Method and device for artificial source electromagnetic detection in beach and shallow sea area, storage medium
By employing artificial source electromagnetic detection methods in shallow coastal areas, utilizing land-based transmitters and seawater receivers, the detection challenges caused by complex geology and turbulent water flow were solved. This approach enabled the acquisition of high signal-to-noise ratio signals and accurate interpretation of underground structures, providing strong support for resource surveys and engineering exploration.
Patent Information
- Application Number
- CN202210146966.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-02-17
- Publication Date
- 2026-02-06
- Estimated Expiration
- 2042-02-17
AI Technical Summary
In shallow sea areas, the complex geological structure, varied landforms, and rapid currents make it impossible for ordinary ships to pass through, and traditional geophysical exploration methods are difficult to carry out. In particular, the large differences between land and seawater make it impossible to obtain effective geophysical and engineering geological data.
The artificial source electromagnetic detection method is adopted. The transmitter is placed on land, and a bipolar step current is sent in the transmitter with a long wire grounded at both ends using a high-power transmitter. The secondary field electromagnetic signal is received in the seawater area, and the underground electrical structure of the measurement area is obtained through noise reduction processing and inversion calculation.
It enables high signal-to-noise ratio signal acquisition and accurate interpretation of underground electrical structures in shallow sea areas, providing an effective means for resource surveys and engineering exploration, and overcoming the difficulties of traditional methods.
Smart Images
Figure CN114509819B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of geophysical exploration, and particularly relates to an artificial source electromagnetic detection method and device for a beach shallow sea area and a storage medium. BACKGROUND
[0002] The beach shallow sea area is a key region for the construction of national major projects such as ports, nuclear power plants and bridges and tunnels, and is also a potential region for the development of oil and gas, mineral resources and water resources at present. The basis and key for the exploration and development of beach shallow sea resources and the construction of large-scale nearshore projects is to obtain geophysical and engineering geological data of the beach shallow sea area. According to the different physical properties of rock strata, using geophysical methods for detection is an effective means to obtain the above data. However, the beach shallow sea area in the sea-land interaction zone generally has complex geological structure, variable topography, large dynamic change of water depth (generally 0-25 meters), turbulent flow, and is a beach during ebb tide. Especially affected by tides and beach sediments such as mud and sandy mud, personnel and ordinary ships cannot pass through the area within 0-2 meters of water depth, which is commonly known as the "people can't go down, and the ship can't reach" zone. In addition to the great physical property difference between land and seawater media, it is impossible to carry out geophysical detection work. SUMMARY
[0003] The technical problem to be solved by the present application is to provide an artificial source electromagnetic detection method and device for a beach shallow sea area, and a storage medium, to solve the problem that it is currently difficult to carry out work in the beach shallow sea area, and to provide a powerful means for resource investigation and engineering investigation in the beach shallow sea area.
[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solution:
[0005] An artificial source electromagnetic detection method for a beach shallow sea area, which places a transmitting source on land and carries out observation in a seawater area, comprising the following steps:
[0006] Step S1, sending a bipolar step current in a long wire transmitting source with both ends grounded by using a high-power transmitter;
[0007] Step S2, receiving a secondary field electromagnetic signal during the off period of the bipolar step current in the observation area;
[0008] Step S3, carrying out denoising processing on the secondary field electromagnetic signal to obtain a useful signal with high signal-to-noise ratio;
[0009] Step S4, carrying out inversion processing on the useful signal with high signal-to-noise ratio to obtain the electrical structure of the earth in the predetermined depth range of the measurement area.
[0010] As a preferred, in step S1, a long wire transmitting source with both ends grounded is arranged on the coast land.
[0011] As preferred, in step S2, the observation area is in a range of 300m-3000m offset distance from the transmitting source.
[0012] As preferred, in step S3, the secondary field electromagnetic signal is denoised by using a pre-filter and independent component analysis to remove human noise, seawater noise, motion noise and sferics noise in the secondary field electromagnetic signal.
