Nuclear magnetic resonance pulse sequences for determining bound fluid volume
US5389877A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 27, 1991 |
| Grant date | Feb 14, 1995 |
| Priority date | — |
| Expiry date | Nov 27, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/32
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An NMR pulse sequence for use in a borehole logging tool includes a series of CPMG pulses according to: EQU T.sub.r -90.degree..sub..+-.x -(t.sub.cp -180.degree..sub.y -t.sub.cp -echo.sub.j) where j is the index of CPMG echoes gathered, T.sub.r is wait time, t.sub.cp is the Carr-Purcell spacing. This pulse sequence is used to determine Bound Fluid Volume (BFV) which is subtracted from total porosity to yield Unbound Fluid Volume (UFV) of a formation surrounding the borehole. Measuring the BVF, the amount of rapidly relaxing fluid (less than 50 ms), is more efficient than measuring UFV (up to 2 secs), and is insensitive to motion of the logging tool.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.