Method and system for calculating extent of a formation treatment material in a formation

A method and system for calculating extent of a formation treatment material in a formation. At least some of the illustrative embodiments are methods comprising releasing neutrons into a formation from a neutron source of a logging tool within a borehole having an axis, sensing energies of gammas produced by materials in the formation, the sensing by a gamma detector on the logging tool, generating a measured spectrum of the energies of the gammas sensed by the gamma detector, determining elemental concentrations of materials in the formation based on a basis spectrum, and calculating axial extent of a formation treatment material in the formation in relation to the axis of the borehole based on the elemental concentrations of at least some materials in the formation.