| 摘要 |
A logging device for measuring nuclear magnetic resonance characteristics of earth formations surrounding a borehole having means for producing a static magnetic field in formations surrounding the borehole, means for producing an audio frequency magnetic field in the formations, means for rotating the static magnetic field with respect to the audio frequency magnetic field, and means for detecting nuclear magnetic resonance signals from spins in the formation precessing around the earth's magnetic field. A method of measuring nuclear magnetic resonance characteristics of earth formations surrounding a borehole using such a device is also described. In its preferred form, the invention involves an NMR technique and apparatus in which spins in the formations are tipped by adiabatic fast passage, resulting in a relatively large depth of investigation, but does not require treating of the borehole fluid.
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