Method for obtaining NMR bound fluid volume using partial polarization
US6232778A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 11, 1998 |
| Grant date | May 15, 2001 |
| Priority date | — |
| Expiry date | Jun 11, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N24/081
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The present invention provides methods for determining the bound fluid volume (BFV) of a formation utilizing nuclear magnetic resonance (NMR) techniques in which less than full polarization occurs and in which less than a complete NMR distribution is acquired. The effect of the polarizing static magnetic field is shortened in time by applying a shortened wait time between NMR measurements so that only the bound fluid of the formation is polarized. The shortened wait time is effectuated by early application of the oscillating magnetic field to the formation which, in conjunction with a limited number of refocusing pulses, induces signals in the formation that are measured by the NMR tool. The peak amplitude of these signals corresponds to the BFV. The present invention provides information so that a partial polarization calculation curve in T.sub.2 lies almost equally between an empirical tapered cutoff curve and a theoretical tapered cutoff curve. Moreover, because no T.sub.2 information must be acquired, the method is especially suited for logging-while-drilling operations, where the drill string moves uncontrollably during the NMR measurement.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.