Apparatus and method for resistivity well logging
US6777940B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Nov 8, 2002 |
| Grant date | Aug 17, 2004 |
| Priority date | — |
| Expiry date | Nov 8, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/30
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Well logging apparatus and methods for determining formation resistivity at multiple (>3) depths of investigation. At least one transmitter antenna and at least two receiver antennas are mounted in a logging tool housing, on substantially a common axis. The antennas are untuned coils of wire. Electromagnetic energy is emitted at multiple frequencies from the transmitter into the formation. The receiver antennas, which are spaced apart from each other and from the transmitter, detect reflected electromagnetic energy. Formation resistivity at multiple depths of investigation is determined using only phase differences in the reflected energy at the different frequencies, minimizing false indications of invasion due to mismatch of vertical response with attenuation measurements and also permitting correcting for the effects of varying dielectric constant of the formation. The apparatus minimizes the number of antennas, electronics complexity, required power, and measurement time required to determine resistivity at multiple depths of investigation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.