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This paper aims to demonstrate the feasibility of the proposed compensated neutron logging (CNL) tool for the absolute measurement of the porosity of subsurface formation based on the computational simulation study. Conventional CNL tools use 3He gas detectors, but solid-state scintillation detectors such as stilbene and CLYC are explored in this study. Monte Carlo simulations were conducted to investigate the advantages of the proposed CNL tool and the effects of environmental parameters such as pore fluid, borehole radius, and rock type on the absolute porosity measurement. Comparing simulated responses from the stilbene and CLYC detectors with conventional 3He detector, the stilbene-based logging system was expected to exhibit the highest neutron detection efficiency, while the porosity calibration performance was evaluated to be better with the CLYC-based system. Pore fluid makes differences in porosity calibration curves associated with the hydrogen content. The larger borehole radius decreases the porosity calibration performance. The shape of porosity calibration curve was altered for a certain rock type. Neutron-induced gamma spectroscopy may reveal the rock type information based on gammas from certain elements. One can identify the rock type from the CLYC results based on photopeaks from silicon, which may be relatively hard to accomplish with the stilbene-based system. The proposed system is expected to allow absolute porosity measurement in a broader environmental configuration compared to the conventional system.
Han et al. (Thu,) studied this question.