# A standard calibration method based on a symmetric resistance network matrix for galvanic logging instruments

## TL;DR

This paper introduces a new calibration method for galvanic logging instruments using a symmetric resistance network to improve measurement accuracy in complex geological formations.

## Contribution

The novel contribution is the development of a symmetric resistance network model derived from a balanced bridge method for accurate galvanic logging calibration.

## Key findings

- A symmetric resistance network model was successfully derived using the balanced bridge method for complex formations.
- The calibration method improved measurement accuracy when tested on a nine-electrode logging tool in a simulated well.
- The method was validated in an actual oil well, showing effectiveness in evaluating invasion degree.

## Abstract

An increasing number of measurement electrodes have been designed to satisfy the demand for high-resolution detection using galvanic logging technology in complex formations. The forward modeling response analysis of logging tools has important guiding significance in the design of galvanic logging tools. Based on a three-dimensional finite element numerical simulation method, we established a forward model of galvanic multi-electrodes in a complex formation. We also designed a symmetrical resistance network model of the formation with equivalent resistance between two electrodes. A symmetrical resistance network was derived using the balanced bridge method. The asymmetrical admittance matrix was extended to a symmetrical extended admittance matrix to realize a convenient calculation of the equivalent symmetrical resistance network in complex formations. Verification of the microcolumn-focused logging tool, with nine electrodes in a simulated standard well, and an evaluation of the degree of invasion in an actual oil well indicate that this calibration method can improve the measurement accuracy of galvanic logging instruments.