A magnetic dipole device for transient electromagnetic method dynamic measurement and a measurement method thereof

Abstract

The application discloses a magnetic dipole device for transient electromagnetic method dynamic measurement and a measurement method thereof, and relates to the technical field of geophysical exploration. The device comprises a transmitting device and a receiving device which are arranged separately and are in a vertical magnetic dipole structure. The transmitting device comprises a transmitter and a transmitting wire frame, and the transmitter is arranged on the transmitting wire frame. The receiving device comprises a receiver and a receiving wire frame, and the receiver is arranged on the receiving wire frame. The transmitting device and the receiving device are both provided with a back plate which forms a portable backpack structure. The transmitting wire frame and the receiving wire frame are respectively integrated with a positioning sensing unit, an inertial measurement unit and a magnetic sensing unit. The application has the effect of improving the measurement precision of transient electromagnetic method dynamic measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geophysical exploration, in particular to a magnetic dipole device for transient electromagnetic method dynamic measurement and a measurement method thereof. BACKGROUND

[0002] At present, transient electromagnetic method (TEM) dynamic measurement realizes geophysical exploration through a moving transmitting source and a receiving coil, and can be applied to airborne, vehicle-mounted and ship-mounted scenes.

[0003] The existing shallow transient electromagnetic method dynamic measurement requires high precision and earlier data. The current working mode is to fix the coil and instrument on a non-magnetic vehicle and tow the non-magnetic vehicle by manpower or a vehicle to realize dynamic measurement of data. In order to save space, a central loop or an overlapping loop device is usually arranged on the non-magnetic vehicle for towed travel measurement, that is, the receiving coil is located in the middle of the transmitting coil or overlaps the transmitting coil, as shown in FIG. 1. Figure 1 In order to increase the exploration depth, a multi-turn coil is usually used to increase the magnetic moment, but the increase in the number of turns of the coil increases the self-inductance and mutual inductance of the coil, which increases the influence on the early data, increases the turn-off time, and causes distortion of the early data. Reducing the influence of the inductance of the coil is a key problem that needs to be solved in transient electromagnetic method dynamic measurement.

[0004] The equivalent counter-flux transient electromagnetic method is a kind of transient electromagnetic method variant specially used for suppressing the influence of the inductance of the transmitting coil, improving the quality of early signals and the resolution of shallow layers. The transmitting coil is two transmitting coils placed strictly coaxially and in parallel, with equal area and number of turns (i.e., equal magnetic moment). The upper and lower coils are connected in series, but the driving current directions are opposite. The measurement mode of the double transmitting coil also significantly increases the weight and volume, and the coil shakes more during towing, which increases the background noise of the primary field.

[0005] In summary, the mode of fixing the coil on the non-magnetic vehicle for towed dynamic measurement in the prior art limits the application scene and is not suitable for construction in places with dense vegetation or steep terrain. The equivalent counter-flux device is also relatively bulky. Therefore, there is a defect that the measurement precision for transient electromagnetic method dynamic measurement is poor, and improvement is needed. SUMMARY

[0006] In order to improve the measurement precision for transient electromagnetic method dynamic measurement, the present application provides a magnetic dipole device for transient electromagnetic method dynamic measurement and a measurement method thereof.

[0007] In the first aspect, the application aims to realize the following technical scheme:

[0008] A magnetic dipole device for transient electromagnetic method dynamic measurement, comprising a transmitting device and a receiving device arranged in a vertical magnetic dipole structure in a transceiving separation mode.

[0009] The transmitting device comprises a transmitter and a transmitting frame, and the transmitter is arranged on the transmitting frame; the receiving device comprises a receiver and a receiving frame, and the receiver is arranged on the receiving frame; the transmitting device and the receiving device are both provided with a backboard forming a portable backpack structure; the transmitting frame and the receiving frame are respectively integrated with a positioning sensing unit, an inertial measurement unit and a magnetic sensing unit.

[0010] By adopting the technical scheme, the magnetic dipole device for transient electromagnetic method dynamic measurement is provided, the magnetic dipole design of the application can improve the measurement precision for transient electromagnetic method dynamic measurement, the transmitting frame and the receiving frame are taken as independent magnetic dipoles, based on the Biot-Savart law, the received signal mainly comes from the secondary magnetic field of the underground conductive medium, and theoretically the primary field induced voltage is zero. This directly avoids the problems of early data distortion and increased off time caused by the self-induction and mutual induction of the multi-turn coil, and the transmitting frame and the receiving frame respectively correspond to vertical magnetic dipoles, ensuring signal synchronism to obtain high-fidelity transient electromagnetic attenuation data. In actual construction measurement, the magnetic dipole device is artificially carried out for transient electromagnetic method dynamic measurement, which can effectively avoid the influence of the inductance effect of the transmitting coil, compared with the traditional overlapping loop or central loop device method, the device eliminates the interference of the coil inductance on the early data, and the measurement method of the application is more flexible. In measurement, two operators carry the transmitting device and the receiving device respectively and walk along the measuring line, the interval distance is adjustable, the cumbersome nature of the non-magnetic car is avoided, and the device is suitable for various construction environments. By recording the kinematic parameters such as the position and the inclination, the azimuth and the pitch angle of the transmitting frame and the receiving frame in real time, the data can be finely processed in the later stage, the accuracy of data interpretation is improved, and the exploration requirements of high-precision electromagnetic method are met.

[0011] In a preferred example of the application, the backboard and the transmitting frame or the receiving frame are connected through a connecting rod, and the connecting rod fixes the backboard and the transmitting frame or the backboard and the receiving frame in a vertically unfolded state or folds the transmitting frame or the receiving frame and the backboard.

[0012] By adopting the above technical scheme, the connecting rod is used to fix the transmitting device or the receiving device in a vertically unfolded state, which ensures that the transmitting frame and the receiving frame always maintain stable vertical orientation during the carrying process, effectively prevents the inclination or torsion of the frame caused by human motion, and guarantees the consistency of the magnetic dipole direction.

