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

Abstract

The invention provides a multi-source multi-resolution artificial source electromagnetic exploration method and system. The method comprises the following steps: constructing high-order pseudo-random signals used by far and near parallel field sources; simultaneously exciting far and near field sources, acquiring observation data of a plurality of receiving points in the measurement area, and extracting receiving data of the corresponding field sources according to frequency components of transmitted high-order pseudo-random signals; an underground space large-scale electrical structure initial model based on prior information is constructed, and large-scale inversion imaging is carried out based on the initial model and far field source middle-low frequency band electromagnetic field data; a result of large-scale inversion imaging is used as an initial model, and small-scale fine inversion imaging is carried out based on high-frequency electromagnetic data in a near-field source. According to the invention, high-quality artificial source electromagnetic data can be successfully obtained, and a high-precision inversion interpretation result is realized.

Description

Technical Field

[0001] The 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] For the frequency domain electromagnetic method, it is necessary to transmit electromagnetic signals of 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, the lower the frequency, the deeper the detection, and the higher the frequency, the smaller the shallow blind area; at the same time, the denser the spectrum, the more frequencies, and the higher the resolution under the same bandwidth. 2) The greater the transmission and reception distance, the deeper the detection, but the weaker the signal, especially the medium and high frequencies attenuate quickly, and the detection resolution and accuracy are not enough; when the transmission and reception distance becomes smaller, the medium and high frequency signal strength is improved, and the detection resolution and accuracy are also improved, but the detection depth is shallow.

[0004] In summary, a single transmitting device cannot take into account both deep exploration and high resolution, and a single transmitting signal cannot take into account both wide bandwidth and high density of exploration frequency. Moreover, a single transmitting device cannot support the above two requirements because the frequency band is too wide, that is, deep exploration (low frequency) must meet high power, and shallow exploration (high frequency) must meet high-speed shutdown. In this context, single-source frequency domain electromagnetic detection cannot take into account these two requirements, and it is urgent to carry out research on multi-source and multi-resolution detection methods. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a multi-source and 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 and multi-resolution artificial source electromagnetic exploration method by arranging improved emission signals, two kinds of far and near field sources, and developing a multi-source progressive inversion method, successfully acquiring high-quality artificial source electromagnetic data and achieving high-precision inversion 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] Construct 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 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 according to the frequency components of the transmitted high-order pseudo-random signal;

[0011] Constructing an initial model of the large-scale electrical structure of the underground space based on prior information, and performing large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data of 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 medium and high frequency electromagnetic data of near-field sources.

[0013] As an optional implementation, in the process of constructing the high-order pseudo-random signal used for the 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 contained 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 building 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 where the receiving and transmitting distance exceeds a predetermined value. A wire source with a length greater than a set value is used in the far-field source to transmit low and medium frequency signals. A wire source with a length less than a 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 a 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, arrange multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source according to the frequency components 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 to perform large-scale inversion imaging based on the initial model and the low-frequency electromagnetic field data of the far-field source; the result of the large-scale inversion imaging is used as the initial model, and 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] Construct 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 of multiple receiving points in the measurement area, and extract the receiving data of the corresponding field source according to the frequency component of the transmitted high-order pseudo-random signal;

[0029] Constructing an initial model of the large-scale electrical structure of the underground space based on prior information, and performing large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data of 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 medium and high frequency electromagnetic data of near-field sources.

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

[0032] Construct 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 of multiple receiving points in the measurement area, and extract the receiving data of the corresponding field source according to the frequency component of the transmitted high-order pseudo-random signal;

[0034] Constructing an initial model of the large-scale electrical structure of the underground space based on prior information, and performing large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data of 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 medium and high frequency electromagnetic data of near-field sources.

[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 macroscopically controlled. By deploying near-field sources, shallow information of key areas can be finely 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, which is 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 arranged in the survey area for simultaneous observation. According to the frequency components of the transmitted high-order pseudo-random signals, 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 has a great influence on the quality of the inversion results. In the same survey area, the effective information collected by the two sources of far and near is essentially the same, and reflects the underground structure in the same way. Although the resolution of the inversion results of the far-field source is low, it can still reflect the underground medium information of the survey area macroscopically. Therefore, using the inversion results of the far-field source as the initial model can obtain a near-field source inversion result with a higher resolution than directly using the initial model built 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 in the specification, 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] FIG. 1( a ) and FIG. 1( b ) are schematic diagrams of spectrum of high-order pseudo-random signals of far-near field sources according to an embodiment;

[0043] Figure 2 A field work mode diagram of 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 schematic diagram of the basic implementation flow of the supervised descent method according to an embodiment. DETAILED DESCRIPTION

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

[0047] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those 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 exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

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

[0050] Embodiment 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 mid-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 groups of signals are constructed. Figure 1(a) is the low-frequency signal of 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] Degree Frequency / Hz Degree Frequency / Hz Degree 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 transmission 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] Degree Frequency / Hz Degree Frequency / Hz Degree Frequency / Hz Degree 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, and there are 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 place with a large transmission and reception distance, and use a long wire source to transmit medium and low 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 far-field source and a near-field source are arranged. The far-field source transmits the signal shown in Figure 1(a), and the receiving and sending distance is generally 10 to 20 km. The wire source is generally 1 km to 2 km long. The near-field source transmits the signal shown in Figure 1(b), and the receiving and sending distance is generally 1 to 3 km. The wire source is generally 0.1 km to 0.3 km long.

