Spontaneous potential measurement apparatus connected between metallic housings of a wellbore apparatus for measuring the spontaneous potential of an earth formation
US5402069A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 18, 1993 |
| Grant date | Mar 28, 1995 |
| Priority date | — |
| Expiry date | Jun 18, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/265
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A spontaneous potential (SP) sub is interconnected between two metallic housings of a wellbore apparatus and is lowered into a wellbore. A spontaneous potential (SP) of an earth formation trasversed by the wellbore is measured by the SP sub, and a log is generated from the sub which is representative of the spontaneous potential of the formation, the log being substantially free of a special type of distortion which typified the prior art SP measurements taken by prior art SP measurement apparatus. The SP sub includes a measurement electrode, monitoring electrodes placed on both sides of the measurement electrode, a bucking electrode placed on both sides of the monitoring electrodes, current driving circuitry connected to the bucking electrodes, and receiving circuitry connected to the monitoring electrodes. The current driving circuitry delivers a current of sufficient magnitude to each bucking electrode such that the voltage potential between the monitoring electrodes is approximately equal to zero. The current from each bucking electrode is grounded via its own respective metallic housing and not via a surface oriented electrode. The receiving circuitry monitors the voltage betw…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.