Patent ID: 6366086
Filing Date: 2002-04-02
Classification: G01N,G01V

Abstract:
Apparatus for determining a nuclear magnetic resonance characteristic of earth formations surrounding a borehole, comprising:a logging device movable through the borehole, said logging device having a longitudinal axis; magnetic field generating means, in said logging device, for generating a magnetic field in the formations; magnetic field detecting means, in said logging device, for detecting magnetic resonance signals from the formations, said magnetic field detecting means being separate from said magnetic field generating means; means for applying a polarizing signal to said magnetic field generating means; said magnetic field detecting means being operative, after said polarizing signal, to detect magnetic resonance of spins in the formations that are precessing around earth's magnetic field; and further magnetic field generating means in said logging device, said further magnetic field generating means being operative to produce a further magnetic field in the borehole that reduces the contribution of spins in the borehole to the magnetic resonance detected by said magnetic field detecting means.