[0013] In a preferred example of the application, the positioning sensing unit is an RTK positioning module, which is used to obtain the longitude, latitude and elevation coordinates of the transmitting frame or the receiving frame in real time.

[0014] The inertial measurement unit comprises three-component accelerometers for measuring linear acceleration of the transmitting frame or the receiving frame and three-component gyroscopes for measuring angular velocity of the transmitting frame or the receiving frame, and determines the inclination angle and the pitch angle in combination with a sensor fusion algorithm;

[0015] The magnetic sensing unit is a three-component magnetoresistance sensor for measuring a geomagnetic field vector to obtain the azimuth angle;

[0016] The transmitting device or the receiving device generates a set of kinematic parameters including the position coordinates, the inclination angle, the azimuth angle and the pitch angle based on the measurement data of the positioning sensing unit, the inertial measurement unit and the magnetic sensing unit.

[0017] By using the above technical solutions, the measurement data of the positioning sensing unit, the inertial measurement unit and the magnetic sensing unit are used to realize high-precision real-time sensing of the frame position, the inclination angle, the azimuth angle and the pitch angle, so as to achieve the purpose of accurately detecting and monitoring the motion changes of the transmitting device and the receiving device and the changes of the measurement data.

[0018] In a preferred example of the present application, the transmitter generates a periodic current pulse sequence with preset starting time T0, transmission duration T, interval time ΔT, current amplitude I and frequency F as parameters, and the nth transmission time interval is [T0+(n-1)(T+ΔT), T0+(n-1)(T+ΔT)+T].

[0019] The acquisition time interval of the receiver for data acquisition is strictly aligned with the transmission time interval; the acquired time-domain signal is normalized to obtain transient electromagnetic decay data; and the transient electromagnetic decay data and the set of kinematic parameters are sent to an external terminal.

[0020] By using the above technical solutions, accurate transmission timing parameters and receiving timing parameters are set, the acquisition time interval of the receiver is strictly aligned with the transmission time interval of the transmitter, so as to ensure that the transient electromagnetic decay data is strictly aligned on the time axis and the accuracy is ensured. The periodic current pulse is generated and collected synchronously, which avoids signal distortion or misjudgment caused by timing deviation, effectively eliminates amplitude drift caused by current fluctuation or environmental interference, and improves the data acquisition quality.

[0021] In a second aspect, the application aims to achieve the following technical solutions:

[0022] A transient electromagnetic method dynamic cooperative measurement method based on a magnetic dipole device, applied to the magnetic dipole device for transient electromagnetic method dynamic measurement as described above, the method comprising:

[0023] Based on the exploration needs, set the emission current amplitude I, the emission frequency F, the collection starting time T0, the single emission duration T and the collection interval ΔT; two operators respectively carry the transmitting device and the receiving device, and are fixed on the back through the back plate;

[0024] Two operators synchronously walk along the survey line direction with a preset interval; the transmitter controls the transmitting line frame to generate a transient electromagnetic excitation signal, and the receiver synchronously collects the induction signal of the receiving line frame;

[0025] Through the positioning and sensing unit, the inertial measurement unit and the magnetic sensing unit integrated in the transmitting line frame and the receiving line frame, the position coordinates, the inclination angle, the azimuth angle and the pitch angle of the line frame are obtained in real time;

[0026] The receiver performs normalization processing on the collected induction signal to generate transient electromagnetic attenuation data, and stores the attenuation data in association with the motion parameters; the attenuation curve and the geophysical inversion result are displayed in real time through an external terminal.

[0027] By adopting the above technical solutions, when actually performing the measurement task, two operators carry the transmitting and receiving devices to synchronously walk along the survey line, realizing continuous dynamic measurement of the transient electromagnetic method. Combined with the real-time collected position and attitude information and the induction signal, comprehensive data stream containing spatial and electromagnetic information is generated, which is suitable for complex terrain and large-scale detection scenarios.

[0028] In a preferred example of the present application, the method further comprises:

[0029] Obtaining a target exploration area, based on the geological structure characteristics, dividing high-conductive areas, low-resistance areas and interference source areas;

[0030] According to the area division result, determining high-conductive abnormal areas and low-resistance areas;

[0031] According to the high-conductive abnormal area, a first set of geological electrical property characteristic parameters is extracted; according to the low-resistance area, a second set of geological electrical property characteristic parameters is extracted;

[0032] Based on a preset interference correlation factor, the first set of geological electrical property characteristic parameters is screened to obtain a first interference correlation factor; based on the second set of geological electrical property characteristic parameters, a second interference correlation factor is obtained by screening;

[0033] According to the first interference correlation factor and the second interference correlation factor, a first measurement area and a second measurement area are divided;

[0034] Obtaining the division result, based on the division result, dynamically adjusting the transmitting parameters and the receiving parameters of the magnetic dipole device.

[0035] By adopting the technical scheme, a regional interference identification and monitoring mode is established, high-conductivity, low-conductivity and interference source regions are divided, corresponding sets of geological electrical characteristic parameters are extracted, first and second interference correlation factors are screened based on preset interference correlation factors, different types of geological environment interference sources are classified and identified, the magnetic dipole device can dynamically respond according to the electrical characteristic of different regions, and the adaptability to complex geological backgrounds is enhanced.

