Radius-adjustable compensation antimagnetic flux transient electromagnetic measurement device and method

Abstract

The invention discloses a radius-adjustable compensation anti-magnetic flux transient electromagnetic measurement device and method, and relates to the field of transient electromagnetic exploration, and the device comprises a transmitter, a receiver, a transmitting coil, a compensation coil and a receiving coil. The transmitting coil and the compensating coil are connected in series and are connected with two poles of the transmitter, and the receiver is connected with two ends of the receiving coil; the compensating coil is arranged on the outer side of the receiving coil; the transmitting coil is arranged on the outer side of the compensating coil; an adjustable buckle is arranged on the compensation coil; the adjustable buckle is used for adjusting the radius of the compensation coil. The reverse magnetic flux is adjusted by adjusting the radius of the compensation coil, so that primary field influences such as self-inductance and mutual inductance are effectively eliminated, more accurate secondary field response signals are obtained, and more reliable transient electromagnetic exploration data can be obtained.

Description

Technical Field

[0001] This application relates to the field of transient electromagnetic exploration, and in particular to a compensated inverse magnetic flux transient electromagnetic measurement device and method with adjustable radius. Background Art

[0002] The transient electromagnetic method (TEM) is a time-domain electromagnetic exploration method, which is mainly based on the conductivity differences of rocks and ores in the earth's crust. The basic principle is to use a grounded or ungrounded transmitter to establish a stable magnetic field in the exploration area, and then quickly turn off the field source. According to the law of electromagnetic induction, a secondary field that changes with time will be induced in the underground medium. By observing and recording the induced transient electromagnetic response, the electrical property distribution of the underground medium can be further inferred, so as to identify and locate hidden abnormal bodies. The transient electromagnetic method has the advantages of being sensitive to low-resistance abnormal bodies, having small volume effects, large exploration depth, and high work efficiency, and is widely used in exploration fields such as energy minerals, hydrogeology, environmental geology, engineering geology, and geological disasters. The small loop is a common device of the transient electromagnetic method, which has the unique advantages of being light and portable, simple to deploy, and having a fast response, and has played an important role in application scenarios such as metal vein exploration, water body leakage detection, tunnel advance prediction, civil air defense project exploration, and underground pipeline detection.

[0003] However, in actual work, since the transmitting current cannot be turned off instantaneously, that is, the turning-off process takes a certain amount of time, the receiving coil receives both the primary field generated by the transmitting coil and the secondary field induced by the underground medium during this turning-off time period, making the data during the turning-off time period unusable directly. And because the transmitting coil and the receiving coil of the small loop device are very close in space, the self-inductance and mutual-inductance effects of the coils are more obvious, resulting in early signal distortion and shallow exploration blind areas, and it is difficult to accurately obtain information about underground geological bodies. Summary of the Invention

[0004] The purpose of this application is to provide a compensated inverse magnetic flux transient electromagnetic measurement device and method with adjustable radius, which can obtain more reliable transient electromagnetic exploration data.

[0005] To achieve the above purpose, this application provides the following solutions: In the first aspect, this application provides a compensated inverse magnetic flux transient electromagnetic measurement device with adjustable radius, including: a transmitter, a receiver, a transmitting coil, a compensation coil, and a receiving coil; One end of the transmitting coil is connected to one pole of the transmitter, the other end of the transmitting coil is connected to one end of the compensation coil, and the other end of the compensation coil is connected to the other pole of the transmitter; the receiver is connected to both ends of the receiving coil; the transmitter is used to generate a single-frequency sine wave or a transient electromagnetic square wave and feed current into the transmitting coil and the compensation coil; the receiver is used to measure, display, and record the voltage across both ends of the receiving coil. The compensation coil is arranged outside the receiving coil; the compensation coil and the receiving coil are arranged at intervals; the transmitting coil is arranged outside the compensation coil; the transmitting coil and the compensation coil are arranged at intervals. An adjustable buckle is provided on the compensation coil; the adjustable buckle is used to adjust the radius of the compensation coil.

