DUAL DETECTOR PULSED NEUTRON LOGGING FOR PROVIDING INDICATION OF FORMATION POROSITY

摘要

DUAL DETECTOR PULSED NEUTRON LOGGING FORPROVIDING INDICATION OF FORMATION POROSITYAbstract of the Disclosure. A logging instrumentcontains a pulsed neutron source and a pair of radiation detec-tors spaced along the length of the instrument. The radiationdetectors are gated differently from each other to provide anindication of formation porosity which is substantially independ-ent of the formation salinity. In the preferred embodiment, theelectrical signals indicative of radiation detected by the long-spaced detector are gated for almost the entire interval betweenneutron pulses and the short-spaced signals are gated for a sig-nificantly smaller time interval which commences soon after thetermination of a given neutron burst. The signals from the twodetectors are combined in a ratio circuit for determination ofporosity.-1a-