[0036] In a preferred example of the present application: the first set of geological electrical characteristic parameters includes a first formation resistivity distribution parameter and a first ambient noise intensity spectrum; the first set of geological electrical characteristic parameters is screened based on the preset interference correlation factors to obtain the first interference correlation factor; the second interference correlation factor is obtained by screening based on the second set of geological electrical characteristic parameters, which includes:

[0037] The preset interference correlation factors include formation noise coupling characteristics for high-conductivity abnormal regions, effects of device motion posture changes on signals, and multi-path propagation characteristics and electromagnetic wave phase distortion characteristics for low-resistance regions;

[0038] According to the electromagnetic interference intensity and background noise distribution characteristics of the high-conductivity abnormal region, a formation noise coupling weight is extracted from the first set of geological electrical characteristic parameters, the formation noise coupling weight is calculated based on the first formation resistivity distribution parameter and the first ambient noise intensity spectrum; a device motion posture interference coefficient is calculated according to the motion posture data of the magnetic dipole device in the exploration process, and the first interference correlation factor is obtained;

[0039] According to the multi-path propagation data of the low-resistance region, a multi-path interference propagation attenuation coefficient is extracted from the second set of geological electrical characteristic parameters; an electromagnetic wave phase distortion factor is extracted from the second set of geological electrical characteristic parameters according to the electromagnetic wave phase delay and quantization error of the low-resistance region, and the second interference correlation factor is obtained.

[0040] By adopting the technical scheme, the main interference sources of the high-conductivity abnormal region are quantified, and the signal distortion law under the low-resistance background is analyzed, and the interference factors under different geological environments are analyzed in detail, so as to facilitate subsequent detailed regional division.

[0041] In a preferred example of the present application: according to the first interference correlation factor and the second interference correlation factor, the first measurement region and the second measurement region are divided, which includes:

[0042] According to the first interference correlation factor and the second interference correlation factor, the formation noise coupling weight and the multi-path interference propagation attenuation coefficient are taken as the division basis of the high-conductivity abnormal region; the device motion posture interference coefficient and the electromagnetic wave phase distortion factor are taken as the division basis of the low-resistance region;

[0043] The spatial distribution of the first interference correlation factor and the second interference correlation factor is converted into a continuous probability field by Kriging interpolation method; based on the distribution difference of the probability field, in combination with a preset noise coupling weight threshold and a preset attitude interference coefficient threshold, the boundary of a high conductivity anomaly area and a low resistance area is dynamically divided to form a first measurement area and a second measurement area.

[0044] By adopting the technical scheme, the spatial distribution of the interference correlation factor is converted into a continuous probability field by Kriging interpolation method, the leap from discrete point measurement to regional prediction is realized, the boundary of the high conductivity anomaly area and the low resistance background area is dynamically divided in combination with the preset noise coupling weight threshold and the preset attitude interference coefficient threshold, and the lag problem of interference response to static regional division is solved.

[0045] In a preferred example of the present application, the dynamic adjustment of the emission parameters and the receiving parameters of the magnetic dipole device includes:

[0046] The emission parameter adjustment rule is: adjusting the emission current intensity and the frequency of the emission coil according to the formation noise coupling weight, or adjusting the motion attitude correction strategy of the emission device according to the device motion attitude interference coefficient;

[0047] The receiving parameter adjustment rule is: optimizing the sampling rate and the filtering threshold of the receiving coil based on the multi-path interference propagation attenuation coefficient, or correcting the phase compensation algorithm of the receiving signal through the electromagnetic wave phase distortion factor;

[0048] A dynamic cooperative instruction is generated according to the adjusted parameters to control the magnetic dipole device to perform a measurement task.

[0049] By adopting the technical scheme, the differential parameter adjustment strategy is implemented based on different interference correlation factors: the emission current and the frequency are optimized in the high conductivity area to suppress noise coupling, and the sampling rate and the phase compensation are optimized in the low resistance background area to cope with multi-path and phase distortion, thereby enhancing the recognition ability and accuracy of the geological anomaly body in a complex environment.

[0050] In a preferred example of the present application, the division result is obtained, and the emission parameters and the receiving parameters of the magnetic dipole device are dynamically adjusted based on the division result, specifically including:

[0051] In the first measurement area, the emission parameters are preferentially optimized to reduce the influence of formation noise coupling;

[0052] In the second measurement area, the receiving parameters are preferentially optimized to suppress multi-path propagation and phase distortion.

[0053] By adopting the technical scheme, the emission parameters are preferentially optimized in the first measurement area, and the receiving parameters are preferentially optimized in the second measurement area, thereby realizing efficient allocation of resources and precision of interference suppression.

[0054] In summary, the present application includes at least one of the following beneficial technical effects:

[0055] 1. The present application provides a device that can simultaneously solve signal fidelity, environmental adaptability and motion error correction to improve the overall accuracy of transient electromagnetic method dynamic measurement; The transmitting device and the receiving device adopt a vertical magnetic dipole configuration with separate transmitting and receiving, based on the Biot-Savart law, the induced primary field voltage theoretical value of the receiving wire frame on the symmetry plane of the transmitting wire frame is zero, thereby limiting the signal response to the secondary field attenuation process of the underground medium. This design fundamentally avoids the early signal distortion and shutdown time delay problems caused by the self-induction and mutual induction effects of the coil in the traditional overlapping loop or central loop device, and the lightweight backpack structure design is also conducive to expanding the effective exploration scene coverage range of the transient electromagnetic method, and enhancing the adaptability in complex environments;

[0056] 2. Improve the response efficiency and measurement flexibility of the system, and implement regional optimization by combining regional division results, so that the transient electromagnetic system has stability and adaptability in large-scale dynamic measurement, and meets the high-precision exploration demand under complex geological conditions. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 is a device structure diagram of the existing overlapping loop device and the central loop device in an embodiment of the present application;

[0058] Figure 2 is a whole structure diagram of a transmitting device of a magnetic dipole device for transient electromagnetic method dynamic measurement in an embodiment of the present application;

[0059] Figure 3 is a side view of a transmitting device of a magnetic dipole device for transient electromagnetic method dynamic measurement in an embodiment of the present application;

[0060] Figure 4 is a top view of a transmitting device of a magnetic dipole device for transient electromagnetic method dynamic measurement in an embodiment of the present application;

[0061] Figure 5 is a schematic diagram of an actual measurement mode of a magnetic dipole device for transient electromagnetic method dynamic measurement in an embodiment of the present application

[0062] Figure 6 is a flowchart of a transient electromagnetic method dynamic collaborative measurement method based on a magnetic dipole device in an embodiment of the present application.

