# Development of a High-Temperature Co-Fe-Si-B Amorphous Wire Fluxgate Magnetometer for Downhole Attitude Measurement in MWD Systems at Temperatures up to 175 °C

## TL;DR

A new high-temperature magnetometer is developed for drilling systems to work accurately in extreme heat.

## Contribution

A miniaturized fluxgate magnetometer using Co-Fe-Si-B amorphous wire is developed for high-temperature drilling applications.

## Key findings

- The magnetometer operates effectively at 175 °C with noise below 200 pT/√Hz at 1 Hz.
- The sensor has a 300 Hz bandwidth and a compact size of 23 × 23 × 21 mm³.
- The probe survives temperatures exceeding 200 °C.

## Abstract

Measurement While Drilling (MWD) systems require high-precision triaxial magnetometers for real-time downhole attitude sensing, yet conventional fluxgates fail to meet the stringent size, noise, bandwidth, and temperature demands of deep reservoirs (>175 °C). To bridge this gap, we present a miniaturized triaxial fluxgate magnetometer (23 × 23 × 21 mm3) leveraging Co-Fe-Si-B amorphous wire cores—a material selected for its near-zero magnetostriction and tunable magnetic anisotropy. The sensor achieves breakthrough performance: a 300 Hz bandwidth combined with noise levels below 200 pT/√Hz at 1 Hz when operating at 175 °C while maintaining full functionality with the probe surviving temperatures exceeding 200 °C. This advancement paves the way for more accurate wellbore positioning and steering in high-temperature hydrocarbon and geothermal reservoirs.