[0013] As preferred, step S4 comprises:
[0014] Step 41, establishing an initial earth resistivity model with a seawater layer according to the high signal-to-noise ratio signal obtained after step S3;
[0015] Step 42, performing inversion calculation by a land-sea electrical source transient electromagnetic three-dimensional inversion method according to the initial earth resistivity model with a seawater layer to obtain the earth electrical structure in a predetermined depth range of the measurement area.
[0016] As preferred, the land-sea electrical source transient electromagnetic three-dimensional inversion is carried out by using a particle swarm-gradient hybrid algorithm.
[0017] The present application also provides a beach and shallow sea area artificial source electromagnetic detection device, comprising:
[0018] The sending module is configured to send a bipolar step current in the long wire transmitting source with both ends grounded by using a high-power transmitter;
[0019] The observation module is configured to receive the bipolar step current in a range of 300m-3000m offset distance from the transmitting source to observe the secondary field electromagnetic signal;
[0020] The denoising module is configured to denoise the secondary field electromagnetic signal to obtain a high signal-to-noise ratio useful signal;
[0021] The inversion module is configured to perform inversion processing on the high signal-to-noise ratio useful signal to obtain the earth electrical structure in a predetermined depth range of the measurement area.
[0022] As preferred, the denoising module denoises the secondary field electromagnetic signal by using a pre-filter and independent component analysis to remove human noise, seawater noise, motion noise and sferics noise in the secondary field electromagnetic signal.
[0023] As preferred, the inversion module performs inversion calculation on the high signal-to-noise ratio useful signal by using a land-sea electrical source transient electromagnetic three-dimensional inversion method to obtain the earth electrical structure in a predetermined depth range of the measurement area.
[0024] The application further provides a storage medium which stores machine executable instructions, the machine executable instructions, when called and executed by a processor, cause the processor to implement the artificial source electromagnetic detection method for a beach and shallow sea area.
[0025] The application is based on the transient electromagnetic method of land fixed transmission and sea mobile reception, arranges a long wire transmission source with two ends grounded on the land of the coast, supplies with a bipolar step current, uses a receiver to observe the secondary electromagnetic field in the sea area, and performs inversion interpretation on the observed signal to obtain the underground electrical structure. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 A flowchart of the artificial source electromagnetic detection method for a beach and shallow sea area of the application;
[0027] Figure 2 A schematic diagram of the electromagnetic detection method of the application;
[0028] Figure 3 A schematic diagram of the arrangement of the transmission source;
[0029] Figure 4 A schematic diagram of the particle swarm and BFGS hybrid algorithm;
[0030] Figure 5 A schematic diagram of the measured induced voltage multi-channel curve;
[0031] Figure 6 A schematic diagram of the induced voltage multi-channel curve after filtering and denoising;
[0032] Figure 7 An inversion resistivity-depth contour section. DETAILED DESCRIPTION
[0033] To make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application. The components of the embodiments of the application described and shown in the drawings can be arranged and designed in various different configurations.
[0034] Embodiment 1:
[0035] As shown in the drawings, Figure 1 The application provides an artificial source electromagnetic detection method for a beach and shallow sea area, which places a transmission source on land and performs observation in a sea area, and includes the following steps:
[0036] Step S1, arranging a long wire transmission source with two ends grounded on the land of the coast, and using a high-power transmitter to send a bipolar step current in the long wire transmission source with two ends grounded.
[0037] Step S2: Receive the secondary field electromagnetic signal during the bipolar step current turn-off period within the observation area;
[0038] Step S3: Denoise the secondary field electromagnetic signal to obtain a useful signal with a high signal-to-noise ratio;
[0039] Step S4: Perform inversion processing on the useful signal with high signal-to-noise ratio to obtain the geoelectric structure within a predetermined depth range of the measurement area.
