Radioactive well logging system with shale (boron) compensation by gamma ray build-up
US3988581A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 14, 1975 |
| Grant date | Oct 26, 1976 |
| Priority date | — |
| Expiry date | Apr 14, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V5/102
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Earth formations in the vicinity of a well borehole are repetitively bombarded with bursts of high energy neutrons. A radiation detector in a sonde in the borehole senses the gamma rays induced by the capture of thermal neutrons and sends signals representative thereof to the surface. At the surface, two single channel energy analyzers, such as from 1.30 to 2.92 Mev and from 3.43 to 10.0 Mev, sense the formation thermal neutron capture gamma ray response after each neutron burst. The counts of thermal neutron capture gamma rays in these analyzers are used to distinguish between the presence of salt water and hydrocarbons, which is logged. By controlling the repetition rate of the neutron source, measured counting rates in formations with relatively large thermal neutron lifetimes are emphasized, compensating for borehole effects which could otherwise give rise to erroneous results in shale formations, which have a high boron content.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.