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

Abstract

The present invention discloses a method and device, system, and storage medium for electrical source transient electromagnetic data imaging, including: Step S1, observing the horizontal electric field Ex and the vertical induced voltage Vz at the same measuring point; Step S2, respectively obtaining the first-order derivative with respect to time t for the horizontal electric field Ex and the vertical induced voltage Vz; Step S3, calculating the full-period apparent resistivity according to the first-order derivative; Step S4, performing time-depth transformation based on the full-period apparent resistivity to achieve apparent resistivity depth imaging. By adopting the technical solution of the present invention, the influence of the emission source is eliminated, and the imaging accuracy and convenience of the electrical source transient electromagnetic method can be significantly improved.

Description

Technical Field

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

[0002] The electrical source transient electromagnetic method uses a long wire grounded at both ends as the emission source, and observes the secondary electromagnetic field signals within a certain range on both sides of the wire. Then, data processing methods such as imaging or inversion are used to obtain the electrical structure within a certain depth range underground. Apparent resistivity-depth imaging is a fast and convenient data processing method, and the key step is the calculation of the full-period apparent resistivity. Traditional full-period apparent resistivity calculation methods require a monotonic relationship between the field value and the resistivity, so the calculation can only be based on the vertical magnetic field Bz component. However, the components actually observed by the electrical source transient electromagnetic method are mostly the horizontal electric field Ex and the vertical induced voltage Vz. But these two components have a double-valued relationship with the resistivity, and the full-period apparent resistivity cannot be directly calculated based on them. At the same time, when calculating the full-period apparent resistivity based on the Bz component traditionally, the actual shape and form of the emission source need to be strictly considered. When the emission source is bent or undulating, it will have a greater impact on the accuracy of the full-period apparent resistivity result. 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 solutions:

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

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

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

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

[0009] Step S4, performing time-depth transformation according to the full-period apparent resistivity to realize 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] Wherein, 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’), and the variable μ 0 =4×10 -7 H / A is the magnetic permeability;

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

[0014]

[0015] Preferably, in step S3, use and to calculate the resistivity during the entire period,

[0016]

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

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

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

[0020] A second calculation module, used to calculate the apparent resistivity during the entire period according to the first-order derivatives;

[0021] A third calculation module, used to perform time-depth transformation according to the apparent resistivity during the entire period to realize apparent resistivity depth imaging.

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

[0023]

[0024] Wherein, 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’), and the variable μ 0 =4×10 -7 H / A is the magnetic permeability;

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

[0026]

[0027] Preferably, the second calculation module uses and Calculate the resistivity for the entire period using the ratio,

[0028]

[0029] The present invention also provides an electrical source transient electromagnetic data imaging system, including: a memory and a processor. A computer program is stored on the memory and run by the processor. When the computer program is run by the processor, it executes the electrical source transient electromagnetic data imaging method.

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

[0031] The present invention can directly utilize the measured Ex and Vz components 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 technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

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

[0034] Figure 2 is the imaging result of the numerical case.

[0035] Figure 3 is the imaging result of the measured data. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0037] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0038] Embodiment 1:

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

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

[0041] Step S2: Take the first derivative of the horizontal electric field Ex and the vertical induced voltage Vz with respect to time t respectively;

[0042] Step S3: Calculate the full-period apparent resistivity according to the first derivative;

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

[0044] As an implementation manner 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’), and the variable μ 0 = 4×10 -7 H / A is the magnetic permeability;

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

[0048]

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

[0050]

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

[0052]

[0053] As an implementation manner of the 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 imaging. Thus, the resistivity distribution within a certain depth range underground can be obtained, and the apparent resistivity-depth imaging of the electrical source transient electromagnetic data is realized.

[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 the method applicable to the case of complex emission source forms affected by factors such as terrain.

[0057] Numerical case:

[0058] Figure 2 This is an imaging case of a numerical simulation model implemented using the embodiments of the present invention. The model parameters are as follows: a four-layer model, the resistivity of the first layer is 100 Ω·m, the thickness is 200 m, the resistivity of the second layer is 10 Ω·m, the thickness is 200 m, the resistivity of the third layer is 100 Ω·m, the thickness is 200 m; the resistivity of the fourth layer is 10 Ω·m, and the thickness is infinite. The length of the emission source of the electrical source transient electromagnetic is 500 m, the emission current is 1 A, and the offset distance of the observation point is 1000 m. 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 the embodiments of the present invention. In this case, the length of the emission source is 1430 m, the emission current is 30 A, the survey line is parallel to the emission source, and the offset distance is 420 m. From Figure 3 It can be seen that the imaging method of the embodiments of the present invention can well restore the resistivity distribution of the real earth and has a good coincidence with the borehole.

[0061] Embodiment 2:

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

[0063] An acquisition module for observing the horizontal electric field Ex and the vertical induced voltage Vz at the same measurement point;

[0064] A first calculation module for respectively obtaining the first-order derivative with respect to time t of the horizontal electric field Ex and the vertical induced voltage Vz;

[0065] A second calculation module for calculating the full-period apparent resistivity according to the first-order derivative;

[0066] A third calculation module for performing time-depth transformation according to the full-period apparent resistivity to realize apparent resistivity depth imaging.

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

[0068]

[0069] where I is the emission current intensity, ds is the length of the dipole source, and ρ is the resistivity, is the distance from the observation point (x, y) to the emission source (x’, y’), and the variable μ 0 = 4×10 -7 H / A is the magnetic permeability;

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

[0071]

[0072] As an implementation manner of an embodiment of the present invention, the second calculation module calculates the full-period resistivity using the ratio of and

[0073]

[0074] Example 3:

[0075] The embodiment of the present invention further provides an electrical source transient electromagnetic data imaging system, including: a memory and a processor. A computer program is stored on the memory and is run by the processor. When the computer program is run by the processor, it executes the electrical source transient electromagnetic data imaging method.

[0076] Example 4:

[0077] The embodiment of the present invention further provides a storage medium. A computer program is stored on the storage medium. When the computer program runs, it executes the electrical source transient electromagnetic data imaging method.

[0078] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall 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: Observe the horizontal electric field e at the same measuring point x and the vertical induced voltage v z ; Step S2: horizontal electric field e x and the vertical induced voltage v z Calculate the first-order derivative 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; In step S2, the horizontal electric field e x and the vertical induced voltage v z The expression is: 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; For x and v z Calculate the first-order derivative with respect to time t respectively: in, For e x Find the first-order derivative with respect to time t, For v z Find the first derivative with respect to time t.

2. The electrical source transient electromagnetic data imaging method according to claim 1, characterized in that: In step S3, using and The total resistivity is calculated by the ratio of 3. An electrical source transient electromagnetic data imaging device, characterized in that: include: Acquisition module, used to observe the horizontal electric field at the same measuring point x and the vertical induced voltage v z ; The first calculation module is used to calculate the horizontal electric field e x and the vertical induced voltage v z Calculate the first-order derivative 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; Horizontal electric field x and the vertical induced voltage v z The expression is: 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; For x and v z Calculate the first-order derivative with respect to time t respectively: in, For e x Find the first-order derivative with respect to time t, For v z Find the first derivative with respect to time t.

4. The electrical source transient electromagnetic data imaging device according to claim 3, characterized in that: The second calculation module uses and The total resistivity is calculated by the ratio of 5. 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 2 is executed.

6. 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 2.

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