[0040] In one implementation of this embodiment, in step S1, a long conductor transmitter, grounded at both ends, is arranged on the coastal land, with a length generally between 500 and 2000 meters. A high-power transmitter is used to send a bipolar step current with a duty cycle of 50%, the current intensity generally being 10-30 amperes, and the power supply cycle generally not less than 400 milliseconds. The distance between the transmitter and the observation area should not be too large, generally between 300 and 3000 meters. To obtain the ability to detect underground targets with different properties, transmitters in two directions should be arranged sequentially, such as... Figure 2 , 3 As shown, source 1 is an equatorial source and source 2 is an axial source.
[0041] In one implementation of this embodiment, in step S2, a receiver is arranged within the observation area of the seawater region to receive the secondary field electromagnetic signal during the bipolar step current turn-off period. A hollow coil can be used to observe the vertical induced voltage component, or electrodes can be used to observe the horizontal electric field component. The effective area of the hollow coil should be no less than 1000 m², and the distance between the receiving electrodes should be no less than 20 meters. When observing the vertical induced voltage component, the hollow coil should be placed above the seawater, generally no more than 5 meters above the sea surface. When observing the electric field component, the electrodes should be placed below the seawater. The number of superpositions during signal observation should generally be no less than 512. The seawater thickness at each observation point is recorded.
[0042] In one implementation of this embodiment, step S3 involves using a pre-filter and independent component analysis to denoise the secondary field electromagnetic signal, removing human noise, seawater noise, motion noise, and atmospheric noise. First, a pre-filter is used to remove seawater noise and atmospheric noise. Then, based on the independence relationship between the useful signal and motion noise and human noise, a negative entropy objective function is established. Finally, an optimization algorithm is used to achieve denoising and extract the useful signal with a high signal-to-noise ratio.
[0043] As one implementation of this embodiment, step S4 includes:
[0044] Step 41: Based on the high signal-to-noise ratio signal obtained after processing in step S3, establish an initial georesistivity model with a seawater layer.
[0045] Step 42, according to the initial earth resistivity model with seawater layer, the land-sea electrical source transient electromagnetic three-dimensional inversion is carried out to obtain the earth resistivity structure in the measurement area in the predetermined depth range, that is, the resistivity and depth of the stratum.
[0046] Further, the land-sea electrical source transient electromagnetic three-dimensional inversion is carried out based on the particle swarm-gradient hybrid algorithm.
[0047] The method is applied in a practical detection in Zhuhai, Guangdong, China. The construction parameters are: the length of the transmission source is 1125 meters, the transmission current is 14 amperes, the power supply cycle is 1 second, the transmitting-receiving distance is 985 meters, the seawater depth range is 25-40 meters, the vertical induced voltage component is observed, the effective area of the receiving coil is 3000 square meters, and the superposition number is 1024 times. The length of the measuring line is 2300 meters, and the point distance is 40 meters. Figure 5 The measured induced voltage multi-channel curve is shown in FIG. 2. Figure 6 The filtered and denoised induced voltage multi-channel curve is shown in FIG. 3. Since the seawater depth is greater than 1 meter, the three-dimensional inversion is used in the inversion calculation, and the maximum depth of the inversion model is 1000 meters. The seawater layer thickness is set to 30 meters in the initial model, the resistivity is 0.1 Ω·m, and the underlying stratum is a uniform earth with a resistivity of 10 Ω·m. The inversion iteration number is set to 20 times. The resistivity-depth section obtained by inversion is shown in FIG. 4. Figure 7
[0048] Embodiment 2:
[0049] The application further provides a beach shallow sea area artificial source electromagnetic detection device, which comprises:
[0050] The sending module is used for sending a bipolar step current in the long wire transmission source grounded at both ends by using a high-power transmitter;
[0051] The observation module is used for receiving the bipolar step current in the offset distance range of 300 meters-3000 meters from the transmission source to observe the secondary field electromagnetic signal;
[0052] The denoising module is used for denoising the secondary field electromagnetic signal to obtain a useful signal with high signal-to-noise ratio;
[0053] The inversion module is used for inverting the useful signal with high signal-to-noise ratio to obtain the earth resistivity structure in the measurement area in the predetermined depth range.
