A wide azimuth man-made source electromagnetic observation method, device and medium

Abstract

This invention discloses a wide-azimuth artificial source electromagnetic observation method, device, and medium. The method includes: selecting the construction area of ​​the detection task as the measurement area according to the preset detection task requirements; determining the minimum distance between the field source and the measurement area according to the induction number requirement, and determining the maximum distance between the field source and the measurement area according to the signal-to-noise ratio requirement, and then defining the annular area formed between the minimum and maximum distances between the field source and the measurement area as the field source area; arranging measurement points in the measurement area, and arranging field sources in the field source area; collecting data of any electromagnetic field component at the measurement points and recording the corresponding device acquisition parameters; and using the electromagnetic field component data and the device acquisition parameters, solving for the apparent resistivity using an iterative method. This invention can deploy field sources in all azimuth angles of the measurement area and observe all electromagnetic field components, providing great flexibility in the selection of field source locations and data acquisition.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration, and in particular relates to a wide-azimuth artificial source electromagnetic observation method, device and medium. Background Technology

[0002] The transmitting system, consisting of a generator and instruments, extends wires that are grounded at points A and B, forming a loop with the earth. Points A and B each consist of several electrodes, typically made of aluminum plates, but copper rods can also be used. Current is transmitted into the ground through points A and B, forming what is called the field source (i.e., the origin of the electromagnetic field). A rectangular coordinate system is established with the midpoint of the field source as the origin, where x represents parallel to AB, y represents perpendicular to AB, and z represents perpendicular to the earth's surface downwards.

[0003] Artificial source electromagnetic method transmits currents of different frequencies into the ground through a field source, and then obtains electromagnetic field signals of the same frequency from a distance and analyzes these signals to obtain the properties of the underground medium.

[0004] The electric field components are collected by leading wires from the measuring instrument and grounding them on both sides of the measuring point, forming a potential difference measuring device. The midpoint of the line connecting the grounding points is the measuring point, and the electric field can be calculated from the measured potential difference. The angle between the line connecting the two grounding points and the x-axis indicates the different electric field components; for example, Ex indicates an angle of 0, 180, or 360 degrees, and Ey indicates an angle of 90 or 270 degrees. The electric field only has a horizontal component, so only the variation in the horizontal direction needs to be considered, i.e., the xoy plane.

[0005] Magnetic field components are collected directly at the measurement point using magnetic field sensors (magnetic rods, fluxgates, etc.). The angle between the orientation of the magnetic field sensor and the x-axis represents the magnetic field component, similar to the observation of the electric field. Magnetic fields have three directional components; we need to consider both the horizontal and vertical variations, i.e., three-dimensional space.

[0006] Conventional artificial source electromagnetic method observation devices can only collect the field strength within a specific azimuth angle of the source (60 degrees on each side) when acquiring electromagnetic field signals, and can only collect specific electromagnetic field components at the measurement point, including the electric field component E. x E y Magnetic field component H x H y H z Five types of traditional observation devices have a small range of field source locations to choose from, resulting in low utilization of the field source. Under complex terrain conditions, it is difficult to select a suitable field source location and it is also difficult to ensure the accuracy of electromagnetic field components, leading to low observation accuracy and even making construction impossible. Summary of the Invention

[0007] This invention provides a wide-directional artificial source electromagnetic observation method, device, and medium, which can expand the flexibility of the field source deployment location and improve the flexibility of data acquisition at the measurement points.

[0008] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0009] A wide-azimuth artificial source electromagnetic observation method includes:

[0010] Based on the preset requirements of the detection mission, the construction area of ​​the detection mission is selected as the survey area;

[0011] The minimum distance between the field source and the measurement area is determined according to the required number of inductions, and the maximum distance between the field source and the measurement area is determined according to the required signal-to-noise ratio. The annular area formed between the minimum and maximum distances between the field source and the measurement area is then defined as the field source area.

[0012] Set up measuring points in the measuring area and set up field sources in the field source area;

[0013] Collect data of any electromagnetic field component at the measuring point and record the corresponding device acquisition parameters;

[0014] The apparent resistivity is solved using electromagnetic field component data and parameters collected by the device through an iterative method.

[0015] Furthermore, the minimum distance between the field source and the measurement area is determined based on the required induction number. , specifically:

[0016]

[0017] In the formula, This is the minimum induction number in electromagnetic methods. The average resistivity of the formation within the detection depth range of the survey area. This is the minimum frequency at which the field source emits light.

