High frequency induction log for determining resistivity and dielectric constant of the earth
US4278941A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 30, 1978 |
| Grant date | Jul 14, 1981 |
| Priority date | — |
| Expiry date | Oct 30, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/28
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for logging rock formations penetrated by a borehole to determine both the resistivity and dielectric constant of the formations. The apparatus comprises an induction logging tool having at least a transmitting coil and two receiver coils and operating in the radio frequency range from 20 to 60 megahertz. The method utilizes both the in-phase and out-of-phase, with respect to the transmitter current, voltage components which are measured at each receiver. The in-phase and out-of-phase voltage components are used to compute the phase shift between the voltage signals and the relative attenuation of the voltage amplitudes between the receivers. The phase shifts and relative attenuations are relatively insensitive to the borehole (e.g., borehole radius and drilling mud resistivity) and can be used as inputs into theoretically constructed nomograms to determine both the resistivity and dielectric constant of the formation. If the invasion of the drilling mud into the formation is not negligible then a tool with four spatially separated receiver coils is employed and the phase shifts and relative attenuations between the three adjacent pairs of receiver coils are …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.