Research On Transient Electromagnetic Multifrequency Fusion Detection Method

The transient electromagnetic method(TEM)is a geophysical method for detecting underground bodies by emitting a step pulse electromagnetic field and analyzing the secondary induction electromagnetic field.In practical engineering,we often used to collect the data of the detection site with two or more frequencies for complex geological bodies.Because of the different frequency,the vertical resolution is different,and different frequency resistivity results tend to appear contradictory resistivity response in the interpretation of multiple single frequency results,for the same depth.This makes the uncertainty of the detection results,causes the wrong explanation,and affects the safety construction of the project.In order to solve the contradictory problem of resistance response,eliminate interference factors and reduce the phenomenon of interpretation errors caused by different transient electromagnetic frequencies,a processing method of transient electromagnetic multi-frequency data fusion is proposed in this paper.This method can make full use of the advantages of different frequency resolution,more intuitively and accurately judge the geological body condition,and provide a theoretical basis for the optimization of the acquisition mode and the development of the subsequent related instruments.Therefore,it is very necessary to study the transient electromagnetic frequency fusion method.At present,there is little research on transient electromagnetic multi-frequency data fusion imaging.(1)In this paper,based on the equivalent conductive plane inversion method,we use regression and interpolation fusion methods to study the imaging characteristics of frequency fusion data through numerical simulation.The effects of different time channel distribution and smooth processing methods on the imaging effect are analyzed,and we selected a transient electromagnetic frequency fusion step.(2)By establishing a complex model in a homogeneous medium site,we test and verify the frequency fusion method,and the experimental data are collected by using two kinds of emission frequencies.The resistance image obtained by frequency fusion is the closest to the parameters of the model.It can not only accurately locate the buried position of the low resistance body,but also correctly reflect the distribution characteristics of the formation,which further verifies the effectiveness and feasibility of the transient electromagnetic frequency fusion method.(3)We apply the method to an engineering example to further verify the effectiveness and feasibility of the transient electromagnetic frequency fusion method A transient electromagnetic frequency fusion method is established.Therefore,the transient electromagnetic multi-frequency fusion detection method can effectively reflect the unique vertical resolution advantages of different frequencies,solve the problem of different frequency resistivity imaging,reduce the multi-solution,and improve the resolution of the target at different depths.