[0063] BRIEF DESCRIPTION OF DRAWINGS

[0064] 1, transmitter; 2, transmitting wire frame; 3, back plate; 4, connecting rod. DETAILED DESCRIPTION

[0065] The application will be further described in detail below with reference to the accompanying drawings.

[0066] In an embodiment, as shown in the drawings, the application discloses a magnetic dipole device for transient electromagnetic method dynamic measurement, which comprises a transmitting device and a receiving device arranged in a vertical magnetic dipole structure. Figures 2 to 4 The transmitting device comprises a transmitter 1, a transmitting frame 2 and a backboard 3; the receiving device comprises a receiver, a receiving frame and the backboard 3, and the backboard 3 is arranged in a portable backpack structure; the backboard 3 is connected with the transmitting frame 2 or the receiving frame through a connecting rod 4, and the connecting rod 4 on the transmitting frame 2 fixes the backboard 3 and the transmitting frame 2 in a vertical unfolded state. The connecting rod 4 on the receiving frame fixes the backboard 3 and the receiving frame in a vertical unfolded state or folds the transmitting frame or the receiving frame together with the backboard, and the transmitting frame or the receiving frame can also be folded together with the backboard through a hinged structure. The frame and the backboard 3 form a 90° angle in the vertical unfolded state, and the frame and the backboard can be fixed by welding or a pin.

[0067] The positioning and sensing unit is an RTK positioning module, which is used to obtain the longitude, latitude and elevation coordinates of the transmitting frame 2 or the receiving frame in real time; the inertial measurement unit comprises a three-component accelerometer for measuring the linear acceleration of the transmitting frame 2 or the receiving frame and a three-component gyroscope for measuring the angular velocity of the transmitting frame 2 or the receiving frame, and the inclination and the pitch angle are determined by combining a sensor fusion algorithm. The magnetic sensing unit is a three-component magnetoresistance sensor, which is used to measure the geomagnetic field vector to obtain the azimuth angle; the sensor fusion algorithm adopts a Kalman filter fusion motion compensation algorithm. The transmitting device or the receiving device generates a kinematic parameter set containing position coordinates, inclination, azimuth angle and pitch angle based on the measurement data of the positioning and sensing unit, the inertial measurement unit and the magnetic sensing unit after denoising, filtering and standardizing the measurement data.

[0068] As shown in the drawings, Figure 5As shown, when actually performing the measurement task, two operators carry the transmitter and receiver device along the survey line synchronously to achieve continuous dynamic measurement of transient electromagnetic method. The transmitter 1 generates a periodic current pulse sequence with preset starting time T0, transmission time T, interval time ΔT, current amplitude I and frequency F as parameters. The transmitter 1 starts from T0, transmits a current with frequency F, amplitude I and duration T, then after interval time ΔT, transmits a current with frequency F, amplitude I and duration T again, and so on. That is, the first transmission time is [T0, T0+T], the second transmission time is [T0+T+△T, T0+2*T+△T]. The nth transmission time interval is [T0+(n-1)(T+△T), T0+(n-1)(T+△T)+T]; the acquisition time interval of the receiver for data acquisition is strictly aligned with the transmission time interval; that is, the transmitter 1 starts from T0+T / 2, records the position and kinematics information of the transmitting frame 2 every interval time T+△T, and sends it to the receiver through Wifi.

[0069] The receiver starts from T0, collects data with a duration of T, then after interval time ΔT, collects data with a duration of T again, and so on. Each acquisition time is consistent with the transmission time. The receiver also starts from T0+T / 2, records the position and kinematics information of the receiving frame every interval time T+△T. The receiver processes the time series data collected each time to obtain transient electromagnetic decay data, normalizes it using the transmitted current, and stores the position and kinematics information of the transmitting frame 2 and the receiving frame. The receiver obtains transient electromagnetic decay data by normalizing the collected time domain signals; sends the transient electromagnetic decay data and kinematics parameter set to an external terminal (mobile phone or tablet computer) through a wireless communication network, and the external terminal generates a transient electromagnetic decay curve, a multi-channel diagram and can perform real-time one-dimensional inversion based on the transient electromagnetic decay data and the kinematics parameter set.

[0070] The implementation principle of the magnetic dipole device for dynamic measurement of transient electromagnetic method in the embodiment of the application is as follows: the dynamic measurement of transient electromagnetic method is performed by using the artificially carried magnetic dipole device, which can effectively avoid the influence of the inductance effect of the transmitting coil. Compared with the traditional method, it is more flexible and suitable for various construction environments. By recording the position and kinematics parameters of the transmitting and receiving frames in real time, the data can be finely processed in the later stage, and the accuracy of data interpretation is improved.

[0071] In another embodiment, the application also discloses a dynamic cooperative measurement method for transient electromagnetic method based on a magnetic dipole device, which is applied to the magnetic dipole device for dynamic measurement of transient electromagnetic method. The dynamic cooperative measurement method for transient electromagnetic method based on a magnetic dipole device specifically includes the following steps:

[0072] S1: Two operators synchronously walk along the survey line direction with a preset interval; the transmitter controls the transmitting line frame to generate a transient electromagnetic excitation signal, and the receiver synchronously collects the induction signal of the receiving line frame.

[0073] In this embodiment, the transmitter generates a periodic current pulse sequence with preset starting time T0, transmission duration T, interval time DT, current amplitude I, and frequency F as parameters. The collection starting time T0 is synchronized by GPS timing. By way of example, the transmission current amplitude I is calculated according to the target detection depth d: I = k x d^1.5, where k is the lithology coefficient, and the sedimentary rock takes 0.8 and the bedrock takes 1.2. The transmission frequency F needs to avoid the power frequency interference of 50 / 100 Hz, and is preferably 2-25 Hz. The single transmission duration T is 10 ms, and the collection interval DT is 50 ms. To facilitate personnel to carry the magnetic dipole device, the back plate can also be provided with a shoulder strap, etc. The operator adjusts the back plate shoulder strap to make the center point of the line frame 1.2 m away from the ground. The connecting rod locks the line frame in a vertical state.