[0006] In a second aspect, the present application provides a method for measuring compensated reverse magnetic flux transient electromagnetic with adjustable radius, including: Adjust the radius of the compensation coil in the compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius to the target radius; the target radius is the radius of the compensation coil corresponding to the minimum voltage modulus at both ends of the receiving coil; the compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius is the above-mentioned compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius. Place the compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius on the observation surface of the target measurement point, and use the transmitter to generate a transient electromagnetic square wave and feed the transient electromagnetic square wave current into the transmitting coil and the compensation coil. Use the receiver to record the voltage across both ends of the receiving coil to obtain the transient electromagnetic data of the target measurement point.

[0007] According to the specific embodiments provided by the present application, the following technical effects are disclosed: The present application provides a compensated reverse magnetic flux transient electromagnetic measuring device and method with adjustable radius. The direction of the induced voltage generated by the compensation coil in the receiving coil is opposite to the direction of the induced voltage generated by the transmitting coil in the receiving coil. By adjusting the radius of the compensation coil to adjust the magnitude of the reverse magnetic flux, the influence of the primary field such as self-inductance and mutual inductance can be effectively eliminated, and a more accurate secondary field response signal can be obtained, improving the reliability and anti-interference ability of the small-loop transient electromagnetic exploration data, thereby reducing the shallow detection blind area, facilitating subsequent geological interpretation, and realizing the effective identification and positioning of underground abnormal bodies. In addition, the present application does not need to introduce other electronic devices, the circuit structure is relatively simple, the coupling factors are reduced, and the system controllability is improved. Description of the Drawings

[0008] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for use in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0009] Figure 1 Schematic diagram of the open - circuit state of the radius - adjustable compensated inverse - flux transient electromagnetic measurement device provided in Embodiment 1 of the present application; Figure 2 Schematic diagram of the closed - circuit state of the radius - adjustable compensated inverse - flux transient electromagnetic measurement device provided in Embodiment 1 of the present application; Figure 3 Schematic diagram of an adjustable buckle structure provided in Embodiment 1 of the present application; Figure 4 Schematic flow chart of a radius - adjustable compensated inverse - flux transient electromagnetic measurement method provided in Embodiment 2 of the present application; Figure 5 Schematic diagram of the variation of the voltage modulus at both ends of the receiving coil with the adjustable radius provided in Embodiment 2 of the present application.

[0010] Reference numerals: Transmitter - Tx; Receiver - Rx; Receiving coil - C1; Transmitting coil - T1; Compensating coil - T2; Current - limiting resistor - R1; Adjustable buckle - B; 1 - Local adjustment area of a single - turn coil; 2 - Coil limiting component. Detailed implementation manners

[0011] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0012] To make the above - mentioned objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0013] Embodiment 1 As Figure 1 and Figure 2 shown, the present application provides a radius - adjustable compensated inverse - flux transient electromagnetic measurement device, including: Transmitter Tx, Receiver Rx, Transmitting coil T1, Compensating coil T2, Receiving coil C1, etc.

[0014] The transmitter Tx is used to generate a single - frequency sine wave or a transient electromagnetic square wave and feed corresponding currents into the transmitting coil T1 and the compensating coil T2.

[0015] The receiver Rx is used to measure, display, and record the voltage across the receiving coil C1 as the received voltage.

[0016] The receiving coil C1 is a multi-turn coil. The two ends of the coil are connected to the receiver Rx and are used to measure the induced voltage generated due to the magnetic field change.

[0017] As an example, the receiving coil C1 can be a 30-turn circular coil with a coil radius of 0.12 m and is wound with enameled wire with a diameter of 0.5 mm.

[0018] The transmitting coil T1 is a multi-turn coil. One end of the coil is connected to one pole of the transmitter Tx. The transmitting coil T1 surrounds the outside of the receiving coil C1. As an example, the transmitting coil T1 can be a 12-turn circular coil with a coil radius of 0.60 m and is wound with enameled wire with a diameter of 2 mm.

[0019] The transmitting coil T1 serves as the loop for a single-frequency sine wave or transient electromagnetic square wave current and is used to generate an induced voltage in the receiving coil C1. The calculation formula for the magnetic flux of the magnetic field emitted by the transmitting coil T1 in the receiving coil C1 is as follows.

