Large depth-of-investigation pulsed neutron measurements and enhanced reservoir saturation evaluation

摘要

A method, including emitting from a source of ultrafast neutrons within a logging tool deployed in a borehole, a pulse of ultrafast neutrons into an irradiated portion of a formation surrounding the borehole. The method further includes detecting, with one or more gamma ray detectors located at increasing distances from the source of ultrafast neutrons, a flux of stimulated gamma rays generated within the irradiated portion of the formation by the pulse of ultrafast neutrons; and determining, from the detected flux of stimulated gamma rays, one or more petrophysical properties of the irradiated portion of the formation.