In this section of the website, the origins of micro
geophysical modeling are touched upon and four LVPM OUTPUTS - fast neutron
slowing down length (Ls), thermal neutron diffusion coefficient (D), thermal
neutron diffusion length (L), and thermal neutron capture cross section
(SIGMA) - are seen in their native habitat.
Figure 1, taken from US
Patent 3,906,224 and a full copy, are provided below.This Figure forms the starting point for a
discussion of the effects that different
neutron sources and their energiesand
modes of operation have on nuclear well logging tools.
Figure 2 was generated by LVPM: it forms the basis for a
novel way to measure neutron porosity with a neutron generator-based logging
tool that has both good porosity measurement sensitivity and good count
rates.The genesis of this method is US Patent 3,818,225 and a copy is also
provided below.The main idea is to
directly measure the thermal neutron
diffusion coefficient and then use the relationships shown in Figure 2 to
obtain neutron porosity.