Neutron well logging
US4492864A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 31, 1981 |
| Grant date | Jan 8, 1985 |
| Priority date | — |
| Expiry date | Jul 31, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V5/102
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
This invention relates to an improved method for determining the oil saturation of subsurface earth formations in the vicinity of a well borehole. High energy neutrons irradiate the subsurface earth formations and gamma rays caused by inelastic scatter with the subsurface earth formation constituent materials are measured. For a chosen borehole depth, gamma ray logs are taken in different situations: first, with the formation fluid water and oil mixture in an undisturbed state; second, after flushing the formation with alcohol to displace the formation water and oil mixture; and, finally, after flushing the alcohol from the formation with water to obtain a measurement with no oil in the formation. The gamma ray measurements obtained are then used to determine the oil saturation without requiring knowledge of the porosity of the earth formation, borehole conditions or formation type. When the original oil content of the formation is at a naturally flushed, or residual, oil saturation, the present invention may be used to determine the residual oil saturation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.