Pulsed neutron well logging techniques with background radiation removal

A method is described for producing inelastic gamma ray measurements of earth formations in the vicinity of a well borehold, which measurements are corrected for background gamma rays caused by other than inelastic neutron scattering events. The method comprising the steps of: 1) repetitively irradiating the earth formations surrounding the well bore with relatively short duration pulses of fast neutrons; 2) detecting, in the intervals between such pulses of fast neutrons, the background gamma radiation in the borehole; 3) storing counts representative of the detected background gamma radiation in counter memory means; 4) detecting, during each such pulse of fast neutrons, total gamma radiations due to the inelastic scattering of neutrons by materials comprising the earth formations in the vicinity of the borehold plus background gamma radiations; 5) making counts representative of the total gamma radiations; and 6) correcting the total radiation counts by means of the stored background radiation counts to provide resultant corrected counts. (author)