Formation evaluation combination system for petrophysical well log analysis

摘要

A method of measuring characteristics of a geologic formation, using the time, energy and spatial spectra of gamma rays induced by an accelerator, which allows (i) the measurement of the photoelectric absorption (P_e) factor of the formation using a gamma-ray spectrum detected from gamma rays induced in the formation, (ii) the calculation of a neutron porosity of the formation using the gamma-ray spectrum, and (iii) the determination of a bulk density of the formation using the spectroscopic measurements. The P_e factor may be inferred by directly mapping the spectroscopic measurements. The porosity may be calculated by relating the gamma-ray spectrum to a hydrogen content of the formation. The density may be determined by computing a gamma diffusion length of the formation based on the gamma-ray spectrum. In addition to these measurements, the resistivity of the formation and its spontaneous potential may also be measured using an electromagnetic induction system.