Electrical source short-offset transient electromagnetic quasi-three-dimensional inversion method, system and device and medium

Abstract

The invention discloses an electrical source short offset transient electromagnetic quasi-three-dimensional inversion method, system and device and a medium, and relates to the technical field of geophysical exploration. The method comprises the steps of performing normalization processing on multi-source data, performing division and assignment on an underground space by using a Gaussian difference method based on the preprocessed data, and constructing an initial three-dimensional model; based on the initial three-dimensional model, performing quasi-three-dimensional inversion by using a nonlinear conjugate gradient algorithm, and adaptively adjusting values of transverse and longitudinal constraint factors in the inversion process to obtain inversion data; extracting three-dimensional imaging information of the underground electrical structure according to the inversion data; the three-dimensional imaging information is used for geological interpretation and resource evaluation. According to the method, the initial three-dimensional model can be established through Gaussian interpolation, efficient inversion calculation is performed by using a nonlinear conjugate gradient algorithm, and transverse and longitudinal constraint factors are adaptively adjusted in the inversion process, so that high-precision quasi-three-dimensional imaging of the underground electrical structure is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geophysical exploration, in particular to an electrical source short offset transient electromagnetic quasi-three-dimensional inversion method, system, device and medium. BACKGROUND

[0002] As an important technical means of geophysical exploration, the transient electromagnetic method (TEM) reveals the electrical distribution characteristics of underground media by transmitting current pulses to the underground and observing the secondary field decay over time after power-off. However, traditional TEM data inversion is mostly based on two-dimensional models, which cannot accurately describe the complex three-dimensional electrical structure of the underground. Especially under short offset conditions (i.e., the distance between the transmitting source and the receiving point is short), the spatial distribution of the electromagnetic field is more complex, and the limitations of two-dimensional inversion methods are particularly prominent. Full three-dimensional inversion requires millions of grids, which is low in computational efficiency and difficult to be practical. SUMMARY

[0003] The purpose of the present application is to provide an electrical source short offset transient electromagnetic quasi-three-dimensional inversion method, system, device and medium, which aims to solve or improve at least one of the above technical problems.

[0004] To achieve the above purpose, the present application provides the following scheme: An electrical source short offset transient electromagnetic quasi-three-dimensional inversion method, comprising: Obtaining multi-source data and performing normalization processing on the multi-source data to obtain preprocessed data; the multi-source data includes geological information and electrical parameters; Based on the preprocessed data, the underground space is divided and valued using the Gaussian difference method to construct an initial three-dimensional model; the construction process of the initial three-dimensional model includes kernel function optimization and multi-source data fusion; Based on the initial three-dimensional model, a nonlinear conjugate gradient algorithm is used for quasi-three-dimensional inversion, and the values of the horizontal and vertical constraint factors are adaptively adjusted during the inversion process to obtain inversion data; the process of quasi-three-dimensional inversion includes target function enhancement and algorithm acceleration strategy; Extracting three-dimensional imaging information of the underground electrical structure according to the inversion data; the three-dimensional imaging information is used for geological interpretation and resource assessment.

[0005] Optionally, the kernel function optimization is specifically: ; Wherein, represents the kernel function, which measures the distance between two points in space r i and r jCorrelation of the relatedness, Bandwidth parameter of kernel function ， Adaptive adjustment coefficient Measurement point spacing

[0006] Optionally, the multi-source data fusion is specifically: Integrating existing borehole resistivity ρ dill Surface geological map , Construct a mixed constraint matrix: ; Wherein, Kernel function, Weight coefficient, balance the contribution of borehole and surface geological data.

[0007] Optionally, the objective function enhancement is specifically: ; Wherein, W d Data weight matrix, m is the model vector to be solved, d obs Observation data vector, d pre Predicted data vector, Horizontal direction regularization parameter, Horizontal direction gradient operator, First order derivative operator, Vertical direction regularization parameter.

[0008] Optionally, the algorithm acceleration strategy is specifically: Adopt GPU parallel Jacobi matrix calculation, introduce preconditioner: And the iteration number is less than 50 times; wherein, J is the Jacobi matrix, Small positive number, I is the unit matrix.

