3-D Forward Of Spectrum Induced Polarization Method Based On Unstructured Mesh Finite Element

Spectral induced polarization method mainly conducts geological surveys based on differences in the conductivity and polarization of the medium.Because of its advantages of lightness,speed,and high efficiency,this method has been widely used in resource exploration,engineering geology and other fields.Combined with the characteristics of the finite element method derivation process is simple and can effectively simulate complex geological bodies,it is of practical significance to study the three-dimensional forward problem of the excitation polarization method in the frequency domain.This article combined with the development needs of the national prospecting strategy,carried out a three-dimensional forward modeling research work on the spectrum induced polarization method.The article first derives the expression of the complex conductivity equivalent tensor of spherical polarized particles based on the principle of generalized equivalent medium,and then converts the specific expression of the GEMTIP equivalent IP model,and expounds the specific meaning of the parameters of the IP;The practical significance of the parameters in petrology is discussed in detail by changing the frequency response curve and controlling the variation of the parameters of the electric shock.Then,starting from the basic equation of stable current field potential,the boundary value problem satisfied by the equation is solved,and the corresponding variational problem is obtained;based on the principle of finite element method,the unstructured tetrahedral mesh is used to discretize.the mesh generation method,linear interpolation,element analysis process and non-zero element storage method of large sparse matrix are introduced in detail.The 3D The spectrum of the IP forward program under unstructured mesh generation is realized.Based on previous studies,the analytical solution of the G-type layered medium with polarization effects was used to verify the effectiveness of the algorithm program used in this paper.Then the K-type and HK-type layered media with polarized layers are simulated,and the response characteristics of the sounding curve at different power supply frequencies are analyzed and compared.In order to simulate the complex geoelectric conditions that may be encountered in real situations,several classic geoelectric models are given,such as a three-phase low-resistance polarized sphere model,three-phase high-resistance polarized plate model,and polarized graben model,high-low dualpolarization block model,etc.Through the analysis of the response results of multiple models,the advantage of the spectrum IP method is explained: the real part of the complex resistivity cannot yet show the existence of the anomaly,while the imaginary part clearly shows the spatial burial range of the anomaly.The research results of the thesis provide a new idea for explaining more anomalies in actual production.