Two-dimensional Focusing Inversion Of Time Domain Induced Polarization Method

Based on the induced polarization two dimensional data space inversion,this paper realizes induced polarization two dimensional focusing inversion.The key to the inversion is to obtain the stable result, which can reduce the real situation of the underground, and highlight the boundary of the geological body.For solving the problem that inversion results of underground electrical parameters interface characterization is not clear, have done a lot of basic research work on time domain induced polarization two dimensional data space inversion.In this paper, a new objective function is formed by introducing a model focusing constraint function into the inversion of the time domain IP data.By using the least square method to solve the optimization problem, a time domain induced polarization 2D focusing inversion is realized.In this paper, using the finite element method, based on the existing direct current method, the application of the equivalent resistivity method, the program will be adapted to get the IP forward program. The direct current method is verified by the vertical contact zone model, which is verified by the comparison with the analytical solution. IP forward verification, by setting the model respectively using this method and mature time domain ipmethod 3D finite difference forward forward, and compare the polarizability data to complete the verification.The inversion procedure based on data space Occam inversion, changing theobjective function with focusing image technique to derive the formula, using the least squares method to solve the optimal solution of the objective function. Focuses on the objective function derivation, the matrix processing was optimized by a certain way, simplified formula derivation. The inversion process is as follows, first inversion of synthetic resistivity data obtained resistivity model, the resistivity model in again into the polarizability inversion polarization rate model.At last the synthetic data were calculated by using different theoretical models.Compared with traditional smoothing constrained inversion method results,it is proved that this algorithm is in stable inversion results at the same time, inversion results in abnormal body are more focused, more prominent geologic body’s boundary,so as to prove the correctness and validity of the focusing inversion.