Patent ID: 6522136
Filing Date: 2003-02-18
Classification: G01N,G01R,G01V

Abstract:
A method for determining a characteristic of formations surrounding an earth borehole, comprising the steps of:(a) providing a logging device that is moveable through the borehole; (b) producing, from said logging device, a static magnetic field in the formations; (c) transmitting, into said formations, from said logging device, a first magnetic pulse sequence and receiving, during said first pulse sequence, magnetic resonance spin echo signals; said first pulse sequence having a portion of a pulse acquisition sequence during which spin echoes are subject to decay due to local magnetic field internal gradients in the formations, and having another portion of the pulse acquisition sequence during which spin echoes are not substantially subject to decay due to said local magnetic field internal gradients in the formations; (d) transmitting, into said formations, from said logging device, a second magnetic pulse sequence and receiving, during said second pulse sequence, magnetic resonance spin echo signals; said second pulse sequence having a portion of a pulse acquisition sequence during which spin echoes are subject to decay due to said local magnetic field internal gradients in the formations, and having another portion of the pulse acquisition sequence during which spin echoes are not substantially subject to decay due to said local magnetic field internal gradients in the formations; one of the portions of the pulse acquisition sequence of said second magnetic pulse sequence having at least one different pulse parameter than the corresponding one of the portions of the pulse acquisition sequence of said first magnetic pulse sequence; and (e) determining said characteristic of the formations from the spin echo signals of said first pulse sequence and the spin echo signals of said second pulse sequence.