Research On Cole-Cole Model Of 2.5D Time-lapse Complex Resistivity Inversion

The complex resistivity method(CR)exploration is a widely used geophysical exploration method based on the difference of electrochemical properties of different rocks and ores excited in the frequency domain as the main physical property.With the continuous development of the complex resistivity conventional exploration and the complex resistivity dynamic monitoring technology,it is of great significance to carry out the inversion study of the complex resistivity multi-parameter inversion and the complex resistivity monitoring data.In this thesis,under the premise of neglecting electromagnetic coupling effect,the Cole-Cole equivalent complex resistivity model is introduced,the 2.5-dimensional finite element normalization calculation of complex resistivity method is carried out,and on the basis of the normalization,the corresponding Gauss-Newton optimization algorithm is used to carry out the multiparameter regularized inversion of complex resistivity amplitude and phase,and the time-shift inversion algorithm based on space-time domain regularization is combined to construct the time-shift inversion algorithm between the apparent complex resistivity and Cole-Cole model inversion parameters.Cole model inversion parameters to form a theoretical system of time-shift inversion method for processing complex resistivity monitoring data.For the 2.5-dimensional forward calculation of the complex resistivity method,the Poisson equation of the complex potential based on the Cole-Cole complex resistivity model is solved by the finite element method,and the 3-dimensional complex potential forward calculation of the complex resistivity method generated by the point source under the 2-dimensional configuration is completed.Three typical polarization anomaly models are set up,and the dipole-dipole profile observation system is used for the calculation of the apparent complex resistivity spectra at different supply frequencies.The results show that both the apparent amplitude spectrum and the apparent phase spectrum reflect the polarized anomalies significantly,and the anomalous features of the profiles can correspond to the actual anomalous patterns,which indicates that the apparent complex resistivity profiles can reflect the assignment information of the subsurface anomalies to a certain extent.For the study of the complex resistivity 2.5-dimensional inversion algorithm,the inversion calculation of the complex resistivity model parameters is carried out according to the Tikhonov regularized inversion theory and the Gauss-Newton optimization algorithm.The stability and reliability of the complex resistivity inversion algorithm is verified by selecting reasonable regularization factors and adding different levels of Gaussian random noise to the forward data for multiple inversion calculations,and the inversion iterative process still converges stably.The results show that the amplitude and phase parameters have good inversion effects on the polarized anomalies of different shapes and locations below the measurement line.For the inversion study of complex resistivity 2.5-dimensional monitoring data,various theories of time-shifted inversion algorithms are derived.Among them,the active time-constrained algorithm pre-evaluates the degree of variation of model parameters in different regions of the subsurface during the monitoring cycle before inversion and imposes different time-constrained factors,so that the inversion process does not affect the actual change imaging of dynamic anomaly targets,and also can effectively eliminate the spurious anomalies of background region changes.In order to verify the reliability and inversion accuracy of the time-shift inversion algorithm,two typical dynamic anomalies models are set up to carry out time-shift inversion calculations of the complex resistivity monitoring,and the magnitude and phase parameters of the inverse complex resistivity model of the subsurface medium can reflect the location and change range of the anomalies.The inversion effect of the active time constraint algorithm on the complex resistivity monitoring data is better than that of the independent inversion algorithm and the time-shift constraint algorithm,and the inversion accuracy and resolution of the dynamic changes of the anomalies are also higher.