Study And Application Of Full-parameter Inversion Method In Time-frequency Electromagnetic Method

TFEM is an electromagnetic exploration method that integrates time domain and frequency domain.It has been widely used in oil and gas,shale gas and other exploration.The collected data can be processed to obtain IP information and electrical information.In order to study the induced polarization effect of TFEM this paper first introduced the Cole-Cole model in the frequency domain,and analyzed the effects of polarizability,frequency correlation coefficient,and time constant on the components of complex resistivity,and then introduced the numerical expression of the Cole-Cole model in the time domain also discusses the effect of each of the parameters on the time-varying resistivity.Secondly,the time domain and frequency domain electromagnetic response formulas of the horizontal electric dipole are deduced.Then the electromagnetic response in the time domain and frequency domain of the finite length source is calculated based on the Gaussian integration method,and the electromagnetic response calculated by the direct integration method is compared.The method can obtain higher-accuracy calculation results through a finite number of iterations.Finally,the Cole-Cole model in the frequency domain and the Cole-Cole model in the time domain are introduced into the one-dimensional forward calculation of the finite-length wire source.The levels of each parameter in the homogeneous half-space and layered media are discussed separately.The influence of the electric field E_x.According to the simulation results,the polarizability has the greatest impact on the horizontal electric field E_x,followed by the frequency correlation coefficient,and finally the time constant;the ability of different geo-electric models to reflect the induced polarization effect is also not the same,the H-type capability is the strongest,the K-type ground The electric model is the weakest,and the Q-type and A-type are located between the two electric models.In this paper,an adaptive differential evolution algorithm is used to perform full-parameter inversion of E_x data of horizontal electric field in time-frequency electromagnetic method.Firstly,the theoretical model inversion of A-type,Q-type,H-type,and K-type three-layer models is performed.The time domain and frequency domain inversion results are compared.It is found that the accuracy of this algorithm in the frequency domain is higher than that in the time domain.In order to further investigate the adaptability of this algorithm,HKH type and KHA type geo-electric models are designed.According to the inversion results of frequency domain,the distribution of subsurface media can be well reflected.At the end of this paper,a more complex model is designed based on the actual drilling results to perform forward modeling.The random noise data is inverted.The inversion results can indicate the deep low impedance high polarization anomaly.Based on the above inversion results,it is shown that this method has certain feasibility and provides reference for time-frequency electromagnetic method full parameter inversion.