Borehole measurement of NMR characteristics of earth formations, and interpretations thereof
US4933638A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 19, 1989 |
| Grant date | Jun 12, 1990 |
| Priority date | — |
| Expiry date | Jun 19, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/32
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Borehole NMR logging apparatus and methods, and methods for the interpretation thereof. A logging tool is provided which produces a strong, static and homogeneous magnetic field B.sub.0 in a Volume of an adjacent formation on one side of the tool to measure nuclear magnetic resonance characteristics thereof. In the preferred embodiment, the tool has an RF antenna mounted on the outside of the metal body of the tool, directing focussed oscillating magnetic fields B.sub.1 at said Volume to polarize or tip the magnetic moments of hydrogen nuclei of fluids within rock pores. The same antenna can be used to receive signals of proton precession in the Volume of interest immediately after transmission of the RF polarizing field B.sub.1. Extremely rapid damping of the antenna between the transmitting and receiving modes of operation is accomplished by a Q-switch disclosed herein. The invention provides for the direct measurement of NMR decay having transverse relaxation time T.sub.2 behavior, and further provides for the fast repetition of pulsed measurements from within a borehole. An additional magnet array may be mounted offset from the first magnet configuration to prepolarize a format…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.