| 摘要 |
A well logging instrument that has a neutron source for irradiating earth formations traversing a borehole used in deriving useful information pertaining to said formations. Three detectors are mounted in a spaced-apart vertical relationship within a pressure-resistant housing. The detectors nearest and farthest from the neutron source detect thermal neutrons while the third detector from the neutron source detects a rare earth compensated aggregate capture gamma ray spectrum. By comparing the irradiated formations as detected by the three detectors, certain formation fluid, matrix, and pore volume parameters are derived. Also, by comparing the count rates of high and low energy ranges of the third detector in earth coal formation matrix, an ash volume is determined. From this value, a bulk density is derived from the corresponding earth coal formation.
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