A multi-source and multi-resolution artificial source electromagnetic exploration method and system

Abstract

The present invention provides a multi-source, multi-resolution artificial source electromagnetic exploration method and system. The method constructs high-order pseudo-random signals for near and far parallel field sources. The system simultaneously excites near and far field sources to acquire observation data from multiple receiving points within the survey area. The system then extracts the received data from the corresponding field sources based on the frequency components of the emitted high-order pseudo-random signals. An initial model of the large-scale electrical structure of the underground space based on prior information is constructed. Large-scale inversion imaging is performed based on this initial model and low- and medium-frequency electromagnetic field data from far-field sources. The results of the large-scale inversion imaging are used as the initial model for fine-scale inversion imaging based on high- and medium-frequency electromagnetic data from near-field sources. This method can successfully acquire high-quality artificial source electromagnetic data and achieve highly accurate inversion interpretation results.

Description

Technical Field

[0001] The present invention belongs to the technical field of geophysical exploration, and in particular relates to a multi-source and multi-resolution artificial source electromagnetic exploration method and system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Frequency-domain electromagnetic methods require the transmission of electromagnetic signals at multiple frequencies to obtain electrical characteristics at different depths: 1) The wider the frequency band of the transmitted signal, the wider the detectable depth range; lower frequencies allow for deeper detection, while higher frequencies reduce shallow blind spots. Furthermore, a denser spectrum and more frequencies yield higher resolution for the same bandwidth. 2) The greater the transmission / reception distance, the deeper the detection, but the weaker the signal, especially in the mid- and high-frequency ranges, which attenuate rapidly, resulting in insufficient detection resolution and accuracy. As the transmission / reception distance decreases, the mid- and high-frequency signal strength increases, improving detection resolution and accuracy, but at a shallower depth.

[0004] In summary, a single transmitter cannot achieve both deep detection and high resolution, and a single transmission signal cannot achieve both wide bandwidth and high density. Furthermore, a single transmitter with a wide bandwidth cannot support both of these requirements: high power for deep detection (low frequency) and high-speed shutdown for shallow detection (high frequency). In this context, single-source frequency-domain electromagnetic detection cannot meet these two requirements, necessitating the urgent need for research into multi-source, multi-resolution detection methods. Summary of the Invention

[0005] To address the above-mentioned problems, the present invention proposes a multi-source, multi-resolution artificial source electromagnetic exploration method and system. Starting from the emission waveform, observation method, and data processing method of the artificial source frequency domain electromagnetic method, the present invention constructs a multi-source, multi-resolution artificial source electromagnetic exploration method by deploying improved emission signals, two types of field sources, far and near, and developing a multi-source progressive inversion method. This method successfully acquires high-quality artificial source electromagnetic data and achieves high-precision inversion and interpretation results.

[0006] According to some embodiments, the present invention adopts the following technical solutions:

[0007] A multi-source and multi-resolution artificial source electromagnetic exploration method comprises the following steps:

[0008] Constructing high-order pseudo-random signals used for near and far parallel field sources;

[0009] Arrange a far-field source, and arrange a near-field source parallel to the far-field source between the far-field source and the measurement area;

[0010] Simultaneously stimulate near and far field sources, deploy multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal;

[0011] Construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data from far-field sources;

[0012] The results of large-scale inversion imaging are used as the initial model, and small-scale fine inversion imaging is performed based on the electromagnetic data of the near-field source in the medium and high frequency bands.

[0013] As an optional implementation, in the process of constructing the high-order pseudo-random signal used for far and near parallel field sources, the frequency band of the signal used by the far-field source is medium and low frequency, and the frequency band of the signal used by the near-field source is medium and high frequency.

[0014] As an optional implementation, the signal frequency bands have overlapping parts in the mid-frequency band, but all frequencies included in the signals used by the far-field and near-field sources do not overlap with each other.

