Patent ID: 6121774
Filing Date: 2000-09-19
Classification: G01N,G01R,G01V

Abstract:
A method for eliminating ringing while measuring a nuclear magnetic resonance property of earth formations surrounding a borehole, comprising the steps of:a) applying a static magnetic field in a volume of the formation which polarizes the spin nuclei within the volume of formation;b) applying oscillating magnetic fields in the volume of formation according to a selected pulse sequence for a plurality of cycles so that a nuclear magnetic resonance signal is generated in the volume of formation;c) during a single pulse sequence cycle, step (b) further comprises the steps of:i) during a first time period, applying a first plurality of oscillating pulses in the volume of formation and measuring the generated signals in the formation, the measured signals comprise a ringing component and a plurality of spin-echoes;ii) canceling the spin-echoes;iii) during a second time period, applying a second plurality of oscillating pulses in the volume of formation and measuring the generated signals in the formation, the measured signals comprise the ringing component and substantially exclude the spin-echoes; and,iv) correcting the signals measured during the first time period to eliminate the ringing component.