Disclosed herein are methods and
system for determining an
elemental composition of a downhole formation using
neutron-induced
gamma ray spectroscopy and
doping the borehole fluid with a
neutron absorber to remove at least part of the borehole thermal
neutron flux before it can capture borehole nuclei and emit gamma rays within a spectral range of interest. For example, a method for determining the
elemental composition includes adding a
dopant to a borehole fluid, wherein the
dopant absorbs thermal neutrons in the borehole, lowering a
logging tool comprising a
gamma ray spectrometer, emitting neutrons into a downhole environment, generating neutron-induced gamma rays comprising borehole gamma rays and formation gamma rays, detecting gamma rays from the downhole formation, and extracting the
elemental composition of the downhole formation. The
dopant may not emit gamma rays above 0.5 MeV or their peaks background should be predictable and / or consistent to be removed during
data processing.