[0015] As an optional implementation, the construction equation of the high-order pseudo-random signal is:

[0016]

[0017] Among them, f i It is the basic construction unit of a series of step signals. When constructing non-logarithmic uniform signals, it is necessary to select f according to the needs. i The highest frequency and the lowest frequency in the , that is, the custom basic unit for constructing high-order pseudo-random signals, the sign function is the symbol function, S n is a set of high-order pseudo-random signals.

[0018] As an optional implementation, the far-field source is arranged in a place where the transmission and reception distance exceeds a predetermined value. A wire source with a length greater than the set value is used in the far-field source to transmit low and medium frequency signals, and a wire source with a length less than the preset value is used in the near-field source to transmit high and medium frequency signals.

[0019] As an optional implementation, one far-field source is arranged and one or more near-field sources are arranged. When there are multiple near-field sources, the exploration effective frequency of the signal used by each near-field source, that is, the main frequency in the high-order pseudo-random signal does not overlap with each other, and the frequency band of each near-field source has an overlapping part with the far-field source.

[0020] A multi-source and multi-resolution artificial source electromagnetic exploration system, comprising:

[0021] Signal construction module, used to construct high-order pseudo-random signals used by near and far parallel field sources;

[0022] A far-field source, used to transmit the corresponding high-order pseudo-random signal;

[0023] A near-field source, used to transmit a corresponding high-order pseudo-random signal;

[0024] The signal acquisition module is used to simultaneously excite the near and far field sources, deploy multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal;

[0025] The signal processing module is used to construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and the low-frequency electromagnetic field data of the far-field source; using the results of the large-scale inversion imaging as the initial model, small-scale fine inversion imaging is performed based on the high-frequency electromagnetic data of the near-field source.

[0026] A computer-readable storage medium for storing computer instructions, wherein when the computer instructions are executed by a processor, the following steps are performed:

[0027] Constructing high-order pseudo-random signals used for near and far parallel field sources;

[0028] Simultaneously stimulate near and far field sources to obtain observation data from multiple receiving points within the measurement area, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal;

[0029] Construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data from far-field sources;

[0030] The results of large-scale inversion imaging are used as the initial model, and small-scale fine inversion imaging is performed based on the electromagnetic data of the near-field source in the medium and high frequency bands.

[0031] An electronic device includes a memory and a processor, and computer instructions stored in the memory and executed by the processor, wherein when the computer instructions are executed by the processor, the following steps are performed:

[0032] Constructing high-order pseudo-random signals used for near and far parallel field sources;

[0033] Simultaneously stimulate near and far field sources to obtain observation data from multiple receiving points within the measurement area, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal;

[0034] Construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data from far-field sources;

[0035] The results of large-scale inversion imaging are used as the initial model, and small-scale fine inversion imaging is performed based on the electromagnetic data of the near-field source in the medium and high frequency bands.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention deploys two field sources with different transmission and reception distances (one far and one or multiple near) to transmit exploration signals of different frequency bands. Based on the far-field source, the geoelectric information of the survey area is macro-controlled. By deploying the near-field source, the shallow information of the key areas can be precisely outlined. While meeting the requirements of large-scale and large-depth detection, high-resolution shallow detection data can be obtained.

[0038] 2. The present invention adopts a multi-source exploration method. Different from the traditional multi-source detection method that uses the same frequency transmission signal for excitation, simultaneous excitation can be achieved by customizing transmission signals in different frequency bands and without overlapping frequencies. In addition, multiple receiving points are deployed in the measurement area for simultaneous observation. According to the frequency component of the transmitted high-order pseudo-random signal, the receiving data of the corresponding field source can be extracted, which greatly improves the efficiency of multi-source observation.