[0020]

[0021] Where, Φ 1 is the magnetic flux of the magnetic field emitted by the transmitting coil T1 in the receiving coil C1; n 1 is the number of turns of the transmitting coil T1; n r is the number of turns of the receiving coil C1; μ 0 is the permeability of free space; I 1 is the magnitude of the transmitting current; L 1 is the closed curve enclosed by the transmitting coil T1 and serves as the integration path; is the differential element on the integration path; is the vector from the current element to the field point to be determined; r is the distance from the current element to the field point to be determined; S is the plane enclosed by the receiving coil C1 and serves as the integration plane; is the differential element on the integration plane.

[0022] The compensation coil T2 is a multi-turn coil. One end of the coil is connected to the other pole of the transmitter Tx and is in series with the transmitting coil T1 (the other end of the compensation coil T2 is connected to the other end of the transmitting coil T1). The compensation coil T2 is located between the transmitting coil T1 and the receiving coil C1 and is arranged at intervals. The compensation coil T2, the transmitting coil T1, and the receiving coil C1 are coplanar at the center, and their symmetry axes and center points coincide. As an example, the compensation coil T2 is a 6-turn circular coil with an adjustable coil radius of 0.25 - 0.35 meters and is wound with a rigid wire.

[0023] The current direction in the compensation coil T2 is opposite to the current direction in the transmitting coil T1. The direction of the induced voltage generated by the compensation coil T2 in the receiving coil C1 is opposite to the direction of the induced voltage generated by the transmitting coil T1 in the receiving coil C1. The calculation formula for the magnetic flux of the magnetic field emitted by the compensation coil T2 in the receiving coil C1 is as follows.

[0024]

[0025] Among them, Φ 2 is the magnetic flux of the magnetic field emitted by the compensation coil T2 in the receiving coil C1; n 2 is the number of turns of the compensation coil T2; n r is the number of turns of the receiving coil C1; μ 0 is the permeability of free space; I 2 is the magnitude of the compensation current; L 2 is the closed curve enclosed by the compensation coil T2, serving as the integration path; is the differential element on the integration path; is the vector from the current element to the field point to be calculated; r is the distance from the current element to the field point to be calculated; S is the plane enclosed by the receiving coil C1, serving as the integration plane; is the differential element on the integration plane.

[0026] In order to adjust the radius of the compensation coil T2 to finely adjust the compensation field, an adjustable buckle B is provided on the compensation coil T2; the adjustable buckle B is used to adjust the radius of the compensation coil T2. The adjustable buckle B has multiple adjustment gears; different adjustment gears correspond to different radii of the compensation coil. By positioning to different adjustment gears, the radius and area of the compensation coil T2 are adjusted, thereby adjusting the compensation magnetic moment.

[0027] Transient electromagnetic primary field U 1( t ) The expression is:

[0028] Among them, M is the mutual inductance coefficient between the transmitting coil, the compensation coil and the receiving coil, t is the measurement time, which is 0 when the transmitting current starts to turn off; dI ( t ) / d t is the rate of change of the transmitting current with time; t 0 is the current turn-off time.

[0029] Located in a homogeneous medium, the electromagnetic response expression of a circular loop carrying a step current is:

[0030] Among them I is the current magnitude, ρ is the resistivity of the medium, R is the radius of the transmitting coil, μ 0 is the magnetic permeability of vacuum; B z represents the axial component of the magnetic induction intensity. is the normalized distance, representing the distance of the observation point from the field source after normalization of the resistivity and the observation time.

[0031] In order to ensure that the compensation coil T2 has a certain resistance value to play a current-limiting role and avoid device damage caused by excessive current, a current-limiting resistor R1 is connected in series on the compensation coil T2. As an example, the resistance value of the current-limiting resistor R1 can be selected as 3 ohms.

[0032] When designing the compensation coil T2, factors such as the shape, size, number of turns, wire diameter, and arrangement of the coil need to be comprehensively considered, and appropriate materials are selected to ensure the expected compensation effect. As an example, the receiving coil C1 is a 30-turn circular coil with a coil radius of 0.12 m, wound with enameled wire with a diameter of 0.5 mm. The transmitting coil T1 is a 12-turn circular coil with a coil radius of 0.60 m, wound with enameled wire with a diameter of 2 mm. The compensation coil T2 is a 6-turn circular coil with an adjustable coil radius of 0.25 - 0.35 m, wound with hard wire.

