Electrical source transient electromagnetic data imaging method, device and system and storage medium

Abstract

The invention discloses an electrical source transient electromagnetic data imaging method, device and system, and a storage medium. The method comprises the following steps: S1, observing a horizontal electric field Ex and a vertical induced voltage Vz at the same measuring point; s2, respectively solving first-order derivatives of the horizontal electric field Ex and the vertical induced voltage Vz to the time t; s3, calculating the whole-period apparent resistivity according to the first-order derivative; and S4, time-depth transformation is carried out according to the whole-period apparent resistivity, and apparent resistivity depth imaging is realized. By adopting the technical scheme of the invention, the influence of the emission source is eliminated, and the imaging precision and convenience of the electrical source transient electromagnetic method can be obviously improved.

Description

Technical Field

[0001] The present invention belongs to the field of geophysical exploration technology, and in particular relates to an electrical source transient electromagnetic data imaging method and device, a system, and a storage medium. Background Art

[0002] The electrical source transient electromagnetic method uses a long wire with both ends grounded as the transmitting source, and observes the secondary electromagnetic field signal within a certain range on both sides of the wire, and then uses data processing methods such as imaging or inversion to obtain the electrical structure within a certain depth range underground. Apparent resistivity-depth imaging is a fast and convenient data processing method, in which the key step is the calculation of the full-period apparent resistivity. The traditional full-period apparent resistivity calculation method requires that the field value is monotonically related to the resistivity, so it can only be calculated based on the vertical magnetic field Bz component. The components actually observed by the electrical source transient electromagnetic method are mostly the horizontal electric field Ex and the vertical induced voltage Vz. However, these two components have a dual-value relationship with the resistivity, and the full-period apparent resistivity cannot be directly calculated based on them. At the same time, when the traditional full-period apparent resistivity calculation based on the Bz component is performed, the actual shape and form of the transmitting source must be strictly considered. When the transmitting source is bent or undulating, it will have a significant impact on the accuracy of the full-period apparent resistivity results. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method and device, system, and storage medium for electrical source transient electromagnetic data imaging, which can significantly improve the imaging accuracy and convenience of the electrical source transient electromagnetic method.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A method for imaging electrical source transient electromagnetic data, comprising:

[0006] Step S1, observing the horizontal electric field Ex and the vertical induced voltage Vz at the same measuring point;

[0007] Step S2, obtaining first-order derivatives of the horizontal electric field Ex and the vertical induced voltage Vz with respect to time t respectively;

[0008] Step S3, calculating the apparent resistivity of the entire period according to the first-order derivative;

[0009] Step S4: performing time-depth transformation according to the full-period apparent resistivity to achieve apparent resistivity depth imaging.

[0010] Preferably, in step S2, the expressions of the horizontal electric field Ex and the vertical induced voltage Vz are:

[0011]

[0012] Where I is the emission current intensity, ds is the length of the dipole source, ρ is the resistivity, is the distance from the observation point (x, y) to the emission source (x', y'), the variable μ0=4×10 -7 H / A is the magnetic permeability;

[0013] Take the first-order derivative of Ex and Vz with respect to time t:

[0014]

[0015] As a preferred embodiment, in step S3, using and The total resistivity is calculated by the ratio of

[0016]

[0017] The present invention also provides an electrical source transient electromagnetic data imaging device, comprising:

[0018] Acquisition module, used to observe the horizontal electric field Ex and vertical induced voltage Vz at the same measuring point;

[0019] A first calculation module is used to obtain the first-order derivatives of the horizontal electric field Ex and the vertical induced voltage Vz with respect to time t respectively;

[0020] The second calculation module is used to calculate the full-period apparent resistivity according to the first-order derivative;

[0021] The third calculation module is used to perform time-depth transformation according to the full-period apparent resistivity to achieve apparent resistivity depth imaging.

[0022] Preferably, the expressions of the horizontal electric field Ex and the vertical induced voltage Vz are:

[0023]

[0024] Where I is the emission current intensity, ds is the length of the dipole source, ρ is the resistivity, is the distance from the observation point (x, y) to the emission source (x', y'), the variable μ0=4×10 -7 H / A is the magnetic permeability;

[0025] Take the first-order derivative of Ex and Vz with respect to time t:

[0026]

[0027] Preferably, the second computing module uses and The total resistivity is calculated by the ratio of

[0028]

[0029] The present invention also provides an electrical source transient electromagnetic data imaging system, comprising: a memory and a processor, wherein the memory stores a computer program executed by the processor, and the computer program executes the electrical source transient electromagnetic data imaging method when executed by the processor.

