Research On The Joint Inversion Of 3D DC Resistivity And Polarizability Based On The Equivalent Resistivity Method

Induced polarization method and direct current resistivity method play an important role in metal ore exploration.The traditional polarizability inversion depends on the result of resistivity inversion greatly,and the inversion effect is not ideal in the area with violent resistivity change.In order to obtain more accurate information of underground resistivity and polarizability,the indirect inversion using the equivalent resistivity method can obtain the polarizability information independent of the resistivity inversion results.At the same time,in practical work,we generally expect that the abnormal structure of the resistivity is the same as that of the resistivity.The joint inversion can simultaneously invert the two physical properties of the resistivity and the polarization through the constraint of the cross gradient,and find the approximate solution of their physical structure.In this paper,we first study the forward and independent inversion of 3D DC resistivity method.On this basis,the forward modeling and independent inversion of 3D polarizability are realized.The cross gradient function is introduced into the inversion objective function to realize the joint inversion of 3D DC resistivity and polarizability.At the same time,in the process of calculating the cross gradient term,this paper proposes a new method to deal with the boundary of the cross gradient term,which improves the programming efficiency.In the process of joint inversion of polarizability,a method of indirect joint inversion of polarizability is proposed.The joint inversion of polarizability is completed without relying on the objective function of polarizability inversion.Finally,the theoretical models of single anomaly body with the same structure and double anomaly body with different structures are designed,and the results of single inversion and cross gradient joint inversion are compared and discussed.It can be concluded that the inversion effect of joint inversion on the same structure of abnormal body is obviously better than that of single inversion,and the inversion effect on different structure of abnormal body is the same as that of single inversion.Thus,the reliability and validity of cross gradient joint inversion are verified.