electromagnetic data set. The specific steps are as follows: Search for the terrain elevation data of each acquisition point in the digital elevation model of the detection area to obtain the actual elevation data. Use a high-precision GPS device to record the initial elevation data of each acquisition point. Process the actual elevation data and the initial elevation data of each acquisition point to obtain the terrain correction factor for each acquisition point, and use the terrain correction factor to correct the electromagnetic response signal to obtain the corrected electromagnetic response signal.

[0057] Use a high-precision GPS device to record the initial elevation data of each acquisition point, calculate the terrain correction factor and correct the electromagnetic response signal, significantly reducing the interference of terrain changes on the signal.

[0058] On the other hand, as Figure 3 shown, a transient electromagnetic ground-air detection system with an electrical source is provided, including an equipment layout module, a data acquisition module, a data preprocessing module, an inversion module, and a 3D modeling module; among them,

[0059] The equipment layout module is used to arrange the transient electromagnetic emission device and the receiving device in the detection area;

[0060] The data acquisition module is used to conduct ground-air transient electromagnetic measurements at different flight altitude positions to obtain the transient electromagnetic data set;

[0061] The data preprocessing module is used to preprocess the electromagnetic data in the transient electromagnetic data set to obtain the preprocessed data;

[0062] The inversion module is used to interpret the preprocessed data, use the inversion algorithm to reconstruct the underground electrical structure, obtain the resistivity distribution image of the underground geological body, and identify the low-resistance anomaly area;

[0063] The 3D modeling module is used to express the spatial distribution and physical property parameters of the deep geological body based on the inversion results using 3D modeling technology.

[0064] In this article, specific examples are used to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An electrical source transient electromagnetic ground-air detection method, characterized in that The specific steps include the following: Arrange transient electromagnetic transmitting devices and receiving devices in the detection area; Conduct ground-to-air transient electromagnetic measurements at different flight altitudes to obtain a total set of transient electromagnetic data; Preprocessing the electromagnetic data in the transient electromagnetic data collection to obtain preprocessed data; Performing data interpretation on the preprocessed data, reconstructing the underground electrical structure using an inversion algorithm, obtaining a resistivity distribution image of the underground geological body, and identifying low-resistance abnormal areas; Based on the inversion results, three-dimensional modeling technology is used to express the spatial distribution and physical parameters of deep geological bodies.

2. The transient electromagnetic ground-air detection method of an electrical source according to claim 1, characterized in that, The transmitting device uses a grounded long wire or multiple wires of arbitrary shape as a transmitting source, and transmits an electromagnetic field pulse signal to the underground through an electrode. The transmitting current waveform uses a step waveform or a pseudo-random signal to excite the secondary induced eddy current field of the underground medium and generate an electromagnetic response signal; the receiving device is a drone, helicopter or rotorcraft equipped with a magnetic sensor to collect the secondary induced electromagnetic field signal of the underground medium in the air.

3. A transient electromagnetic ground-air detection method for an electrical source according to claim 1, characterized in that The specific steps of preprocessing the electromagnetic data in the transient electromagnetic data set are: Perform noise filtering on each transient electromagnetic data; Normalize the transient electromagnetic data after noise is filtered out; Perform time series analysis on the normalized data to identify and remove outliers; The processed data are integrated to obtain the preprocessed data.

4. A transient electromagnetic ground-air detection method for an electrical source according to claim 1, characterized in that The specific steps of interpreting the pre-processed data and reconstructing the underground electrical structure using the inversion algorithm are as follows: An initial model is set according to the preprocessed data, and an objective function of ground-to-air transient electromagnetic regularization inversion is constructed; Set the inversion termination conditions, including the maximum number of iterations and the minimum fitting error, use the Gauss-Newton method to iteratively calculate the model update amount, obtain a new iterative model, and optimize the solution of the Jacobian matrix; Set various inversion parameters, adaptively calculate regularization parameters, repeat iterations until termination conditions are met, output the inversion model vector, and obtain the final inversion model.

5. A transient electromagnetic ground-air detection method for an electrical source according to claim 1, characterized in that The method also includes performing terrain correction on the electromagnetic data in the transient electromagnetic data set, the specific steps of which are: The terrain elevation data of each collection point is searched in the digital elevation model of the detection area to obtain the actual elevation data. The initial elevation data of each collection point is recorded using a high-precision GPS device. The actual elevation data and the initial elevation data of each collection point are processed to obtain the terrain correction factor of each collection point. The electromagnetic response signal is corrected using the terrain correction factor to obtain the corrected electromagnetic response signal.

6. The transient electromagnetic air-earth detection method of an electric source according to claim 2, characterized in that, When the receiving device collects data, the flight altitude of the helicopter or UAV is 30-150 meters while ensuring flight safety.

7. An electrical source transient electromagnetic ground-air detection system, characterized in that, It includes equipment layout module, data acquisition module, data preprocessing module, inversion module and 3D modeling module; among them, The equipment arrangement module is used to arrange transient electromagnetic transmitting devices and receiving devices in the detection area; The data acquisition module is used to carry out ground-to-air transient electromagnetic measurements at different flight altitudes to obtain a total set of transient electromagnetic data; The data preprocessing module is used to preprocess the electromagnetic data in the transient electromagnetic data collection to obtain preprocessed data; The inversion module is used to interpret the preprocessed data, reconstruct the underground electrical structure using an inversion algorithm, obtain the resistivity distribution image of the underground geological body, and identify the low-resistance anomaly area; The 3D modeling module is used to express the spatial distribution and physical property parameters of the deep geological body based on the inversion results using 3D modeling technology.

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