Patent ID: 6646438
Filing Date: 2003-11-11
Classification: G01R,G01V

Abstract:
A method for determining a parameter of interest of a volume of earth formation surrounding a borehole with a Nuclear Magnetic Resonance (NMR) logging tool conveyed in the borehole, the method comprising:(a) using a magnet assembly on the NMR logging tool to produce a static magnetic field in said volume of the formation; (b) producing a radio frequency (RF) magnetic field in said volume of the formation with an antenna on the logging tool, said RE magnetic field having a component in a direction orthogonal to a direction of the static field, the RF field including at least one pulse sequence comprising a tipping pulse and at least four refocusing pulses, each refocusing pulse producing at least one corresponding spin echo signal; and (c) measuring with the logging tool spin echo signals induced by the RE field in the formation; wherein at least three successive later ones of said at least four refocusing pulses of a single one of said at least one pulse sequence have a time intervals greater than time intervals between earlier successive refocusing pulses, and wherein at least one of said at least four refocusing pulses produces more than one echo signal.