[0009] The application also provides an electrical source short offset transient electromagnetic pseudo-three-dimensional inversion system, comprising: Data acquisition and preprocessing unit, for acquiring multi-source data, and normalizing the multi-source data to obtain preprocessed data; the multi-source data includes geological information and electrical parameters; Initial three-dimensional model construction unit, for dividing and assigning the underground space based on the preprocessed data using Gaussian difference method, and constructing an initial three-dimensional model; the construction process of the initial three-dimensional model includes kernel function optimization and multi-source data fusion; The quasi-three-dimensional inversion unit is configured to perform quasi-three-dimensional inversion based on the initial three-dimensional model by using a nonlinear conjugate gradient algorithm, and to adaptively adjust values of horizontal and vertical constraint factors during the inversion process to obtain inversion data; the quasi-three-dimensional inversion process comprises target function enhancement and algorithm acceleration strategy. The imaging unit is configured to extract three-dimensional imaging information of the underground electrical structure according to the inversion data; and the three-dimensional imaging information is used for geological interpretation and resource evaluation.

[0010] The present application also provides an electronic device comprising a memory and a processor, wherein the memory is configured to store a computer program, and the processor is configured to execute the computer program to enable the electronic device to perform the quasi-three-dimensional inversion method for short-offset transient electromagnetic method of electrical source as described above.

[0011] The present application also provides a computer readable storage medium storing a computer program, wherein the computer program is executed by a processor to implement the quasi-three-dimensional inversion method for short-offset transient electromagnetic method of electrical source as described above.

[0012] According to the embodiments of the present application, the following technical effects are achieved: The present application discloses a quasi-three-dimensional inversion method, system, device and medium for short-offset transient electromagnetic method of electrical source, which comprises the following steps: performing normalization processing on the multi-source data, and based on the preprocessed data, dividing and assigning values to the underground space by using a Gaussian difference method to construct an initial three-dimensional model; performing quasi-three-dimensional inversion based on the initial three-dimensional model by using a nonlinear conjugate gradient algorithm, and adaptively adjusting values of horizontal and vertical constraint factors during the inversion process to obtain inversion data; and extracting three-dimensional imaging information of the underground electrical structure according to the inversion data; and the three-dimensional imaging information is used for geological interpretation and resource evaluation. The present application can establish an initial three-dimensional model by using Gaussian interpolation, perform efficient inversion calculation by using a nonlinear conjugate gradient algorithm, and adaptively adjust horizontal and vertical constraint factors during the inversion process to realize high-precision quasi-three-dimensional imaging of the underground electrical structure. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0014] Figure 1 The present application also provides an electronic device comprising a memory and a processor, wherein the memory is configured to store a computer program, and the processor is configured to execute the computer program to enable the electronic device to perform the quasi-three-dimensional inversion method for short-offset transient electromagnetic method of electrical source as described above. Figure 2This is a schematic diagram of the initial 3D model constructed using Gaussian interpolation in this embodiment. Figure 3 This is a diagram showing the pseudo-3D inversion results in this embodiment. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The purpose of this invention is to provide a method, system, device and medium for short offset transient electromagnetic pseudo-three-dimensional inversion of electrical sources, aiming to solve or improve at least one of the above-mentioned technical problems.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figures 1-3 As shown, this invention provides a method for short-offset transient electromagnetic pseudo-three-dimensional inversion of electrical sources, comprising: Step 100: Acquire multi-source data and normalize the multi-source data to obtain preprocessed data; the multi-source data includes geological information and electrical parameters.

[0019] Step 200: Based on the preprocessed data, the underground space is divided and assigned values ​​using the Gaussian difference method to construct an initial three-dimensional model; the construction process of the initial three-dimensional model includes kernel function optimization and multi-source data fusion.

[0020] Step 300: Based on the initial 3D model, a pseudo-3D inversion is performed using a nonlinear conjugate gradient algorithm, and the values ​​of the horizontal and vertical constraint factors are adaptively adjusted during the inversion process to obtain inversion data; the pseudo-3D inversion process includes objective function enhancement and algorithm acceleration strategies.

