Patent ID: 8847149

Claim:
A method, comprising: irradiating a portion of a geological formation with neutrons in a neutron burst generated by a switchable electronic source; measuring, with one or more detectors, flux of gamma rays recorded over time with respect to the neutron burst, at least a portion of the gamma rays being generated by the neutrons; obtaining a decay time spectrum from the flux measured as a function of time by recording gamma counts using small time windows, spanning an interval from the neutron burst to the next neutron burst event, sufficient to generate a functional relationship of the flux with respect to time; determining at least one of a formation capture cross section or a borehole capture cross section from the decay time spectrum; and determining at least one of a neutron porosity, a density, or a photoelectric factor of the geological formation based on the at least one of the formation capture cross section or the borehole capture cross section and using one or more functional relationships from a plurality of data.