[0039] 3. The selection of the initial model significantly impacts the quality of the inversion results. Within the same survey area, the effective information collected by both near- and far-field sources is essentially identical, reflecting the subsurface structure in the same way. While the inversion results from far-field sources have lower resolution, they still provide a macroscopic view of the subsurface medium within the survey area. Therefore, using the far-field source inversion results as the initial model yields higher-resolution near-field source inversion results than directly using an initial model constructed based on prior information.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0042] FIG1(a) and FIG1(b) are schematic diagrams of spectrum of high-order pseudo-random signals of far-field and near-field sources according to an embodiment;

[0043] Figure 2 A diagram of a field work mode for an embodiment;

[0044] Figure 3 A schematic diagram of a step-by-step inversion scheme according to an embodiment;

[0045] Figure 4 The figure is a basic implementation flow chart of the supervised descent method according to an embodiment. DETAILED DESCRIPTION

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0047] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0048] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0049] In the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0050] Example 1

[0051] This embodiment discloses a multi-source and multi-resolution artificial source electromagnetic exploration method, comprising the following steps:

[0052] 1. Based on the construction method of high-order pseudo-random signals, high-order pseudo-random signals used for far and near parallel field sources are constructed; the frequency band of the signal used by the far-field source is generally medium and low frequency (generally 0.01Hz~10000Hz), and the frequency band of the signal used by the near-field source is generally medium and high frequency (generally 50Hz~50000Hz). The signal frequency band has overlapping parts in the medium frequency band to facilitate the subsequent joint processing of far and near field source data, but all frequencies contained in the signals used by far and near field sources do not overlap with each other.

[0053] As shown in Figure 1(a) and Figure 1(b), two sets of signals are constructed. Figure 1(a) shows the low-frequency signal from the far-field source. The upper figure is the time domain sequence, and the lower figure is the spectrum. The ○ in the spectrum represents the exploration frequency. A third-order 39-frequency signal is used with a frequency band of 0.0625 to 768 Hz, for a total of 39 frequencies.

[0054] Its frequency components are shown in Table 1.

[0055] Table 1 Signal frequency table of far-field source

[0056] Order Frequency / Hz Order Frequency / Hz Order Frequency / Hz 1 0.0625 2 0.1875 3 0.3125 1 0.125 2 0.375 3 0.625 1 0.25 2 0.75 3 1.25 1 0.5 2 1.5 3 2.5 1 1 2 3 3 5 1 2 2 6 3 10 1 4 2 12 3 20 1 8 2 24 3 40 1 16 2 48 3 80 1 32 2 96 3 160 1 64 2 192 3 320 1 128 2 384 3 640 1 256 2 768 1 512

[0057] Figure 1(b) shows the high-frequency emission signal from the near-field source, which uses a 4th-order 31-frequency signal with a frequency range of 134.4 to 49152 Hz, for a total of 41 frequencies.

[0058] Its frequency components are shown in Table 2.

[0059] Table 2 Signal frequency table of near-field source

[0060] Order Frequency / Hz Order Frequency / Hz Order Frequency / Hz Order Frequency / Hz 1 134.4 2 307.2 3 230.4 4 1536 1 268.8 2 614.4 3 460.8 4 3072 1 537.6 2 1228.8 3 921.6 4 6144 1 1075.2 2 2457.6 3 1843.2 4 12288 1 2150.4 2 4915.2 3 3686.4 4 24576 1 4300.8 2 9830.4 3 7372.8 4 49152 1 8601.6 2 19660.8 3 14745.6 4 1 17203.2 2 39321.6 3 29491.2 4

[0061] The exploration frequencies of the two do not overlap at all, with 8 and 7 exploration frequencies respectively in the frequency band of 134.4 to 768 Hz.

[0062] 2. Place the far-field source in a location with a large transmission and reception distance, and use a long wire source to transmit low- and medium-frequency signals. Place a near-field source parallel to the far-field source between the far-field source and the measurement area, and use a relatively short wire source to transmit medium- and high-frequency signals.

[0063] like Figure 2 As shown in Figure 1(a), a far-field source and a near-field source are deployed. The far-field source transmits the signal shown in Figure 1(a), with a typical transmission and reception distance of 10 to 20 km and a typical conductor length of 1 to 2 km. The near-field source transmits the signal shown in Figure 1(b), with a typical transmission and reception distance of 1 to 3 km and a typical conductor length of 0.1 to 0.3 km.

[0064] 3. Simultaneously stimulate the near and far field sources, set up multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal.

[0065] like Figure 2 As shown in the figure, multiple receiving points are deployed in the measurement area for simultaneous observation. The detectable depth of different field sources is approximately equal to 1 / 10 of the transmission and reception distance of the field source.

