Apparatus and method for measuring downhole fluid composition and properties

An apparatus for estimating at least one property of an earth formation, comprising:

• a carrier configured to be disposed in the formation;
• a pulsed neutron tool disposed at the carrier, the pulsed neutron tool including a neutron source configured to irradiate the formation with neutrons and at least one detector configured to measure gamma rays emitted by the formation and generate at least one pulsed neutron measurement;
• and
• a processor in communication with the at pulsed neutron tool and configured to receive the at least one pulsed neutron measurement, the processor configured to:
• estimate a pulsed neutron fluid saturation by analyzing the at least one pulsed neutron measurement via a pulsed neutron model of the earth formation, the pulsed neutron model including expected pulsed neutron measurements relative to selected fluid composition and properties;
• compare the pulsed neutron fluid saturation to a reference fluid saturation estimated via a downhole tool;
• adjust the pulsed neutron model to at least substantially eliminate a difference between the pulsed neutron fluid saturation and the reference fluid saturation by adjusting at least one of the selected fluid composition and the selected fluid properties;
• and
• estimate at least one of the fluid composition and the fluid properties based on the adjusted model.