Numerical simulation method of controllable source in 3D frequency domain

Abstract

The invention provides a three-dimensional frequency domain controllable source numerical simulation method. The method comprises the steps of S100: defining a calculation region in a resistivity anomaly body and an adjacent wrapping layer, and dividing the calculation region into multiple regular unit bodies; S200: calculating an initial electric field under an artificial source excitation condition, and by adopting a weighted residual method, establishing a finite element equation set of edge midpoints of the unit bodies in the calculation region; S300: defining an observation point as a boundary node by using a Green function, and enabling a secondary electric field of an internal node to express a secondary electric field of the boundary node; S400: substituting a Green function expression into a mixed equation set to obtain a first equation set only about the secondary electric field of the internal node; and S500: solving the first equation set to obtain secondary electric fieldvalues of nodes comprised in the unit bodies. According to the method, a vector finite element method and a volume integral equation method are applied; the calculation region is reduced; the calculation amount is reduced; the calculation precision is improved; formed equations are sparse in coefficient matrix and good in condition number; and a calculation result is accurate.

Description

technical field [0001] The invention relates to the technical field of controllable source electromagnetic method forward modeling, in particular to a three-dimensional frequency domain controllable source numerical simulation method. Background technique [0002] The controllable source electromagnetic method has the characteristics of strong anti-interference ability and high efficiency compared with natural sources through the electromagnetic field generated by artificial source excitation. The working area of ​​controlled source electromagnetic method has been developed to land, ocean, aviation and underground. Controlled source electromagnetic method has been widely used in various periods of engineering survey, geothermal resource development, metal mining, oil exploration and other fields. [0003] The controllable source electromagnetic method can simulate the observation data corresponding to different geological conditions, analyze the morphological characteristic...

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Problems solved by technology

[0008] (1) The vector finite element method uses infinite boundary conditions, so that its calculation area is not only large, but also because it contains air layers, the condition number of the linear equations formed is poor. When using iterative method to solve, the efficiency is often low, and it becomes lower with frequency The number of iterations needs to increase continuously, which reduces the computational efficiency;

[0009] (2) When using the vector finite element method, the electric field value of the measuring point often needs to be obtained by interpolation of the grid nodes around the measuring point, which affects the accuracy

[0011] (1) When using the integral equation method, when the current source and the electromagnetic field measuring point are at the same position, there will be singularity, and it is difficult to obtain high-precision calculation results;

[0012] (2) The coefficient matrix formed by the integral equation method is full rank and dense. After the large-scale area is divided, the large dense matrix formed is difficult to solve and the efficiency is low;

[0013] (3) The pulse basis function used in the integral equation method, the precondition is that the electric field in the subdivided unit is uniform, which is not applicable to the high conductivity contrast difference model

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