Detecting system and method for oil or gas well
US5323856A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 31, 1993 |
| Grant date | Jun 28, 1994 |
| Priority date | — |
| Expiry date | Mar 31, 2013 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B47/092
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A system for sensing the passage of a member past a predetermined location along a tubing disposed in an oil or gas well comprises: a magnet connected to the member, the magnet having a soft body so that the magnet can be drilled out by a drill bit lowered into the well after the member has passed the predetermined location; and a sensor, connected to the outside of the tubing at the predetermined location, for detecting a magnetic field of the magnet as the member with the magnet connected thereto passes the sensor. A method for assisting the proper placement of a cement slurry in an oil or gas well comprises: pumping a cement slurry through a tubing into an oil or gas well; releasing a cementing plug into the tubing in series with the cement slurry, the cementing plug having a magnet as referred to above; and sensing the cementing plug at a predetermined location along the tubing, including: generating a null signal in response to providing a biasing magnetic field in opposition to a magnetic field naturally occurring in the tubing at the predetermined location; and changing the null signal to an indicator signal in response to the magnet moving in the tubing to the predetermined…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.