[0033] As an example, Figure 3 shows an adjustable buckle structure. In addition to Figure 3 the adjustable buckle structure shown, other adjustment structures can also be adopted. For example, the radius of the compensation coil can be adjusted in the form of cable ties, handcuffs, gears, threads, or rings. Figure 3 In, the wavy part is the local adjustment area 1 of a single-turn coil, and each turn of the coil is Figure 3 the structure shown. Figure 3 The adjustable buckle structure in also includes a coil limiting component 2 to be able to adjust the radius of the compensation coil more stably.

[0034] In this application, by setting an additional coil (i.e., compensation coil T2) near the receiving coil C1, and the radius of the compensation coil T2 is adjustable, a current in the opposite direction to that of the transmitting coil T1 is fed into the compensation coil T2, thereby generating a magnetic field with a magnitude equal to or close to that of the primary field and in the opposite direction. By adjusting the radius of the compensation coil T2, the reverse magnetic flux is adjusted to cancel the self-inductance and mutual inductance responses, improve the aliasing phenomenon of the primary field in small-loop transient electromagnetic exploration, enhance the resolution ability for shallow geoelectric anomaly bodies, and improve the accuracy and reliability of shallow detection. To achieve the function of adjustable radius, the compensation coil T2 is connected by a snap fastener (tooth) at the interface, and multiple gears are set. The radius of the compensation coil is adjusted by opening and closing the snap fastener, which is relatively convenient to operate. In addition, this application can improve the reliability and anti-interference ability of small-loop transient electromagnetic exploration data, thereby reducing the blind area of shallow detection, facilitating subsequent geological interpretation, and realizing the effective identification and positioning of underground anomaly bodies.

[0035] Embodiment 2 As Figure 4 shown, this embodiment provides a method for measuring compensated reverse magnetic flux transient electromagnetic with adjustable radius, including: S1: Adjust the radius of the compensation coil T2 in the compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius to the target radius; the target radius is the radius of the compensation coil T2 when the voltage at both ends of the receiving coil C1 reaches the minimum voltage modulus value; the compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius is the compensated reverse magnetic flux transient electromagnetic measuring device described in Embodiment 1.

[0036] S2: Place the compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius on the observation surface of the target measuring point, and use the transmitter Tx to generate a transient electromagnetic square wave, and feed the transient electromagnetic square wave current into the transmitting coil T1 and the compensation coil T2.

[0037] S3: Use the receiver Rx to record the voltage at both ends of the receiving coil C1 to obtain the transient electromagnetic data of the target measuring point.

[0038] For the transient electromagnetic data of each target measuring point, the process of repeating the above steps S1 to S3 can be carried out.

[0039] As a specific implementation manner, in step S1, adjusting the radius of the compensation coil T2 in the compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius to the target radius specifically includes: S11: Place the compensated reverse magnetic flux transient electromagnetic measuring device with adjustable radius at a preset distance from the ground (such as 3 meters) above the target measuring point, adjust the adjustable snap fastener B of the compensation coil T2, and adjust the radius of the compensation coil T2 to the first preset size; the first preset size is the maximum radius (such as 0.35 meters) or the minimum radius (such as 0.25 meters).

[0040] S12: Start the transmitter Tx and the receiver Rx. Use the transmitter Tx to generate a single-frequency sine wave, feed a single-frequency sine current into the transmitting coil T1 and the compensation coil T2, and use the receiver Rx to record the voltage across the receiving coil C1. The frequency of the single-frequency sine wave is 60 kHz, and the single-frequency sine current is 4 A.

[0041] S13: Gradually adjust the adjustable buckle B of the compensation coil T2, and gradually adjust the radius of the compensation coil T2 to a second preset size; when the first preset size is the maximum radius, the second preset size is the minimum radius; when the first preset size is the minimum radius, the second preset size is the maximum radius.

[0042] S14: Use the receiver Rx to gradually record the voltage across the receiving coil C1.

[0043] S15: Compare the voltage change across the receiving coil C1 during the process of adjusting the radius of the compensation coil T2 from the first preset size to the second preset size, and determine the radius of the compensation coil corresponding to the minimum voltage modulus across the receiving coil C1. Figure 5 It is a schematic diagram of the modulus of the voltage across the receiving coil C1 changing with the adjustable radius.

[0044] S16: Adjust the adjustable buckle B of the compensation coil T2 so that the radius of the compensation coil T2 is the radius of the compensation coil corresponding to the minimum voltage modulus across the receiving coil C1.

