Method for detecting drilling fluid in the annulus of a cased wellbore
US4780266A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 22, 1986 |
| Grant date | Oct 25, 1988 |
| Priority date | — |
| Expiry date | Dec 22, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2223/635
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method for logging a cased well to determine the quantity and location of any barite weighted drilling fluid in the annulus between the casing and the wall of the wellbore. A tool assembly having a neutron generator and a gamma scintillation detector is used to log the zone of interest. The neutrons introduced into the well by the neutron generator convert a portion of the barium-138 in the drilling fluid to barium-137m. The magnitude of the gamma photon peak charactristic of the decayof barium-137 is used to identify the quantity of drilling fluid present in the annulus as a function of depth. This method is especially useful identifying the existence of channels in a cemented wellbore annulus.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.