[0054] As an embodiment of the embodiment, the denoising module uses a pre-filter and an independent component analysis method to denoise the secondary field electromagnetic signal to remove human noise, seawater noise, motion noise and sferic noise in the secondary field electromagnetic signal.
[0055] As an embodiment of the present embodiment, the inversion module adopts a land-sea electric property source transient electromagnetic three-dimensional inversion mode to perform inversion calculation on the high-signal-to-noise ratio useful signal, and obtains the earth electrical structure in the predetermined depth range of the measurement area.
[0056] Embodiment 3:
[0057] The present application also provides a storage medium, the storage medium stores machine executable instructions, the machine executable instructions when being called and executed by a processor, the machine executable instructions cause the processor to realize the artificial source electromagnetic detection method in the shallow sea area.
[0058] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A method for electromagnetic detection using artificial sources in shallow sea areas, characterized in that, Placing the transmitter on land and conducting observations in seawater includes the following steps: Step S1: Use a high-power transmitter to send a bipolar step current through a long wire grounded at both ends; Step S2: Receive the secondary field electromagnetic signal during the bipolar step current turn-off period within the observation area; Step S3: Denoise the secondary field electromagnetic signal to obtain a useful signal with a high signal-to-noise ratio; Step S4: Perform inversion processing on the useful signal with high signal-to-noise ratio to obtain the geoelectric structure within a predetermined depth range of the measurement area; In step S1, a long conductor transmitter with grounded ends is arranged on the coastal land, with a length of 500-2000 meters; a high-power transmitter is used to send a bipolar step current with a duty cycle of 50%, a current intensity of 10-30 amperes, and a power supply cycle of not less than 400 milliseconds. In step S2, the observation area is the range of 300 meters to 3000 meters offset from the emission source; In step S3, a pre-filter and independent component analysis are used to denoise the secondary field electromagnetic signal in order to remove human noise, seawater noise, motion noise and atmospheric noise from the secondary field electromagnetic signal. First, a pre-filter is used to remove seawater noise and atmospheric noise. Then, based on the independence relationship between the useful signal and motion noise and human noise, a negative entropy objective function is established. Finally, an optimization algorithm is used to achieve denoising and extract the useful signal with a high signal-to-noise ratio. Step S4 includes: Step 41: Based on the high signal-to-noise ratio signal obtained after processing in step S3, establish an initial georesistivity model with a seawater layer. Step 42: Based on the initial geoelectric resistivity model with seawater layer, inversion calculation is performed using the land-sea electrical source transient electromagnetic three-dimensional inversion method to obtain the geoelectric structure within the predetermined depth range of the measurement area. A three-dimensional inversion of transient electromagnetic sources from land to sea was carried out using a particle swarm optimization-gradient hybrid algorithm.
2. An artificial source electromagnetic detection device for shallow sea areas, used to implement the artificial source electromagnetic detection method for shallow sea areas as described in claim 1, characterized in that, include: The transmitting module is used to transmit a bipolar step current within a long wire transmitter source grounded at both ends using a high-power transmitter. The observation module is used to receive secondary field electromagnetic signals during the bipolar step current turn-off within an offset range of 300-3000 meters from the transmitter. The noise reduction module is used to denoise the secondary field electromagnetic signal to obtain a useful signal with a high signal-to-noise ratio. The inversion module is used to invert useful signals with high signal-to-noise ratio to obtain the geoelectric structure within a predetermined depth range of the measurement area; The denoising module uses a pre-filter and independent component analysis to denoise the secondary field electromagnetic signal in order to remove human noise, seawater noise, motion noise, and atmospheric noise from the secondary field electromagnetic signal. The inversion module uses a land-sea electrical source transient electromagnetic three-dimensional inversion method to invert useful signals with high signal-to-noise ratio, and obtains the geoelectric structure within a predetermined depth range of the measurement area.
3. A storage medium, characterized in that, The storage medium stores machine-executable instructions, which, when invoked and executed by a processor, cause the processor to implement the artificial source electromagnetic detection method for shallow sea areas as described in claim 1.