| 摘要 |
A downhole tool 100 for measuring angular positions in a borehole 11, the tool being rotatable and comprising two or more magnetometers 2, configured to measure the Earths magnetic field along respective magnetometer axes, arranged such that the normal components are at an angle to each other along a longitudinal direction, a device configured to measure the rotational speed of the tool, a processor unit 4 configured to combine the measurements to calculate angular positions of the downhole tool around the longitudinal direction relative to the direction of the Earths magnetic field. The tool may further comprise a gyroscope 3, computation of speed based on offset term and gyroscope scaling term, as well as re-calibration of said gyroscope. Tool may further comprise calculation of angular position by least squares fit and measurement of signal to noise ratio. |