[0045] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0046] In this article, specific examples are used to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A compensation reverse magnetic flux transient electromagnetic measurement device with adjustable radius, characterized in that, The compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius includes: a transmitter, a receiver, a transmitting coil, a compensating coil and a receiving coil; One end of the transmitting coil is connected to one pole of the transmitter, the other end of the transmitting coil is connected to one end of the compensating coil, and the other end of the compensating coil is connected to the other pole of the transmitter; the receiver is connected to both ends of the receiving coil; the transmitter is used to generate a single-frequency sine wave or a transient electromagnetic square wave and feed current into the transmitting coil and the compensating coil; the receiver is used to measure, display and record the voltage across the receiving coil; The compensating coil is arranged outside the receiving coil; the compensating coil is arranged at an interval from the receiving coil; the transmitting coil is arranged outside the compensating coil; the transmitting coil is arranged at an interval from the compensating coil; An adjustable buckle is provided on the compensating coil; the adjustable buckle is used to adjust the radius of the compensating coil.

2. The radius-adjustable compensation counter-flux transient electromagnetic measurement device according to claim 1, characterized in that, The adjustable buckle has multiple adjustment gears; different adjustment gears correspond to different radii of the compensating coil.

3. The compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius according to claim 1, characterized in that, A current-limiting resistor is connected in series on the compensating coil.

4. The radius-adjustable compensation for the anti-flux transient electromagnetic measuring device according to claim 1, characterized in that, The transmitting coil, the compensating coil and the receiving coil are all multi-turn coils.

5. The compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius according to claim 1, characterized in that, The transmitting coil, the compensating coil and the receiving coil are all circular coils.

6. The compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius according to claim 5, wherein, The centers of the transmitting coil, the compensating coil and the receiving coil are coplanar, and their symmetry axes and center points coincide.

7. The compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius according to claim 1, characterized in that, The transmitting coil is a 12-turn circular coil; the compensating coil is a 6-turn circular coil; the receiving coil is a 30-turn circular coil.

8. A compensation anti-flux transient electromagnetic measurement method with adjustable radius, characterized in that, The method for measuring compensating reverse magnetic flux transient electromagnetic with adjustable radius includes: Adjust the radius of the compensating coil in the compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius to the target radius; the target radius is the radius of the compensating coil corresponding to the minimum voltage modulus across the receiving coil; the compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius is the compensating reverse magnetic flux transient electromagnetic measuring device according to any one of claims 1 to 7; Place the compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius on the observation plane of the target measuring point, and use the transmitter to generate a transient electromagnetic square wave and feed the transient electromagnetic square wave current into the transmitting coil and the compensating coil; Use the receiver to record the voltage across the receiving coil to obtain the transient electromagnetic data of the target measuring point.

9. The radius-adjustable compensation for transient electromagnetic measurement method according to claim 8, wherein Adjusting the radius of the compensating coil in the compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius to the target radius specifically includes: Place the compensating reverse magnetic flux transient electromagnetic measuring device with adjustable radius above the target measuring point at a preset distance from the ground, adjust the adjustable buckle of the compensating coil, and adjust the radius of the compensating coil to the first preset size; the first preset size is the maximum radius or the minimum radius; Start the transmitter and the receiver, use the transmitter to generate a single-frequency sine wave, and feed the single-frequency sine current into the transmitting coil and the compensating coil, and use the receiver to record the voltage across the receiving coil; Gradually adjust the adjustable buckle of the compensation coil, and gradually adjust the radius of the compensation coil to the second preset size; when the first preset size is the maximum radius, the second preset size is the minimum radius; when the first preset size is the minimum radius, the second preset size is the maximum radius; Use the receiver to gradually record the voltages at both ends of the receiving coil; Compare the voltage changes at both ends of the receiving coil during the process of adjusting the radius of the compensation coil from the first preset size to the second preset size; Determine the radius of the compensation coil corresponding to the minimum voltage modulus at both ends of the receiving coil; Adjust the adjustable buckle of the compensation coil so that the radius of the compensation coil is the radius of the compensation coil corresponding to the voltage at both ends of the receiving coil reaching the minimum voltage modulus.

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