[0074] Specifically, the preset interval is 20 meters, and the walking speed is kept at 0.8-1.2 m / s.

[0075] S2: The position coordinates, inclination angle, azimuth angle, and pitch angle of the line frame are obtained in real time through the positioning and sensing unit, the inertial measurement unit, and the magnetic sensing unit integrated with the transmitting line frame and the receiving line frame.

[0076] In this embodiment, the RTK module outputs the latitude, longitude, and elevation. The acceleration components of the X, Y, and Z axes are obtained through the inertial measurement unit to calculate the inclination angle and the pitch angle. The azimuth angle is calculated based on the horizontal geomagnetic field components of the X and Y axes through the magnetic sensing unit, such as the magnetoresistance sensor.

[0077] S3: The receiver performs normalization processing on the collected induction signal to generate transient electromagnetic attenuation data, and stores the attenuation data in association with the motion parameters; the attenuation curve and the geophysical inversion result are displayed in real time through an external terminal.

[0078] In this embodiment, the normalization processing includes dividing the time domain signal (original induction voltage) directly collected by the receiving coil by the actual working current (transmission current amplitude) of the transmitting coil at time t to obtain the normalized voltage, so as to obtain the standardized induction signal after eliminating the influence of the transmission current intensity.

[0079] In one embodiment, as shown in FIG. 1, a dynamic cooperative measurement method based on a magnetic dipole device further includes: Figure 6

[0080] S10: Obtain a target exploration area, and divide the target exploration area into a high-conductivity area, a low-resistance area, and an interference source area based on the geological structure characteristics.

[0081] ​In the embodiment, the target exploration area is a to-be-detected geographical range; the high-conductivity area has a resistivity less than 10 Ω·m, such as a metal ore body or a groundwater enrichment area, a chalcopyrite, a graphitized stratum, the low-conductivity area has a resistivity greater than 10 Ω·m, such as a bedrock or a dry sedimentary layer, and the interference source area includes a power transmission line and a metal pipeline, where the power transmission line generates a 50 Hz power frequency interference, and the metal pipeline generates an eddy current interference.

[0082] Specifically, historical exploration data and a geological database of the target exploration area are acquired, the boundary of the high-conductivity area is expanded outside on the basis of a resistivity mutation zone, and a skin depth model is combined wherein is a skin depth, representing a penetration depth of an electromagnetic wave; is an angular frequency of a transmitted current; is a stratum permeability; is a stratum conductivity. The expanded boundary of the high-conductivity area is 0.5 .

[0083] S20: According to the area division result, a high-conductivity anomaly area and a low-resistivity area are determined.

[0084] In the embodiment, the high-conductivity anomaly area is a continuous block in the high-conductivity area after interference sources are removed, the stratum conductivity is greater than 0.1 S / m, and an apparent resistivity inversion anomaly amplitude is greater than 3 times a variance. The low-resistivity area is a resistivity stable area in the low-resistivity area, and a resistivity gradient of the resistivity stable area is less than 0.05 Ω·m / m.

[0085] S30: According to the high-conductivity anomaly area, a first set of geological electrical property characteristic parameters is extracted; and according to the low-resistivity area, a second set of geological electrical property characteristic parameters is extracted.

[0086] In the embodiment, according to the high-conductivity anomaly area, a first stratum resistivity distribution parameter, a magnetic dipole device coupling influence coefficient, and a first ambient noise intensity spectrum are extracted to obtain the first set of geological electrical property characteristic parameters, and according to the low-resistivity area, a second stratum resistivity distribution parameter, an electromagnetic wave skin depth attenuation coefficient, a second ambient noise intensity spectrum, and a multi-path interference intensity are extracted to obtain the second set of geological electrical property characteristic parameters.

[0087] Specifically, the first formation resistivity distribution parameter is three-dimensional resistivity spatial distribution data in the high-conductivity anomaly region, which is obtained by performing Occam inversion on transient electromagnetic decay data. The magnetic dipole device coupling influence coefficient is a quantitative index of the electromagnetic coupling strength between the transmitting line frame and the receiving line frame, and is used to reflect the interference of the relative position change or attitude change of the line frame on the signal. The first ambient noise intensity spectrum is the noise energy distribution of the 50-100Hz power frequency interference frequency band. The second formation resistivity distribution parameter is the resistivity gradient field of the low-resistivity background area, and the second ambient noise intensity spectrum is a quantitative parameter of the attenuation rate of electromagnetic waves in the low-resistance medium. The faster the attenuation is, the shallower the detection depth is. After the measurement data is collected, the spatial filtering threshold is set based on the multi-path interference intensity , and the calculation formula is as , wherein is the multi-path interference intensity, and k1 is the magnetic sensor calibration coefficient. The calculation formula of the multi-path interference intensity is calculated by the electromagnetic scattering model of the interference source region, , wherein k2 is the terrain scattering coefficient, which is calibrated by laboratory data. d is the distance of the interference source; is the signal source transmission power. The terrain scattering coefficient is different based on different address types, such as the value range of 0.01-0.05 for flat bedrock and the value range of 0.5-0.8 for metal slag piles.

[0088] S40: Based on the preset interference correlation factor, the first set of geological electrical property characteristic parameters is screened to obtain the first interference correlation factor; and based on the second set of geological electrical property characteristic parameters, the second interference correlation factor is obtained.