[0021] Step 400: Extract three-dimensional imaging information of underground electrical structure based on the inversion data; the three-dimensional imaging information is used for geological interpretation and resource assessment.

[0022] As a specific implementation method, the following embodiment is provided.

[0023] In this embodiment, the interpretation accuracy of transient electromagnetic data and the three-dimensional imaging capability of underground structures are improved by constructing more refined models and using more efficient inversion algorithms.

[0024] 1. Establish initial 3D model by Gaussian interpolation method Traditional initial model construction mostly adopts simple uniform distribution or linear interpolation, which is difficult to accurately reflect the real situation of complex underground electrical structure. The present invention innovatively introduces Gaussian interpolation method, uses known geological information and electrical parameters to make more fine division and assignment of underground space, and constructs an initial 3D model closer to the actual situation. Gaussian interpolation method has the advantages of smooth transition, high precision, strong adaptability, etc., which can significantly improve the accuracy and rationality of the initial model, and lay a solid foundation for subsequent inversion calculation.

[0025] Kernel function optimization: ; wherein, represents the kernel function, which measures the correlation between two points in space, r i and r j , represents the bandwidth parameter of the kernel function, is an adaptive adjustment coefficient (0.3-0.7), which increases with the complexity of the stratum, is the distance between measuring points (typical value is 20-50m).

[0026] Multi-source data fusion: Integrate existing borehole resistivity ρdill, surface geological map to construct hybrid constraint matrix: Integrate existing borehole resistivity ρdill, ρ dill , surface geological map , to construct hybrid constraint matrix: ; wherein, represents the kernel function, represents the weight coefficient, which balances the contribution of borehole and surface geological data.

[0027] At this point, the correlation coefficient of the initial model can be improved from 0.35 of the traditional linear difference method to 0.82 of the present method, as shown in Figure 1 .

[0028] 2. Carry out quasi-three-dimensional inversion calculation by using nonlinear conjugate gradient algorithm The inversion calculation is the core link of transient electromagnetic data interpretation. In view of the characteristics of nonlinearity, multi-solution and large amount of calculation of transient electromagnetic data under short offset conditions, the nonlinear conjugate gradient algorithm is used for quasi-three-dimensional inversion calculation. The algorithm has the advantages of fast convergence speed, high calculation efficiency and strong global search ability, which can effectively reduce the calculation time and resource consumption while ensuring the accuracy of inversion. Through the iterative optimization of the nonlinear conjugate gradient algorithm, the real underground electrical structure is gradually approached, and the quasi-three-dimensional inversion target is realized.

[0029] Objective function enhancement: ; Wherein, W d is the data weight matrix, m is the model vector to be solved, d obs is the observation data vector, d pre is the predicted data vector, is the horizontal regularization parameter, is the horizontal gradient operator, is the vertical first derivative operator, is the vertical regularization parameter.

[0030] Algorithm acceleration strategy: GPU parallel Jacobian matrix calculation is adopted, and a preconditioner is introduced: And the iteration number is less than 50 times; wherein, J is the Jacobian matrix, is a small positive number, and I is the unit matrix.

[0031] 3. Adaptive adjustment of horizontal and vertical constraint factors in the inversion process In the inversion process, the selection of horizontal and vertical constraint factors has an important influence on the inversion result. The traditional fixed constraint factor method is difficult to adapt to the inversion requirements under different geological conditions. The present invention proposes a method of adaptively adjusting the horizontal and vertical constraint factors, which dynamically adjusts the value of the constraint factor according to the iteration results and the data fitting degree in the inversion process, to balance the accuracy and stability of the inversion result. Through adaptive adjustment of the constraint factor, the change of the underground complex electrical structure can be more flexibly dealt with, and the reliability and practicality of the inversion result are improved. As shown in Table 1.

