Sensor for detecting the magnetic field in the area of downhole casing
US6597178B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 18, 2002 |
| Grant date | Jul 22, 2003 |
| Priority date | — |
| Expiry date | Oct 18, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/28
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A magnetic receiver with a magnetically permeable core is positioned inside a wellbore casing and operated in a feedback mode to reduce attenuation of a measurable magnetic field. The receiver employs a feedback device to reduce mutual coupling between the core and the casing, which reduces the otherwise normal attenuation of em signals inside the casing. The feedback device may be provided in the form of an extra or feedback winding that effectively cancels the inducing field inside the core and reduces the attenuation otherwise caused by the core-casing interaction. Alternatively, the magnetic receiver may employ, as the feedback device, a current feedback amplifier circuit to cancel the inducing field inside the core. Specifically, the circuit is operated to produce a secondary magnetic field that essentially cancels the inducing field inside the core.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.