[0089] In this embodiment, the preset interference correlation factor includes the formation noise coupling characteristics of the high-conductivity anomaly region, the influence of the device motion attitude change on the signal, and the multi-path propagation characteristics of the low-resistance region and the electromagnetic wave phase distortion characteristics.

[0090] Specifically, step S40 includes:

[0091] S401: According to the electromagnetic interference intensity of the high-conductivity anomaly region and the background noise distribution characteristics, the formation noise coupling weight is extracted from the first set of geological electrical property characteristic parameters, and the formation noise coupling weight is calculated based on the first formation resistivity distribution parameter and the first ambient noise intensity spectrum; the device motion attitude interference coefficient is calculated according to the motion attitude data of the magnetic dipole device in the exploration process, and the first interference correlation factor is obtained.

[0092] In this embodiment, the formation noise coupling weight , wherein is the noise integral energy of the 50-100Hz frequency band; is the resistivity gradient of the high-conductivity region; Function gradient compression range, value range is 0~1; For reference noise, the value is 10 muV / m.

[0093] Device motion posture interference coefficient , wherein The receiving line frame inclination or the transmitting line frame inclination; The pitch angle.

[0094] S402: According to the multi-path propagation data of the low-resistance area, the multi-path interference propagation attenuation coefficient is extracted from the second geological electrical property parameter set; according to the electromagnetic wave phase delay and quantization error of the low-resistance area, the electromagnetic wave phase distortion factor is extracted from the second geological electrical property parameter set, and the second interference correlation factor is obtained.

[0095] In this embodiment, the multi-path interference propagation attenuation coefficient The multi-path interference intensity quantization value is calculated as follows: Wherein, N is the number of effective scatterers affecting the current measuring point, which is based on the historical exploration database statistics; The actual signal power at the receiving end after multi-path scattering is W; The original signal power output by the transmitting coil; The straight-line distance between the scatterer and the receiving line frame; D is the device distance between the transmitting present situation and the receiving line frame, which is 20 meters by default. When less than 0.3, it is weak interference, and the default sampling rate is maintained; When less than 0.7, it is strong interference, and the sampling rate is increased to 2MHz, and the specific increase rate can also be customized.

[0096] Electromagnetic wave phase distortion factor Wherein, k is the device coefficient, which is a calibration constant related to the size of the line frame, and the default value is 0.05. The skin depth; The conductivity variation ratio represents the non-uniformity of the formation conductivity. The electromagnetic wave phase distortion factor is the quantization value of the electromagnetic wave phase delay. When greater than 5°, the phase compensation algorithm is started through the FIR filter, When less than 2°, the default receiving parameters are maintained.

[0097] S50: According to the first interference correlation factor and the second interference correlation factor, the first measurement area and the second measurement area are divided.

[0098] Specifically, step S50 includes:

[0099] S501: According to the first interference correlation factor and the second interference correlation factor, the formation noise coupling weight and the multi-path interference propagation attenuation coefficient are taken as the division basis of the high-conductivity anomaly area; the device motion posture interference coefficient and the electromagnetic wave phase distortion factor are taken as the division basis of the low-resistance area.

[0100] In this embodiment, the device motion posture interference coefficient is the line frame tilt angle deviation, and 90° is the ideal value. The electromagnetic wave phase distortion factor is the waveform distortion caused by the formation non-uniformity.

[0101] Specifically, when measuring in the high-conductivity anomaly area, according to the first interference correlation factor, the corresponding first measurement point set is determined, and the measurement point density is dynamically adjusted based on the formation noise coupling weight, for example, when the formation noise coupling weight is greater than 0.5, the measurement point density is doubled; the measurement path avoids the steep slope area with a device motion posture interference coefficient greater than 10° as much as possible.

[0102] In the low-resistance background area, according to the second interference correlation factor, the second measurement point set of the low-resistance background area is determined, and the measurement point spacing is inversely proportional to the multi-path interference propagation attenuation coefficient, and for every 10 dB increase in attenuation, the spacing is reduced by 25%, and the measurement line direction is perpendicular to the main interference direction of the electromagnetic wave phase distortion factor.

[0103] S502: The spatial distribution of the first interference correlation factor and the second interference correlation factor is converted into a continuous probability field by the Kriging interpolation method; based on the distribution difference of the probability field, combined with the preset noise coupling weight threshold and the preset posture interference coefficient threshold, the boundary of the high-conductivity anomaly area and the low-resistance area is dynamically divided, and the first measurement area and the second measurement area are formed.

[0104] In this embodiment, the measurement area is dynamically divided twice, and the boundary of the high-conductivity and low-resistance background area is adjusted based on the spatial distribution difference of the interference factor. The area with a formation noise coupling weight greater than 0.5 or a device motion posture interference coefficient in the probability field is taken as a high-conductivity anomaly area candidate. The area with a multi-path interference propagation attenuation coefficient greater than 0.8 or an electromagnetic wave phase distortion factor greater than 5° is taken as a low-resistance background area candidate, and finally the isolated noise points are eliminated by morphological filtering or closing operation, to serve as the boundary of the first measurement area (the high-conductivity anomaly area after secondary division) and the second measurement area (the low-resistance background area after secondary division).

[0105] Specifically, the spatial discrete point set of the first interference correlation factor and the second interference correlation factor is extracted, and the grid resolution is 2m×2 m. First, the semi-variogram wherein h is the distance between points, in meters; the base value 0.1 represents the measurement error; and the range 10 m reflects the range of spatial correlation of the interference factors. The semi-variogram function is used to quantify the spatial correlation of the interference factors and determine the weight distribution of the interpolation.

[0106] The probability field calculation formula of the high-conductivity area is: wherein k is 0.7. The probability field calculation formula of the low-resistance area is wherein k is 0.05. When is greater than 10°, the boundary needs to be contracted. In actual measurement, the probability field is recalculated every 5 m of travel.

