| 摘要 |
<p>METHOD AND APPARATUS OF INVESTIGATING AN EARTH FORMATION SPECIFICATION In the illustrative embodiments of the invention disclosed, earth formations surrounding a well bore are irradiated with pulses of fast neutrons, and gamma rays resulting from the ensuing thermal neutron capture interactions with nuclei of the formations are detected, from which measurements of the thermal neutron decay times characterizing the respective formations are derived and the gamma ray energy spectra of the respective formations axe analyzed. Gating of the gamma ray detection periods is automatically controlled, both for the decay time and the spectroscopy functions, in accordance with measured values of the decay times. The duration and repetition rate of the neutron pulses are also controlled as a function of the measured decay times to provide an overall optimized decay time-spectroscopy operating cycle. Spectroscopy outputs representative of formation lithology. salinity, porosity and shaliness are developed to supplement and improve decay time log interpretation.</p> |
