Accuracy and borehole influences in pulsed neutron gamma density logging while drilling

A new pulsed neutron gamma density (NGD) logging has been developed to replace radioactive chemical sources in oil logging tools. The present paper describes studies of near and far density measurement accuracy of NGD logging at two spacings and the borehole influences using Monte-Carlo simulation. The results show that the accuracy of near density is not as good as far density. It is difficult to correct this for borehole effects by using conventional methods because both near and far density measurement is significantly sensitive to standoffs and mud properties.

► Monte Carlo evaluation of pulsed neutron gamma-ray density tools.
► Results indicate sensitivity of the tool to standoff and mudcake properties.
► Accuracy of far spaced detector is better than near spaced.