Patent ID: 6528995
Filing Date: 2003-03-04
Classification: G01N,G01R,G01V

Abstract:
A method of determining flow velocity of a fluid in an earth formation utilizing at least one nuclear magnetic resonance (NMR) tool that is placed in a wellbore in the formation and which produces a static magnetic field and measures induced magnetic signals, the method comprising:inducing the fluid to flow; applying the static magnetic field from the NMR tool to a volume of the formation, the static magnetic field polarizing a substantial portion of the formation that is subject to the static magnetic field; applying an oscillating magnetic field to a specific part of the polarized portion to induce the production of measurable signals, the oscillating magnetic field being applied in accordance with field maps B0 and B1 so that a resonance region having a specific shape corresponding to a desired sensitivity is formed in the formation; measuring the induced signals; determining a decay loss factor from the measured induced signals; and deriving the flow velocity based on the determined decay loss factor.