套管非均匀性对过套管电阻率测井的影响分析

Impact of Casing Non-uniformity on TCFR Logging

套管腐蚀变形所引起的套管电阻率发生变化使单电极供电的过套管地层电阻率测量产生误差或错误。提出双电极双频过套管电阻率测量方法，依据套管井中电场满足霍夫曼定律得出地层电阻率计算公式，用以提高地层电阻率测量精度及测井速度。使用双电极的电阻率计算公式在目的层段有效地降低了地层模型电阻率与测量地层电阻率之间的差异，在电阻率计算公式中体现刻度过程，使原来采用单电极供电时需要2步实现测量的步骤变成了1步实现测量，在提高地层电阻率测量精度的同时也提高了测井速度，为套管井地层电阻率测井仪器实现提供了新选择。

Resistivity changes of casing caused by deformation and corrosion have produced larger errors in TCFR（Through Casing Formation Resistivity） logging. Proposed is a bi-electrod and bifrequency TCFR logging method. In cased holes, the electric field meets Hoffman＇s law. A formula for calculating formation resistivity is derived from Hoffman＇s law to improve the accuracy of measurement and logging speed. Simulation results show that the new formula reduces differ- ence between model resistivity and measured formation resisvity in 0~2 m interval, presents or reflects calibration process and realizes one-step measurement instead of the original two-step measurement with one electrode. The new method is a new concept for TCFR logging tool de sign.