Apparatus and method for electromagnetically detecting the passing of a plug released into a well by a bridge circuit
US5252918A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 20, 1991 |
| Grant date | Oct 12, 1993 |
| Priority date | — |
| Expiry date | Dec 20, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V15/00
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A plug released into an oil or gas well carries one or more metallic strips that affect the inductance of a resistive-inductive bridge circuit mounted adjacent a conduit through which the plug and fluids are pumped into the well. This unbalances the bridge circuit to produce a signal preferably uniquely identified with the plug so that an indicator can be activated to confirm proper release of the plug into the well. When an amorphous metal is used in the metallic strips, the unbalancing of the bridge produces a signal having an identifiable harmonic of a fundamental frequency of an oscillator signal driving the bridge circuit, which harmonic is not present in other signals resulting from the bridge circuit being unbalanced by other materials flowing in the conduit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.