[0107] For example, it is assumed that the initial partition result is shown in Table 1:

[0108] Table 1

[0109] At the coordinate (105, 55), the processing is is greater than 18°, the folding adjustment of the connecting rod is triggered (the connecting rod of the embodiment is in the form of a hinge, which can adjust the included angle between the receiving frame and the receiver, or adjust the included angle between the transmitting frame and the transmitter), and the perpendicularity of the frame is restored to = 4°, the calculation of = 0.82, and the coordinate (102, 52) is classified into the low-resistance background area. The = 6°, which is greater than 5°, and the point distance is encrypted to 0.5 m.

[0110] S60: Obtain the partition result, and dynamically adjust the transmitting parameters and receiving parameters of the magnetic dipole device based on the partition result.

[0111] In the embodiment, in the first measurement area, the transmitting parameters are preferentially optimized to reduce the influence of the formation noise coupling; and in the second measurement area, the receiving parameters are preferentially optimized to suppress the multi-path propagation and phase distortion.

[0112] In the embodiment, the transmitting parameter adjustment rule includes: optimizing the transmitting current intensity and frequency of the transmitting coil according to the formation noise coupling weight, or adjusting the motion posture correction strategy of the transmitting device according to the device motion posture interference coefficient.

[0113] Specifically, the transmitter adjusts the transmitting current intensity and frequency through a current controller. When is greater than 0.5, the current is intensified through the current intensification formula: wherein is the intensified current; is the original current before intensification. The frequency modulation is performed when is greater than , and the frequency is switched to 25 Hz when the 50 Hz power frequency interference occurs. This is conducive to the improvement of the signal-to-noise ratio.

[0114] In the embodiment, the receiving parameter adjustment rule comprises: optimizing the sampling rate and the filtering threshold of the receiving coil based on the multipath interference propagation attenuation coefficient; or correcting the phase compensation algorithm of the receiving signal through the electromagnetic wave phase distortion factor, generating a dynamic coordination instruction according to the adjusted parameters, and controlling the magnetic dipole device to perform a measurement task.

[0115] Specifically, when the electromagnetic wave phase distortion factor is greater than 0.7, an IIR band-stop filter is started for power frequency filtering, and the stop band is 50±2 Hz. A phase compensation algorithm based on FIR filter design is used for phase compensation, the tap number is 64, and the cutoff frequency is 0.2 times the reference frequency. The compensation phase Delta is conducive to reducing the waveform distortion rate.

[0116] Further, when the connecting rod is set to a hinged type, the motion posture correction strategy includes mechanical structure adaptive adjustment, transmission timing dynamic optimization and posture data compensation algorithm, wherein the mechanical structure adaptive adjustment is applicable to the magnetic dipole device with a hinged connecting rod, when is greater than 10°, the angle between the transmission line frame and the back plate can be dynamically adjusted through the hinged connecting rod, and the vertical state is forcibly restored to reduce the attitude interference coefficient to less than or equal to 4°, and when the pitch angle is greater than 5°, the connecting rod fixes the position of the line frame through the fixed lock.

[0117] Transmission timing dynamic optimization is applicable to the scene where the signal is unstable due to sudden changes, such as , when the instantaneous change is greater than 3° per second, the transmission window is delayed, and the delay duration is calculated based on the instantaneous change.

[0118] The posture data compensation algorithm is based on the real-time data of the inertial measurement unit, reconstructs the transmission magnetic moment vector based on the real-time inclination angle and azimuth angle, and applies calculation according to the Biot-Savart law. The kinematic parameter fusion correction is calculated by fusing RTK positioning data, accelerometer or gyroscope data, and magnetoresistance sensor data through Kalman filtering, and the output is the calibrated effective magnetic moment parameter. The specific compensation amount can be set according to actual needs.

[0119] It should be understood that the sequence numbers of the steps in the above embodiments do not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0120] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of each functional unit and module is exemplified, and in actual application, the above-mentioned functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above.

[0121] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand; it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A dynamic coordinated measurement method based on a magnetic dipole device using transient electromagnetic methods, applied to a magnetic dipole device for dynamic measurement using transient electromagnetic methods, characterized in that, The magnetic dipole device for dynamic measurement using transient electromagnetic methods includes a transmitter and a receiver that are separately configured as a vertical magnetic dipole structure. The transmitting device includes a transmitter and a transmitting frame, with the transmitter disposed on the transmitting frame; the receiving device includes a receiver and a receiving frame, with the receiver disposed on the receiving frame; both the transmitting device and the receiving device are provided with a back plate forming a portable backpack structure; The transmitting frame and the receiving frame respectively integrate a positioning sensing unit, an inertial measurement unit, and a magnetic sensing unit. The methods include: Based on exploration requirements, the following parameters are set: transmission current amplitude I, transmission frequency F, acquisition start time T0, single transmission duration T, and acquisition interval ΔT. Two operators carry the transmitter and receiver respectively, which are fixed to their backs by a backplate. Two operators move synchronously along the survey line at a preset interval; the transmitter controls the transmitting frame to generate transient electromagnetic excitation signals, and the receiver synchronously collects the induced signals of the receiving frame; The position coordinates, tilt angle, azimuth angle and pitch angle of the wireframe are obtained in real time through the positioning sensing unit, inertial measurement unit and magnetic sensing unit integrated by the transmitting wireframe and the receiving wireframe. The receiver normalizes the collected induction signals, generates transient electromagnetic attenuation data, and stores it in association with motion parameters; the attenuation curve and geophysical inversion results are displayed in real time through an external terminal. The method also includes: The target exploration area is identified, and based on geological structural characteristics, it is divided into high-conductivity areas, low-resistivity areas, and interference source areas. Based on the region division results, the high-conductivity abnormal region and the low-resistivity region are determined; Based on the high-conductivity anomaly region, a first set of geoelectric characteristic parameters is extracted; based on the low-resistivity region, a second set of geoelectric characteristic parameters is extracted. Based on preset interference correlation factors, the first set of geoelectric characteristic parameters is screened to obtain the first interference correlation factor; based on the second set of geoelectric characteristic parameters, the second interference correlation factor is screened to obtain the second interference correlation factor. Based on the first interference correlation factor and the second interference correlation factor, a first measurement region and a second measurement region are divided; the division result is obtained, and the transmission parameters and reception parameters of the magnetic dipole device are dynamically adjusted based on the division result.