[0018] Furthermore, the maximum distance between the field source and the measurement area is determined based on the signal-to-noise ratio requirements. , specifically:

[0019]

[0020] In the formula, The emission current of the field source, The distance between the field source electrodes, The average resistivity of the formation within the detection depth range of the survey area. External random noise, It represents the lowest signal-to-noise ratio that the receiver can detect.

[0021] Furthermore, based on the preset detection tasks and lateral resolution requirements, measuring points and lines are arranged in the measurement area. The measuring points are distributed in a linear, regular, or irregular network pattern.

[0022] Furthermore, based on the terrain conditions of each measuring point, select electromagnetic field component data that is easy to collect; if the collected electromagnetic field component is an electric field component, then the device acquisition parameters that need to be recorded are the electric field component angles; if the collected electromagnetic field component is a magnetic field component, then the device acquisition parameters that need to be recorded include the attitude angle of the magnetic field sensor.

[0023] Furthermore, if the collected electromagnetic field components are time-domain data of electric field components, the iterative method for solving the apparent resistivity specifically includes:

[0024] A1: Perform Fourier transform on the time-domain data of the electric field component at the measuring point, extract the data corresponding to the emission frequency of the field source, divide by the electrode distance at the measuring point, and obtain the frequency-domain electric field intensity component data E.

[0025] A2: Obtain the initial resistivity ;

[0026] A3: Set the current resistivity Substitute into the following formula:

[0027]

[0028] In the formula, This is the calculated value of apparent resistivity. For transmit and receive distance, The emission current of the field source, The distance between the field source electrodes, The electric field intensity component data obtained in step A1, For wave number, , The imaginary unit, It is the angular frequency. Permeability; For conductivity and resistivity They are reciprocals of each other; For receiving and sending angles, The electric field component angle;

[0029] A4: Calculated value of apparent resistivity With current resistivity The values ​​are compared; if the difference between the two does not meet the preset error requirement, the current resistivity is changed. Return to step A3; otherwise, the current resistivity is the final apparent resistivity obtained. .

[0030] Furthermore, if the collected electromagnetic field components are magnetic field component data, the iterative method for solving the apparent resistivity specifically includes:

[0031] B1: Perform Fourier transform on the magnetic field component data collected at the measuring point, extract the data corresponding to the emission frequency of the field source, divide by the sensor sensitivity, and perform unit conversion to obtain the frequency domain magnetic field strength data H.

[0032] B2: Obtain the initial resistivity ;

[0033] B3: Set the current resistivity Substitute into the following formula:

[0034]

[0035] In the formula, These are the calculated values ​​for the magnetic field components. The emission current of the field source, The distance between the field source electrodes, For transmit and receive distance, For receiving and sending angles, The attitude angles of the magnetic field sensor in the three-axis directions are: These represent the first and second type Bessel functions of order 0, respectively. Let represent the first and second type Bessel functions of order 1, respectively; For wave number, , The imaginary unit, It is the angular frequency. Permeability; For conductivity and resistivity They are reciprocals of each other;

[0036] B4: Calculated values ​​of magnetic field components The frequency domain magnetic field strength data obtained from step B1 The values ​​are compared; if the difference between the two does not meet the preset error requirement, the current resistivity is changed. If the current resistivity is not found, return to step B2; otherwise, the current resistivity is the final apparent resistivity obtained. .

[0037] A wide-azimuth artificial source electromagnetic observation device, comprising:

[0038] The field source determination module is used to: determine the minimum distance between the field source and the measurement area according to the induction number requirement, and determine the maximum distance between the field source and the measurement area according to the signal-to-noise ratio requirement, and then determine the annular area formed between the minimum and maximum distances as the field source area;

[0039] The data acquisition module is used to acquire data of any electromagnetic field component and corresponding device acquisition parameters from the measuring point receiver.

[0040] The apparent resistivity calculation module is used to solve for apparent resistivity using electromagnetic field component data and device-acquired parameters through an iterative method.

[0041] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the wide-azimuth artificial source electromagnetic observation method described above.