[0030] The present invention also provides a storage medium, on which a computer program is stored, and the computer program executes the electrical source transient electromagnetic data imaging method when running.

[0031] The present invention can directly utilize Ex and Vz components measured in the field and eliminate the influence of the emission source, which can significantly improve the imaging accuracy and convenience of the electrical source transient electromagnetic method. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0033] Figure 1 It is a flow chart of the electrical source transient electromagnetic data imaging method according to an embodiment of the present invention;

[0034] Figure 2 Imaging results of numerical cases.

[0035] Figure 3 This is the imaging result of measured data. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Embodiment 1:

[0039] like Figure 1 As shown, an embodiment of the present invention provides an electrical source transient electromagnetic data imaging method, comprising:

[0040] Step S1, observing the horizontal electric field Ex and the vertical induced voltage Vz at the same measuring point;

[0041] Step S2, obtaining first-order derivatives of the horizontal electric field Ex and the vertical induced voltage Vz with respect to time t respectively;

[0042] Step S3, calculating the apparent resistivity of the entire period according to the first-order derivative;

[0043] Step S4: performing time-depth transformation according to the full-period apparent resistivity to achieve apparent resistivity depth imaging.

[0044] As an implementation of the embodiment of the present invention, in step S2, the expressions of the horizontal electric field Ex and the vertical induced voltage Vz are:

[0045]

[0046] Where I is the emission current intensity, ds is the length of the dipole source, ρ is the resistivity, is the distance from the observation point (x, y) to the emission source (x', y'), the variable μ0=4×10 -7 H / A is the magnetic permeability;

[0047] Take the first-order derivative of Ex and Vz with respect to time t:

[0048]

[0049] As an implementation method of the present invention, in step S3, calculate and The ratio of

[0050]

[0051] From this, we can get the expression of resistivity ρ, and to ensure that ρ is positive, take and The absolute value of the ratio is:

[0052]

[0053] As an implementation of an embodiment of the present invention, in step S4, the time-depth transformation is:

[0054]

[0055] Through the above steps, the full-period apparent resistivity value ρ corresponding to the depth d(t) can be obtained, and the corresponding relationship between depth and apparent resistivity can be obtained. This process is called imaging, and the resistivity distribution within a certain depth range underground can be obtained, thus realizing the apparent resistivity-depth imaging of electrical source transient electromagnetic data.

[0056] In step S2, the influence of the emission source term Ids is eliminated by using a ratio method, which can significantly improve the calculation accuracy of the full-period apparent resistivity and make this method applicable to the case of complex emission source shapes affected by factors such as terrain.

[0057] Numerical example:

[0058] Figure 2 This is an imaging case of a numerical simulation model implemented using an embodiment of the present invention. The model parameters are: four-layer model, the first layer has a resistivity of 100Ω·m and a thickness of 200m, the second layer has a resistivity of 10Ω·m and a thickness of 200m, the third layer has a resistivity of 100Ω·m and a thickness of 200m; the fourth layer has a resistivity of 10Ω·m and an infinite thickness. The emission source length of the electrical source transient electromagnetic is 500m, the emission current is 1A, and the observation point offset is 1000m. From Figure 2 It can be seen that the imaging method of this embodiment can well restore the resistivity distribution of the real model.

[0059] Measured case:

[0060] Figure 3 This is an imaging case of measured profile data implemented using an embodiment of the present invention. In this case, the length of the emission source is 1430m, the emission current is 30A, the survey line is parallel to the emission source, and the offset distance is 420m. Figure 3 It can be seen that the imaging method of the embodiment of the present invention can well restore the resistivity distribution of the real earth, which is in good agreement with the borehole.

