Numerical Method of Evaluating Elemental Content of Oil-/Water-Saturated Formations Based on Pulsed-Neutron Gamma Inelastic Log Data

Summary A numerical method is proposed for solving an inverse problem for a pulsed-neutron gamma inelastic log. The objective is to determine a composition of the in-pore fluid and of the rock skeleton by gamma ray measurement data in spectral windows of four elements: C, O, Ca, and Si. Inversion of the data is based on an iteration procedure, on each step of which the corresponding direct problem is solved for transport equations of neutrons and gamma quanta. Results of numerical experiments are presented that confirm a convergence to exact solution for most of the unknowns. The proposed numerical method is the development of an approach for solving inverse problems in nuclear geophysics (Khisamutdinov and Blankov 1989; Khisamutdinov and Minbaev 1995; Khisamutdinov 1999; Khisamutdinov and Phedorin 2003; Khisamutdinov 2005).