Bulk density logging with high-energy gammas produced by fast neutron reactions with formation oxygen atoms

Borehole logging for formation density has been an important geophysical measurement for many years in the minerals, geotechnical, oil, and natural gas industries. The conventional gamma-gamma backscatter method has performed well in open, smooth boreholes. However, the method has limited depth of investigation and has not been quantitative in cased holes. A new method of logging earth formations for bulk density uses 14-MeV neutrons to produce high threshold energy reactions with formation nuclei, resulting in emission of high-energy gamma rays. The attenuation of the high-energy gammas as they transport back to the logging tool provides a measure of formation density. Computer modeling indicates the new density logging method penetrates deeply into the formation and can compensate for many interfering borehole and formation effects.