[0032] Table 1 Dynamic adaptive constraint adjustment

[0033] 4. Uncertainty quantification The method of posterior covariance analysis is used to quantitatively evaluate the uncertainty of the inversion result: ; In the formula, The residual between the measured value and the model prediction is denoted as . Let W be the posterior covariance matrix, J be the Jacobian matrix, and W be the posterior covariance matrix. d For the data weight matrix, Here, L is the regularization parameter, and L is the prior constraint matrix.

[0034] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0035] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for short-offset transient electromagnetic pseudo-three-dimensional inversion of an electrical source, characterized in that, include: Acquire multi-source data and normalize the multi-source data to obtain preprocessed data; The multi-source data includes geological information and electrical parameters; Based on the preprocessed data, the underground space is divided and assigned values ​​using the Gaussian difference method to construct an initial three-dimensional model; The initial 3D model construction process includes kernel function optimization and multi-source data fusion; Based on the initial three-dimensional model, a pseudo-three-dimensional inversion is performed using a nonlinear conjugate gradient algorithm, and the values ​​of the horizontal and vertical constraint factors are adaptively adjusted during the inversion process to obtain inversion data. The pseudo-3D inversion process includes objective function enhancement and algorithm acceleration strategies; Three-dimensional imaging information of the underground electrical structure is extracted based on the inversion data; The three-dimensional imaging information is used for geological interpretation and resource assessment.

2. The method for short-offset transient electromagnetic pseudo-three-dimensional inversion of electrical sources according to claim 1, characterized in that, The kernel function optimization specifically involves: ； in, Represents a kernel function, which measures the difference between two points in space. r i and r j The correlation, This represents the bandwidth parameter of the kernel function. This represents the adaptive adjustment coefficient. Indicates the distance between measuring points.

3. The method for short-offset transient electromagnetic pseudo-three-dimensional inversion of electrical sources according to claim 1, characterized in that, The multi-source data fusion specifically refers to: Integrating existing borehole resistivity ρ dill Surface geological map Construct a hybrid constraint matrix: ； in, Represents the kernel function. This represents the weighting coefficient.

4. The method for short-offset transient electromagnetic pseudo-three-dimensional inversion of electrical sources according to claim 1, characterized in that, The enhancement of the objective function specifically includes: ； Among them, W d Let m be the data weight matrix, m be the model vector to be determined, and d be the weight matrix. obs For the observed data vector, d pre To predict data vectors, This is the horizontal regularization parameter. For the horizontal gradient operator, For the vertical first derivative operator, This is the regularization parameter in the vertical direction.

5. The method for short-offset transient electromagnetic pseudo-three-dimensional inversion of electrical sources according to claim 1, characterized in that, The algorithm acceleration strategy is specifically as follows: GPU-parallel Jacobian matrix computation is employed, and preconditioners are introduced: The iteration count is less than 50; where J is the Jacobian matrix. Let I be a small positive number, and let I be the identity matrix.

6. A short-offset transient electromagnetic pseudo-three-dimensional inversion system with an electrical source, characterized in that, include: The data acquisition and preprocessing unit is used to acquire multi-source data and normalize the multi-source data to obtain preprocessed data. The multi-source data includes geological information and electrical parameters; The initial 3D model construction unit is used to divide and assign values ​​to the underground space based on the preprocessed data using the Gaussian difference method, and construct the initial 3D model. The initial 3D model construction process includes kernel function optimization and multi-source data fusion; The pseudo-3D inversion unit is used to perform pseudo-3D inversion based on the initial 3D model using a nonlinear conjugate gradient algorithm, and adaptively adjust the values ​​of the horizontal and vertical constraint factors during the inversion process to obtain inversion data. The pseudo-3D inversion process includes objective function enhancement and algorithm acceleration strategies; An imaging unit is used to extract three-dimensional imaging information of underground electrical structures based on the inversion data; The three-dimensional imaging information is used for geological interpretation and resource assessment.

7. An electronic device, characterized in that, The device includes a memory and a processor, the memory being used to store a computer program, and the processor running the computer program to enable the electronic device to perform the short-offset transient electromagnetic pseudo-three-dimensional inversion method for electrical sources according to any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the short-offset transient electromagnetic pseudo-three-dimensional inversion method for electrical sources as described in any one of claims 1-5.

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