Patent ID: 6825459
Filing Date: 2004-11-30
Classification: G01V

Abstract:
An apparatus for conducting well logging, comprising:a housing for lowering into a borehole; a source of neutrons for irradiating borehole surrounding formations; a first detector mounted in said housing at a first pre-selected distance above said neutron source, said first detector for detecting a first set of signals of capture gamma rays emitted by the irradiated formation indicative of hydrogen and insensitive to chlorine content of the formation, and a second set of signals indicative of both hydrogen and chlorine content of the formation; a first detector shield surrounding said first detector, said first detector shield being constructed from a lanthanide series rare earth metal and characterized by having a significant thermal neutron induced capture gamma radiation energy response within the first set of signals; a second detector mounted in said housing at a second pre-selected distance above said first detector, said second detector for detecting a third set of signals of capture gamma rays emitted by the irradiated formation indicative of hydrogen and insensitive to chlorine content of the formation, and a fourth set of signals indicative of both hydrogen and chlorine content of the formation; and a second detector shield surrounding said second detector, said second detector shield being constructed from a lanthanide series rare earth metal and characterized by having a significant thermal neutron induced capture gamma radiation energy response within the third set of signals.