Patent ID: 6642715
Filing Date: 2003-11-04
Classification: G01N,G01R,G01V

Abstract:
A method of measuring permeability of an earth formation, the measurement utilizing a plurality of nuclear magnetic resonance (NMR) tools that are included within a drill string, the method comprising:inducing fluid to flow; applying a first static magnetic field from a first NMR tool to a first volume of the formation, the first static magnetic field polarizing a first substantial portion of the formation that is subject to the first static magnetic field; applying a first oscillating magnetic field to a specific part of the first polarized portion to induce the production of measurable signals, the first oscillating magnetic field being applied in accordance with specific field maps B0 and B1 to produce a first resonance region having a thin, long cylindrical shell-shape in the first volume, the first resonance region having a sensitivity to radial flow; applying a second static magnetic field from a second NMR tool to a second volume of the formation, the second static magnetic field polarizing a second substantial portion of the formation that is subject to the second static magnetic field; applying a second oscillating magnetic field to a specific part of the second polarized portion to induce the production of measurable signals, the second oscillating magnetic field being applied in accordance with specific field maps B0 and B1 to produce a second resonance region having a flattened torus shape in the second volume, the second resonance region having a sensitivity to vertical flow; measuring the induced signals; taking a local pressure gradient measurement; deriving a horizontal component of flow velocity from the measurable signals induced by the first NMR tool; deriving a vertical component of flow velocity from the measurable signals induced by the second NMR tool; and deriving a measurement of permeability from the horizontal component, the vertical component and the local pressure gradient measurement.