2. The transient electromagnetic dynamic coordinated measurement method based on a magnetic dipole device according to claim 1, characterized in that, The back plate is connected to the transmitting frame or the receiving frame by a connecting rod. The connecting rod fixes the back plate and the transmitting frame, or the back plate and the receiving frame, in a vertically unfolded state, or folds the transmitting frame or the receiving frame to fit the back plate.

3. The transient electromagnetic dynamic coordinated measurement method based on a magnetic dipole device according to claim 1, characterized in that, The positioning sensing unit is an RTK positioning module, used to acquire the latitude, longitude and elevation coordinates of the transmitting frame or the receiving frame in real time. The inertial measurement unit includes a three-component accelerometer for measuring the linear acceleration of the transmitting frame or the receiving frame and a three-component gyroscope for measuring the angular velocity of the transmitting frame or the receiving frame, and determines the tilt angle and pitch angle by combining sensor fusion algorithms. The magnetic sensing unit is a three-component magnetoresistive sensor used to measure the geomagnetic field vector and obtain the azimuth angle; The transmitting device or the receiving device generates a set of kinematic parameters, including position coordinates, tilt angle, azimuth angle and pitch angle, based on the measurement data of the positioning sensing unit, inertial measurement unit and magnetic sensing unit.

4. The transient electromagnetic dynamic coordinated measurement method based on a magnetic dipole device according to claim 3, characterized in that, The transmitter generates a periodic current pulse sequence using preset start time T0, transmission duration T, interval time ΔT, current amplitude I, and frequency F as parameters. The time interval of the nth transmission is [T0+(n-1)(T+ΔT), T0+(n-1)(T+ΔT)+T]. The data acquisition time interval of the receiver is strictly aligned with the transmission time interval. The acquired time-domain signal is normalized to obtain transient electromagnetic attenuation data; the transient electromagnetic attenuation data and the kinematic parameter set are sent to an external terminal.

5. The transient electromagnetic dynamic coordinated measurement method based on a magnetic dipole device according to claim 1, characterized in that, The first set of geoelectric characteristic parameters includes a first formation resistivity distribution parameter and a first environmental noise intensity spectrum; the first set of geoelectric characteristic parameters is screened based on preset interference correlation factors to obtain a first interference correlation factor; Based on the second set of geoelectric characteristic parameters, the second interference correlation factor is obtained, including: The preset interference correlation factors include the ground noise coupling characteristics in the high-conductivity anomaly region, the influence of device motion attitude changes on the signal, and the multipath propagation characteristics and electromagnetic wave phase distortion characteristics in the low-resistivity region. Based on the electromagnetic interference intensity and background noise distribution characteristics of the high-conductivity anomaly region, formation noise coupling weights are extracted from the first set of geoelectric characteristic parameters. The formation noise coupling weights are calculated based on the first formation resistivity distribution parameters and the first environmental noise intensity spectrum. The motion attitude interference coefficient of the magnetic dipole device is calculated based on the motion attitude data of the magnetic dipole device during the exploration process, and the first interference correlation factor is obtained. Based on the multipath propagation data in the low-resistivity region, the multipath interference propagation attenuation coefficient is extracted from the second set of geoelectric characteristic parameters; based on the electromagnetic wave phase delay and quantization error in the low-resistivity region, the electromagnetic wave phase distortion factor is extracted from the second set of geoelectric characteristic parameters to obtain the second interference correlation factor.

6. The transient electromagnetic dynamic coordinated measurement method based on a magnetic dipole device according to claim 5, characterized in that, The step of dividing the first measurement region and the second measurement region according to the first interference correlation factor and the second interference correlation factor includes: Based on the first interference correlation factor and the second interference correlation factor, the formation noise coupling weight and the multipath interference propagation attenuation coefficient are used as the basis for dividing the high-conductivity anomaly region; the device motion attitude interference coefficient and the electromagnetic wave phase distortion factor are used as the basis for dividing the low-resistivity region. The spatial distributions of the first interference correlation factor and the second interference correlation factor are converted into a continuous probability field using Kriging interpolation. Based on the distribution differences of the probability field, combined with a preset noise coupling weight threshold and a preset attitude interference coefficient threshold, the boundaries between the high-conductivity anomaly region and the low-resistivity region are dynamically divided to form a first measurement region and a second measurement region.

7. The transient electromagnetic dynamic coordinated measurement method based on a magnetic dipole device according to claim 5, characterized in that, The dynamic adjustment of the transmission and reception parameters of the magnetic dipole device includes: Transmission parameter adjustment rules: Optimize the transmission current intensity and frequency of the transmission coil according to the formation noise coupling weight, or adjust the motion attitude correction strategy of the transmission device according to the device motion attitude interference coefficient; Receiver parameter adjustment rules: Optimize the sampling rate and filtering threshold of the receiving coil based on the multipath interference propagation attenuation coefficient; Alternatively, a phase compensation algorithm for correcting the received signal using the electromagnetic wave phase distortion factor; Based on the adjusted parameters, dynamic coordination commands are generated to control the magnetic dipole device to perform measurement tasks.

8. The transient electromagnetic dynamic coordinated measurement method based on a magnetic dipole device according to claim 7, characterized in that, The process of obtaining the partitioning result and dynamically adjusting the transmission and reception parameters of the magnetic dipole device based on the partitioning result specifically includes: In the first measurement area, the transmission parameters are optimized first to reduce the impact of formation noise coupling. In the second measurement region, the receiving parameters are optimized to suppress multipath propagation and phase distortion.

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