[0066] 4. Based on the basic principle that low-frequency electromagnetic information mainly reflects the electrical structure information deep in the underground space, and high-frequency electromagnetic information mainly reflects the electrical structure information shallow in the underground space, a step-by-step inversion imaging scheme is adopted.

[0067] like Figure 3 As shown in the figure, the overall scheme is divided into three steps: constructing an initial model of the large-scale electrical structure of the underground space based on prior information; performing large-scale inversion imaging based on the above initial model and the electromagnetic field data of the far-field source in the low and medium frequency bands; using the above large-scale inversion imaging results as the initial model, performing small-scale fine inversion imaging based on the electromagnetic field data of the near-field source in the high and medium frequency bands.

[0068] like Figure 4 As shown, in this embodiment, in the process of step-by-step inversion imaging, based on the known geological and borehole lithological data, the advantages of seismic data in identifying stratum structure, magnetic data in identifying rock mass, and electrical logging data in describing vertical electrical characteristics are fully utilized to construct a large-scale electrical structure model of the underground space;

[0069] Both near and far field sources use a massive data rapid inversion algorithm based on the supervised descent method, combining a mathematical optimization model with multivariate geological information, and continuously iteratively adaptively correcting the target model until a result that conforms to both mathematical fitting and geological laws is obtained.

[0070] The formula for minimizing the objective function of the supervised descent method inversion imaging is:

[0071]

[0072] Where F is the forward model operator, d obs is the observed data, and m is the model parameter.

[0073] Example 2

[0074] A multi-source and multi-resolution artificial source electromagnetic exploration system, comprising:

[0075] Signal construction module, used to construct high-order pseudo-random signals used by near and far parallel field sources;

[0076] A far-field source, used to transmit the corresponding high-order pseudo-random signal;

[0077] A near-field source, used to transmit a corresponding high-order pseudo-random signal;

[0078] The signal acquisition module is used to simultaneously excite the near and far field sources, deploy multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal;

[0079] The signal processing module is used to construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and the low-frequency electromagnetic field data of the far-field source; using the results of the large-scale inversion imaging as the initial model, small-scale fine inversion imaging is performed based on the high-frequency electromagnetic data of the near-field source.

[0080] Example 3

[0081] A computer-readable storage medium for storing computer instructions, wherein when the computer instructions are executed by a processor, the following steps are performed:

[0082] Constructing high-order pseudo-random signals used for near and far parallel field sources;

[0083] Simultaneously stimulate near and far field sources to obtain observation data from multiple receiving points within the measurement area, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal;

[0084] Construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data from far-field sources;

[0085] The results of large-scale inversion imaging are used as the initial model, and small-scale fine inversion imaging is performed based on the electromagnetic data of the near-field source in the medium and high frequency bands.

[0086] Example 4

[0087] An electronic device includes a memory and a processor, and computer instructions stored in the memory and executed by the processor, wherein when the computer instructions are executed by the processor, the following steps are performed:

[0088] Constructing high-order pseudo-random signals used for near and far parallel field sources;

[0089] Simultaneously stimulate near and far field sources to obtain observation data from multiple receiving points within the measurement area, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal;

[0090] Construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data from far-field sources;

[0091] The results of large-scale inversion imaging are used as the initial model, and small-scale fine inversion imaging is performed based on the electromagnetic data of the near-field source in the medium and high frequency bands.

[0092] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made by those skilled in the art that fall within the spirit and principles of the present invention and do not require creative effort are intended to be within the scope of protection of the present invention.

