Variance reduction techniques for improved derived elemental concentrations from fitting prompt neutron capture gamma ray spectra

Advances in the post-acquisition neutron-induced gamma-ray-spectroscopy spectral fitting techniques provide a means for improving both the precision and accuracy of the elements measured in subsurface petroleum reservoir formations. Rigorous stepwise-elimination multiple regressions and a novel analytical hierarchy technique are examined using synthetic spectral logs and field data. These approaches lead to adaptive dimensioning of the least-squares spectral fitting process, which reduces the uncertainties associated with the elemental concentrations without sacrificing important contributions