Method and apparatus for controlling the effect of contact impedance on a galvanic tool in a logging-while-drilling application
US6373254B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | May 25, 1999 |
| Grant date | Apr 16, 2002 |
| Priority date | — |
| Expiry date | May 25, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/20
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The present invention describes a method and apparatus to control the effect of contact impedance on a formation resistivity measurement during a logging-while-drilling operation. The control of contact impedance is accomplished by maintaining a substantially zero difference in potential between two monitor electrodes positioned on the resistivity logging tool near a current electrode. The tool can employ a ring electrode configuration and/or a button electrode, configuration. The ring electrode configuration incorporates two pairs of ring monitor electrodes on each side of a ring current electrode. The button electrode configuration incorporates. a monitor electrode, surrounded by a current electrode, surrounded by a second monitor electrode. Insulation gaps are positioned between each electrode to separate the electrodes. A variable current is supplied to the current electrode in each configuration to maintain the same potential at each monitor electrode. The effect of contact impedance is controlled through maintaining the same potential at each monitor electrode.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.