Study On The Forward And Inverse Of Electromagnetic Transient Electromagnetic Source With IP Effect Based On Genetic Algorithm

With the gradual development of shallow surface minerals and the strategic development of deep prospecting in the country,the traditional exploration method can not meet the conditions of the depth of exploration.The transient electromagnetic method with large power source as the source of excitation has been paid more and more attention because of its high exploration depth,strong anti-interference and good resolution.In the field observation of transient electromagnetic data,it is found that there is a sign reversal phenomenon in the late signal.A large number of studies have proved that when the underground polarizability is affected by the dispersion characteristics of the geological body,the observation data may appear the phenomenon of the sign reversal.Therefore,in order to study the response characteristics of the electric source in the detection of the polarization of the polarized formation,It is necessary to study the influence law of the excitation effect in the electric source,and if the excitation signal can be extracted,it is of great significance to expand the application range of transient electromagnetic and to find the deep mine.In this paper,based on the frequency domain response of the horizontal electric dipole,the Cole-Cole model complex resistivity is introduced and the frequency time conversion is realized by the numerical calculation method,and the transient electromagnetic forward simulation of the electrical source with the excitation effect is realized.The response of different excitation parameters in the uniform half space is analyzed and discussed.It is found that the polarizability has the greatest influence on the transient electromagnetic effect,the time constant and the frequency correlation coefficient are second,and the influence of the resistivity and the transmission distance is studied.The magnitude of the resistivity affects the amplitude of each component and the occurrence of the excitation effect.The smaller the gap is,the stronger the excitation effect is.The three layer model of the polarization layer of the intermediate layer is forward.The results show that the response of the transient electromagnetic induced by different models is different,and the polarization effect is more obvious when the polarization layer is low resistance.The influence of the excited electric parameters on the is the smallest.When the middle layer is relatively low and the surrounding rock is low resistance,there will be an inverse sign in the.The sign of the horizontal electric field is reversed when the middle layer is relatively low,and the induced polarization effect is obvious.Most of the geophysical problems are nonlinear.In this paper,the idea of genetic algorithm is applied to the inversion of transient electromagnetic effect.The objective function and fitness function are set up,and the model response is fitted with full parameter inversion.Because the inversion search space is too large,the retrieval range is restrained in order to restrain the multi solution and restrain the search range.The theoretical model D,G,H,K,A,Q are established by using the full parameter inversion of genetic algorithm.The inversion curve is fit well with the theoretical curve,and the error is small,which verifies the feasibility of this algorithm.The inversion results show that when the polarizable body exists in the underground,the response curve can be fitted by the inversion method,and the IP information of the underground medium can be obtained.