Magnetic source transient electromagnetic method time domain vector finite element forward modeling method and device

Abstract

The invention discloses a magnetic source transient electromagnetic method time domain vector finite element forward modeling method and device. The method comprises the steps that a simulation geological model is established; applying an excitation source to the simulated geologic model after mesh generation, and obtaining a Maxwell equation set of the simulated geologic model to obtain an electric field control equation; discretizing a control equation by adopting a weighted margin method and selecting a first kind of Whitney primary function to establish a finite element equation; selecting a time difference format to carry out time discretization on the finite element equation; assembling an overall stiffness matrix, and calling a PADISO solver to solve a large linear sparse equation set; determining an iterative time step length according to the current turn-off characteristic of the excitation source, performing iteration at a variable time step length to obtain each component of an electric field, and obtaining an electric field value of each node through a primary function; and according to the Faraday's law of electromagnetic induction, a transient electromagnetic observation value and an apparent resistivity parameter are obtained. By applying the method, the calculation efficiency of the iteration process is greatly improved.

Description

technical field [0001] The invention relates to the technical field of geophysics, and more particularly to a method and device for forward modeling of magnetic source transient electromagnetic method time-domain vector finite element. Background technique [0002] The development of electromagnetics is reflected in various applied disciplines including the field of geophysics. Due to historical reasons, the focus of electromagnetic field theory is more on frequency domain electromagnetics, especially the theory of solving time-harmonic steady-state electromagnetic fields. It is quite mature now. With the birth and development of electronic computers, the numerical method of time-domain electromagnetic field analysis gradually occupies a dominant position and becomes a research hotspot in the field of geophysical electromagnetic methods. [0003] In the field of geophysics, electromagnetic method is an indispensable method, including transient electromagnetic method, also k...

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Problems solved by technology

However, the time-domain finite element three-dimensional simulation of the transient electromagnetic method still has obstacles, the most important of which is the problem of efficiency. The transient electromagnetic method needs to simulate the diffusion field of the fast turn-off current, which requires a small time step , so the traditional finite element method needs tens of thousands of iterations, and when the time step changes, it needs to solve large sparse equations of hundreds or tens of millions of orders, which greatly affects the three-dimensional Forward modeling efficiency is low

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