[0042] The beneficial effects of this invention are that the electromagnetic field component data collected by this invention can be used to calculate the apparent resistivity using a formula. Therefore, field sources can be set up in all azimuth angles of the survey area to observe all electromagnetic field components, providing great flexibility in the selection of field source locations and data acquisition. Attached Figure Description

[0043] Figure 1 This is a flowchart of a wide-azimuth artificial source electromagnetic observation method provided in an embodiment of this application;

[0044] Figure 2 This application provides an example of a wide-azimuth electromagnetic observation device field source arrangement.

[0045] Figure 3 This application provides a comparison of the received signal strength at a field source transmission frequency with background electromagnetic noise in an embodiment.

[0046] Figure 4 This is an example of an electric field component acquisition device provided in the embodiments of this application;

[0047] Figure 5 This is an example of a magnetic field component acquisition device provided in the embodiments of this application;

[0048] Figure 6 This is a diagram showing the apparent resistivity of an electric field component, provided in an embodiment of this application.

[0049] Figure 7 This is a graph showing the apparent resistivity of a magnetic field component, provided in an embodiment of this application. Detailed Implementation

[0050] The embodiments of the present invention will be described in detail below. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operation processes to further explain the technical solutions of the present invention.

[0051] Example 1

[0052] This embodiment provides a wide-azimuth artificial source electromagnetic observation method, referencing... Figure 1As shown, it includes:

[0053] Step 1: Select the construction area of ​​the preset detection task as the survey area according to the preset detection task requirements.

[0054] Step 2: Determine the minimum distance between the field source and the measurement area based on the required number of inductions, and determine the maximum distance between the field source and the measurement area based on the required signal-to-noise ratio. Then, determine the annular region formed between the minimum and maximum distances between the field source and the measurement area as the field source region.

[0055] Among them, the selectable location of the field source is the nearest boundary of the survey area, that is, the minimum distance between the field source and the survey area. Specifically, it is determined based on the minimum induction number requirement of the electromagnetic method:

[0056] (1)

[0057] In the formula, This is the minimum induction number in electromagnetic methods. The average resistivity of the formation within the detection depth range of the survey area. This is the minimum frequency at which the field source emits light.

[0058] Among them, the selectable location of the source is the farthest boundary of the survey area, that is, the maximum distance between the field source and the survey area. The specific requirement depends on the signal-to-noise ratio.

[0059] (2)

[0060] In the formula, The emission current of the field source, The distance between the field source electrodes, The average resistivity of the formation within the detection depth range of the survey area. External random noise, It represents the lowest signal-to-noise ratio that the receiver can detect.

[0061] Step 3: Set up measuring points in the measuring area and set up field sources in the field source area.

[0062] According to the preset detection task and lateral resolution requirements, measuring points and measuring lines are arranged in the measuring area. The measuring points are distributed in a linear, regular or irregular network pattern.

[0063] Within the annular field source region formed by the nearest and farthest boundaries of the field source location, such as Figure 2As shown, select a suitable location (e.g., a flat location without surface water or buildings) to place field source electrodes A and B. Dig pits for electrodes A and B, bury the electrodes, extend the electrodes with wires, pour salt water over them, and then cover them. Set the transmitter's transmission current, collect signals in the test area, test the signal strength, and change the positions of field source electrodes A and B to ensure that the signal strength at the main transmission frequency of the field source is higher than the background electromagnetic noise, clearly visible in the spectrum curve, as shown. Figure 3 As shown.

[0064] Step 4: Collect data of any electromagnetic field component at the measuring point and record the corresponding device acquisition parameters.

[0065] Based on the terrain conditions of each measuring point, select the electromagnetic field component data that is easy to collect, such as... Figure 4 and Figure 5 As shown. For example, the x-axis direction of a certain measuring point passes through a mountain, while the y-axis direction does not. Therefore, the electromagnetic field component in the x-axis direction is chosen for the measuring point to facilitate data acquisition.

[0066] If the electromagnetic field component being collected is an electric field component, then the device parameter that needs to be recorded is the electric field component angle. .

[0067] If the collected electromagnetic field component is a magnetic field component, then the device parameters that need to be recorded include the attitude angle of the magnetic field sensor. .

[0068] Step 5: Using electromagnetic field component data and parameters acquired by the device, solve for the apparent resistivity using an iterative method.

