Thermal decay time logging method and apparatus
US4926044A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 20, 1987 |
| Grant date | May 15, 1990 |
| Priority date | — |
| Expiry date | Oct 20, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V5/108
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A novel neutron burst timing, detection, and calculation method and apparatus are disclosed for a Thermal Decay Time Logging System. A neutron bursting regime is provided which includes a short burst, long burst repetitive sequence. After a short delay from the short burst, a first series of time gates is provided for accumulating gamma ray counts. After a relatively longer delay from the long burst, a second series of time gates is provided for accumulating gamma ray counts. The thermal neutron decay time constant .tau. and the macroscopic capture cross-section .SIGMA. of the formation are determined through an iterative procedure by which the formation .tau. is estimated from the second series of time gates which have been stripped of borehole decay counts determined from the first series of time gates. Similarly, the borehole .tau. is estimated from the first series of time gates which have been stripped of formation decay counts determined from the second series of time gates.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.