Pulsed induction logging for determining conductivity and invaded zone properties
US4481472A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 19, 1981 |
| Grant date | Nov 6, 1984 |
| Priority date | — |
| Expiry date | Aug 19, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/28
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus and method for measuring properties of earth formations surrounding a borehole and, particularly, conductivity properties of the formations and certain properties of the invaded zone of the formations. In accordance with one embodiment of the invention, a logging device, movable through the borehole, has a transmitter coil and first and second spaced receiver coils mounted thereon. A short pulse of electrical energy is applied to the transmitter coil. Signals are induced in the first and second receiver coils. A conductivity property of the surrounding formations is then determined as a function of the times of occurrence of predetermined characteristics of the signals detected in the first and second receiver coils. In particular, the elapsed time between a zero-crossing of the signal induced in the first receiver coil and a zero-crossing of the signal induced in the second receiver coil is measured, and the conductivity of the surrounding formations is determined as being substantially proportional to said elapsed time. In another embodiment of the invention the polarities of the initial portions of the signals detected at a number of receiver locations are used in d…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.