[0069] If the collected electromagnetic field components are time-domain data of electric field components, the iterative method for solving the apparent resistivity specifically includes:

[0070] A1: Perform Fourier transform on the time-domain data of the electric field components collected at the measuring point, extract the data corresponding to the emission frequency of the field source, divide it by the electrode distance of the measuring point, and obtain the frequency-domain electric field intensity component data E.

[0071] A2: Obtain the initial resistivity ;

[0072] A3: Set the current resistivity Substitute into the following formula:

[0073]

[0074] In the formula, This is the calculated value of apparent resistivity. For transmit and receive distance, The emission current of the field source, The distance between the field source electrodes, The electric field intensity component data obtained in step A1, For wave number, , The imaginary unit, It is the angular frequency. Permeability; For conductivity and resistivity They are reciprocals of each other; For receiving and sending angles, The electric field component angle;

[0075] A4: Calculated value of apparent resistivity With current resistivity The values ​​are compared; if the difference between the two does not meet the preset error requirement, the current resistivity is changed. Return to step A3; otherwise, the current resistivity is the final apparent resistivity obtained. .

[0076] Figure 6 Showing the electric field component angle Example of apparent resistivity of electric field at time.

[0077] If the collected electromagnetic field components are magnetic field component data, the iterative method for solving the apparent resistivity specifically includes:

[0078] B1: Perform Fourier transform on the magnetic field component data collected at the measuring point, extract the data corresponding to the emission frequency of the field source, divide by the sensor sensitivity, and perform unit conversion to obtain the frequency domain magnetic field strength data H.

[0079] B2: Obtain the initial resistivity ;

[0080] B3: Set the current resistivity Substitute into the following formula:

[0081]

[0082] In the formula, These are the calculated values ​​for the magnetic field components. The emission current of the field source, The distance between the field source electrodes, For transmit and receive distance, For receiving and sending angles, The attitude angles of the magnetic field sensor in the three-axis directions are: These represent the first and second type Bessel functions of order 0, respectively. Let represent the first and second type Bessel functions of order 1, respectively; For wave number, , The imaginary unit, It is the angular frequency. Permeability; For conductivity and resistivity They are reciprocals of each other;

[0083] B4: Calculated values ​​of magnetic field components The frequency domain magnetic field strength data obtained from step B1 The values ​​are compared; if the difference between the two does not meet the preset error requirement, the current resistivity is changed. Return to step B3; otherwise, the current resistivity is the final apparent resistivity obtained. .

[0084] Figure 7 The angles between the magnetic field sensor and each coordinate axis are shown. Example of apparent resistivity of magnetic field at time.

[0085] Example 2

[0086] This embodiment provides a wide-azimuth artificial source electromagnetic observation device, including:

[0087] The field source determination module is used to: determine the minimum distance between the field source and the measurement area based on the required number of inductions, and determine the maximum distance between the field source and the measurement area based on the required signal-to-noise ratio, and then determine the annular area formed between the minimum and maximum distances as the field source area; wherein, the measurement area is determined based on the construction area of ​​the preset detection task;

[0088] The data acquisition module is used to acquire data of any electromagnetic field component and corresponding device acquisition parameters from the measuring point receiver.

[0089] The apparent resistivity calculation module is used to solve for apparent resistivity using electromagnetic field component data and device-acquired parameters through an iterative method.

[0090] The implementation of each component module of the observation device described in this embodiment is the same as that of the observation method described in Embodiment 1.

[0091] Example 3

[0092] This embodiment provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in Embodiment 1.

[0093] The above embodiments are preferred embodiments of this application. Those skilled in the art can make various changes or improvements based on them. Without departing from the overall concept of this application, such changes or improvements should fall within the scope of protection claimed in this application.

Claims

1. A method for electromagnetic observation of a wide-azimuth artificial source, characterized in that, include: Based on the preset requirements of the detection mission, the construction area of ​​the detection mission is selected as the survey area; The minimum distance between the field source and the measurement area is determined according to the required number of inductions, and the maximum distance between the field source and the measurement area is determined according to the required signal-to-noise ratio. The annular area formed between the minimum and maximum distances between the field source and the measurement area is then defined as the field source area. Set up measuring points in the measuring area and set up field sources in the field source area; Collect data of any electromagnetic field component at the measuring point and record the corresponding device acquisition parameters; The apparent resistivity is solved using electromagnetic field component data and parameters collected by the device through an iterative method.

