Frequency Domain Controlled Source Two-dimensional Finite Element Forward Modeling

Because of the artificial source, fCSEM has overcome the weakness of natural source, which is the shortcoming of MT, so it has been widely used in the mineral, oil and gas exploration and so on. This paper has done some studies on the 2D forward problem of fCSEM, and uses the whole range apparent resistivity to rectify the date which are collected near the source.The finite element method was used for numerical simulation. Based on Matlab as programming tool, we adopted the finite element method of linear interpolation and second interpolation in a rectangular element for solving the fCSEM forward problem and derived the corresponding formulas for calculating. In order to simulate the infinity border and meet the demand of computer memory, the non-uniform gird is designed to ensuring the accuracy. In programming, we only stored the non-zero elements of the finite element matrix for saving the calculation memory. By numerical simulation of several typical models, we verified the correctness of the forward modeling algorithm.The iterative formula of the whole range apparent resistivity was develpped to solving the problem of distortion of Cagniard apparent resistivity when the date are collected near the source. Typical 1D layered model and simple 2D model are calculated. After rectify the date, it can accurately reflect the characteristics of the model which verified the fact that the exploration near the source is possible.