High-precision magnetotelluric forward modeling method

A magnetotelluric and forward modeling technology, applied in the field of geophysical exploration, can solve problems such as poor adaptability and great influence on the calculation accuracy of forward modeling, achieve high adaptability, improve the calculation accuracy of forward modeling, and promote the effect of popularization and application

Inactive Publication Date: 2019-07-05
CENT SOUTH UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The finite difference method is simple and easy to calculate in the process of forward modeling, but when the distribution of physical parameters is complex or the ge

Method used

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  • High-precision magnetotelluric forward modeling method
  • High-precision magnetotelluric forward modeling method
  • High-precision magnetotelluric forward modeling method

Examples

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Embodiment 1

[0085] A uniform half-space model with a conductivity value of 0.1S / m, such as image 3 (a) shown. In the forward modeling process, the length of the calculation area is set to 8km, the width is 4km, the number of horizontal subdivision units is Ny=40, and the number of vertical subdivision units is respectively taken as Nz=40, Nz=30, Nz=20 and Nz=10 , the schematic diagram of its grid division is shown in image 3 (b). Compare the numerical calculation results of the Chebyshev spectrum method with the analytical expression calculation results of the magnetic field response of the uniform half-space model, as shown in Figure 4 As shown, even when the number of subdivided grids is small, the numerical approximate solution and the analytical solution still agree well, which shows the correctness of the magnetotelluric forward calculation method based on the Chebyshev spectrum algorithm of the present invention.

Embodiment 2

[0087] Two-story G-type geoelectric model, its model parameter is ρ 1 = 10ohm-m, ρ 2 = 100ohm-m and h 1 =1000m, such as Figure 5 shown. In the forward calculation process of the Chebyshev spectrum method, the horizontal grid unit is set to Ny=40, while the vertical grid unit is set to Nz=100, Nz=50 and Nz=20 respectively. Figure 6 The apparent resistivity and the impedance phase curve obtained by the G-type geoelectric model under the transverse magnetic (TM) polarization mode calculated by the Chebyshev spectrum method are provided, which are in good agreement with the theoretical value curve, which further illustrates the forward calculation algorithm of the present invention accuracy. However, with the increase of the vertical unit subdivision spacing, the calculation accuracy of the Chebyshev spectrum method will decrease, which is mainly reflected in the increase of the apparent resistivity value and phase value error in the high frequency band. Through simulation ...

Embodiment 3

[0089] A two-dimensional geoelectric model such as Figure 7 As shown in (a), in the surrounding rock with a conductivity of 100ohm-m, there is a high-conductivity anomaly with a conductivity of 0.5ohm-m, and the anomaly is 250m away from the top. In the process of numerical simulation, the number of horizontal grid units and the number of vertical grid units are both taken as 50. Compare the numerical calculation results of the Chebyshev spectrum method with the numerical results of the finite difference, such as Figure 7 As shown in (b-c), the calculation results of the present invention are in good agreement with the reference solution provided by the US COMMEMI organization, and are better than the finite difference numerical solution.

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Abstract

The invention provides a high-precision magnetotelluric forward modeling method, which comprises the following steps of establishing a geophysical model, and dividing a geoelectric model by adopting Chebyshev points; establishing a Chebyshev derivation matrix; utilizing the Chebyshev derivation matrix to convert a partial differential equation of the magnetotelluric forward modeling calculation into an algebraic equation; carrying out the boundary condition processing; solving a large asymmetric dense complex coefficient linear equation set; carrying out the magnetotelluric response calculation. In order to improve the forward modeling calculation precision of the magnetotelluric response, the invention provides the magnetotelluric forward modeling method with high precision, high adaptability and high efficiency. According to the method, the magnetotelluric high-precision forward modeling can be performed, so that the magnetotelluric inversion calculation efficiency can be greatly improved, and the method has the important practical significance for promoting the popularization and application of the magnetotelluric method in the deep resource exploration field.

Description

technical field [0001] The invention relates to the field of geophysical exploration, in particular to a high-precision magnetotelluric forward modeling method for deep resource exploration. Background technique [0002] Magnetotelluric sounding is a kind of branch method of electrical method for detection by changing the frequency of electromagnetic field. It uses the skin effect of electromagnetic induction, that is, the penetration of high-frequency electromagnetic field is shallow, and the penetration of low-frequency electromagnetic field is deep. Under changing conditions, change the frequency of the electromagnetic field to achieve the purpose of sounding. In the field of exploration, forward modeling refers to deriving the distribution properties of the field from the properties of the source, while inversion refers to deriving the properties of the source from the distribution of the field. [0003] The magnetotelluric forward modeling problem is based on the harmo...

Claims

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Application Information

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IPC IPC(8): G06F17/50
CPCG06F30/20
Inventor 童孝忠谢维
Owner CENT SOUTH UNIV
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