2. The wide-azimuth artificial source electromagnetic observation method according to claim 1, characterized in that, Determine the minimum distance between the field source and the measurement area based on the required induction number. , specifically: ； In the formula, This is the minimum induction number in electromagnetic methods. The average resistivity of the formation within the detection depth range of the survey area. This is the minimum frequency at which the field source emits light.

3. The wide-azimuth artificial source electromagnetic observation method according to claim 1, characterized in that, Determine the maximum distance between the field source and the test area based on the signal-to-noise ratio requirements. , specifically: ； In the formula, The emission current of the field source, The distance between the field source electrodes, The average resistivity of the formation within the detection depth range of the survey area. External random noise, It represents the lowest signal-to-noise ratio that the receiver can detect.

4. The wide-azimuth artificial source electromagnetic observation method according to claim 1, characterized in that, According to the preset detection task and lateral resolution requirements, measuring points and measuring lines are arranged in the measuring area. The measuring points are distributed in a linear, regular or irregular network pattern.

5. The wide-azimuth artificial source electromagnetic observation method according to claim 1, characterized in that, Based on the terrain conditions of each measuring point, select electromagnetic field component data that is easy to collect; if the collected electromagnetic field component is an electric field component, the device parameters to be recorded are the electric field component angles; if the collected electromagnetic field component is a magnetic field component, the device parameters to be recorded include the attitude angles of the magnetic field sensor.

6. The wide-azimuth artificial source electromagnetic observation method according to claim 1, characterized in that, If the collected electromagnetic field components are time-domain data of electric field components, the iterative method for solving the apparent resistivity specifically includes: A1: Perform Fourier transform on the time-domain data of the electric field component at the measuring point, extract the data corresponding to the emission frequency of the field source, divide by the electrode distance at the measuring point, and obtain the frequency-domain electric field intensity component data E. A2: Obtain the initial resistivity ; A3: Set the current resistivity Substitute into the following formula: ； In the formula, This is the calculated value of apparent resistivity. For transmit and receive distance, The emission current of the field source, The distance between the field source electrodes, The electric field intensity component data obtained in step A1, For wave number, , The imaginary unit, It is the angular frequency. Permeability; For conductivity and resistivity They are reciprocals of each other; For receiving and sending angles, The electric field component angle; A4: Calculated value of apparent resistivity With current resistivity The two values ​​are compared; if the difference does not meet the preset error requirement, the current resistivity is changed. Return to step A3; otherwise, the current resistivity is the final apparent resistivity obtained. .

7. The wide-azimuth artificial source electromagnetic observation method according to claim 1, characterized in that, If the collected electromagnetic field components are magnetic field component data, the iterative method for solving the apparent resistivity specifically includes: B1: Perform Fourier transform on the magnetic field component data collected at the measuring point, extract the data corresponding to the emission frequency of the field source, divide by the sensor sensitivity, and perform unit conversion to obtain the frequency domain magnetic field strength data H. B2: Obtaining the initial resistivity ; B3: Set the current resistivity Substitute into the following formula: ； In the formula, These are the calculated values ​​for the magnetic field components. The emission current of the field source, The distance between the field source electrodes, For transmit and receive distance, For receiving and sending angles, The attitude angles of the magnetic field sensor in the three-axis directions are: These represent the first and second type Bessel functions of order 0, respectively. Let represent the first and second type Bessel functions of order 1, respectively; For wave number, , The imaginary unit, It is the angular frequency. Permeability; For conductivity and resistivity They are reciprocals of each other; B4: Calculated values ​​of magnetic field components The frequency domain magnetic field strength data obtained from step B1 The two values ​​are compared; if the difference does not meet the preset error requirement, the current resistivity is changed. If the current resistivity is not found, return to step B2; otherwise, the current resistivity is the final apparent resistivity obtained. .

8. A wide-azimuth artificial source electromagnetic observation device, characterized in that, include: The field source determination module is used to: determine the minimum distance between the field source and the measurement area according to the induction number requirement, and determine the maximum distance between the field source and the measurement area according to the signal-to-noise ratio requirement, and then determine the annular area formed between the minimum and maximum distances as the field source area; The data acquisition module is used to acquire data of any electromagnetic field component and corresponding device acquisition parameters from the measuring point receiver. The apparent resistivity calculation module is used to solve for apparent resistivity using electromagnetic field component data and device-acquired parameters through an iterative method.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method as described in any one of claims 1 to 7.

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