Claims

1. A multi-source and multi-resolution artificial source electromagnetic exploration method, characterized by: The following steps are involved: Constructing high-order pseudo-random signals used for near and far parallel field sources; Arrange a far-field source, and arrange a near-field source parallel to the far-field source between the far-field source and the measurement area; Simultaneously stimulate near and far field sources, deploy multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal; Construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data from far-field sources; Using the results of large-scale inversion imaging as the initial model, small-scale fine inversion imaging is performed based on the electromagnetic data of the near-field source in the medium and high frequency bands; In the process of constructing the high-order pseudo-random signal used for the far-field and near-field parallel source, the frequency band of the signal used by the far-field source is medium-low frequency, and the frequency band of the signal used by the near-field source is medium-high frequency; One far-field source is arranged, and one or more near-field sources are arranged. When there are multiple near-field sources, the exploration effective frequencies of the signals used by each near-field source, that is, the main frequencies in the high-order pseudo-random signals do not overlap with each other, and the frequency bands of each near-field source have overlapping parts with the far-field source.

2. The multi-source and multi-resolution artificial source electromagnetic exploration method according to claim 1, characterized in that: The signal frequency bands overlap in the mid-frequency band, but all frequencies contained in the signals used by far-field and near-field sources do not overlap.

3. The multi-source and multi-resolution artificial source electromagnetic exploration method according to claim 1, characterized in that: The construction equation of the high-order pseudo-random signal is: ； in, It is the basic construction unit of a series of step signals. When constructing non-logarithmic uniform signals, it is necessary to select The highest frequency and the lowest frequency in the , that is, the custom basic unit for building high-order pseudo-random signals, the sign function is the symbol function, is a set of high-order pseudo-random signals.

4. The multi-source and multi-resolution artificial source electromagnetic exploration method according to claim 1, characterized in that: The far-field source is placed where the transmission and reception distance exceeds a predetermined value. A wire source with a length greater than the set value is used in the far-field source to transmit medium and low frequency signals, and a wire source with a length less than the preset value is used in the near-field source to transmit medium and high frequency signals.

5. The multi-source and multi-resolution artificial source electromagnetic exploration method according to claim 1, characterized in that: Both near- and far-field sources use a massive data rapid inversion algorithm based on the supervised descent method, combining a mathematical optimization model with multivariate geological information, and continuously iteratively and adaptively modifying the target model until a result that conforms to both mathematical fitting and geological laws is obtained. The formula for minimizing the objective function of the supervised descent method inversion imaging is: ； Where F is the forward model operator, is the observed data, and m is the model parameter.

6. A multi-source multi-resolution artificial source electromagnetic exploration system using the multi-source multi-resolution artificial source electromagnetic exploration method according to claim 1, characterized in that: include: Signal construction module, used to construct high-order pseudo-random signals used by near and far parallel field sources; A far-field source, used to transmit the corresponding high-order pseudo-random signal; A near-field source, used to transmit a corresponding high-order pseudo-random signal; The signal acquisition module is used to simultaneously excite the near and far field sources, deploy multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal; The signal processing module is used to construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and the low-frequency electromagnetic field data of the far-field source; using the results of the large-scale inversion imaging as the initial model, small-scale fine inversion imaging is performed based on the high-frequency electromagnetic data of the near-field source.

7. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, complete the following steps: Constructing high-order pseudo-random signals used for near and far parallel field sources; Simultaneously stimulate near and far field sources to obtain observation data from multiple receiving points within the measurement area, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal; Construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data from far-field sources; Using the results of large-scale inversion imaging as the initial model, small-scale fine inversion imaging is performed based on the electromagnetic data of the near-field source in the medium and high frequency bands; When the computer instructions are executed by a processor, the steps described in any one of claims 1 to 5 are completed.

8. An electronic device, characterized in that: The system comprises a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein the computer instructions are executed by the processor to complete the following steps: Constructing high-order pseudo-random signals used for near and far parallel field sources; Simultaneously stimulate near and far field sources to obtain observation data from multiple receiving points within the measurement area, and extract the receiving data of the corresponding field source based on the frequency component of the transmitted high-order pseudo-random signal; Construct an initial model of the large-scale electrical structure of the underground space based on prior information, and perform large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data from far-field sources; Using the results of large-scale inversion imaging as the initial model, small-scale fine inversion imaging is performed based on the electromagnetic data of the near-field source in the medium and high frequency bands; When the computer instructions are executed by a processor, the steps described in any one of claims 1 to 5 are completed.

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