Stochastic approach to the pulsed neutron logging methods

Neutron emissions from a steady state neutron source (of the α-Be or Cf-252 types) can be treated as a white noise stochastic process. In the rock space, according to different neutron well logging methods, different types of radiation resulting from the nuclear reactions between the source neutrons and the nuclei of the rock elements appear. This resulting radiation is in this case the shot noise process. By doing the time cross correlation between the input (white noise) and the output (shot noise) processes, or the auto-correlation of the output process alone, the transmission function of the system is obtained. Here the transmission function is just the die-away curve observed in all kinds of pulsed neutron logs. Experimental principles and the conditions of the correlation measurements are discussed. Nuclear reactions together with the space and time distribution of different types of radiation observed in the neutron well logging methods are presented with a view to getting the rock nuclear parameters from the correlation methods. (author)