[0061] Embodiment 2:

[0062] The present invention also provides an electrical source transient electromagnetic data imaging device, comprising:

[0063] Acquisition module, used to observe the horizontal electric field Ex and vertical induced voltage Vz at the same measuring point;

[0064] A first calculation module is used to obtain the first-order derivatives of the horizontal electric field Ex and the vertical induced voltage Vz with respect to time t respectively;

[0065] The second calculation module is used to calculate the full-period apparent resistivity according to the first-order derivative;

[0066] The third calculation module is used to perform time-depth transformation according to the full-period apparent resistivity to achieve apparent resistivity depth imaging.

[0067] As an implementation method of the present invention, the expressions of the horizontal electric field Ex and the vertical induced voltage Vz generated by the horizontal electric dipole source on the surface of the uniform half-space earth are:

[0068]

[0069] Where I is the emission current intensity, ds is the length of the dipole source, ρ is the resistivity, is the distance from the observation point (x, y) to the emission source (x', y'), the variable μ0=4×10 -7 H / A is the magnetic permeability;

[0070] Take the first-order derivative of Ex and Vz with respect to time t:

[0071]

[0072] As an implementation method of the embodiment of the present invention, the second calculation module uses and The total resistivity is calculated by the ratio of

[0073]

[0074] Embodiment 3:

[0075] An embodiment of the present invention also provides an electrical source transient electromagnetic data imaging system, comprising: a memory and a processor, wherein the memory stores a computer program executed by the processor, and the computer program executes an electrical source transient electromagnetic data imaging method when executed by the processor.

[0076] Embodiment 4:

[0077] An embodiment of the present invention further provides a storage medium, on which a computer program is stored, and the computer program executes the electrical source transient electromagnetic data imaging method when running.

[0078] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for imaging electrical source transient electromagnetic data, characterized in that: include: Step S1, observing the horizontal electric field Ex and the vertical induced voltage Vz at the same measuring point; Step S2, obtaining first-order derivatives of the horizontal electric field Ex and the vertical induced voltage Vz with respect to time t respectively; Step S3, calculating the apparent resistivity of the entire period according to the first-order derivative; Step S4: performing time-depth transformation according to the full-period apparent resistivity to achieve apparent resistivity depth imaging.

2. The electrical source transient electromagnetic data imaging method according to claim 1, characterized in that: In step S2, the expressions of the horizontal electric field Ex and the vertical induced voltage Vz are: Where I is the emission current intensity, ds is the length of the dipole source, ρ is the resistivity, is the distance from the observation point (x, y) to the emission source (x', y'), the variable μ0=4×10 -7 H / A is the magnetic permeability; Take the first-order derivative of Ex and Vz with respect to time t:

3. The electrical source transient electromagnetic data imaging method according to claim 2, characterized in that: In step S3, using and The total resistivity is calculated by the ratio of 4. An electrical source transient electromagnetic data imaging device, characterized in that: include: Acquisition module, used to observe the horizontal electric field Ex and vertical induced voltage Vz at the same measuring point; A first calculation module is used to obtain the first-order derivatives of the horizontal electric field Ex and the vertical induced voltage Vz with respect to time t respectively; The second calculation module is used to calculate the full-period apparent resistivity according to the first-order derivative; The third calculation module is used to perform time-depth transformation according to the full-period apparent resistivity to achieve apparent resistivity depth imaging.

5. The electrical source transient electromagnetic data imaging device according to claim 4, characterized in that: The expressions of horizontal electric field Ex and vertical induced voltage Vz are: Where I is the emission current intensity, ds is the length of the dipole source, ρ is the resistivity, is the distance from the observation point (x, y) to the emission source (x', y'), the variable μ0=4×10 -7 H / A is the magnetic permeability; Take the first-order derivative of Ex and Vz with respect to time t:

6. The electrical source transient electromagnetic data imaging device according to claim 5, characterized in that: The second calculation module uses and The total resistivity is calculated by the ratio of 7. An electrical source transient electromagnetic data imaging system, characterized in that: include: A memory and a processor, wherein the memory stores a computer program executed by the processor, and when the computer program is executed by the processor, the electrical source transient electromagnetic data imaging method as described in any one of claims 1 to 3 is executed.

8. A storage medium, characterized in that: The storage medium stores a computer program, which, when running, executes the electrical source transient electromagnetic data imaging method as described in any one of claims 1 to 3.

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