[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 components of the transmitted high-order pseudo-random signal.

[0065] like Figure 2 As shown, multiple receiving points are arranged in the measurement area for simultaneous observation. The detectable depth of different field sources is approximately equal to 1 / 10 of the receiving and transmitting 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 plan 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 initial model and low-frequency electromagnetic field data of far-field sources; using the above large-scale inversion imaging results as the initial model, and performing small-scale fine inversion imaging based on high-frequency electromagnetic data of near-field sources.

[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 lithology data, the advantages of seismic data in identifying stratigraphic 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 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 iterating and 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] Embodiment 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 a 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, arrange multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source according to the frequency components 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 to perform large-scale inversion imaging based on the initial model and the low-frequency electromagnetic field data of the far-field source; the result of the large-scale inversion imaging is used as the initial model, and small-scale fine inversion imaging is performed based on the high-frequency electromagnetic data of the near-field source.

[0080] Embodiment 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] Construct 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 of multiple receiving points in the measurement area, and extract the receiving data of the corresponding field source according to the frequency component of the transmitted high-order pseudo-random signal;

[0084] Constructing an initial model of the large-scale electrical structure of the underground space based on prior information, and performing large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data of 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 medium and high frequency electromagnetic data of near-field sources.

[0086] Embodiment 4

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

[0088] Construct 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 of multiple receiving points in the measurement area, and extract the receiving data of the corresponding field source according to the frequency component of the transmitted high-order pseudo-random signal;

[0090] Constructing an initial model of the large-scale electrical structure of the underground space based on prior information, and performing large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data of 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 medium and high frequency electromagnetic data of near-field sources.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention without creative labor shall be included in the protection scope of the present invention.

Claims

1. A multi-source and multi-resolution artificial source electromagnetic exploration method, characterized in that: The following steps are involved: Construct 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 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 according to the frequency components of the transmitted high-order pseudo-random signal; Constructing an initial model of the large-scale electrical structure of the underground space based on prior information, and performing large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data of far-field sources; The results of large-scale inversion imaging are used as the initial model, and small-scale fine inversion imaging is performed based on the medium and high frequency electromagnetic data of near-field sources.

2. The multi-source and multi-resolution artificial source electromagnetic exploration method according to claim 1, characterized in that: In the process of constructing the high-order pseudo-random signal used for the far and near parallel field sources, the frequency band of the signal used by the far-field source is the medium and low frequency, and the frequency band of the signal used by the near-field source is the medium and high frequency.

3. A multi-source and multi-resolution artificial source electromagnetic exploration method as claimed in claim 1 or 2, 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.

4. A multi-source and multi-resolution artificial source electromagnetic exploration method as claimed in claim 1 or 2, characterized in that: The construction equation of the high-order pseudo-random signal is: 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 building high-order pseudo-random signals, the sign function is the symbol function, S n is a set of high-order pseudo-random signals.

5. The multi-source and multi-resolution artificial source electromagnetic exploration method according to claim 1, characterized in that: The far-field source is arranged where the receiving and transmitting distance exceeds a preset 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. 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.

6. A multi-source and multi-resolution artificial source electromagnetic exploration method as claimed in claim 1 or 2, characterized in that: 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.

7. 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 iterating and adaptively correcting 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, d obs is the observed data, and m is the model parameter.

8. A multi-source and multi-resolution artificial source electromagnetic exploration system, 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 a 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, arrange multiple receiving points in the measurement area for simultaneous observation, and extract the receiving data of the corresponding field source according to the frequency components 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 to perform large-scale inversion imaging based on the initial model and the low-frequency electromagnetic field data of the far-field source; the result of the large-scale inversion imaging is used as the initial model, and small-scale fine inversion imaging is performed based on the high-frequency electromagnetic data of the near-field source.

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

10. 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: Construct high-order pseudo-random signals used for near and far parallel field sources; Simultaneously stimulate near and far field sources to obtain observation data of multiple receiving points in the measurement area, and extract the receiving data of the corresponding field source according to the frequency component of the transmitted high-order pseudo-random signal; Constructing an initial model of the large-scale electrical structure of the underground space based on prior information, and performing large-scale inversion imaging based on the initial model and low-frequency electromagnetic field data of far-field sources; The results of large-scale inversion imaging are used as the initial model, and small-scale fine inversion imaging is performed based on the medium and high frequency electromagnetic data of near-field sources.

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