Monte Carlo Comparison of Alternatives to 3He Thermal Neutron Detectors for Logging Applications

Abstract

The survey of oil and gas often employs two radiation-based measurements in a rock formation: the electron density with γ-ray density tools; and the hydrogen content with neutron porosity tools. The former tools are composed of a γ-ray source and a γ-rays detector, such as NaI(Tl). The latter tools comprise a neutron source and a thermal neutron (25 meV) detector, such as 3He tube. However, γ-ray density and neutron porosity tools must be used conjointly. Additionally, the demand for neutron detection technology is increasing while the supply of 3He gas is extremely scarce. These issues have led to the development of alternative neutron detection technology based on 10B and 6Li. Here, the first aim was to review detectors belonging to 10B and 6Li families. The second aim was to compare 3He tube and some 10B and 6Li detectors selected from the review. Their counting rates were calculated with Geant4 Monte Carlo simulations. In the tested configurations, it was shown that both 10B and 6Li families present counting rates similar to 3He tubes. Furthermore, 6Li detectors are capable of measuring both electron density and hydrogen content, eliminating the need for two separate tools.