基于柯尔—柯尔模型的一维视复电阻率真参数反演

在求取多层极化介质模型的真柯尔—柯尔参数时,需要以多层极化介质为正演模型,以视复电阻率的振幅或相位为响应进行反演。若直接对振幅谱或相位谱反演计算,反演参数过多将导致反演失败。本文利用振幅与极距相关的曲线(本文称为"振幅测深曲线")可以确定多层极化介质层数和层厚的特点,将真参数的求取过程分为两步。第一步采用一维自动迭代法反演振幅测深曲线,求取层状介质的层数和层厚;第二步采用郭涛演化算法反演振幅谱或相位谱,求取层状介质的其他参数(零频电阻率、极化率、时间常数和频率相关系数)。整体反演结果较好,求取的真参数与理论值相同,证明两步法的可行性。并得出了两个结论:一是振幅测深曲线含有多层极化介质模型的分层信息;二是振幅谱比相位谱包含更多零频电阻率的信息。

One-dimensional Inversion of True Parameters of Complex Resistivity Based on Cole-Cole Model

The multilayer polarized medium needs to be used as forward model,taking the amplitude or phase of apparent resistivity as the response to conduct an inversion when it seeks for true cole-cole parameters of multilayer polarization medium.If the spectrum of amplitude and phase are calculated directly,overmuch inversion parameters will cause inversion failure.This paper can make sure the layer number of multilayer polarized medium and its characteristics of layer thickness by using the correlated curve of amplitude and distance(namely,sounding curve of amplitude).The acquiring process of true parameter can be divided into two steps:the first step is to use 1D automatic iterative method to invert sounding curve of amplitude for the purpose of seeking the number and thickness of layered medium;the second step is to use the Guo Tao evolutionary algorithm to invert amplitude spectrum or phase spectrum for the purpose of seeking other parameters of layered medium(zero frequency resistivity,polarizability,time constant and frequency correlation coefficient).The results of the whole inversion are good and the true parameters calculated are the same with the theoretical values,which proves the feasibility of two steps method.At last,two conclusions can be drawn:① the sounding curve of amplitude contains layered information of multilayer polarization medium;② the amplitude spectrum contains more information than phase spectrum,such as zero frequency resistivity.