Method and apparatus for measuring formation resistivity through casing using single-conductor electrical logging cable
US5543715A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 14, 1995 |
| Grant date | Aug 6, 1996 |
| Priority date | — |
| Expiry date | Sep 14, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/24
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method of determining resistivity of an earth formation penetrated by a wellbore having conductive casing. The preferred embodiment includes inserting a sonde into the wellbore, the sonde having a plurality of electrodes at axially spaced apart locations adapted to electrically contact the casing, applying electrical current between a first and a second one of the electrodes and measuring the current, measuring a first voltage between a first pair of electrodes axially disposed between the first and second electrodes and measuring a second voltage between a second pair of electrodes also axially disposed between the first and second electrodes and disposed externally to the first pair to determine casing resistance in between the pairs of electrodes. A second difference between the first and second voltages is also measured. Current is applied between other electrodes axially disposed to exclude a third pair of electrodes therebetween, and a third voltage is measured between the third pair to determine characteristic impedance. Current is applied between the first electrode and a surface return electrode, a fourth voltage is measured between the first pair of electrodes, a fifth …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.