The formation consists of limestone with 20% porosity. The generic tool is pushed up against the wall of the water borehole. The tool sonde consists of solid iron and contains an Americium-Berylium neutron source. Two detectors with different sizes contain 3He at a pressure of 4 atm, and are placed at different distances from the source along the axis of the tool. The modeled system and the energy spectrum of neutrons used in the simulation can be seen in the Figures 3 and 4.