用直流电极排列测量通过套管地层是电阻率方法的基础是电流及电位分布近似式。根据该近似式可导出地层电阻率与由位场测量值及其在套管内的二阶导数求得的横向电阻率的简单关系。本文导出了位场及其导数的数值解,考察了环带半径可变的有限长度套管情况下近似式的精度,以及存在环带半径突变 Using DC electrode arrangements to measure the resistivity through the casing formation is based on the approximation of current and potential distribution. From this approximation, a simple relationship between the resistivity of the formation and the transverse resistivity obtained from the measured value of the field and its second derivative within the casing can be derived. In this paper, the numerical solutions of the field and its derivative are deduced. The accuracy of the approximation in the case of a finite length casing with a variable annular zone radius is investigated, and the abrupt changes of the annular zone radius